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... The Chacoan peccary is absent in areas that lack forest cover (Altrichter and Boaglio 2004). They are also absent in areas dominated by intensive soy-production, even when forest curtains are left (Núñez-Regueiro et al. 2015). Altrichter and Boaglio (2004) found that the Chacoan peccary's presence in a site is inversely related to human presence. ...
... Despite new records, it remains categorized as Endangered (Torres and Camino 2019), because it is seriously threatened by habitat loss and fragmentation, as the Chaco has one of the highest deforestation rates in the world (Hansen et al. 2013). Chacoan peccaries cannot inhabit productive matrices (Altrichter and Boaglio 2004;Núñez-Regueiro et al. 2015). It is also threatened by high hunting pressures (Altrichter 2006;Camino et al. 2018). ...
... Despite differences, both studies coincide with its absence in totally converted areas. Research in intensive-productive landscapes also found that whitelipped peccaries are absent (Núñez-Regueiro et al. 2015). Forest curtains are insufficient to maintain white-lipped peccaries in productive matrices (Núñez-Regueiro et al. 2015). ...
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Argentina has an extensive and diverse terrain classified into 11 ecoregions. Seven of these ecoregions, occupying the north and north-central parts of the country, house the 11 tropical ungulate species found here. The ecoregions are lowland and subtropical, some beginning in the tropics, some extending to temperate climates. The principal topographical characteristics, hydrology, climate, vegetation and fauna are described for these seven ecoregions. Each of the 11 species is then treated in detail with respect to its ecology and conservation. Emphasis is placed on distribution, habitat and density, feeding ecology, threats and conservation in Argentina, based on the most recent studies. Data on reproductive biology and behaviour are included where information is relatively recent and unlikely to be covered elsewhere. The species include the following: the Brazilian tapir (Tapirus terrestris), found in northern subtropical ecoregions, three species of peccary (Tayassu pecari, Pecari tajacu and Parachoerus wagneri) from northern subtropical and drier regions, of which the Chacoan peccary (P. wagneri) is endemic while the other two species have more extensive distributions. The guanaco (Lama guanicoe) occurs only in relict populations in the ecoregions considered. The taruca (Hippocamelus antisensis) occupies the eastern boundary between the Yungas and drier, high altitude ecoregions. Three species of brocket deer (Mazama americana, M. gouazoubira and M. nana) occupy the northern tropical, subtropical and Chacoan areas. The marsh deer (Blastocerus dichotomus), the largest South American deer, has small populations occupying wetlands from the northern border to the Parana delta, while the pampas deer (Ozotocerus bezoaticus) is found in four isolated populations from Ibera to Buenos Aires province. Argentina represents the southern limit to the distribution of all these species and thus threats are often magnified. Ongoing conservation activities include the maintenance of protected areas, promotion (difusion, education, sensitization), investigation and the reintroduction of some species of formerly extinct ungulates into the Ibera wetlands area.
... Such is the case of the chacoan peccary (Catagonus wagneri), that is endemic to the Dry Chaco (over 90% of its habitat occurs in the region; Altrichter et al. 2016;Ferraz et al. 2016). The chacoan peccary (ChP hereafter) is a habitat specialist that only occupies areas with high forest-cover (Altrichter and Boaglio 2004;Ferraz et al. 2016;Taber et al. 1993;Torres et al. 2018), and it has not been detected in landscapes dominated by industrial agriculture (Ferraz et al. 2016;Núñez-Regueiro et al. 2015). Habitat loss is, therefore, the main threat to the species (Altrichter et al. 2015Camino and Torres 2019) and its populations are also negatively affected by high hunting pressure (Altrichter 2005;Camino et al. 2018;Romero-Muñoz et al. 2020;Saldivar-Bellassai et al. 2021). ...
... The chacoan peccary (ChP) is a species associated with the Dry Chaco forests and it is not found in landscapes dominated by industrial agriculture (Altrichter and Boaglio 2004;Núñez-Regueiro et al. 2015;Ferraz et al. 2016;Taber et al. 1993;Torres et al. 2018). It is Fig. 1 Study areas. ...
... The loss of natural ecosystems was mainly due to advance of industrial agriculture (Vallejos et al. 2015). Because the ChP does not occupy areas dominated by industrial agriculture (Altrichter and Boaglio 2004;Núñez-Regueiro et al. 2015;Ferraz et al. 2016;Taber et al. 1993;Torres et al. 2018), we changed the category of transformed areas from suitable to unsuitable (Fig. 2). Subsequently, we eliminated all habitat patches that remained too small and isolated to sustain a group of ChPs (Fig. 2C, D). ...
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The Dry Chaco has one of the highest deforestation rates of the world. The chacoan peccary (Catagonus wagneri; ChP) is endemic to the forests of this region and faces a high risk of extinction. However, we lack sufficient information about this species to develop effective conservation actions. This is the first study to determine the relevance of primary and secondary forest as habitat for the species and to address opportunities for conservation. We used occupancy modelling to study habitat selection. Using additional information on the species and the region, we then estimated the time left before the ChP’s habitat outside of protected areas is completely lost, and the number of ChP generations likely to exist before this happens. Finally, we identified protected areas that can sustain viable populations, and estimated the number of individuals that can survive within them. We found that the ChP occupies both primary forests and secondary forests. Also, that if deforestation rates remain consistent, the habitat for the ChP outside protected areas will have disappeared before 2051 (< 6 peccary generations). Furthermore, we found that most protected areas are too small and isolated to sustain viable populations. Our results have great management implications. Well-managed forests may allow the conservation of the ChP. Initiatives focused on forest conservation should increase, alongside the restoration of degraded and deforested areas. We also recommend the creation of new protected areas and wildlife corridors, and working horizontally with local communities.
... All focal species are present in a large portion of the Argentinean DCH and have a large area of suitable habitat. This information is relevant because these species are endangered or vulnerable to extinction at both the local and international levels and have disappeared from a large percentage of their historical distribution (Altrichter and Boaglio 2004;Núñez-Regueiro et al. 2015;Taber et al. 2008). In 9,000 km 2 of a landscape of the DCH, dominated by an intensive productive matrix, white-lipped peccaries may be extirpated (Núñez-Regueiro et al. 2015). ...
... This information is relevant because these species are endangered or vulnerable to extinction at both the local and international levels and have disappeared from a large percentage of their historical distribution (Altrichter and Boaglio 2004;Núñez-Regueiro et al. 2015;Taber et al. 2008). In 9,000 km 2 of a landscape of the DCH, dominated by an intensive productive matrix, white-lipped peccaries may be extirpated (Núñez-Regueiro et al. 2015). Also, hunting of peccaries became unsustainable in the DCH over a decade ago (Altrichter and Boaglio 2004). ...
... Traditional livestock and other productive activities reduce both vegetation cover (Grau and Aide 2008;Morello et al. 2005) and wildlife (Altrichter 2005;Altrichter and Boaglio 2004), therefore, educational and awareness programs should be implemented to reverse the negative effect that human activities have on the large mammals in the DCH (Altrichter 2005;Altrichter and Boaglio 2004). Although the studied species are still present in this territory, they would not survive in totally transformed areas (Matteucci et al. 2016;Núñez-Regueiro et al. 2015). These observations indicate that the Forests Law in the Dry Chaco presents a series of challenges to improve its performance in terms of effectiveness, equity and social legitimacy. ...
... Very few studies have addressed the conservation potential of large farmlands in the Chaco, despite their increase over the past few decades. The mammal communities found in agricultural fields with a landscape configuration similar to that of the Argentinian Chaco (Núñez-Regueiro et al., 2015) are known to be more impoverished than in our study area, especially the threatened species (Núñez-Regueiro et al., 2015). There could be two possible reasons that explain the rich diversity of mammals found in Estancia Montania. ...
... Very few studies have addressed the conservation potential of large farmlands in the Chaco, despite their increase over the past few decades. The mammal communities found in agricultural fields with a landscape configuration similar to that of the Argentinian Chaco (Núñez-Regueiro et al., 2015) are known to be more impoverished than in our study area, especially the threatened species (Núñez-Regueiro et al., 2015). There could be two possible reasons that explain the rich diversity of mammals found in Estancia Montania. ...
... In the case of T. peccary, this species is considered vital for maintaining ecosystem processes, and is important for seed predation and dispersion, plant demography and diversity, as well as being prey for jaguars and pumas (Silman et al., 2003;Beck, 2005;Keuroghlian and Eaton, 2009;Altrichter et al., 2012), and have been proposed as surrogate to monitor ecosystem functioning (Jorge et al., 2013). Forest lost and hunting pose the most significant threat to this species, and, as in other biomes, are driving the steep decline in the number of white-lipped peccary in the Chaco region (Altrichter and Boaglio, 2004;Sowls, 2013;Núñez-Regueiro et al., 2015;Reyna-Hurtado et al., 2016). In our site, the low hunting pressure suggests that forest loss can be enough to cause an irreversible decline in the white-lipped peccary populations if connectivity for this species becomes seriously compromised in the absence of adequate forest corridors between suitable patches. ...
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Cattle ranching has led to a significant decrease in forest cover in the Neotropic. In this study we evaluate how medium- and large-sized mammals cope in these human-modified landscapes in the Paraguayan Dry Chaco, where by state law at least 25% of forest cover must be preserved. Using a camera-trap approach, we studied how the surrounding vegetation matrix and season (dry or rainy) influence the pattern of occurrence and detectability of species around artificial water reservoirs for cattle supply. We registered 26 mammal species, and the responses of 14 different species were modelled. Five species (Tayassu pecari, Leopardus pardalis, Pecari tajacu, Mazama gouazoubira and Myrmecophaga tridactyla) showed a positive response to forest cover, with T. pecari and L. pardalis being extremely sensitive to deforestation. Also, forest cover showed a positive effect on the detectability of Tapirus terrestris and Puma concolor. By contrast, for two generalist canids, Lycalopex gymnocercus and Cerdocyon thous, and the semiaquatic Hydrochoerus hydrochaeris forest cover negatively influenced species detectability. Cattle ranches have the potential to maintain a substantial part of the original chacoan fauna, with forest cover being a main factor in structuring the mammal assemblages found around water reservoirs. Additionally, in ten species there was a moderate to strong increase in the probability of detection around water reservoirs during the dry season. The conservation of large forest tracts combined with strict compliance with poaching bans are key management strategies for the conservation of mammal diversity in the human-altered landscapes of the Chaco.
... Changes to the amount and configuration of forest cover have taxon-specific effects (Núñez-Regueiro et al. 2015). For example, volant taxa such as bats or birds are likely less affected by changes to habitat availability than overland dispersers such as terrestrial mammals (Bélisle 2005). ...
... Our approach was based on landscape patterns rather than species-specific data, which are currently limited in this region for most species. Although some species can survive in agrarian/forest mosaics , their survival may diminish over time (Núñez-Regueiro et al. 2015). ...
... However, we found that the degree of spatial separation of forest remnants was well beyond the dispersal range of most of the mammals of the Dry Chaco and many remnants are now too small to support home ranges of many of these species, with these effects increasing between 2000 and 2019 (Fig. 3). Entire taxonomic orders are often affected by forest loss in the same manner; although some of these species can survive in agrarian/forest mosaics , their survival can diminish over time (Núñez-Regueiro et al. 2015). Additionally, the two components of fragmentation-habitat loss and habitat isolation-act in tandem. ...
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Context The Dry Chaco spans more than 87 million hectares across Argentina, Bolivia, and Paraguay. This unique forest system has experienced extensive loss and fragmentation due to land-use change, with different land-use histories in the three countries. This forest loss has altered landscape connectivity for the Dry Chaco’s associated biota. Objectives We compared patterns of deforestation-induced fragmentation and concomitant changes in structural landscape connectivity between 2000 and 2019 in the three countries to identify consistent patterns that might facilitate biome-wide conservation. Methods We quantified forest cover in the Dry Chaco of Argentina, Bolivia, and Paraguay for the years 2000 and 2019 at 30 m resolution. We analyzed structural connectivity at three scales. Then, we identified and visualized the most important stepping stones per country per year. Results Between 2000 and 2019, the overall extent of Dry Chaco forest cover decreased by 20.2% (9.5 million ha). All three counties experienced substantial reductions, with Paraguay undergoing the greatest loss and fragmentation relative to 2000. Most of the overall network metrics decreased from 2000 to 2019 for Paraguay and Bolivia, but Argentina experienced increased coalescence distance and average nodal connectance. Dispersal-level metrics showed clustering threshold distances between 1000 and 2000 m for each country in both years. Conclusions The large number of forest fragments and distances between them suggest that some mammals characteristic of the biome may be experiencing negative impacts from this fragmentation. Contemporary and future challenges of uncoordinated national conservation and management policies, land speculation, and increased human infrastructure will accelerate the rate of deforestation.
... Additionally, ecosystem services provided by hedgerows, defined as continuous or closely spaced lines of shrubs and trees (Dondina, Kataoka, Orioli, & Bani 2016), common in anthropogenic landscapes of temperate regions (Dainese, Montecchiari, Sitzia, Sigura, & Marini 2017;Van Vooren et al. 2017) have also received much attention. Another common habitat type more frequently used in tropical and subtropical transformed regions are forest strips or linear forest fragments (hereafter, LFF) (Núñez Regueiro et al. 2015), however, they have been poorly studied in relation to their role in the provision of ecosystem services. ...
... Although hedgerows (e.g., shelter belts, fencerows) may be residuals of native woodlands, they are in most cases, humanmade features or new plantations with different management strategies, presenting large differences in their internal structure and quality (Baudry, Bunce, & Burel 2000;Dondina et al. 2016). LFFs, on the other hand, are natural vegetation left in the landscape during land conversion, with a species composition and structure similar to the original forest (Núñez Regueiro et al. 2015). Both hedgerows and LFFs can function as wildlife corridors by connecting larger forest fragments (Davies & Pullin 2007;Lees & Peres 2007;Hawes, Barlow, Gardner, & Peres, 2008;Sreekar, Mohan, Daas, Agarwal, & Vivek 2013) or as windbreaks, controlling soil erosion on adjacent crop and pasture fields (Areskoug 2001;Böhm, Kanzler, & Freese 2014). ...
... This legislation, when fulfilled, turned LFF into a common element of the landscape. Unfortunately, their inefficiency as connector elements of forest patches at landscape scale (Ginzburg, Torrella, & Adámoli 2012) indicated by their poor use by native medium and large mammals (Núñez Regueiro et al. 2015), suggests that they did not work as well as expected. Despite these results, recent field observations within LFFs of native trees (e.g. ...
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The delivery of ecosystem services, such as biotic pollination is a benefit that nature provides us. Pollinators increase the quantity, quality and stability of crops for food production. Previous works show that proximity to natural habitats increases crop production through the delivery of pollination services. However, similar researches in subtropical regions are largely lacking. In this study we evaluated the role of linear forest fragments (LFFs) on the provision of biotic pollination service to soybean crops (Glycine max) and explored whether this service changes with increasing distance to LFFs in subtropical dry Chaco (Argentina). In three agricultural farms and testing two soybean varieties, we covered plots of 0.75 m2 with soybean plants and compared them with equally sized open plots. Plots were placed near (60 m) and far (600 m) from LFFs. We found that plants from the open treatment produced 32% more pods, 41% more seeds and had 42% higher yield (kg/ha) than plants from the covered plots. The difference between open and covered plots in seeds and yield did not change significantly with the distance to LFFs, but the number of pods, contrary to what we expected, was higher far from LFFs. Our findings highlight the possible impact of pollinators on soybean yield in both varieties tested here; but the proximity to LFFs was not directly related to a larger difference in production. Observed patterns are explained by edge effects and competition between soybean plants and trees near LFFs, combined with an underestimation of the distance from the natural hives to which honeybees can efficiently exploit the crops. In this subtropical region, soybean expansion is the most important driver of land cover change and this study represents a first step towards a better understanding of the functioning of these remnants of natural areas within the agricultural land in the region of dry Chaco forests.
... This allows us to test possible relationships between grazing intensity and native mammal species. The grey fox Lycalopex gymnocercus (Fischer, 1814; Carnivora, Canidae) has become relevant in this ecoregion because it is a generalist species that consumes many fruits of woody plants and disperses seeds (Núñez-Regueiro et al., 2015;Periago, Chillo, & Ojeda, 2015;Varela, Cormenzana-Méndez, Krapovickas, & Bucher, 2008). Small mammals can also play an important role in structuring the understory by altering the rate of seed removal (Bricker, Pearson, & Maron, 2010). ...
... The differences with our study could be explained because we sampled in one of the best-conserved areas of the Argentine Chaco (CNP), where grazing intensities are low-intermediate Trigo, 2018). In addition, given that the grey fox is the only fox species present in our area, it does not have to compete for resources with other foxes; as it occurs in other regions where the grey fox and the crab-eating fox co-exist (Di Bitetti, Di Blanco, Pereira, Paviolo, & Pírez, 2009;Nanni, 2015;Núñez-Regueiro et al., 2015). ...
Article
Extensive livestock ranching is one of the main drivers of habitat degradation in terrestrial communities in the dry Chaco forest (Argentina). Grazing intensity could differentially affect native mammals and their interactions, which could impact both, native mammal communities and livestock production systems. Here, we determined how the activity index of grey foxes Lycalopex gymnocercus and capture abundance and richness of small mammals vary along a grazing intensity gradient in a particular region of the dry Chaco forest (Copo National Park, Argentina). Track plots were used to estimate the activity index of foxes and cattle, and Sherman traps for small mammals. Fresh scats were collected to analyse the diet of foxes and to assess possible changes in predator-prey dynamics. Fruit availability and shrub density were measured in 6 plots of 2 m x 50 m. We used generalized linear mixed models, Spearman’s nonparametric rank correlation, Chi-squared test, and Spearman’s partial correlation coefficient to analyse the potential effects of grazing intensity. We found that the activity index of foxes increased (0.06 ± 0.018) while small mammal abundance (-0.08 ± 0.024) and species richness decreased (rs = -0.94) with increasing grazing intensity. However, the proportion of scats with mammalian remains decreased with increasing grazing intensity. Also, we did not find a strong partial correlation between foxes and small mammals when we controlled for grazing intensity. This suggests that the abundance and diversity of small mammals in the study area are determined more by grazing intensity than by predator-prey interactions. Grazing intensity could negatively affect small mammals, but not through changes in fruit availability or shrub density, but possibly by affecting grass cover. Consequently, foxes’ activity could increase to meet caloric intake requirements. Our results suggest that specific cattle management recommendations depend on the wildlife species that serves as a conservation target. We recommend testing whether reducing cattle load can make this productive activity compatible with wildlife conservation in dry Chaco forests.
... Las zonas de continuidad entre ambas ecorregiones se encuentran reducidas en la actualidad a corredores constituidos por franjas de hábitats naturales que conectan parches de bosque. Estos corredores, con distinto grado de modificación y de características geográficas variables, atraviesan una matriz dominada por zonas transformadas a cultivos y generalmente están asociados a zonas ribereñas, constituyendo así elementos naturales del paisaje que guían el movimiento de las especies de animales (Noss 1991). ...
... Estudios recientes han evaluado los patrones de ocupación de corredores de bosques en ambientes de Chaco por parte de los mamíferos medianos y grandes (Núñez-Regueiro et al. 2015) y de vertebrados en general (Areskoug 2001), documentando patrones de uso muy diferentes. Sin embargo, estos estudios fueron diseñados a una escala local, en la región chaqueña, y no involucraron corredores regionales entre está última y las Yungas. ...
Article
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La transformación del ambiente natural constituye la principal amenaza para la conservación de muchas de las especies de mamíferos. La agricultura ha reducido la conectividad del pedemonte de Yungas con el Chaco, limitándola a corredores de hábitats naturales modificados que atraviesan una matriz de zonas transformadas. Mediante relevamientos con cámaras trampa, identificamos las especies medianas y grandes de mamíferos que utilizan corredores boscosos en dos sectores latitudinales del pedemonte de Yungas de Argentina. Estudiamos la diversidad de especies, la influencia de la distancia a través del corredor hasta el bosque continuo sobre la riqueza, cuantificamos similitudes en la composición y estructura de las comunidades entre ambas situaciones ambientales y evaluamos si los corredores constituyen zonas de paso o si los mamíferos establecen sus áreas de acción en los mismos. Registramos 22 especies en los corredores. Sólo seis taxones registrados en bosque continuo no fueron documentados en los corredores, y tres fueron fotografiados sólo en corredores. Para ambos sectores latitudinales, la equitatividad fue levemente mayor en corredores (aunque las diferencias fueron significativas solo en el sector norte), mientras que la riqueza de especies mostró tendencias opuestas entre sectores latitudinales, siendo mayor en el bosque del sector norte pero menor en el bosque del sector sur (aunque las diferencias no fueron significativas en ningún caso). No encontramos una influencia de la distancia al bosque continuo sobre la riqueza de mamíferos, ni diferencias importantes en la composición y estructura de las comunidades de ambas situaciones ambientales. En el norte, Dasyprocta punctata fue más frecuente en bosques continuos, mientras que Mazama gouazoubira y Leopardus pardalis prefirieron los corredores. En el sur, Leopardus pardalis y Pecari tajacu fueron más frecuentes en bosque continuo, mientras que Didelphis albiventris y las especies omnívoras utilizaron más los corredores. No encontramos diferencias significativas entre especies generalistas y especialistas en el uso de estos hábitats. Nuestro trabajo constituye la primera aproximación a esta temática en la región de las Yungas, aportando información relevante para el establecimiento de políticas de conservación.
... This PES program is part of Argentina's Native Forest Law (law 26331, Ley de Presupuestos Mínimos de Protección Ambiental de los Bosques Nativos, or Ley de Bosques Nativos). This program aims to preserve forest and its environmental services, such as biodiversity and forest cover for carbon storage, in the face of industrial-scale agriculture in one of the most threatened forested ecosystems in the world, the Chaco forest (Hansen et al., 2013;Núñez-Regueiro et al., 2015;Kuemmerle et al., 2017). This dry forest has suffered high levels of deforestation fueled by rapid expansion of agriculture, mainly to produce soybeans and pasture for cattle (Grau et al., 2008;Hansen et al., 2013;Volante et al., 2016;Fehlenberg et al., 2017). ...
... Sixty percent of the Chaco occurs in Argentina where many rural and indigenous communities rely on it to sustain their livelihoods. The Argentine Chaco is a patchwork comprising remnant forest strips, small forest patches, and some larger forest blocks embedded in a matrix of large farms primarily used for soybeans or pasture for cattle (Núñez-Regueiro et al., 2015). ...
Article
Payments for Ecosystem Services (PES) programs are increasingly emphasized to address challenges of conserving forests. However, concerns remain regarding the ability of PES programs to ensure long-term conservation of threatened lands. Evaluation of large-scale PES programs, including the spatial and temporal patterns of enrollment, is scarce, especially for programs that aim to protect forest from severe threats such as expansion of industrial agriculture. Using information on PES enrollment across 252,319 km2 in the Argentine Chaco, we examined both the duration for which lands are enrolled in PES and their suitability for agriculture. Specifically, we examined whether the PES program has resulted in adverse selection not only in space but also in time. We built spatially explicit generalized linear models using information on participants' length of contract and the potential of their land for agricultural use. We found the PES program enrolled land in areas with high agricultural potential, but enrollment of these lands occurred for shorter time periods than lands with lower levels of threat from deforestation. Consequently, adverse selection occurred over time but not in space. Our work demonstrates the importance of evaluating both temporal and spatial dimensions of adverse selection in PES for informing policy.
... Our study focuses on the four provinces in Northwestern Argentina that hold the largest tracts of Chaco forest: Chaco, Formosa, Salta, and Santiago del Estero (252,319 km 2 , Fig. 1). This landscape consists of remnant forest strips, small forest patches, and some larger forest blocks embedded in a matrix of large farms primarily used for soybeans or cattle pasture (Núñez -Regueiro et al., 2015). ...
... Additionally, offering the highest-tiered payment levels for conservation and restoration lands in yellow and green zones could maximize the program's additionality by incentivizing land-use practices highly aligned with the program's goals in areas with high threat of land-use conversion. Third, our results indicate that large parcels are least likely to achieve long-term enrollment in highly productive areas, which could accentuate already alarming levels of habitat fragmentation and biodiversity loss (Núñez -Regueiro et al., 2015;Quiroga et al., 2014). Thus, strategies need to be developed and implemented that promote enrollment of large parcels of forest under high threat. ...
... Increasing evidence suggests important interactions between habitat destruction and hunting in this region. For example, large mammals disappear from remaining forest patches soon after the surrounding areas are deforested because they are easily hunted out (Núñez-Regueiro et al. 2015, Semper-Pascual et al. 2019. Likewise, cattle ranchers in areas where pastures expand often persecute large predators over fears of attacks on cattle (Quiroga et al. 2016, Romero-Muñoz et al. 2019b). ...
... Hunters often kill mammals crossing such clearings; and workers cutting the forest, building fences and producing charcoal actively hunt animals in the remaining forest patches (Altrichter 2006;unpubl.). Accordingly, large mammals tend to disappear from forest strips and smaller forest patches soon after the surrounding areas are deforested (Núñez-Regueiro et al. 2015, Semper-Pascual et al. 2019. Furthermore, in areas already converted to agriculture, ranchers and farmers often persecute carnivores and herbivores thought to cause livestock or crop losses, respectively (Quiroga et al. 2016, Camino et al. 2018. ...
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Habitat destruction and overexploitation are the main threats to biodiversity and where they co-occur, their combined impact is often larger than their individual one. Yet, detailed knowledge of the spatial footprints of these threats is lacking, including where they overlap and how they change over time. These knowledge gaps are real barriers for effective conservation planning. Here, we develop a novel approach to reconstruct the individual and combined footprints of both threats over time. We combine satellite-based land-cover change maps, habitat suitability models and hunting pressure models to demonstrate our approach for the community of larger mammals (48 species > 1 kg) across the 1.1 million km 2 Gran Chaco region, a global deforestation hotspot covering parts of Argentina, Bolivia and Paraguay. This provides three key insights. First, we find that the footprints of habitat destruction and hunting pressure expanded considerably between 1985 and 2015, across ~40% of the entire Chaco-twice the area affected by deforestation. Second, both threats increasingly acted together within the ranges of larger mammals in the Chaco (17% increase on average, ± 20% SD, cumulative increase of co-occurring threats across 465 000 km 2), suggesting large synergistic effects. Conversely, core areas of high-quality habitats declined on average by 38%. Third, we identified remaining priority areas for conservation in the northern and central Chaco, many of which are outside the protected area network. We also identify hotspots of high threat impacts in central Paraguay and northern Argentina, providing Research 2 a spatial template for threat-specific conservation action. Overall, our findings suggest increasing synergistic effects between habitat destruction and hunting pressure in the Chaco, a situation likely common in many tropical deforestation frontiers. Our work highlights how threats can be traced in space and time to understand their individual and combined impact, even in situations where data are sparse.
... Since the 1990s, the region experiences among the highest deforestation rates worldwide, mainly due to the expansion of cattle ranching and soybean production . As a consequence, the region is undergoing massive defaunation (Quiroga et al. 2014;Núñez-Regueiro et al. 2015;Periago, Chillo & Ojeda 2015;. How species of conservation concern respond to land-use changes in the Chaco, however, is poorly understood, in part because the few existing studies used occurrence models only (Núñez-Regueiro et al. 2015). ...
... As a consequence, the region is undergoing massive defaunation (Quiroga et al. 2014;Núñez-Regueiro et al. 2015;Periago, Chillo & Ojeda 2015;. How species of conservation concern respond to land-use changes in the Chaco, however, is poorly understood, in part because the few existing studies used occurrence models only (Núñez-Regueiro et al. 2015). ...
Thesis
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Landnutzungswandel ist eine der Hauptursachen von Biodiversitätsverlust. In den Tropen und Subtropen führt eine Ausweitung von Agrarflächen zu vermehrter Abholzung der Wälder. Selbst wenn zukünftige Waldrodungen vermieden werden können, ist ein weiterer Artenrückgang sehr wahrscheinlich, da viele Arten zeitverzögert auf Veränderungen reagieren. Die Hauptziele dieser Arbeit waren die Auswirkungen vergangener und aktueller Landnutzung auf Biodiversität im argentinischen Chaco besser zu verstehen und Ansätze zu entwickeln, um negative Effekte schon vor einem lokalen Aussterben zu erkennen. Der argentinische Chaco ist aufgrund seiner Landnutzungsgeschichte, den hohen Abholzungsraten und der hohen Biodiversität bestens für eine solche Untersuchung geeignet. Meine Arbeit zeigt, dass der Artenreichtum an Vögeln und Säugetieren stark durch vergangene Landschaftsmuster beeinflusst wurde, was auf zeitverzögerte Reaktionen auf Landnutzungswandel hindeutet, sowie darauf, dass ein Teil der momentan vorkommenden Arten durch vergangene Landnutzungsänderungen noch aussterben wird. Die zeitverzögerten Reaktionen sind hauptsächlich eine Folge von Lebensraumfragmentierung, mehr noch als von Lebensraumverlust. Meine Ergebnisse zeigen, dass das Vorkommen von Ameisenbären seit 1985 stark rückläufig ist, insbesondere seit 2000, als die Ausweitung von Agrarflächen besonders stark zunahm. Abschließend konnte ich zeigen, dass Pekaris meist in abgelegenen Regionen mit hohem Waldanteil vorkommen, sowie dass physiologischer Stress bei Pekaris negativ mit Nahrungsverfügbarkeit korreliert, jedoch nicht mit Abholzung. Meine Arbeit legt nahe, dass Abholzung generell zum Artensterben im argentinischen Chaco beiträgt. Während manche Arten sehr schnell verschwinden, sterben andere nicht direkt aus, was ein Zeitfenster für Naturschutzmaßnahmen eröffnet. Die hier vorgestellten Ergebnisse können dabei helfen solche Zeitfenster in von Abholzung bedrohten Gebieten zu identifizieren.
... understanding of their presence and behavior will bolster baseline knowledge needed for developing effective conservation strategies. The cryptic and often nocturnal nature of many medium-and large-sized mammals can make them challenging to study in the wild (Núñez-Regueiro et al. 2015;Silveira et al. 2003); thus, there is a paucity of reliable data on the distribution and occurrence of these species at local scales in the remote areas of southwest China, making it difficult to design and evaluate conservation strategies within the region (Hodge and Arbogast 2016). ...
... Camera trapping studies have been used across a broad range of mammals to address specific research questions including distribution, occurrence, habitat association, activity patterns, and relationship among sympatric species (Bhattacharya et al. 2012;Burton et al. 2015;Núñez-Regueiro et al. 2015;Tobler et al. 2009). Camera trapping is also one of the most important tools in conservation, especially through occupancy studies (Bender et al. 2014). ...
Article
Full-text available
Here, we present a camera trap survey at a Tibetan sacred mountain to ascertain the status and activity patterns of medium- to large-sized ground-dwelling mammalian fauna. We recorded 15 medium- to large-sized mammal species including 9 carnivores, 4 ungulates, 1 primate, and 1 rodent. Six of the species were categorized by IUCN as globally threatened. The results suggested that the sacred mountain was particularly important for alpine ungulates. The mean occupancy probabilities of blue sheep Pseudois nayaur, Chinese goral Naemorhedus griseus, Chinese serow Capricornis milneedwardsii, and alpine musk deer Moschus chrysogaster were 0.93, 0.91, 0.87, and 0.44 respectively. Domestic dog Canis familiaris also occurs widely across the mountain, with a mean occupancy of 0.60. Temporal activity patterns showed that alpine musk deer were mostly nocturnal, with most captures occurring at night. Chinese serow were active at all periods, with an activity peak at dawn. Blue sheep were strictly diurnal, without any captures at night. Although Chinese goral were predominantly diurnal, captures also frequently occurred at night. Our study not only unveiled a wildlife haven benefiting from religious beliefs about sacred mountains but also pointed to the critical situation of the fauna in the sacred site. The fauna in such sacred sites are diverse but poorly studied, and are subject to threats from domestic dogs, garbage pollution, and population isolation. Future conservation and management efforts in such areas should evaluate the population genetic diversity and assess the impact of non-lethal human disturbance on the wildlife communities.
... Instead, evidence on the effects of forest strips on biodiversity and ecosystem functioning in the Dry Chaco is lacking. Previous local scale analysis discarded a contribution of forest strips to habitat or biological corridor for mammals (Núñez-Regueiro et al., 2015) and to pollination of soybean crops (Zelaya et al., 2018). At landscape level, Ginzburg et al. (2012) dismissed the potential role of forest strips in forest conservation because of their high exposure to edge effects. ...
... Small patches were found to be important as habitat and connectivity providers (Saura et al., 2014;Wehling and Diekmann, 2009;Wintle et al., 2019), and enhanced crop pollination, seed dispersal and carbon sequestration (Bodin et al., 2006;Ziter et al., 2013). In the Dry Chaco, forest strips have been dismissed as potential biological corridors due to their exposure to the edge effect (Ginzburg et al., 2012) and to a lower presence of mammals with respect to continuous forests (Núñez-Regueiro et al., 2015). However, our results suggest that the forest strip connectivity contribution enhances forests' functioning. ...
Article
Land use changes are occurring with unprecedented magnitude and intensity, imposing global impacts on ecosystem services (ES) and biodiversity. While the impacts of land use changes are increasingly recognized, understanding how landscape connectivity is related to ecosystem functioning is lacking. In the Argentinian Dry Chaco, deforestation increased forest fragmentation but strips of native forest (linear remnants) were usually left after clearings. Although the number of ecological studies on forest strips has increased, their contribution to forest connectivity and functioning has not been assessed. We evaluated the contribution of forest strips to forest connectivity and estimated its effect on forests' functioning considering low, moderate, and high species' dispersal abilities in our estimation. The effects of forest strip connectivity contribution to the forests' Ecosystem Services Supply Index (Forests' ESSI) was also analyzed. Forest strips contributed on average 6% and up to 40% to forest connectivity for moderate dispersal abilities, while low and high dispersals presented low values in almost all cases. The connectivity contribution was highest (between 15 and 40%) and variable for moderate dispersal abilities in landscapes with between 25 and 35% of forest cover. High connectivity contribution was generally achieved for low and moderate dispersals when forest strips conformed a network among forest patches. Forest strip connectivity significantly increased the forests' ESSI (between 1.3 and 2.4% per unit of connectivity contribution) and its effect was higher in comparison to forest amount and fragmentation. This study provides insights for planning the location of forest strips and forest remnants in agricultural landscapes, thus increasing forest connectivity for enhancing ecosystem functioning.
... Furthermore, such observations suggest that both threats may often synergise in the Gran Chaco, producing rapid defaunation. Despite the potentially large impacts of hunting on biodiversity, this issue has received even less attention than the impacts of deforestation in the Gran Chaco (Núñez-Regueiro et al. 2015;Semper-Pascual et al. 2019). Furthermore, no study has yet assessed the impacts of hunting pressure on biodiversity across the Gran Chaco. ...
... Hunters often kill mammals crossing such clearings; and workers cutting the forest, building fences, and producing charcoal actively hunt animals in the remaining forest patches (Altrichter 2006;authors' own observations). Accordingly, large mammals tend to disappear from forest strips and smaller forest patches soon after the surrounding areas are deforested (Núñez-Regueiro et al. 2015;Semper-Pascual et al. 2019). Furthermore, in areas already converted to agriculture, ranchers and farmers often persecute carnivores and herbivores thought to cause livestock or crop losses, respectively Camino et al. 2018). ...
Thesis
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Die Hauptursachen für die derzeitige weltweite Krise der biologischen Vielfalt sind Lebensraumzerstörung und Übernutzung. Wir wissen jedoch nicht, wie sich diese beiden Faktoren einzeln und zusammen auf die verschiedenen Aspekte biologischer Vielfalt auswirken und wie sie sich im Laufe der Zeit verändern. Da beide Bedrohungen weit verbreitet sind, verhindern dies die Entwicklung wirksamer Schutzstrategien. Das übergeordnete Ziel dieser Arbeit war räumliche und zeitliche Veränderungsmuster der Auswirkungen von Lebensraumzerstörung und Übernutzung auf die biologische Vielfalt zu verstehen. Ich habe diese Bedrohungsgeographien mit hoher räumlicher Auflösung und über drei Jahrzehnte hinweg für verschiedene Aspekte biologischer Vielfalt untersucht: Arten, Lebensgemeinschaften und taxonomische, phylogenetische und funktionale Facetten biologischer Vielfalt. Ich konzentrierte mich auf den 1,1 Millionen km² großen Gran Chaco, den größten tropischen Trockenwald der Welt und einen globalen Entwaldungs-Hotspot. Meine Ergebnisse zeigen, dass sich im Laufe von 30 Jahren die räumlichen Auswirkungen der einzelnen Bedrohungen auf größere Gebiete ausdehnten als nur auf die abgeholzte Fläche. Dies führte zu einem Verlust an hochwertigen und sicheren Gebieten für den Jaguar, die gesamte Großsäugergemeinschaft und alle Facetten der Säugetiervielfalt. Beide Bedrohungen trugen wesentlich zum Rückgang biologischer Vielfalt bei, ihre relative Bedeutung variierte jedoch je nach Art und Facette der biologischen Vielfalt. Zudem haben die Gebiete, in denen beide Bedrohungen zusammenwirken, im Laufe der Zeit zugenommen, was den Verlust der biologischen Vielfalt wahrscheinlich noch verschlimmert hat. Diese Arbeit unterstreicht, wie wichtig es ist, die Auswirkungen mehrerer Bedrohungen im Laufe der Zeit gemeinsam zu bewerten, um den menschlichen Einfluss auf die biologische Vielfalt besser verstehen zu können und wirksame Schutzstrategien zu finden.
... Since the 1990s, the region experiences among the highest deforestation rates worldwide, mainly due to the expansion of cattle ranching and soybean production (Baumann et al., 2017). As a consequence, the region is undergoing massive defaunation (Núñez-Regueiro et al., 2015;Periago et al., 2015;Quiroga et al., 2014;Semper-Pascual et al., 2018). How species of conservation concern respond to land-use changes in the Chaco, however, is poorly understood, in part because the few existing studies used occurrence models only (Núñez-Regueiro et al., 2015). ...
... As a consequence, the region is undergoing massive defaunation (Núñez-Regueiro et al., 2015;Periago et al., 2015;Quiroga et al., 2014;Semper-Pascual et al., 2018). How species of conservation concern respond to land-use changes in the Chaco, however, is poorly understood, in part because the few existing studies used occurrence models only (Núñez-Regueiro et al., 2015). ...
... First, the probability of encountering roads can be influenced by how the animal moves in the landscape and acquires resources (Grilo et al., 2018). Previous studies have shown higher risks for passerine birds that forage on foliage or bark and inhabit woodlands (Santos et al., 2016), for herbivorous and omnivorous mammals (Barthelmess, & Brooks, 2010;Cook & Blumstein, 2013) and for more habitat-generalist mammals (Núñez-Regueiro et al., 2015). Second, the probability of crossing an encountered road may be affected by how the road is perceived and by the mobility of the animal (Jaeger et al., 2005). ...
Article
Aim Collisions between wildlife and vehicles are recognized as one of the major causes of mortality for many species. Empirical estimates of road mortality show that some species are more likely to be killed than others, but to what extent this variation can be explained and predicted using intrinsic species characteristics remains poorly understood. This study aims to identify general macroecological patterns associated with road mortality and generate spatial and species‐level predictions of risks. Location Brazil. Time period 2001–2014. Major taxa Birds and mammals. Methods We fitted trait‐based random forest regression models (controlling for survey characteristics) to explain 783 empirical road mortality rates from Brazil, representing 170 bird and 73 mammalian species. Fitted models were then used to make spatial and species‐level predictions of road mortality risk in Brazil, considering 1,775 birds and 623 mammals that occur within the continental boundaries of the country. Results Survey frequency and geographical location were key predictors of observed rates, but mortality was also explained by the body size, reproductive speed and ecological specialization of the species. Spatial predictions revealed a high potential standardized (per kilometre of road) mortality risk in Amazonia for birds and mammals and, additionally, a high risk in Southern Brazil for mammals. Given the existing road network, these predictions mean that >8 million birds and >2 million mammals could be killed per year on Brazilian roads. Furthermore, predicted rates for all Brazilian endotherms uncovered potential vulnerability to road mortality of several understudied species that are currently listed as threatened by the International Union for Conservation of Nature. Conclusion With a rapidly expanding global road network, there is an urgent need to develop improved approaches to assess and predict road‐related impacts. This study illustrates the potential of trait‐based models as assessment tools to gain a better understanding of the correlates of vulnerability to road mortality across species, and as predictive tools for difficult‐to‐sample or understudied species and areas.
... Very large forest patches of natural habitat are critical as population sources of mammal and bird species in productive landscapes (Núñez-Regueiro et al., 2015;Yue et al., 2015). The conservation and restoration of wide areas of forest immersed or buffered by the productive landscape are essential for the persistence and resilience of the original assemblages in the landscape (Brockerhoff et al., 2013;Lindenmayer and Hobbs, 2004). ...
Conference Paper
Large scale plantations of exotic trees (mostly Pinus and Eucalyptus) are replacing vast areas of native environments in South America, with still poorly known consequences on local communities. This is particularly worrisome in endangered ecoregions of high biodiversity that contain endemic and endangered species. This study was aimed at assessing the effects of pine plantations on the mammal assemblages of NE Argentina, in areas where plantations are rapidly increasing. We evaluated the effects of the native forest replacement by non-native pine (Pinus sp.) plantations on the composition of the assemblages of terrestrial mammals in two forest productive landscapes. In the first study area, of approximately 5,000 km2 and located in the endangered Atlantic Forest of N Misiones province, we deployed 184 camera-trap stations in three different "treatments": 53 in continuous forest, 69 in forest fragments and 62 in tree plantations. In the second, of approximately 20,000 km2 and located in the vulnerable Southern Cone Mesopotamian Savanna ecoregion of NE Corrientes province and S Misiones, we deployed 234 camera-trap stations: 35 in grasslands without cattle, 54 in grasslands with cattle, 35 in forests without cattle, 19 in forests with cattle, 54 in pine plantations without cattle and 37 in plantations with cattle. We used NMDS and PERMANOVA to assess the effect of the treatment, the structural complexity of the vegetation, the presence of cattle (in Corrientes) and several landscape variables (cost-distance to the continuous forest in Misiones, the percentage of different environments within different radiuses, and the cost of human access as a proxy for hunting pressure) on species composition. We recorded 34 species (4735 records) in Misiones and the same number of species (4460 records) in Corrientes. Mean recording rate (a proxy of relative abundance or activity) and richness were much lower in pine plantations than in natural environments in both landscapes (e.g., mean mammal richness per station in Misiones was (X±SD) 7.54±2.65 species in continuous forest, 5.97±2.46 in fragments and 3.39±1.90 in plantations). In both landscapes mammal composition was affected by treatment, the proportion of native environments in the landscape, and human access. In Misiones, the distance to the continuous forest also had a strong effect on the compositions of the assemblage. Different management practices (e.g. pruning and thinning), the presence-absence of cattle and landscape features can partially mitigate the negative effect of tree plantations on mammal assemblages. Large areas of native environments that function as population sources and forest fragments immersed in the matrix of plantations (in Misiones) are necessary to preserve the original native mammal assemblage at the landscape level. Promoting connectivity of the native environments and improving hunting controls will also mitigate negative impacts.
... First, the probability of encountering roads can be influenced by how the animal moves in the landscape and acquires resources (Grilo et al., 2018). Previous studies have shown higher risks for passerine birds that forage on foliage or bark and inhabit woodlands (Santos et al., 2016), for herbivorous and omnivorous mammals (Barthelmess, & Brooks, 2010;Cook & Blumstein, 2013) and for more habitat-generalist mammals (Núñez-Regueiro et al., 2015). Second, the probability of crossing an encountered road may be affected by how the road is perceived and by the mobility of the animal (Jaeger et al., 2005). ...
... En relación con las características ecológicas, Núñez-Regueiro et al. (2015) hallaron que las cortinas forestales excluyen especies de mamíferos de gran porte o especialistas, en comparación con el bosque continuo. En tanto, Torrella et al. (2013) describieron que la tasa de reclutamiento de múltiples especies arbóreas se ve muy disminuida, aunque los remanentes mantienen individuos adultos. ...
Article
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El vasto territorio del Chaco Seco y el Espinal se consolida como uno de los centros globales de producción de granos y carne. Tanto por distintas normas legales y limitaciones productivas, como por causas culturales, el bosque nativo se preserva en grandes porciones y numerosos pequeños fragmentos inmersos en la matriz agrícola. Estos remanentes suelen pasar desapercibidos para la comunidad científca y para los tomadores de decisiones, y quedan al margen de la planifcación territorial y de acciones de conservación. En este trabajo describimos la estructura espacial de los remanentes y generamos un esquema de clasifcación que permite identifcar distintos tipos según sus propiedades espaciales. Por medio de una estrategia de clasifcación basada en objetos, cartografamos ~22000 remanentes en ocho áreas focales (AF) dispersas en el territorio, para lo cual usamos imágenes satelitales CBERS-2B. Mediante índices espaciales, estos remanentes de tamaños, formas y niveles de aislamiento variables fueron categorizados en cinco clases, desde "isletas" hasta "bloques compactos". La superfcie de remanentes resultó mayor en el Chaco Seco que en el Espinal (entre 10.1% y 19.4% en la primera región, y entre 3.1% y 7.3% en la segunda). Las diferencias en el nivel de fragmentación se amplifcaron entre AF, dependiendo tanto de la superfcie total de remanentes como de la ocurrencia relativa de distintos tipos. Así, en el AF de San Luis, la fragmentación resultó 70 veces superior a la del AF de Anta (Salta). En este trabajo brindamos herramientas para identifcar y monitorear estos remanentes; estas herramientas podrán ser consideradas tanto con fnes productivos como de conservación. Finalmente, las acciones de manejo y conservación deben reconocer la existencia de estos fragmentos de bosques en paisajes muy transformados por la actividad agropecuaria.
... These subsistence activities exert pressure on wildlife through habitat degradation and overhunting in remnant forests (Torrella & Adámoli 2006). Medium-sized and large native mammals with large area requirements are the most affected by these human pressures (Altrichter & Boaglio 2004;Núñez-Regueiro et al. 2015;Quiroga et al. 2016). Subsistence hunting in other regions (i. ...
Article
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The Chaco has high richness of medium-and large-sized mammal species and is one of the most endangered ecoregions in the world. Our goal was to assess associations between livestock and medium and large mammals in Bañados del Quirquincho of the Chaco of Northwestern Argentina. In five habitat types, we set 15 to 20 camera traps during at least 30 consecutive days to determine native mammal species and livestock camera trapping rate. We used generalized linear mixed models to compare the camera trapping rate of native mammals and livestock among habitat types. We recorded 15 mammal species in all habitat types and found a significantly higher camera trapping rate of native mammal species-with the exception of foxes-in habitats with lower livestock camera trapping rate. Our results provide evidence that unplanned, intensive livestock production have negative effects on most native mammals in remnants forest of the Bañados del Quirquincho. We highlight the need to implement sustainable livestock management plans in the forests of the Chaco ecoregion to ensure the conservation of native mammal species.
... Very large forest patches of natural habitat are critical as population sources of mammal and bird species in productive landscapes (Núñez-Regueiro et al., 2015;Yue et al., 2015). The conservation and restoration of wide areas of forest immersed or buffered by the productive landscape are essential for the persistence and resilience of the original assemblages in the landscape (Brockerhoff et al., 2013;Lindenmayer and Hobbs, 2004). ...
Article
Forest plantations of fast-growing exotic species constitute an important economic activity in tropical and temperate regions of developing countries. Large areas of native forests and grasslands are being turned into tree plantations without assessing their impacts on natural communities. We evaluated the effects of replacing native forests by non-native pine (Pinus taeda) plantations on the diversity and composition of assemblages of terrestrial mammals and ground-dwelling and understory birds, in a forest productive landscape of the Upper Paraná Atlantic Forest of Misiones, Argentina. Camera-trap stations were deployed in three different "environments": 53 in a continuous forest, 69 in forest fragments, and 62 in tree plantations. The evaluation focused on the effect of the environment, the structural complexity of the vegetation, the cost-distance (distance weighted by con-nectivity) to the continuous forest, the percentage of native forest within different radii, and the cost of human access (as a proxy for hunting pressure) on both mean species richness per station and species composition. Alpha diversity of the assemblages of each environment was estimated using Hill numbers (effective number of species): q 0 = richness, q 1 = number of common species and q 2 = number of dominant species. Changes in community composition were evaluated by comparing the assemblages of the three environments using three similarity indices: Sorensen (q0 = similarity in species identity), Horn (q1 = similarity in common species), and Morisita-Horn (q2 = similarity in dominant species). For mammals and birds, richness was significantly higher in forest stations (both continuous and fragmented) than in those located in plantations. For both taxa, it also decreased with the distance to the continuous forest (but with a negative quadratic term in birds). Tree plantation stands contained biased and impoverished subsets of the original assemblages. Mammal composition was affected by the environment, the distance to the continuous forest, the proportion of native forest in the landscape , and human access. The bird assemblages of plantations were seriously affected, and their composition was also influenced by changes in vegetation structure. Alternative management practices (e.g. pruning, thinning) and landscape features can partially mitigate the negative effect of tree plantations on mammal and bird assemblages. Large areas of forest that function as population sources and forest fragments immersed in the matrix of plantations are strictly necessary to preserve the original native mammal and bird assemblages in the productive landscape. Promoting connectivity and improving hunting controls will also support their conservation.
... Water is a fundamental need of all species. Positive associations with water likely reflect the use of riparian forests for movement and dispersal as thanks to legislation these forests tend to be the only ones to remain in modified landscapes like our study sites (Núñez-Regueiro et al., 2015). ...
... Our estimates of puma density in northern La Payunia, the part of the reserve with highest protection, are higher than estimates from further south in Patagonia [60,76], the Mediterranean Andes [77], and sites in northern Argentina with high poaching pressure (Atlantic Forest and Chaco, [39,40]; Table 3), but closer to estimates for sites with low poaching pressure in the Atlantic Forest and semiarid Calden Forest in the province neighboring La Payunia [33,76]. Even though poaching occurs in La Payunia, this threat likely is lower than in most of the Atlantic Forest and Argentine Chaco, which have much larger human populations as well as higher habitat loss and degradation [39,78,79]. ...
Article
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Large-scale ungulate migrations result in changes in prey availability for top predators and, as a consequence, can alter predator behavior. Migration may include entire populations of prey species, but often prey populations exhibit partial migration with some individuals remaining resident and others migrating. Interactions of migratory prey and predators have been documented in North America and some other parts of the world, but are poorly studied in South America. We examined the response of pumas (Puma concolor) to seasonal migration of guanacos (Lama guanicoe) in La Payunia Reserve in northern Patagonia Argentina, which is the site of the longest known ungulate migration in South America. More than 15,000 guanacos migrate seasonally in this landscape, and some guanacos also are resident year-round. We hypothesized that pumas would respond to the guanaco migration by consuming more alternative prey rather than migrating with guanacos because of the territoriality of pumas and availability of alternative prey throughout the year at this site. To determine whether pumas moved seasonally with the guanacos, we conducted camera trapping in the summer and winter range of guanacos across both seasons and estimated density of pumas with spatial mark–resight (SMR) models. Also, we analyzed puma scats to assess changes in prey consumption in response to guanaco migration. Density estimates of pumas did not change significantly in the winter and summer range of guanacos when guanacos migrated to and from these areas, indicating that pumas do not follow the migration of guanacos. Pumas also did not consume more alternative native prey or livestock when guanaco availability was lower, but rather fed primarily on guanacos and some alternative prey during all seasons. Alternative prey were most common in the diet during summer when guanacos also were abundant on the summer range. The response of pumas to the migration of guanacos differs from sites in the western North America where entire prey populations migrate and pumas migrate with their prey or switch to more abundant prey when their primary prey migrates.
... These passive methods of detection are typically used in combination with non-edible lures or edible baits. Lures are often deemed functional on the basis of the practitioner's impressions, as illustrated in the cases compiled by Novak et al. (1987). Most studies formally addressing lure functionality have confirmed that using attractants may actually increase the frequency of mammal detection (e.g. ...
Article
Full-text available
Whereas high lure specificity for mammal monitoring is often sought, little effort has been put into identifying general-purpose attractants for multispecies mammal surveys. We examined whether the olfactory lures ‘fatty acid scent’ (FAS) and catnip oil differ in their ability to detect Iberian larger mammals (body mass > 800 g, i.e. lagomorphs, ungulates and most carnivores); whether the addition of visual and acoustic stimuli increases detection efficiency; and whether environmental variables interact with lures to influence detection. Three treatments were randomly assigned to 192 detection plots: olfactory lures only, visual lures (a combination of olfactory and visual stimuli) and auditory lures (all three types of stimuli). The design was balanced across two detection methods and three landscapes. Out of 13 target species, two were absent in the study plots and six (three common and three rare species) were detected with low frequency. The two olfactory attractants produced similar detection rates for species allowing analysis. The addition of visual and auditory stimuli did not increase detection and apparently induced repulsion for some species. Environmental variables associated with scent diffusion and lure visibility did not significantly influence mammal detection. Monitoring of mammal communities over large areas may gain efficiency by selecting lures that are simple, have a constant chemical composition, require short handling times and allow detection of all occurring species. A single olfactory attractant (FAS) could be suitable for designing large-scale monitoring programmes at least for five common mammal species, provided that passive detection methods and lure use are chosen.
... In this scenario, the anteater population, which is already classified as "Vulnerable," will probably be restricted to a few individuals isolated in the few remnants of suitable habitat. Although anteaters have been recorded in anthropogenic areas, such as soy plantations in central Brazil (Vynne et al. 2011) and timberland surrounding native remnants (Kreutz et al. 2012;Miretzki and Braga 2014;Timo et al. 2015), the proportion of anteater occurrences in forest strips surrounded by crops is much lower when compared to native habitat (Nunez-Regueiro et al. 2015). ...
Article
Land-use changes impact biodiversity, and biofuel crop production and its expansion pose as an important driver of negative effects in the tropics. Understanding the influence of land-use changes on suitable habitats for species is a worldwide conservation challenge, particularly on large-sized mammals. We modeled habitat suitability of the threatened giant anteater (Myrmecophaga tridactyla) in the Brazilian State of São Paulo. The region is the most populous and economically developed of the country and is the world’s main sugarcane production area. We aimed to 1) map habitat suitability for the giant anteater population in the State; 2) assess the contributions of selected landscape and anthropogenic predictors to species habitat suitability; and 3) quantify suitable habitats in environmental protection areas and in areas threatened by the sugarcane expansion. We used a two-step analysis: First, we created a suitability map in the species’ distributional range (Drange); from this map, we extracted the results for São Paulo State. Second, we built a regional model to predict the current scenario of São Paulo using the following environmental layers: 1) the resulting distributional range map for giant anteater (Drange); 2) landscape metrics; and 3) anthropogenic factors that might affect anteaters. The State of São Paulo presented, in general, very low values of habitat suitability. The following predictors made the greatest contribution: Drange, vegetation connectivity and distance to protected areas. Suitable habitats for anteaters within strictly protected areas are very scarce (1.6% of the total area), and 22% of the suitable areas are expected to be altered by future sugarcane expansion. Suitable habitats on private lands must play a role in conserving biodiversity.
... Emerging approaches based on multi-criteria optimization can identify configurations of land uses that maximize agricultural production while minimizing environmental impacts at the landscape scale [45]. Designing agricultural landscapes to maintain connectivity among natural areas can lower biodiversity impact substantially [46,47]. While such 'optimized' landscapes can in practice be difficult to achieve, such research can be insightful as to which landscape configurations are more advantageous than others, thus leading to concrete policy and management suggestions. ...
Article
Sustainable intensification of agricultural production is expected to be an important pathway for achieving future food security while protecting the environment. Recognizing that there is no single answer to how different dimensions of intensification can be achieved sustainably, we identify opportunities for research across spatial scales. We focus specifically on research questions around advances in technology and management and suggest that progress on these questions can be made by (i) improving understanding of trade-offs, especially across scales, (ii) recognition of the context-specificity of how agricultural intensification can become more sustainable, and (iii) development, access and wider use of global datasets for integrative research.
... The giant armadillo is a difficult species to observe, and its presence is most often revealed by the large burrows it digs for itself for refuge ( Carter and Encarnação, 1983;Arteaga andVenticinque, 2007 and2010;Ceresoli and Fernández Duque, 2012). Although diurnal activity has been reported ( Leite Pitman, 2004), its nocturnal and fossorial habits, combined with its usually low population density, make it difficult to study ( Nowak, 1991;Redford, 1994;Anacleto, 1997;Noss et al., 2004;Aguiar and Da Fonseca, 2008;Cuéllar, 2008;Meritt, 2008;Silveira et al., 2009;Blake et al., 2012). Research on this species has been undertaken in the Amazon, Cerrado, Pantanal and Bolivian Chaco (Carter, 1985;Noss et al., 2004;Silveira et al., 2009;Desbiez and Kluyber, 2013), but is limited to a couple of general studies in the Argentine Chaco ( Abba et al., 2012;Porini, 2001;Torres and Jayat, 2010), with no systematic population evaluations. ...
Article
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The giant armadillo (Priodontes maximus) is a difficult species to study because of low population densities, combined with nocturnal and fossorial habits. No systematic population studies have been undertaken to date in Argentina. Our objectives were to evaluate the species’ presence, relative abundance, and temporal activity patterns across five locations with different levels of human disturbance and legal protection in the Argentine Chaco. Between June 2006 and January 2014, we completed 10 surveys, using camera trap and / or track plots, searches for burrows and tracks, and observations by local people and park rangers. We used camera trap records to determine presence, relative abundance (records / 100 camera days) and activity patterns. We only recorded the species at three locations: Copo National Park, Aborigen Reserve and La Fidelidad Resource Reserve. At the Aborigen Reserve we documented burrows and tracks but obtained no photographs. At Copo and La Fidelidad we estimated relative abundance at 0.08 and 0.40 records per 100 camera days, respectively. We did not record giant armadillos near the edges of La Fidelidad, nor in the two locations with greater human disturbance. Camera trap records indicate that giant armadillos in the Argentine Chaco are strongly nocturnal. The population status of giant armadillos in Argentina is a matter of concern. With few or no records at other study locations, La Fidelidad may harbor one of the few relict populations of giant armadillos in the Argentine Chaco.
... Es importante, sin embargo, que los corredores cumplan con los requisitos mínimos de las especies que queremos proteger. Núñez-Regueiro et al. (2015), en su estudio con cámaras trampa durante la época seca, encontraron que la corzuela parda y el zorro pampa fueron detectados en ambos sitios (17 y 16 observaciones en corredores de bosque, respectivamente, y 20 y 11 observaciones en el interior de bosque) y que el pecarí de collar, en cambio, fue detectado más en el interior del bosque que en el corredor (9 observaciones vs 3). ...
Thesis
La diversidad de especies de mamíferos se ha visto afectada negativamente por los procesos de intensificación del uso del suelo que han tenido lugar en el Chaco durante las últimas décadas. Los cambios en el uso de la tierra afectan a los mamíferos nativos de esta región, que son de gran importancia no solo por su tamaño corporal, en relación a otros grupos taxonómicos, sino también por los roles que ejercen en el ambiente. En este contexto, se analizó si diferentes tipos de hábitat chaqueños producto de diferentes usos actuales e históricos de la tierra, son habitados por poblaciones de mamíferos nativos medianos (3-35 kg aproximados). Asimismo, se analizó la dieta y evaluó la dispersión de semillas por parte de estas especies en el ecosistema chaqueño. Se seleccionaron tres especies: corzuela parda (Mazama gouazoubira), zorro pampa (Lycalopex gymnocercus) y pecarí de collar (Pecari tajacu) y seis hábitats disponibles en el oeste de Córdoba. Se encontró que ninguna de las especies utilizaba el hábitat agricultura intensiva. La corzuela parda se encontró significativamente más en el bosque primario y bosque secundario. A su vez, solamente se encontraron heces de pecarí de collar dentro de la Reserva Chancaní. El zorro pampa, en cambio, utilizó principalmente los hábitats intermedios, aunque no de manera significativa. En cuanto a dieta, la corzuela parda exhibió una dieta totalmente herbívora, destacándose el consumo de algarrobos, solanáceas, Schinus fasciculatus (solamente en el bosque primario) y Tricomaria usillo. Las proporciones consumidas y la selección sobre cada ítem variaron según el hábitat. El zorro pampa y el pecarí de collar exhibieron dietas altamente frugívoras, destacándose el consumo de algarrobos y Ziziphus mistol, en ambos casos. En cuanto al rol como dispersores de semillas, no se encontraron semillas en las heces de corzuela parda, pero sí en las de zorro pampa y pecarí de collar. Más del 50% de las semillas de Acacia gilliesii, A. aroma, cactáceas, Prosopis flexuosa, P. torquata y Z. mistol encontradas en las heces del zorro pampa fueron viables. A su vez, más del 50% de las semillas de A. aroma, Bromelia urbaniana, Celtis ehrenbergiana y Z. mistol encontradas en las heces de pecarí de collar fueron viables, aunque la cantidad de muestras fue reducida. Un equilibrio entre la caza sostenible y la protección efectiva de los parches de bosques no perturbados es esencial para la futura conservación de la corzuela parda, el zorro pampa, el pecarí de collar y el propio bosque chaqueño.
... These subsistence activities exert pressure on wildlife through habitat degradation and overhunting in remnant forests (Torrella & Adámoli 2006). Medium-sized and large native mammals with large area requirements are the most affected by these human pressures (Altrichter & Boaglio 2004;Núñez-Regueiro et al. 2015;Quiroga et al. 2016). Subsistence hunting in other regions (i. ...
... Given that most of the vertebrates cannot adequately be protected inside crop fields or in highly modified areas (Pimm et al., 2014) and most of them are vulnerable to high levels of habitat fragmentation (e.g., Núñez-Regueiro et al., 2015;Quiroga et al., 2016), we assigned negative weights or "penalization" values to sites covered by crops and high human influence. For this, we used the Human Footprint Index's map (Venter et al., 2016) and the reclassified land cover maps for current and future scenarios (see above). ...
Article
In the context of the global climate and biodiversity crises, forecasting the effectiveness of Protected Areas (PAs) and forest management to conserve biodiversity in the long-term is a high priority, especially in threatened environments. By combining distribution models and conservation planning protocols, we analyzed the effect of global climate and agriculture-linked activities in the long-term conservation opportunities of one most threatened deforestation hotspots: the South American Gran Chaco. We showed that assessing the effects of each driver of global change individually, promotes inaccurate long term policies in deforestation hotspots. Our future scenarios indicated a low impact of climate change on the species distributions when it was analyzed individually. However, its effects were strongly exacerbated when both drivers of threat were combined in the same analyses, strongly diminishing conservation opportunities in the region: more than 50% of the remaining species' distribution and hotspot areas could be lost in the near future. In this dramatic context, we identified important opportunities to improve the level of long-term protection by increasing at least 5.6% the protection coverage and placing PAs strategically. It is imperative policymakers promote policies to generate a long-term improvement of conservation areas that are resilient to both threats as soon as possible for these threatened environments.
... In areas where there has already been substantial loss of forest on private lands, landowners' preference not to enroll remaining forested lands in PES may result in scattered conservation lands, fragmented landscapes, and isolated patches of habitat that do not support essential processes for ecosystem health. Habitat fragmentation in the Chaco can lead to biodiversity loss with forest interior species, like giant anteaters, being most impacted (Núñez-Regueiro et al., 2015). Habitat fragmentation can also lead to alteration of water and nutrient cycles, lower carbon storage, and reduced production of non-timber forest products, all of which have negative implications for human welfare (Laurance et al., 2011). ...
Article
To effectively conserve forests and the ecosystem services they provide, mechanisms are needed to promote conservation on private lands that reduce forest fragmentation, secure lands with high conservation value, and enhance landscape connectivity. Incentive-based programs like payments for ecosystem services (PES) are important policy tools for attaining conservation on private lands. In 2019, we conducted 81 in-person surveys with private forestland owners, whose properties are located on the border of protected areas and in corridors connecting protected areas in Argentina's Chaco forest. We examined landowners' preferences for alternative conservation incentives, how Argentina's current PES program could be altered to increase landowner enrollment, and the amount of compensation landowners require to enroll in PES. We found that knowledge of Argentina's PES program, motivations for forest ownership, attitudes toward forest conservation policy, and property characteristics influenced landowners' preferences for conservation program design. Although indigenous communities preferred conservation easements, other private landowners were more likely to choose a PES program. Research participants preferred PES programs with shorter contract lengths or that permitted them to engage in silvopasture. The payments research participants required to engage in land uses currently authorized under Argentina's PES program exceed current PES funding. Relying solely on PES to engage landowners in conservation may result in lost opportunities to conserve forest on private lands.
... As predators are frequently secretive and nocturnal, most tests of mesopredator release or temporal or spatial segregation are based on camera-trap surveys, often logistically constrained to small spatial scales and extents (but see Núñez-Regueiro et al. 2015, Rich 2017, Davis 2018. However, apex predators are typically large bodied and their home ranges span large areas (for example, 151 km 2 for male pumas Puma concolor; Sunquist and Sunquist 2002), and thus small-scale surveys may record a limited number of individuals. ...
Article
Apex predators drive top‐down effects in ecosystems and the loss of such species can trigger mesopredator release. This ecological process has been well documented in human‐modified small areas, but for management and conservation of ecological communities, it is important to know which human factors affect apex predator occurrence and which mediate mesopredators release at large scales. We hypothesized that mesopredators would avoid spatial and temporal overlap with the apex predator, the puma; but that human perturbations (i.e. cattle raising and trophy hunting) would dampen top‐down effects and mediate habitat use. We installed 16 camera traps in each of 45, 10x10‐km grid cells in the Caldén forest region of central Argentina resulting in 706 total stations covering 61,611km2. We used single‐season occupancy and two‐species co‐occurrence models and calculated the species interaction factor (SIF) to explore the contributions of habitat, biotic, and anthropic variables in explaining co‐occurrence between carnivore pairs. We also used kernel density estimation techniques to analyze temporal overlap in activity patterns of the carnivore guild. We found that puma habitat use increased with abundance of large prey and with proximity to protected areas. Geoffroy's cats and skunks spatially avoided pumas and this effect was strong and mediated by distance to protected areas and game reserves, but pumas did not influence pampas fox and pampas cat space use. At medium and low levels of puma occupancy, we found evidence of spatial avoidance between 3 pairs of mesocarnivores. All predators were mostly nocturnal and crepuscular across seasons and mesopredators showed little consistent evidence of changing activity patterns with varying levels of puma occupancy or human interference. We found potential for mesopredator release at large scale, especially on the spatial niche axis. Our results suggest that a combination of interacting factors, in conjunction with habitat features and intervening human activities, may make mesopredator release unlikely or difficult to discern at broad scales. Overall, we believe that promoting the creation of new protected areas linked by small forest patches would likely lead to increased predator and prey abundances, as well as the interactions among carnivores inside and outside of protected areas.
... The variability in the strength of the direct effects of habitat loss depends on the overall habitat amount at the landscape, as well as the species group considered (Püttker et al. 2020). Specialist species are more likely to respond adversely to lose and habitat conversion than are generalist species (Devictor et al. 2008;Núñez-Regueiro et al. 2015;Zimbres et al. 2017). Our results also can indicate that the matrix serves as a functional filter. ...
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The vast majority of empirical studies on regional mammal defaunation across the Atlantic Forest biome of South America are concentrated in Southeastern and Northeastern regions. Thus, the lack of empirical information on the medium- to large-bodied mammal population declines across the subtropical region of this tropical biome and its major causes are paramount to conservation efforts. We investigate the influence of land use on mammal defaunation across the subtropical Atlantic Forest by sampling 91 points using 65 camera-traps installed for five consecutive years—totaling an effort of 30,189 camera-trap-days. We observed that the average defaunation across the Devonian Kniferidges Environmental Protection Area meta-region (spanning over subtropical Atlantic Forest plateaus) was 42% (D = 0.42; ± 0.17) when compared to presumed assemblages of historical times going back to the Pre-Columbian era (ca. 500 years ago). The main landscape predictors of regional defaunation were silviculture and agriculture, once the highest defaunation indexes were concentered in sites intensely human-modified by these features. Protected areas had significantly lower defaunation indexes in comparison with the unprotected areas. Although our results of defaunation were 29.2% lesser than the average for the entire biome, the negative consequences of regional defaunation on ecosystem services are already occurring, once two in each five local species presumably are locally extinct or present low abundances (i.e. functionally extinct). Given that habitat conversion is the primary cause of global biodiversity decline, our results reinforce that biodiversity conservation is still strongly dependent on natural protected areas networks.
... In addition, the distances of influence are based on literature review, which for several of our variables (e.g., wells, trails, deforestation, forest plantations, etc.) are based on studies of birds, plants, or are an average of multiple vertebrate species. For many large mammals these distances are likely conservative (Núñez-Regueiro et al., 2015). ...
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Conserving the remaining wildest forests is a top priority for conservation, and human footprint maps are a practical way to identify wild areas. However, available global assessments of wild areas are too coarse for land use decisions, especially in countries with high deforestation rates, such as Argentina. Our main goal was to map the human footprint in Argentina’s forested areas to improve conservation planning at regional and country levels. Specifically, we quantified the level of human influence on the environment and mapped the wildest native forests (i) across forest regions, and (ii) in the different land-use categories of the National Forest Plan, which is a key policy instrument for conserving the nation’s native forests through zoning, and (iii) identified wildest forests that are at risk due to human activities. We analyzed detailed spatial data on settlements, transportation, energy, and land use change, and estimated the areal extent to which these various human activities disrupt natural processes. We defined pixels with human footprint index of zero as wildest areas. We found that a substantial portion (43%) of Argentina’s forested area remains wild, which suggests there are opportunities for conservation. However, levels of human influence varied substantially among forest regions, and Atlantic and Chaco forests have the highest levels of human influence. Further, we found that the National Forest Plan does not conserve the wildest forests of the nation, as most (78%) of the wildest native forests are located in zones that allow silvopasture, timber production, and/or forest conversion to crops, thus potentially threatening biodiversity in these areas. Our map of wildest forests is an important, but first, step in identifying wildland forests in Argentina, as available spatial data layers of human activities capture many, but not all, human influences on forests. For instance, small human features, like certain rural roads, trails, and rural settlements exist in our wildest areas. Our study provides new datasets to assist land use planners and conservationists, and identifies areas for conservation attention in Argentina. More broadly, our analyses highlight the value of detailed human footprint data to support conservation decisions in forest landscapes.
... Widlife-friendly practices and regional land-use planning can mitigate the negative impacts of tree plantations on the natural assemblages (Gardner et al., 2009). However, as occurs in other environments around the world (Núñez-Regueiro et al., 2015;Yue et al., 2015), to protect biodiversity and retain source populations of native animals and thus mitigate the homogenizing effects of monoculture plantations, it is essential to maintain a large proportion of natural habitats. ...
Article
Aim The expansion of agriculture is promoting the loss of natural environments and their biotic homogenization. We aimed at understanding whether the replacement of forests and grasslands by tree plantations leads to biotic homogenization of mammal assemblages of two contrasting Neotropical ecoregions or if dispersal or environmental limitations keep their original assemblages clearly differentiated. Location Argentina, Upper Paraná Atlantic Forest, Southern Cone Mesopotamian Savannas and Iberá marshes. Taxon Mammals. Methods We conducted two camera‐trap surveys, deploying 184 camera‐trap stations in continuous forest, fragmented forest and pine plantations in the Atlantic Forest, and 234 in grassland, fragmented forest and pine plantations in the Mesopotamian Savannas. We evaluated the similarity of the assemblages among the environments and regions, generating all possible pairwise comparisons using three similarity indices: Sørensen (species identity), Horn (common species) and Morisita‐Horn (dominant species). Using variation partitioning diagrams and redundancy analysis, we evaluated the spatial structure of mammal assemblages and the influence of environmental variables. Results There was a greater similarity in species identity between different environments within each region than between similar environments in different regions. Common and dominant mammal assemblages of tree plantations tended to be similar between regions and were different from assemblages of the natural environments within the same region. Fragmented forest assemblages were very similar among regions. Assemblages were spatially structured but most of the variation between regions was explained by the environmental variables. Main conclusions Each region has a distinct pool of species, which is partially explained by environmental factors, such as the differential representation of native environments in the landscape. However, an expansion of tree plantations and forest fragmentation in the Atlantic Forest could lead to biotic homogenization between regions due to an increase in the abundance of generalist species.
... There, widespread agricultural expansion and intensification have translated into very high deforestation rates recently (Zak et al. 2008;Aide et al. 2012;Kuemmerle et al. 2017), with widespread biodiversity loss, translating into an urgent need for conservation planning (Torres et al. 2014;Nori et al. 2016;Semper-Pascual et al. 2018). Existing, local-scale work on the biodiversity/agriculture trade-offs in the Chaco is inconclusive, with some studies suggesting land sparing and others land sharing might minimize trade-offs more (Mastrangelo and Gavin 2012;Macchi et al. 2013;Núñez-Regueiro et al. 2015;Marinaro et al. 2017). An assessment of how agriculture/biodiversity trade-offs play out at broader scales, and are impacted by landscape configuration and composition, is still missing. ...
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Context Better balancing agricultural production and biodiversity conservation is a central goal for many landscapes. Yet, empirical work on how to best achieve such a balance has focused mainly on the local scale, thereby disregarding that landscape context might mediate biodiversity-agriculture trade-offs. Objectives Focusing on vertebrates in the Argentine Chaco, we evaluate how trade-offs between agriculture and biodiversity vary with landscape context, from landscapes where agricultural and natural areas are separated to landscapes where both are interspersed. Methods We modelled the distributions of 226 vertebrates and use the resulting maps to describe the species richness of ecosystem-service providing guilds. We calculated three agricultural intensity metrics, and evaluated how both species richness and agricultural intensity vary along a gradient of landscape configuration, while controlling for landscape composition. Results Species richness and agricultural yields both varied with landscape configuration. Biodiversity was highest in mixed landscapes where agricultural and natural area are interspersed, whereas agricultural yields showed a more heterogeneous response, with some yield metrics highest in mixed and others in separated landscapes. As a result, agriculture/biodiversity trade-offs depended strongly on landscape configuration, irrespective of landscape composition. We also identified large areas with low vertebrate richness and agricultural yields, suggesting considerable potential for improving in at least one dimension. Conclusions Agriculture/biodiversity trade-offs varied with landscape configuration, suggesting that landscape design can balance these trade-offs. Our simple and broadly applicable approach can provide baseline information for landscape planning aimed at realizing co-benefits between agriculture and biodiversity—in the Gran Chaco and elsewhere.
... Similar results were observed by Piquer-Rodriguez et al. (2018b), where both magnitude of the land-use change, and the type of simulated policy intervention resulted in similar general land-use conversions trajectories but with spatial pattern differences. This variation has a great relevance, since it modifies the location of the remaining woodlands and the connectivity between forest patches (Torrella et al. 2018), a fundamental aspect for biodiversity preservation (Quiroga et al. 2014;Periago et al. 2015;Núñez-Regueiro et al., 2015). ...
Article
In the last decades, dry Chaco forests experienced both intensive deforestation and land use changes. The in-tensification of deforestation at the national level led to the enactment of the National Forest Law (N°26.331) in 2007. However, after its implementation, deforestation continued at high rates in explicitly protected areas (Categories I and II) in the provinces of Salta, Chaco and Santiago del Estero. In this article we estimated carbon (C) emission due to deforestation in a portion of the Argentine semi-arid Chaco (around 11 M ha) along 12 land use scenarios. A spatial model (InVEST) was used to prospectively analyze land use in the next 20 years, considering 4 levels of Forest Law compliance (denominated Current, Permissive, Partial and Strict) and 3 deforestation rates based on 2009-2015 records (denominated Expansion, Deceleration and Acceleration). We simulated the deforestation and its subsequent replacement by productive land uses (croplands, pastures and silvopastoral systems) based on a supervised land use classification for the year 2015. The C contents in different compartments (above and belowground biomass, litter and soil) were obtained from previous studies, based on a simulation model (CENTURY). The level of Forest Law compliance did not define the cleared area, except for those scenarios that considered a Strict compliance. Thus, productive land uses increased between 0.9 and 3.5 M ha after 20 years, depending on the deforestation rate. The total C emission was estimated between 51 and 169 Tg, where the burning of biomass and the decomposition of the remaining organic material represented about 96% of the emissions. Carbon changes in the upper 20 cm of the soil, represented a very low proportion of total emission. Although these estimations were conservative, given that not all sources have been considered, the study area showed a high potential contribution to the C emission at national scale.
... As a result of expansion of agriculture and pasture, this region suffers one of the highest deforestation rates worldwide and is among the most threatened regions in the world [33][34][35][36]. In northwest Argentina [37,38], the landscape is dominated by soybeans and pastures with remnant forest patches between large agricultural fields [37][38][39]. Only a few large tracts of old-growth forest persist, separated by broad expanses of agriculture [40]. ...
Article
Disparity between the knowledge produced and knowledge required to address complex environmental challenges, such as biodiversity conservation and climate adaptation, continues to grow. Systems thinking under the Open Standards for Conservation framework can help close this gap by facilitating interdisciplinary engagement, advancing conversations on how environmental systems work, and identifying actions that could be implemented to achieve defined conservation goals. Here, we present a modelling exercise for one of the most endangered forested systems in the world: The Gran Chaco. We focus on unsustainable hunting, a pressing threat to this system. We highlight knowledge gaps that underpin all parts of an adaptive management process from understanding key relationships in social-ecological systems to design and implementation of strategies for Gran Chaco conservation as well as evaluation of outcomes.
... The conservation status of these forests is critical. This is because of accelerated rates of habitat loss driven by the expansion of the agricultural frontier (Gasparri and Grau, 2009;Hansen et al., 2013;Núñez-Regueiro et al., 2015) and, therefore, it is one of the most threatened ecoregions in the world (Kuemmerle et al., 2017). Extensive livestock ranching is one of the main land uses in dry Chaco forest remnants (Morello and Adámoli, 1974;Morello, 1983). ...
Article
Livestock grazing can be a problem for forest conservation because it can generate heterogeneous and unpredictable changes in plant communities. Understanding these changes is important for generating management strategies that are compatible with long-term conservation of threatened forests. Livestock exclusion is a useful experimental approach used to evaluate grazing effects. However, the evidence showing the effects of grazing on forests is mixed and little in know about the responses of different plant life forms, especially in dry forests. In this study, we evaluated the effects of a 7-8 year of livestock exclusion experiment on understory plant community structure in the dry Chaco forest (Argentina). We categorized understory plant life forms as shrubs, succulents (Cactaceae family + Bromelia hieronymi), and herbs (forbs, grasses and vines). Then, we compared the plant community structure (richness, diversity, density and cover) and understory structure (soil hardness, bare soil and vegetation vertical and horizontal structure) between five excluded plots and five grazed plots, in a paired design. We found that livestock exclusion lead to an increase in grass species richness and grass cover as well as an increase in lower understory biomass (0-0.5 m) and a decrease in percentage of bare soil. On excluded plots, dominant herbs were Setaria nicorae (grass), Trichloris crinita (grass), and Justicia squarrosa (forb). Grass species that were recorded exclusively on excluded plots were Gouinia latifolia, T. crinita, and Pappophorum mucronulatum, all forage species preferred by livestock. In contrast, on grazed plots, the dominant species was Stenandrium dulce (forb), a species with resistance strategies to grazing. As for the other variables, we did not find strong differences between excluded and grazed plots. Livestock grazing did not modify the ensemble structure of shrubs and succulents nor did it change the horizontal vegetation structure or soil hardness. Our evidence suggests that the assemblage composed by shrubs and succulents seems to be tolerant to livestock grazing, and that the grass assemblage has the ability to quickly recover when grazing stops. Finally, the effectiveness of exclusion as a management tool will depend on which attribute of the plant community to be conserved or recovered. In dry Chaco forests after many years of grazing at moderate stocking rates, livestock exclusion could help recover grass cover, generate opportunities for the establishment of certain grass species that are sensitive to grazing, and increase ground cover.
... The three species are difficult 144 to detect with standard-methods, particularly the cryptic chacoan peccary (e.g. Ayala and Noss 145 2000;Altrichter and Boaglio 2004;Núñez-Regueiro et al. 2015). Most information about 146 peccaries of the Dry Chaco comes from untested LEK-methods (e.g. ...
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Field information is essential for developing conservation actions, but standard methods for surveying wildlife are often inefficient in large, remote areas. Without efficient methods, surveying is difficult or even impossible. Consequently, some of the most threatened species and regions remain un- or under-surveyed, e.g. South American Chaco. Survey methods based on local ecological knowledge (LEK-methods) could be useful for surveying these areas and species. However, LEK-methods may be inaccurate and are rarely evaluated or compared to standard-methods. This is the first large-scale study evaluating the performance of two LEK-methods, and comparing it with the performance of standard-methods, for detecting three species of large terrestrial mammals. We used a locally-based survey (LBS) and interviews as LEK-methods, and transect and camera trapping as standard survey methods. We estimated the probability of detecting each species with each method, of having false-presences and their cost. We also quantitatively analysed the ability of LBS to build local capacity, focusing on conservation, research and working skills. We found that compared to standard-methods, LEK-methods increase detection probabilities of three species while providing accurate information. LBSs are more expensive than interviews but improve local capacities, raising the chances of successful implementation of community-based conservation programmes. Interviews are optimal for rapid assessments and can be useful for wildlife monitoring. Before using LEK-methods, we recommend pilot studies to determine estimators´ variability. Overall, this study shows that LEK-based methods can be efficient and accurate for detecting large mammals in remote areas. Furthermore, LEK-methods can help develop legitimate conservation initiatives.
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Agricultural expansion threatens biodiversity due to habitat loss and fragmentation. In the Gran Chaco, a global deforestation hotspot, rampant cropland and pasture expansion raise concerns about the sustainability of these land-use changes. Zoning policies were recently enacted in the Argentine Chaco to balance agriculture and conservation, yet the environmental outcomes of implementing these policies remain unclear. Here, we focused on the province of Formosa (Argentina) to evaluate how fully implementing zoning there would affect forest loss and connectivity, and how multiscale landscape planning could enhance environmental outcomes. Specifically, we simulated potential future forest cover for different spatial planning scenarios to assess the effect of (a) implementing regional corridors and (b) enacting additional policies to minimize forest fragmentation at the plot level, under both high and low deforestation rates. We then quantified forest connectivity and fragmentation using morphological image segmentation and landscape indices. Our results show that implementing regional corridors reduced the extent of potential deforestation by 650,000 ha (43%), and this alone strongly increased forest connectivity compared with scenarios without corridors. However, how deforestation would be carried out at the plot level was critically important. Plot-level spatial planning could have a strong and positive effect on mitigating fragmentation and on maintaining connectivity, even in scenarios with high deforestation rates (i.e., reducing the number of forest fragments by up to 35%, increasing the core forest by up to 6%). Moreover, under high deforestation rates, implementing regional corridors and plot-level design had a strong complementary effect on mitigating forest fragmentation (17% less forest fragments than when implementing either of the two strategies alone). Our analyses clearly highlight the opportunities of multiscale spatial planning and the need to complement broad-scale zoning with plot-level landscape design in order to mitigate the negative impacts of deforestation in the Chaco and other active agricultural frontiers.
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Obtaining reliable species observations is of great importance in animal ecology and wildlife conservation. An increasing number of studies use camera traps (CTs) to study wildlife communities, and an increasing effort is made to make better use and reuse of the large amounts of data that are produced. It is in these circumstances that it becomes paramount to correct for the species-and study-specific variation in imperfect detection within CTs. We reviewed the literature and used our own experience to compile a list of factors that affect CT detection of animals. We did this within a conceptual framework of six distinct scales separating out the influences of (a) animal characteristics, (b) CT specifications, (c) CT setup protocols, and (d) environmental variables. We identified 40 factors that can potentially influence the detection of animals by CTs at these six scales. Many of these factors were related to only a few overarching parameters. Most of the animal characteristics scale with body mass and diet type, and most environmental characteristics differ with season or latitude such that remote sensing products like NDVI could be used as a proxy index to capture this variation. Factors that influence detection at the microsite and camera scales are probably the most important in determining CT detection of animals. The type of study and specific research question will determine which factors should be corrected. Corrections can be done by directly adjusting the CT metric of interest or by using covariates in a statistical framework. Our conceptual framework can be used to design better CT studies and help when analyzing CT data. Furthermore, it provides an overview of which factors should be reported in CT studies to make them repeatable, comparable, and their data reusable. This should greatly improve the possibilities for global scale analyses of (reused) CT data.
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Habitat loss is a significant threat to biodiversity worldwide, and the Argentine Dry Chaco is one of the most active global deforestation hotspots. Medium-large mammals are especially vulnerable to land-cover change, and in the Dry Chaco, they are subjected to the combined effect of habitat loss and hunting. In agroe-cosystems, blocks of natural habitat can contribute to maintaining biodiversity and ecosystem functionality, and it is necessary to identify human-modified landscape configurations that are compatible with wildlife conservation. Through camera-trapping in five agroecosystems of the Argentine Dry Chaco, we assessed the role of local-scale forest proportion and distance to large forest patches on medium-large mammal richness and frequency of records. Forest proportion positively influenced medium-large mammal estimated richness, and large-bodied mammals were more frequent in stations near large forest blocks and in stations with higher forest proportion when larger forest blocks were distant. Small-medium sized generalist car-nivores were more frequent in stations with lower forest proportion. Forest remnants and the presence of large forest patches are thus important for medium-large mammals in the region and more specifically for the conservation of larger-bodied species. Forest loss may also facilitate the increase of mesopredator populations , with potential consequences on the dynamics of ecosystems and human-wildlife interactions. For agroecosystems to contribute to the conservation of mammals in the Dry Chaco, the preservation or restoration of forest remnants and of large extensions of forests should be incorporated in regional and local land-use planning .
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The area of geographical distribution of mammal populations in the Argentine Chaco ecoregion is being increasingly reduced and this is mainly due to the progressive destruction of habitats. In this context, several species have been affected, among which is the endemic Catagonus wagneri (Tayassuidae), currently classified as "endangered" and with a trend of population decline. In this work, the predictions estimated by three algorithms were compared to establish the potential geographic distribution of this species at the southern limit of its natural distribution. Priority locations for landscape connectivity were identified by comparing intrinsic variations in the PC index based on data classification methods. With the use of foot transects, trap cameras and surveys with the local population, the presence of chacoan peccary was recorded on 25 occasions. From the GLM, Random Forest and Maxent algorithms (mean AUC 0.74), a reference model was obtained. Using it as an input and the PC index, the variation in the importance of the connectivity surfaces of the landscape was evaluated using three classification methods: quantile, equal interval and natural breaks. The consensus model (SDM) occupies 55,674 km2 of Argentina, representing 10% of the Chaco Seco ecoregion. The distribution occupies not only forest ecosystems, but also environments with less tree coverage. Coefficients of variation of 170% were recorded between the classification methods for the number of patches of classes 9 and 10 of the priority habitat for landscape connectivity. The SDM shows a fragmented distribution in line with the Chaco's land use change process.The results suggest a great variability of the PC index depending on the method of classifying data in class intervals, an aspect that was not discussed in previous studies.
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New records of the Endangered Catagonus wagneri (Rusconi, 1930) are reported in Campo Grande Community of peasants, northwestern Santiago del Estero, Argentina. The new records were obtained through camera traps as well as the finding of a skull and footprints. We conducted interviews confirmed the historical presence of the species. The records indicate the presence of C. wagneri in the North Biological Corridor, expanding this species’ distribution in Santiago del Estero province, providing initial evidence of potential connection between northern and southern populations.
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The population of jaguars Panthera onca in the semi-arid Chaco Province is the least well-known in Argentina. Its status in the region is described only from interviews that confirmed its presence until 2003. To update information on the distribution and population density of this species we undertook three camera-trap surveys, combined with searches for sign, at sites across latitudinal and protection gradients, and 156 interviews with local inhabitants across three larger areas. The camera-trap sites were located in areas with the highest density of records in the Argentine Chaco: Copo National Park (1,204 trap days, 24 stations, 344 km of transects), Aborigen Reserve (1,993 trap days, 30 stations, 251 km of transects) and El Cantor (2,129 trap days, 35 stations, 297 km of transects). We did not obtain any photographs of jaguars. We recorded very few jaguar tracks, and only in the Aborigen Reserve (n = 3) and El Cantor (n = 1). The map of distribution points confirmed through interviews suggests that the jaguar range has not changed significantly in the past 10 years; however, the camera-trap and sign surveys suggest that densities are extremely low. Before our study the Chaco population was thought to be the largest in Argentina. This perception was incorrect: the Chaco jaguar population is the most threatened in the country. Systematic, intensive studies are essential to provide the necessary information for decision-making for the management and conservation of threatened species.
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Land-use change is the main driver of habitat loss and fragmentation worldwide. The rate of dry forest loss in the South American Chaco is among the highest in the world, mainly due to the expansion of soybean production and cattle ranching. Argentina recently implemented a national zoning plan (i.e., the Forest Law) to reduce further forest loss. However, it is unclear how the effects of past deforestation and the implementation of the Forest Law will affect forest connectivity in the Chaco.Our main goal was to evaluate the potential effect of the Forest Law on forest fragmentation and connectivity in the Argentine Chaco. We studied changes in the extent, fragmentation, and connectivity of forests between 1977 and 2010, by combining agricultural expansion and forest cover maps, and for the future in a scenario analysis. Past agricultural expansion translated into an overall loss of 22.5 % of the Argentine Chaco’s forests, with deforestation rates in 2000–2010 up to three times higher than in the 1980s. Forest fragmentation and connectivity loss were highest in 1977–1992, when road construction fragmented large forest patches. Our future scenario analysis showed that if the Forest Law will be implemented as planned, forest area and connectivity in the region will decline drastically.Land-use planning designed to protect stepping stones could substantially mitigate connectivity loss due to deforestation, with the co-benefit of preserving the greatest amount of biodiversity priority areas across all evaluated scenarios. Including scenario analyses that assess forest fragmentation and connectivity at the ecoregion scale is thus important in upcoming revisions of the Argentine Forest Law, and, more generally, in debates about sustainable resource use.
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The population of jaguars Panthera onca in the semi-arid Chaco Province is the least well-known in Argentina. Its status in the region is described only from interviews that confirmed its presence until 2003. To update information on the distribution and population density of this species we undertook three camera-trap surveys, combined with searches for sign, at sites across latitudinal and protection gradients, and 156 interviews with local inhabitants across three larger areas. The camera-trap sites were located in areas with the highest density of records in the Argentine Chaco: Copo National Park (1,204 trap days, 24 stations, 344 km of transects), Aborigen Reserve (1,993 trap days, 30 stations, 251 km of transects) and El Cantor (2,129 trap days, 35 stations, 297 km of transects). We did not obtain any photographs of jaguars. We recorded very few jaguar tracks, and only in the Aborigen Reserve (n 5 3) and El Cantor (n 5 1). The map of distribution points confirmed through interviews suggests that the jaguar range has not changed significantly in the past 10 years; however, the camera-trap and sign surveys suggest that densities are extremely low. Before our study the Chaco population was thought to be the largest in Argentina. This perception was incorrect: the Chaco jaguar population is the most threatened in the country. Systematic, intensive studies are essential to provide the necessary information for decision-making for the management and conservation of threatened species.
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Quantification of global forest change has been lacking despite the recognized importance of forest ecosystem services. In this study, Earth observation satellite data were used to map global forest loss (2.3 million square kilometers) and gain (0.8 million square kilometers) from 2000 to 2012 at a spatial resolution of 30 meters. The tropics were the only climate domain to exhibit a trend, with forest loss increasing by 2101 square kilometers per year. Brazil's well-documented reduction in deforestation was offset by increasing forest loss in Indonesia, Malaysia, Paraguay, Bolivia, Zambia, Angola, and elsewhere. Intensive forestry practiced within subtropical forests resulted in the highest rates of forest change globally. Boreal forest loss due largely to fire and forestry was second to that in the tropics in absolute and proportional terms. These results depict a globally consistent and locally relevant record of forest change.
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Palm forests of Copernicia alba are a rare habitat in the semi-arid Chaco of Northwestern Argentina, are centres of high species diversity, and provide key resources for many species. Our goal was to assess the conservation status of five C. alba patches in Northwestern Argentina: Reserve; Embarcación; Palma Sola; Vinalito; and, Talar. We compared patches to identify the sites with greatest conservation needs based on four criteria: population size structure; palm density (of individuals with height >1.30 m); probability of seedlings being browsed; and, presence of potential seed dispersers. We found that three (Embarcación, Reserve, and Talar) out of five sites had palm densities greater than 200 individuals/ha and only one site (Embarcación) showed a reverse J-shaped size structure for height. Reserve and Embarcación had the greatest probability of seedlings being browsed (0.99 ± 0.01 and 0.88 ± 0.12, respectively). A total of 14 potential disperser species of mammals and birds were recorded across the five sites. Only Reserve harboured all of the potential dispersers, but at least two potential disperser species were recorded at the other sites. None of the palm patches studied had an adequate conservation status. However, Embarcación met three out of four criteria, and therefore it can be considered to have the best conservation status in the semi-arid Chaco. Palma Sola and Vinalito have the greatest conservation needs. To conserve C. alba in Northwestern Argentina, strategies are needed that ensure seedling establishment for future populations to reach an adequate density and structure.
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Windbreaks often form networks of forest habitats that improve connectivity and thus conserve biodiversity, but little is known of such effects in the tropics. We determined bird species richness and community composition in windbreaks composed of remnant native vegetation amongst tea plantations (natural windbreaks), and compared it with the surrounding primary forests. Fifty-one, ten-minute point counts were conducted in each habitat type over three days. Despite the limited sampling period, our bird inventories in both natural windbreaks and primary forests were nearly complete, as indicated by bootstrap true richness estimator. Bird species richness and abundance between primary forests and windbreaks were similar, however a difference in bird community composition was observed. Abundances of important functional groups such as frugivores and insectivores did not vary between habitat types but nectarivores were more abundant in windbreaks, potentially as a result of the use of windbreaks as traveling routes, foraging and nesting sites. This preliminary study suggests that natural windbreaks may be important habitats for the persistence of bird species in a production landscape. However, a better understanding of the required physical and compositional characteristics for windbreaks to sustain bird communities is needed for effective conservation management.
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Despite much deforestation in the past, the northwestern Argentinean province of Salta still has more than 6 million hectares of native forests. Land use conversion for agriculture is threatening these forests and the survival of indigenous populations and small-scale farmers. In November 2007, Argentina’s National Congress passed a law to regulate the management and conservation of native forests. This “Forest Law” required provincial governments to implement comprehensive and participatory Land Use Planning Processes (LUPPs). In this article, we describe and analyze, within a political ecology framework, the LUPP carried out in Salta. We focus on the conflicts derived from the different visions of development held by the interest groups involved, and we highlight some contradictions between their discourses and practices. We argue that “development” or “progress,” understood as a process of wealth and power accumulation linked to the possession of land and the production of agricultural commodities, was the leading ideology of political and economic elites in Salta during the LUPP. This ideology, and the established institutional power system behind it, was challenged when the National Supreme Court of Justice decided to suspend logging and deforestation activities on land claimed by marginalized ethnic and socioeconomic groups. We assess the implications of this ruling for the conservation of native forests and local livelihoods. As the final outcome of this case is still uncertain, a number of possible scenarios are presented and discussed.
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Subsistence hunting practiced by poor rural and indigenous people in Latin America differentially affects the three species of peccaries (Artiodactyla: Tayassuidae). Sustainability of subsistence hunting of peccaries in the Argentine semi-arid Chaco, where the three species coexist, was unknown. My objectives were to determine the importance of peccaries for the local people, describe the current pattern of hunting and its impact on the three species of peccary and identify the factors that affect hunting sustainability. I found that many rural (70%) and village people (40%) consumed peccaries. White-lipped and chacoan peccaries were more susceptible to overharvesting than collared peccary. Current rates of hunting of white-lipped and chacoan peccaries are likely not sustainable because: (a) density of both species was between two to three times higher inside a protected area than outside; (b) populations have declined near larger villages and in older settlements; (c) herds sizes were small in comparison with other regions; (d) large number of juveniles less than one year old were harvested; (e) hunting did not discriminate based on sex or reproductive status and (f) The unified harvest model indicated unsustainable harvest because more than 40% of the reproductive production was taken and populations densities were less than 60% carrying capacities. In contrast, harvest of collared peccary seems sustainable at the current rates of hunting by rural peasants. Other threats such as forest exploitation, however, are accelerating, and are likely to reduce sustainability.
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We evaluated the conditions under which patch size effects are important determinants of local population density for animals living in patchy landscapes. This information was used to predict when patch size effects will be expected to occur following habitat loss and fragmentation. Using meta-analysis, we quantitatively reviewed the results of 25 published studies that tested for a relationship between patch size and population density. Patch size effects were strong for edge and interior species (negative and positive patch size effects, respectively), but negligible for generalist species that use both edge and interior habitat. We found significant differences in mean patch size effects between migratory and residential species, between herbivores and carnivores, and among taxonomic groups. We found no evidence that patch size effects were related to landscape characteristics such as the proportion of landscape covered by habitat, median patch size, or the scale at which a study was conducted. However, species in the Western Hemisphere tended to have larger absolute effect sizes, and eastern species tended to be more variable in their response. For landscapes undergoing habitat loss and fragmentation, our results predict the following: (1) among generalist species that use both the edge and the interior of a habitat patch, the decline in population size associated with habitat destruction should be accounted for by pure habitat loss alone; (2) for interior species, the decline in population size associated with habitat fragmentation per se will be greater than that predicted from pure habitat loss alone; (3) for edge species, the decline in population size will be less than that predicted by pure habitat loss alone; (4) these relative effects will not be influenced by the extent of habitat loss, but they will be affected by the pattern of habitat when large or small patches are preferentially removed; and (5) as loss and fragmentation increase within a landscape, migratory species will generally suffer less of a decline in population size than resident species.
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This paper describes an interdisciplinary study of the habitat requirements of threatened desert tortoises (Gopherus agassizii) on eight 225-ha study plots in a 14 000 ha study area near the southern boundary of the U.S. Army's National Training Center at Fort Irwin in the central Mojave Desert of southern California. The objective of the study was to produce an empirical, statistical, GIS-based model of desert tortoise habitat use based on a combination of field data and data derived from various spatial databases, including satellite imagery. A total of 11 primary and secondary data layers constitute the spatial database used for this project. Vegetation and tortoise relative density data were obtained from field surveys. Regression-tree methods were used to develop the statistical model. The tree has 11 terminal nodes and a residual mean deviance of 1.985. Out of 73 potential predictors in the model specification, only eight were selected by the algorithm to be used in construction of the tree. The model suggests that tortoises tend to occur on southwest exposures and loamy soils, and that they avoid stony soils, north exposure, and areas of very low plant cover. Our results imply that soil composition and parent materials can be important determinants of habitat suitability for desert tortoises, and for burrowing animals in general. Our study also provides an example of how the interdisciplinary integration of biology, earth sciences, GIS, and statistical modeling can reveal important aspects of the habitat requirements of endangered species.
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Subsistence game bunting has profound negative effects on the species diversity, standing biomass, and size structure of vertebrate assemblages in Amazonian forests that otherwise remain largely undisturbed. These effects are likely to be considerably aggravated by forest fragmentation because fragments are more accessible to hunters, allow no (or very low rates of) recolonization from nonharvested source populations, and may provide a lower-quality resource base for the frugivore-granivore vertebrate fauna. I examined the likelihood of midsized to large-bodied bird and mammal populations persisting in Amazonian forest fragments of variable sizes whenever they continue to be harvested by subsistence hunters in the aftermath of isolation. I used data from a comprehensive compilation of game-harvest studies throughout Neotropical forests to estimate the degree to which different species and populations have been overharvested and then calculated the range of minimum forest areas required to maintain a sustainable harvest. The size distribution of 5564 Amazonian forest fragments-estimated from Landsat images of six regions of southern and eastern Brazilian Amazonia-clearly shows that these are predominantly small and rarely exceed 10 ha, suggesting that persistent overhunting is likely to drive most midsized to large vertebrate populations to local extinction in fragmented forest landscapes. Although experimental studies on this negative synergism remain largely unavailable, the prospect that increasingly fragmented Neotropical forest regions can retain their full assemblages of avian and mammalian species is unlikely.
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Nondetection of a species at a site does not imply that the species is absent unless the probability of detection is 1. We propose a model and likelihood-based method for estimating site occupancy rates when detection probabilities are 1. The model provides a flexible framework enabling covariate information to be included and allowing for missing observations. Via computer simulation, we found that the model provides good estimates of the occupancy rates, generally unbiased for moderate detection probabilities (0.3). We estimated site occupancy rates for two anuran species at 32 wetland sites in Maryland, USA, from data collected during 2000 as part of an amphibian monitoring program, Frog-watch USA. Site occupancy rates were estimated as 0.49 for American toads (Bufo amer-icanus), a 44% increase over the proportion of sites at which they were actually observed, and as 0.85 for spring peepers (Pseudacris crucifer), slightly above the observed proportion of 0.83.
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Over 1,400,000 m of line transect data were collected in collaboration with Ache Indians to determine encounter rates with all large vertebrates in the Mbaracayu Reserve Paraguay. The data were analyzed using logistic regression in order to determine the impact of human hunting on animal encounter rates in the reserve. The method controlled for effects of season, weather, time of day, and habitat in order to statistically isolate the human predation effect. Encounters with the animals themselves as well as fresh signs of their activity allowed us to determine whether lower encounter rates in hunted zones are simply due to increased wariness by target species. Our results show that areas near hunters are hunted more frequently, and that Dasypus novemcinctus, Cebus apella, Tapirus terrestris, and Mazama spp. are all encountered at lower rates in those areas than in unhunted zones. We were unable to show that encounter rates with other important game species have been affected by human hunting. Demonstration of local depletion by central place foragers is expected, however, and cannot be used to conclude that prey species are in danger of regional extirpation.
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