Article

Fragmentation metric proxies provide insights into historical biodiversity loss in critically endangered grassland

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Abstract

Landscape transformation causes habitat loss and fragmentation, which poses the greatest threat to biodiversity globally. In a fragmented landscape the persistence of species is affected by the amount of habitat and the spatial attributes of individual habitat patches. As baseline biodiversity information is often unavailable to assess the effects of transformation on biodiversity, quantifying changes in patch metrics over time could be a useful indicator of biodiversity changes in fragmented landscapes. We investigate historical land cover changes due to increased anthropogenic land uses in a highly fragmented, critically endangered grassland, the Woodbush Granite Grassland, South Africa. We test how the spatial attributes of habitat patches were affected by habitat loss and fragmentation over two extended time-periods, and use these results to infer likely threats to biodiversity over these periods. We used repeat aerial photography to analyse the drivers and extent of land cover loss and the changes in five fragmentation metrics over a 60 year period. The overall grassland extent decreased significantly over the 60-year period, mainly due to increased timber plantations, with an estimated 6.1% of the original extent of the grassland remaining in 2008. Increases in patch isolation due to habitat loss were most pronounced between 1948 and 1977, while between 1977 and 2008 patch sizes decreased and edge effects increased. This extensive habitat loss and increase in fragmentation are likely to have had considerable impacts on the biodiversity of the region, which is supported by anecdotal evidence of species extinctions and local extinctions. Because so little of the vegetation type remains, it is imperative that the last vestiges of this vegetation type are protected from transformation and further habitat degradation. In summary, we show how, faced with a lack of biodiversity data, fragmentation patch metrics can be used to quantify threats to biodiversity.

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... Worldwide, many studies have been carried out to assess the consequences of LULC changes on the natural habitats of native species. For example, Niemandt and Greve (2016) investigated the effects of anthropogenic land use changes by quantifying the fragmentation of the Woodbush Granite Grassland, South Africa, and using landscape metrics. De Montis et al. (2017) assessed the effects of urban growth on landscape fragmentation dynamics of six landscapes units in Sardinia (Italy) and Andalusia (Spain). ...
... Habitat fragmentation has two main negative impacts on living things: first, the many smaller patches are incapable to sustain local populations, and second, edge effects lead to an increase in overall mortality and reduction in reproduction rates (Haddad et al. 2015;Huerta 2007;Farhrig 2003). Fragmentation and diminishing of the natural vegetation, and hence the native species habitat, are the direct effects of land cover change (Ellis et al. 2010;Niemandt and Greve 2016). Eventually, this leads to three closely interrelated impacts: habitat loss and reduction in the total area of the original habitat, fragmented habitat (smaller patches), and replacement of the former vegetative cover by new land use (Fahrig 2003). ...
... Eventually, this leads to three closely interrelated impacts: habitat loss and reduction in the total area of the original habitat, fragmented habitat (smaller patches), and replacement of the former vegetative cover by new land use (Fahrig 2003). Many studies have elucidated the negative impacts of habitat loss on living things, such as amphibians, birds, small mammals, bats, and plants (Niemandt and Greve 2016;Ethier and Fahrig 2011;Smith et al. 2011). ...
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The land use/land cover (LULC) changes in Yarmouk River Basin (YRB) over a period of 22 years (1987–2009) have been analyzed, using remotely sensed data and geographic information system. Methods of LULC changes involved thematic change, image difference, and the normalized difference vegetation index (NDVI). Patch Analyst 5 for ArcGIS was used for the spatial analysis of landscape patches. The results revealed drastic changes in the LULC, with an overall change of more than 79%. Agricultural expansion has occurred at the expense of rangeland (16%) and forest (14%), whereas urban areas have taken over 2.65% of the agricultural areas, 2.11% of the forest, and 1.3% of the rangeland. The values of image difference were in agreement with the increase of urbanization and deforestation activities, besides the increased cultivation activities. The decrease in NDVI values indicates a degradation of vegetation cover. Class area (CA), mean patch size (MPS), and number of patches (NumP) for rangeland have decreased from 39,386 ha, 5.62 ha, and 7010 in 1987 to 17,729 ha, 4.62 ha, and 3838 in 2009, respectively. Similarly, CA, MPS, and NumP for forest land have decreased from 31,551 ha, 0.74 ha, and 42,548 in 1987 to 9558 ha, 0.65 ha, and 14,745 in 2009, respectively. Similar changes were shown to barelands. These results points to fragmentation of the natural land and habitat loss. On the other hand, CA and MPS of agriculture have increased from 35,306 ha and 0.72 ha in 1987 to 78,991 ha and 8 ha in 2009, respectively, indicating agricultural expansion. In addition, CA and NumP of urban have increased from 5513 ha and 89 in 1987 to 16,393 ha and 1536 ha in 2009. At the landscape level, the MPS has increased from ≈ 1 ha in 1987 to 3.7 ha in 2009, whereas NumP has decreased from 146,463 in 1987 to 38,006 in 2009, which means that the landscape became more clumped and continuous. The Shannon diversity index and Shannon evenness index have decreased, indicating that the landscape became more homogenous and more even over the 22 years of the study. It is believed that the major driver of LULC changes in the study area is urban growth, which usually leads to habitat disturbances.
... The Endangered Aloe lettyae Reynolds (IUCN: B1ab(iii,v)+2ab(iii,v)) is endemic to the highly threatened Woodbush Granite Grassland (WGG) in South Africa's Limpopo Province (Von Staden and Kremer-K€ ohne, 2015). Due to large-scale habitat loss through afforestation with exotic trees (Niemandt and Greve, 2016), A. lettyae's distribution has been severely reduced over several decades (Von Staden and Kremer-K€ ohne, 2015;Kremer-K€ ohne, 2018). While the destruction of habitat over time, habitat loss, is considered one of the most significant causes of biodiversity decline (Fahrig, 2017), the fragmentation pattern of the remaining habitat affects plant populations by impacting on a species' population size and density, abiotic disturbances such as fire, and the abundance of interacting species (Hobbs and Yates, 2003). ...
... The original vegetation is classified as WGG (Gm 25), a mesic highveld grassland with a high level of plant species diversity (Mucina et al., 2006a;Dzerefos and Witkowski, 2016;Dzerefos et al., 2017) and consequently a high conservation value (RSA, 2011). Due to extensive afforestation during the last century, only approximately 6% of the WGG estimated at 340 km 2 historically (Mucina et al., 2006b) remained in 2008 (Niemandt and Greve, 2016), rendering the WGG Critically Endangered (Mucina et al., 2006a;RSA, 2011;Desmet et al., 2013;SANBI, 2013). The landscape is highly fragmented (Niemandt and Greve, 2016), and two sizeable WGG fragments are situated near the small town of Haenertsburg. ...
... Due to extensive afforestation during the last century, only approximately 6% of the WGG estimated at 340 km 2 historically (Mucina et al., 2006b) remained in 2008 (Niemandt and Greve, 2016), rendering the WGG Critically Endangered (Mucina et al., 2006a;RSA, 2011;Desmet et al., 2013;SANBI, 2013). The landscape is highly fragmented (Niemandt and Greve, 2016), and two sizeable WGG fragments are situated near the small town of Haenertsburg. The largest remaining WGG fragment is 192 ha in size, 66% of which is formally conserved in the recently established Haenertsburg Nature Reserve (Limpopo Provincial Government, 2016), followed by a peninsula-shaped patch of 60 ha. ...
... The Endangered Aloe lettyae Reynolds (IUCN: B1ab(iii,v)+2ab(iii,v)) is endemic to the highly threatened Woodbush Granite Grassland (WGG) in South Africa's Limpopo Province (Von Staden and Kremer-K€ ohne, 2015). Due to large-scale habitat loss through afforestation with exotic trees (Niemandt and Greve, 2016), A. lettyae's distribution has been severely reduced over several decades (Von Staden and Kremer-K€ ohne, 2015;Kremer-K€ ohne, 2018). While the destruction of habitat over time, habitat loss, is considered one of the most significant causes of biodiversity decline (Fahrig, 2017), the fragmentation pattern of the remaining habitat affects plant populations by impacting on a species' population size and density, abiotic disturbances such as fire, and the abundance of interacting species (Hobbs and Yates, 2003). ...
... The original vegetation is classified as WGG (Gm 25), a mesic highveld grassland with a high level of plant species diversity (Mucina et al., 2006a;Dzerefos and Witkowski, 2016;Dzerefos et al., 2017) and consequently a high conservation value (RSA, 2011). Due to extensive afforestation during the last century, only approximately 6% of the WGG estimated at 340 km 2 historically (Mucina et al., 2006b) remained in 2008 (Niemandt and Greve, 2016), rendering the WGG Critically Endangered (Mucina et al., 2006a;RSA, 2011;Desmet et al., 2013;SANBI, 2013). The landscape is highly fragmented (Niemandt and Greve, 2016), and two sizeable WGG fragments are situated near the small town of Haenertsburg. ...
... Due to extensive afforestation during the last century, only approximately 6% of the WGG estimated at 340 km 2 historically (Mucina et al., 2006b) remained in 2008 (Niemandt and Greve, 2016), rendering the WGG Critically Endangered (Mucina et al., 2006a;RSA, 2011;Desmet et al., 2013;SANBI, 2013). The landscape is highly fragmented (Niemandt and Greve, 2016), and two sizeable WGG fragments are situated near the small town of Haenertsburg. The largest remaining WGG fragment is 192 ha in size, 66% of which is formally conserved in the recently established Haenertsburg Nature Reserve (Limpopo Provincial Government, 2016), followed by a peninsula-shaped patch of 60 ha. ...
Article
This is the first study documenting the distribution and population biology of the Endangered Aloe lettyae, an endemic to the highly threatened Woodbush Granite Grassland (WGG) in Limpopo Province, South Africa. We documented 19 A. lettyae populations and calculated the total area of occupied habitat at 17.5 ha within its extent of occurrence of 123 km 2. Most populations were clustered on the south western side of the WGG, with all known localities less than 40 km apart in this severely fragmented vegetation type. Population size varied from 10 to 6547 plants, with »10,800 individuals estimated in total. Plant size and life history stage demographics were determined in seven of the 19 currently known A. lettyae populations, including two large populations, as well as a high-and a low-lying population, and constituted a representative sample of the entire geographical range of the species. For plant size, four metrics (number of leaves, number of leaf layers, height and diameter of the leaf rosette) were recorded for each sampled A. lettyae plant, and the presence of an inflorescence indicated its reproductive status. By means of the classification tree technique CHAID (Chi-square Automatic Interaction Detection), we determined that of the four plant size metrics, the 'number of leaves' predicts A. lettyae's life history stages and fecundity most accurately, and revealed significant differences in the life history stage structure of the seven surveyed populations. Five populations occurring in relatively undisturbed WGG fragments, including the two large populations, comprised high proportions of adult individuals (77À89%), while only few A. lettyae juveniles were found (3À14%). By contrast, the relatively high percentage of juveniles (25À58%) and low percentage of adults (32À63%) observed in two small populations found in a degraded WGG fragment and in non-natural habitat respectively, appeared atypical. The percentage of subadults varied little across the surveyed populations (8À13%). In slow-growing, long-lived species such as A. lettyae, the dominance of adult individuals with a high probability of survival may be considered as indicative of stable populations. This study provides baseline A. lettyae population data for long-term demographic monitoring which will aid management and conservation of the range restricted, Endangered A. lettyae.
... Água vol. 14 n. 5, e2351 -Taubaté 2019 2017 plant nutrition , favored by the increase in biomass produced, litterfall, root death and the increase in microorganisms, arthropods and others, which improve soil quality (Acevedo and Delibes-Mateos, 2013;Niemandt and Greve, 2016). This indicated that the postharvest vegetative recovery time is a determining factor in the variation and correspondence of soil characteristics with the richness and abundance of species. ...
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The Andean grassland ecosystems undergo natural and anthropogenic degradation processes. The change of land use for agricultural use is the greatest threat, with a great loss of biodiversity followed by a very slow process of revegetalization. The objective was to assess the richness, abundance and diversity, alpha and beta, in areas of two-, three-, five-, six- and eight years of post-harvest abandonment of Lepidium meyenni Walpers. Ten affected areas were selected for agrostological evaluation, through four linear transects of interception points with 100 records each, applied on the edge and inside the affected area, inside and outside the affected areas, as well as samples composed of soils for each area. Composite soil samples were collected from each transect and study area to analyze their physical and chemical properties. The data were analyzed using the generalized linear mixed model with Rstudio v 5.3.2, and the multivariate analysis of canonical correspondence between biological and environmental variables, using CANOCO v.1.4 software. A significant difference was found between floral composition and alpha diversity according to abandonment time and seasonal periods. The greatest richness and abundance was observed between five- and eight years of abandonment, due to the greater presence of perennial species. Linear correspondence of alpha richness and diversity with organic matter, nitrogen, soil phosphorus and abandonment time was observed.
... Changes in the landscape structure also affect the mutualistic relationships between plants and pollinating insects, which may, among others, limit the availability of pollen and consequently decrease the viability of plant populations [28]. It is well known that changes in landscape connectivity affect species distribution, and therefore knowing the historical pattern is crucial for better understanding recent patterns of biodiversity [29][30][31]. Such knowledge also improves management plans at the landscape scale [10,32]. ...
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Historical ecology gives a reference point to explain the contemporary state of particular ecosystems as well as entire landscapes. In this study, we examined the quantitative changes in forest cover in the central part of the Sudety Massif (area ca. 1,120 km<sup>2</sup>) during the last 250 years. The information regarding forest patch distribution and its changes was derived by comparison of maps from 1747 and the 1970s drawn at scales of 1:33,000 and 1:25,000, respectively. To examine the effect of environmental variables (topography and soil conditions) and human population density on forest patch distribution and its changes (afforestation, deforestation), a set of 100 circular plots with a diameter of 1 km was established. The influence of explanatory variables was examined using regression tree methods. Changes at the level of the entire landscape were tested using a set of 25 landscape windows (5 × 5 km each). We found that the overall forest cover increased to 36.4% in the twentieth century from 30.4% in the middle of the eighteenth century. The ancient forests constituted 59% of the total forest area existing more recently. The forests in the eighteenth century occurred mostly on steep slopes, deep valley bottoms, and summits. The land relief explains more than half of the total variation in forest distribution ( R <sup>2</sup> = 0.56). The effects of soil type and human population density were negligible. The contemporary forest pattern results from both land relief and the historical pattern of human population density in the middle of the eighteenth century ( R <sup>2</sup> = 0.64), while the effect of soil type was negligible. The pattern of deforestation ( R <sup>2</sup> = 0.53) and afforestation ( R <sup>2</sup> = 0.36) results from both land relief as well as recent and nineteenth-century human population density. About 83% of the recent forest area is in physical contact with patches of the ancient forest, which provides an optimistic outlook for the migration of ancient forest species into new areas. Furthermore, changes in landscape structure reveal increased connectivity among forest patches, with potential benefits for the migration of forest species with long-range dispersal.
... Habitat suitability models have the potential to become an essential tool to support management decisions and conservation measures (Lauria et al. 2015). Habitat loss is one of the important detrimental impacts to biodiversity which results in loss of biodiversity, population connectedness and gene flow (Niemandt and Greve 2016). Hence, the high-suitability habitats should be considered as priority for implementation of conservation measures. ...
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In this study the goal was to identify critical sites for biodiversity conservation in the Gharesoo River Basin, Iran, based on integration of anthropogenic threats and biodiversity value. Firstly, the spatial patterns of threats were evaluated by combination of thirteen anthropogenic threats using multi-criteria evaluation (MCE) method. Next, the spatial distribution of biodiversity value was mapped via assigning an expert-based value to each land type as habitat for mammals and bird species. Finally, the critical sites for biodiversity conservation were identified by combination of spatial threats and biodiversity value layers. We developed five threat-driven or value-driven scenarios using different weights for biodiversity threats and value. The result showed that, 7% of the river basin had very high conservation priority. We proposed 21 patches as critical sites for biodiversity conservation. Our results can be used by conservation planners to target conservation efforts towards selecting new conservation areas in Gharesoo River Basin.
... The amount and structural complexity of landscapes has often been analyzed using metrics at the landscape and at the fragment level (Neel et al. 2004;Hendrickx et al. 2007, Fahrig 2013). These metrics have been recognized as useful indicators of biodiversity (Syrbe and Walz 2012;Niemandt and Greve 2016). However, as species perceive the environment differently, have different habitat requirements, and have distinct movement capacities, the deforestation process and its impacts may be better understood through landscape analysis within a multi-scale perspective (Urban 2005). ...
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Context Biodiversity is modulated by the spatial structure of the landscape. Thus, landscape metrics can be useful indicators of biota integrity and vulnerability, helping in conservation and management decisions. Objective We performed the first quantitative analysis of the spatial structure of the Caatinga drylands. We estimated the habitat amount and the fragmentation pattern of this region using a multi-scale perspective. Methods Using the Brazilian official database of native remnants, we calculated the number and percentage of remaining fragments per size class and we describe how habitat amount changes along the landscape. By simulating different dispersal capacities, we estimated the functional connectivity among remnants. We also calculated the cumulative core area as a function of different edge effect widths. Results Caatinga is subdivided into 47,100 fragments. Although 91% of them are smaller than 500 ha, 720 fragments are larger than 10,000 ha, corresponding to 78% of the remaining vegetation. Potentially, 95% of the vegetation is accessible to species that can cross 1000 m of matrix. With one kilometer of edge effect, the core area is reduced to a quarter of the remaining vegetation. The habitat amount analyzes reinforced the regional differences in the spatial distribution of the remnants. Conclusions Caatinga remains well connected for species with moderate and high dispersal capacities. However much of its remaining area is vulnerable to anthropogenic disturbances. Expansion of the protected area network and effective natural resource management to avoid overexploitation of the remnants are key strategies for maintaining the Caatinga biodiversity and its services.
... In increasingly fragmented habitats, patches are generally small and isolated. In case they become smaller than the minimum area required to sustain populations with larger-range requirements, or separated more than a minimum distance required to allow gene flow, a reduction of species diversity is expected [27]. Studies more focused on the aquatic environment linked biodiversity loss to controlled emissions from domestic effluents in rural and sparsely populated catchments, and to stream water contamination in urbanized, industrialized and densely populated watersheds [24,25]. ...
Article
Degradation is currently affecting 25% of Earth's land and 40% of Earth's agricultural land. The environmental consequences of land degradation are vast, including amplified soil losses, water quality deterioration, biodiversity decline and degradation of ecosystem services and corresponding values, especially if actual land uses disrespect capability (natural use), in which cases land is in a state of environmental conflict. The global cost of land degradation just looking to agriculture approaches US$ 500 billion/yr. Facing this terrible ecological and economic scenarios, the United Nations General Assembly adopted the “Sustainable Development Goals” in 2015, which comprise a target to combat desertification and restore degraded land. The aim is to achieve land degradation neutrality by 2030. Framework models have already been proposed to unpack this innovative concept and address its operation through the Rio Conventions. While implementing these models, which follow the response hierarchy of avoid > reduce > reverse land degradation, environmental consequences of land degradation should be compensated by sustainable land management practices that render the Earth no net loss of the land-based natural capital relative to a baseline. The ultimate goal is however to attain self sustainability whereby environmental and production potentials are supported by self-regulating processes within the system.
... The ''average flow rate'' index is used to assess the impacts of land-sea connectivity on global freshwater fish diversity (Liermann et al. 2012). Patch isolation metrics have proven to be more effective in predicting and reflecting the exercise capacity of organisms than the more commonly used distance-based metrics Tischendorf et al. 2003;Ng et al. 2013;Niemandt and Greve 2016). Graph theory is used to identify least-cost paths between patches for focal organisms and to interpret the role of a landscape matrix in the context of landscape connectivity (Forman 1995;Urban and Keitt 2001;Correa Ayram et al. 2014). ...
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Land–sea ecological connectivity refers to the interaction (convenience or hindrance) of certain physical, chemical and biological processes between terrestrial and marine ecosystems. Research on land–sea ecological connectivity can provide important scientific bases for the conservation and restoration of biodiversity and ecosystems in terrestrial and coastal areas. On the basis of a literature summary of ecological connectivity, this paper focuses on the following: (1) summarizing basic concepts, representative phenomena on multiple spatiotemporal scales, and analysis methods of land–sea ecological connectivity; (2) discussion of the applications of land–sea ecological connectivity; (3) discussion of the relationship between human activities and land–sea ecological connectivity; (4) presentation of perspectives and recommendations on ecological restoration, protection, and biodiversity research, with emphasis on the principle of land–sea ecological connectivity. On the whole, we believe such connectivity in a region varies with changes in multiple physical and artificial factors, such as climate, land cover, biotic community and human activities. Human activities such as land use, engineering construction, urbanization and industrialization have continuously increased and cause irreversible disturbance and destruction of land–sea ecological connectivity, thereby threatening biodiversity and ecosystem services at various spatiotemporal scales. Hence, achievements of theoretical research and practical experience in ecological connectivity should be fully applied in coastal areas to maintain and restore land–sea ecological connectivity and remedy various problems that arise from the blockage and damage of ecosystem services.
... The main reason for the changes is the drainage of land for the development of agricultural crops. Meadow degradation and its negative impact on the protection of biodiversity have also been recorded in other regions [31]. These are ecosystems that are sensitive to anthropogenic changes and natural ecological succession. ...
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This study assesses the changes in the spatial structure of the landscape between 1825 and 2019 in the isolated, protected forest complex of the Niemodlin Forests. Based on the analysis of changes in this structure, a change the supporting ecosystem services related to the protection of biodiversity was proposed. The landscape metrics were used separately for the analysis of the structure of the whole landscape, and individual types of ecosystems were used in the research. There were no major changes in the share of individual types of ecosystems during the period under review. At the same time, a very large increase in built-up areas and tree stands was found in 1825. Landscape metrics point to internal changes in the landscape composition, which is important for the functioning of the landscape and is related to the fragmentation and increasing isolation of ecosystems. Changes in the share of the surface of individual types of ecosystems in the landscape do not provide enough information about the actual structural and functional changes and ongoing ecosystem support services. There has been ecosystem degradation that is associated with freshwater habitats—surface waters, marshlands, meadows and pastures, as well as ecosystem support services related to these habitats. Changes in the spatial structure of the landscape cannot be solely deduced on the basis of changes in landscape metrics that are calculated for the whole landscape. Changes in the spatial composition of individual groups of ecosystems should be analyzed. Landscape metrics are very helpful in studying changes in the structure and function of ecosystem services.
... The endangered, summer-flowering Aloe lettyae Reynolds (Reynolds 1937;von Staden & Kremer-Köhne 2015) is endemic to the highly fragmented Woodbush Granite Grassland (WGG) vegetation type in the Limpopo Province, South Africa Kremer-Köhne et al. 2020). Although difficult to assess due to the lack of historical biodiversity data, Niemandt & Greve (2016) suggest that WGG biodiversity has been considerably compromised by large-scale habitat loss and fragmentation. As the Limpopo Province contains only a small area of the South African grassland biome (2307 km 2 or 0.7 % of the biome compared, e.g. to the neighbouring Mpumalanga Province with 50 730 km 2 or 15 % of the biome), the province was not included in the biodiversity profile and priority assessment undertaken as part of the National Grassland Biodiversity Programme (Reyers et al. 2005). ...
... Water and wind erosion together are taking 75 billion tons of soil each year (at a rate of 17 tons per hectare (t/ha) in the USA and Europe; and 30-40 t/ ha in South America and Africa. However, the rate of soil formation amounts only 1-2 t/ha (Niemandt and Greve 2016). Land degradation attributable to soil erosion by running water is the most intimidating environmental problem in Ethiopia (Desta et al. 2000;Bewket and Abebe 2013;Amare and Belay 2015). ...
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Background Ethiopia is gifted with abundant natural resources of adequate landmass, fertile soil, favorable climate, water, wildlife, and others. Many of its resources are not properly identified, well managed, and fully exploited. The concern of this review is collating the current state of knowledge about the status of land, water, forest, rangeland and wildlife resources, and hence, assesses their degradation tendencies. Results In Ethiopia, natural resources are under the influence of various interconnected factors like population pressure, agricultural expansion, migration, rapid urbanization, resettlement, climate change, and environmental pollution. Its huge population number had been putting a great burden on the sustainability of almost all types of natural resources. There is, therefore, serious degradation of land, water, forest, rangeland, and wildlife resources that appear to feed off each other. This results in severe soil loss, low vegetative cover, unsustainable farming practice, continuous use of dung and crop residues for fuel, overgrazing, and destruction and/or migration of wildlife, which again are intensifying the degradation of available resources in a vicious circle. The process ends with amplified environmental consequences such as water quality deterioration, biodiversity decline, and averts ecosystem services. It further recapitulates towards diverse socio-economic problems, political instability, marginalization, poverty, and recurrent natural hazards. The Ethiopian governments have taken several steps to address these problems like launching soil and water conservation campaign, tree planting programs, and others; success to date, however, has been limited. Conclusions Special attention has to be given to properly manage the natural resources and ecosystems; so that, it can continue to provide the goods and services the population need.
... Conservation ecology aims to understand how environmental changes can affect habitat quality, seeking the preservation and management of biodiversity and natural resources (Diamond et al. 1987;Niemandt and Greve 2016;Antongiovanni et al. 2018). The Atlantic Forest is represented by high biodiversity and endemism (Mittermeier et al. 2011;Zachos and Habel 2011). ...
Article
ContextUrbanisation and human population growth can generate conflicts, threatening biodiversity. Resource availability and vegetation complexity owing to human influence may increase the potential that a habitat would lose its species. Conservation biology aims to understand how to soften human influence and maintain viable insitu populations. AimsWe evaluated the non-volant mammal’s richness and abundance in an Atlantic Forest protected area. Specifically, we tested (1) the effect of distance from water resource and vegetation (canopy and understorey cover) on richness and abundance and (2) the effects of anthropogenic pressure such as domestic dog abundance, distances from human settlements, and from the road on the community of non-volant mammals. Methods We collected the data from January through December of 2017 in 20 sampling sites by using live traps (for small mammals), active search, sand plots and camera traps. Key resultsWe recorded 22 species of non-volant mammals, among them four endemic, two endangered and two invasive exotic species. The main covariates that affected the structure and composition of the non-volant mammal’s assemblage was the domestic dog abundance, which repels most of the species into the forest and water resources, which attract the species to forest edges. Conclusions Our results indicated that the negative impact of domestic dog presence in the non-volant mammal’s community is so evident that it could generate changes in the composition, richness, and local distribution of the species. ImplicationsWe suggest that management action in this protected area must initiate a control of domestic dogs to minimise their impact.
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Fine-scale data on species of special concern in fragments of highly threatened vegetation types are important for conservation management. This study investigated the vegetation structure and composition associated with the range-restricted long-lived Aloe lettyae and documented mesic Woodbush Granite Grassland (WGG) fragments. Google Earth imagery was used to detect WGG remnants in the highly fragmented landscape within the original WGG polygon as outlined on the National Vegetation Map. Field-verified WGG fragments were described (size, ownership, location, condition, observed threats and surrounding land cover types) and searched for A. lettyae. In six of the currently known 13 WGG fragments boasting an A. lettyae population, including two intact large (60–192 ha), two intact small (9–14 ha) and two degraded small (9–10 ha) WGG fragments, we studied the vegetation structure and composition associated with A. lettyae. For all sampled WGG fragments combined, vegetation structure (percentage aerial cover of grass, forb and woody species, bare soil and rock, maximum height (cm) of grass, forb and woody species and standing vegetation biomass (kg/ha)) within 1 m of each A. lettyae individual (n = 378) and ≥ 5 m away from A. lettyae plants (n = 442) varied very little. However, vegetation structure variables differed significantly between WGG fragments. For the intact large WGG fragments, percentage aerial cover for grass, forb and woody species were 49–50, 26–37 and 5–15%, respectively, with the small remaining percentages being made up of bare soil and rock cover. In the intact small WGG fragments, percentage aerial cover for grass, forb and woody species was similar to that in the large fragments. In the degraded small WGG fragments, however, percentage aerial cover for grass was significantly higher (66–74%) while the percentage forb cover tended to be lower (8–13%) than in the intact fragments. WGG fragment size ranged from <1 to 192 ha, with the estimate of all currently known extant WGG fragments amounting to a total of ∼6 km², or ∼1% of the estimated historical WGG extent. Therefore, it is imperative to conserve all remaining WGG fragments. We provide fine-scale baseline data on the vegetation structure and composition associated with A. lettyae and a description of extant WGG fragments for long-term vegetation monitoring, management and biodiversity conservation decisions and future research.
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Woody-plant encroachment threatens the biodiversity and ecosystem functioning of grasslands and meadows worldwide. An important but rarely described consequence of the transition to woody-plant dominance is the reduction in flowering of herbaceous species. We modeled community-wide relationships between flowering and light in two tree-invaded meadows (BG and M1) in the western Cascade Range, Oregon (USA). At BG, trees established over two centuries, forming a gradient of encroachment states (open meadow to old forest) and declining levels of light (91% to 8%), with most (85%) of the decline occurring within 2–4 decades of tree establishment. At M1, where trees formed distinct edges, we also tested whether distance from edge can serve as proxy for light in modeling flowering response. Flowering declined significantly with reductions in light at both sites: for a 10-percentage-point reduction in light, probability of flowering decreased by 35% (BG) and 21% (M1), median flowering density (flowers per m²) by 15% and 8%, and median flowering effort (density per unit cover) by 10% and 9%, respectively. At M1, distance to edge was a poorer predictor of flowering due to its nonlinear relationship with light: > 80% of the reduction in light occurred within 4.5 m of the edge. Our results reveal strong, nonlinear relationships of flowering in time (most rapid early in the invasion process) and space (steepest at the forest edge). In a landscape dominated by forests, conifer invasion of mountain meadows can reduce the local and larger-scale diversity of plants and their insect pollinators.
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Extensive grassland degradation under climate change and intensified human activities has threatened ecological security and caused a variety of environmental problems. However, it is still challenging to predict the grassland degradation status on a large scale because it is a multi-factorial phenomenon with complex changes in ecosystem structure and function, which is hard to be fully characterized through mechanism models. The emergence of machine learning algorithms provides a potential to model complex systems and mine information from multi-source data without elucidating underlying mechanisms. Here, we utilized random forest and neural network algorithms to predict the grassland degradation represented by the net primary productivity (NPP) changing rate based on multi-source data including geographic, meteorological, plant traits, land use type and microbial variables in the Chinese Northern grassland. Particularly, the microbial roles in determining the degradation status were concerned. Results show that a high prediction precision was achieved by random forest model, rather than by neural network model, with a mean relative error of 16.9% and a mean square error of 9.273e-05. Besides identified longitude, arid index and current NPP state, specific soil microbial groups, mainly Solirubrobacter, were screened as credible biomarkers. Regarding model fitting, geographic, meteorological and plant variables explained 61.8% of the total variance, which was enhanced up to 72.8% by the rest microbial markers. These findings provide a theoretical basis to establish a pre-warning system for grassland management and policy-making.
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Conceptual approaches used to understand conservation in fragmented landscapes are summarized in this chapter by Andrew F. Bennett and Denis A. Saunders. Destruction and fragmentation of habitats are major factors in the global decline of species, the modification of native plant and animal communities and the alteration of ecosystem processes. Habitat destruction, habitat fragmentation (or subdivision) and new forms of land use are closely intertwined in an overall process of landscape change. Landscape change is not random: disproportionate change typically occurs in flatter areas, at lower elevations and on more-productive soils. Altered physical processes (e.g. wind and water flows) and the impacts of human land-use have a profound influence on fragments and their biota, particularly at fragment edges. Different species have different ecological attributes (such as scale of movement, life-history stages, what constitutes habitat) which influence how a species perceives a landscape and its ability to survive in modified landscapes. Differences in the vulnerability of species to landscape change alter the structure of communities and modify interactions between species (e.g. pollination, parasitism). Changes within fragments, and between fragments and their surroundings, involve timelags before the full consequences of landscape change are experienced. Conservation in fragmented landscapes can be enhanced by: (i) protecting and increasing the amount of habitat: (ii) improving habitat quality; (iii) increasing connectivity; (iv) managing disturbance processes in the wider landscape; (v) planning for the long term; and (vi) learning from conservation actions undertaken.
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This paper deals with the question of the role landscape metrics can play in the investigation, evaluation and monitoring of landscape structure, and which linkages between landscape structure and biodiversity are known. In the first part, the scientific state of the art is presented; in the second part, the meaning of landscape metrics for nature protection, landscape management and biodiversity monitoring is discussed. A number of studies indicate that such metrics on an aggregated, overall landscape level are quite appropriate to describe the state of biodiversity. On the other hand, gaps in the knowledge become apparent, and the results of such studies are strongly dependent on the scale of investigation and the underlying database. Nevertheless, the landscape structure approach seems to be expedient for management and planning at the landscape level.
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Fragmentation is a severe threat to tropical rainforests. However the habitat loss and less extensive fragmentation caused by roads can also be a threat, not only through allowing access to remote areas, but also through a suite of insidious associated impacts. These include abiotic and biotic edge effects adjacent to road clearings, the disturbance impacts caused by vehicle operation, invasions by weeds, feral and alien fauna and disease, and faunal mortality from vehicle collisions. In combination, these can create a significant barrier to movements of rainforest biota. Impacts can be ameliorated through clever road design and sustainable vehicle operation.
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We studied effects of forest fragmentation on 15 species of small mammals, including 6 species of forest-dwelling granivorous rodents, in the Indian Pine watershed of west-central Indiana. Presence - absence and population densities of small mammals were assessed in spring in 35 woodlots of various sizes (0.1-150 ha) and 2 continuous forest sites (>1,000 ha) using live traps in 1992-1996. Presence - absence and population density were related to landscape attributes using logistic and multiple linear regression models, respectively. Species richness of forest-dwelling small mammals increased with area and was highest in continuous forest sites. Nested subsets of the full complement of species were found in smaller woodlots. White-footed mice (Peromyscus leucopus) were ubiquitous, and eastern chipmunks (Tamias striatus) were nearly ubiquitous across the landscape; densities of both species were related inversely to forested area. Fox squirrels (Sciurus niger) were found at 84% of study sites, and they did not respond negatively to isolation of forest patches. Red squirrels (Tamiasciurus hudsonicus) were unevenly distributed across the landscape and were found most often in woodlots with large core areas and simple shapes, possibly indicating sensitivity to edge. Southern flying squirrels (Glaucomys volans) and gray squirrels (S. carolinensis) were restricted to continuous forest sites and >4.6-ha woodlots adjacent to other wooded habitat. Species of small mammals differ appreciably in their sensitivities to agriculturally induced fragmentation of forests. Interspecific differences within this assemblage were not due solely, or even primarily, to body size. Rather, differential responses of species to fragmentation likely resulted from variation in habitat breadth and ability to move through an agricultural matrix.
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Human impacts on the natural environment have reached such proportions that in addition to an ‘extinction crisis’, we now also face a broader ‘biome crisis’. Here we identify the world's terrestrial biomes and, at a finer spatial scale, ecoregions in which biodiversity and ecological function are at greatest risk because of extensive habitat conversion and limited habitat protection. Habitat conversion exceeds habitat protection by a ratio of 8 : 1 in temperate grasslands and Mediterranean biomes, and 10 : 1 in more than 140 ecoregions. These regions include some of the most biologically distinctive, species rich ecosystems on Earth, as well as the last home of many threatened and endangered species. Confronting the biome crisis requires a concerted and comprehensive response aimed at protecting not only species, but the variety of landscapes, ecological interactions, and evolutionary pressures that sustain biodiversity, generate ecosystem services, and evolve new species in the future.
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1. Habitat fragmentation is a major threat to biodiversity and can lead to the loss of both species and ecosystem services, but fragmentation effects vary greatly between studies and studied organisms. Understanding the distinct effects of habitat amount and isolation at the patch and landscape scale may account for some of this variation. 2. We studied biodiversity in 30 traditional orchards that were selected for independent variation in habitat amount and habitat isolation at the patch and landscape scale. We analysed species richness and abundance of snails, beetles, true bugs, spiders and breeding birds that avoid open farmland but occur in woody vegetation types. Additionally, the abundances of nine single species were analysed using specific habitat definitions. 3. Surprisingly, the effects of habitat isolation were more important than the effects of habitat amount. Effects at the patch scale were more frequent than landscape-scale effects. 4. Spider species richness decreased with increasing patch-scale habitat amount. Abundance of the weevil Phyllobius oblongus increased with landscape-scale habitat amount. Negative effects of patch isolation were greater for predatory birds and spiders, while the predominately herbivorous beetles, true bugs and snails were less affected. Species richness of birds, spiders and beetles, and abundance of birds, Cyanistes caeruleus, Parus major and Fringilla coelebs, decreased with increasing patch-scale habitat isolation. In contrast, species richness of spiders and beetles increased with increasing landscape-scale habitat isolation. 5. Synthesis and applications. The effects of habitat fragmentation differed between taxonomic groups, with stronger and more consistent responses in birds than invertebrates. Our understanding of fragmentation effects may be biased due to the dominance of bird studies in the literature, and further invertebrate studies are encouraged. Landscape management to improve biodiversity or ecosystem services requires a group-specific approach and coordinated priority setting. High habitat connectivity benefited wood-preferring birds, spiders and beetles, lending support to national initiatives for increased habitat connectedness. The negative effects of patch isolation were greater for natural pest regulators, birds and spiders than for herbivorous beetles and bugs.
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Aim To map and characterize anthropogenic transformation of the terrestrial biosphere before and during the Industrial Revolution, from 1700 to 2000.Location Global.Methods Anthropogenic biomes (anthromes) were mapped for 1700, 1800, 1900 and 2000 using a rule-based anthrome classification model applied to gridded global data for human population density and land use. Anthropogenic transformation of terrestrial biomes was then characterized by map comparisons at century intervals.Results In 1700, nearly half of the terrestrial biosphere was wild, without human settlements or substantial land use. Most of the remainder was in a seminatural state (45%) having only minor use for agriculture and settlements. By 2000, the opposite was true, with the majority of the biosphere in agricultural and settled anthromes, less than 20% seminatural and only a quarter left wild. Anthropogenic transformation of the biosphere during the Industrial Revolution resulted about equally from land-use expansion into wildlands and intensification of land use within seminatural anthromes. Transformation pathways differed strongly between biomes and regions, with some remaining mostly wild but with the majority almost completely transformed into rangelands, croplands and villages. In the process of transforming almost 39% of earth's total ice-free surface into agricultural land and settlements, an additional 37% of global land without such use has become embedded within agricultural and settled anthromes.Main conclusions Between 1700 and 2000, the terrestrial biosphere made the critical transition from mostly wild to mostly anthropogenic, passing the 50% mark early in the 20th century. At present, and ever more in the future, the form and process of terrestrial ecosystems in most biomes will be predominantly anthropogenic, the product of land use and other direct human interactions with ecosystems. Ecological research and conservation efforts in all but a few biomes would benefit from a primary focus on the novel remnant, recovering and managed ecosystems embedded within used lands.
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Habitat isolation can affect the distribution and abundance of wildlife, but it is an ambiguous attribute to measure. Presumably, isolation is a characteristic of a habitat patch that reflects how spatially inaccessible it is to dispersing organisms. We identified four isolation metrics (nearest-neighbor distance, Voronoi polygons, proximity index, and habitat buffers) that were representative of the different families of metrics that are commonly used in the literature to measure patch isolation. Using simulated data, we evaluated the ability of each isolation metric to predict animal dispersal. We examined the simulated movement of organisms in two types of landscapes: an artificially-generated point-pattern landscapes where patch size and shape were consistent and only the arrangement of patches varied, and realistic landscapes derived from a geographic information system (GIS) of forest-vegetation maps where patch size, shape, and isolation were variable. We tested the performance of the four isolation metrics by examining the strength of the correlation between observed immigration rate in the simulations and each patch isolation metric. We also evaluated whether each isolation metric would perform consistently under varying conditions of patch size/shape, total amount of habitat in the landscape, and proximity of the patch to the landscape edge. The results indicate that a commonly-used distance-based metric, nearest-neighbor distance, did not adequately predict immigration rate when patch size and shape were variable. Area-informed isolation metrics, such as the amount of available habitat within a given radius of a patch, were most successful at predicting immigration. Overall, the use of area-informed metrics is advocated despite the limitation that these metrics require parameterization to reflect the movement capacity of the organism studied.
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Landscape ecology has generated much excitement in the past two decades. One reason was that it brought spatial analysis and modeling to the forefront of ecological research. However, high expectations for landscape analysis to improve our understanding and prediction of ecological processes have largely been unfulfilled. We identified three kinds of critical issues: conceptual flaws in landscape pattern analysis, inherent limitations of landscape indices, and improper use of pattern indices. For example, many landscape analyses treat quantitative description of spatial pattern as an end itself and fail to explore relationships between pattern and process. Landscape indices and map data are sometimes used without testing their ecological relevance, which may not only confound interpretation of results, but also lead to meaningless results. In addition, correlation analysis with indices is impeded by the lack of data because of difficulties in large-scale experimentation and by complicated behavior of indices because of their varying responses to changes in scale and spatial pattern. These problems represent significant challenges to landscape pattern analysis, especially in terms of relating pattern to process. In this perspective paper, we examine the underlying problems of these challenges and offer some solutions.
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This study evaluates the relationship between landscape accessibility and land cover change in Western Honduras, and demonstrates how these relationships are influenced by social and economic processes of land use change in the region. The study area presents a complex mosaic of land cover change processes that involve approximately equal amounts of reforestation and deforestation. Landsat Thematic Mapper (TM) satellite imagery of 1987, 1991 and 1996 was used to create three single date classifications and a land cover change image depicting the sequence of changes in land cover between 1987–1991–1996. An accessibility analysis examined land cover change and landscape fragmentation relative to elevation and distance from roads. Between 1987 and 1991, results follow ‘expected’ trends, with more accessible areas experiencing greater deforestation and fragmentation. Between 1991 and 1996 this trend reverses. Increased deforestation is found in areas distant from roads, and at higher elevations; a result of government policies promoting expansion of mountain coffee production for export. A ban on logging, and abandonment of marginally productive agricultural fields due to agricultural intensification in other parts of the landscape, has led to increased regrowth in accessible regions of the landscape. Roads and elevation also present different obstacles in terms of their accessibility, with the smallest patches of cyclical clearing and regrowth, relating mostly to the agricultural fallow cycle, found at the highest elevations but located close to roads. This research highlights the need to locate analyses of land cover change within the context of local socio-economic policies and land use processes.
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Spatial heterogeneity has an important influence on a wide range of ecological patterns and processes, and many landscape metrics in GIS environment are used to facilitate the investigation of the relation between landscape structure and biodiversity. Data reduction analyses have been applied to tackle the problem of highly correlated indices, but valid landscape predictors for fine scale Mediterranean forest-mosaics are still missing. Therefore, we analyzed the landscape structure of Dadia National Park, Greece, a Mediterranean forest landscape of high biodiversity, characterized by pine, oak and mixed woodland. By distinguishing nine land cover classes, 119 variables were computed and factor analysis was applied to detect the statistical dimensions of landscape structure and to define a core set of representative metrics. At landscape level, diversity of habitats, fragmentation and patch shape and at class level dominance of mixed forest and the gradient from one pure forest type to another turned out to be the crucial factors across three different scales. Mapping the encountered dimensions and the representative metrics, we detected that the pattern of landscape structure in Dadia National Park was related to dominating habitat types, land use, and level of protection. The evaluated set of metrics will be useful in establishing a landscape monitoring program, to detect the local drivers of biodiversity, and to improve management decisions in Dadia NP and similar mosaic-landscapes.
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Estimating the relative importance of habitat loss and fragmentation is necessary to estimate the potential benefits of specific management actions and to ensure that limited conservation resources are used efficiently. However, estimating relative effects is complicated because the two processes are highly correlated. Previous studies have used a wide variety of statistical methods to separate their effects and we speculated that the published results may have been influenced by the methods used. We used simulations to determine whether, under identical conditions, the following 7 methods generate different estimates of relative importance for realistically correlated landscape predictors: residual regression, model or variable selection, averaged coefficients from all supported models, summed Akaike weights, classical variance partitioning, hierarchical variance partitioning, and a multiple regression model with no adjustments for collinearity. We found that different methods generated different rankings of the predictors and that some metrics were strongly biased. Residual regression and variance partitioning were highly biased by correlations among predictors and the bias depended on the direction of a predictor’s effect (positive vs. negative). Our results suggest that many efforts to deal with the correlation between amount and fragmentation may have done more harm than good. If confounding effects are controlled and adequate thought is given to the ecological mechanisms behind modeled predictors, then standardized partial regression coefficients are unbiased estimates of the relative importance of amount and fragmentation, even when predictors are highly correlated.
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Transformation of natural vegetation to other land-uses, such as crop cultivation and urban development, presents the most important threat to biodiversity. Plant and animal species distribution data were employed to identify areas of high biodiversity value in the major summer crop production region in north-eastern South Africa. These areas of biodiversity conservation importance were then evaluated in terms of their (1) potential overlap with areas currently transformed by land-uses in the region and (2) potential co-occurrence with areas of natural vegetation cover likely to become cultivated. Integrating species distribution, land-cover and land capability data allowed for potential conflict areas, i.e. areas with a high biodiversity value facing large current or future land transformation threats to be identified. Areas of potential conflict appear to be central Gauteng, the KwaZulu-Natal coastline, Maputuland and the escarpment of Mpumalanga. Most of the arable areas, that are not currently under some form of land-use, are marginal lands where the physical land characteristics demand high input costs, give rise to low yields and are thus not suitable for full scale commercial cultivation. As the results indicate some of these areas have a high biodiversity value, land reform programs should therefore refrain from promoting cultivation on marginal lands in these conflict areas, as they provide the last safe havens for many species. The proportion of bird, butterfly, mammal and plant species’ ranges remaining in an untransformed state was quantified. Animal species with less than 60% of their natural range remaining, referred to as impacted species, comprised 63 bird, 207 butterfly and 15 mammal species. The grid cells containing these impacted species were identified as additional potential conflict areas. This study presents evidence that there is significant overlap between areas of biodiversity conservation interest and transformed or arable land in this region of South Africa and that there is an urgent need for the formulation of appropriate policies to promote biodiversity conservation on private farmland.
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Theory suggests that a disproportionate loss of species occurs when total habitat cover decreases to 10–30% of the landscape. To date, little empirical evidence has been collected to test for such thresholds in habitat cover, especially at the landscape scale. Here, we present empirical data on the species richness of woodland-dependent birds collected systematically from 24 landscapes (each 100 km2) that sample a gradient in habitat cover from <2% to 60%. To compare the relative effects of habitat cover and habitat configuration, landscapes with similar amounts of habitat but contrasting configuration (i.e., aggregated versus dispersed) were surveyed and the richness of woodland-dependent birds collated for each landscape. The relationship between species richness, habitat cover and habitat configuration was examined using analysis of co-variance (ANCOVA), multiple linear regression and univariate non-linear modelling. There was a significant effect of habitat cover (co-variate) in the ANCOVA, but the main treatment effect of configuration was not significant. However, comparison of non-linear models indicated that the shape of the response curve of species loss with decreasing habitat cover differed between aggregated and dispersed landscapes. Species richness was significantly related to habitat cover in all analyses, explaining between 55% and 60% of the variance in regression models. Mean patch shape complexity and the extent of habitat aggregation were also significant explanatory variables, but explained less than 10% of the variance in richness of woodland birds. Biogeographic variables (range in elevation and geographic location) explained up to 14% of the variance in species richness. There was strong evidence for a threshold response in species richness: non-linear models (broken-stick, exponential, inverse) exhibiting a sharp decline in species richness in landscapes with less than 10% habitat cover provided a better fit to the observed data than linear models. To our knowledge, this is the first empirical demonstration of landscape-level thresholds in species richness. We emphasise that thresholds in species richness denote multiple species’ extinction events, the end point of the process of species decline. For viable populations, habitat cover must be maintained well above the threshold level. Finally, thresholds of assemblage measures, such as species richness, potentially mask compositional changes in the avifauna community and may also conceal the loss of species with greater sensitivity to landscape change.
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It is known that habitats composed of spatially heterogeneous abiotic conditions provide a great diversity of potentially suitable niches for plant species. The scientific premises of landscape ecology suggest that, at a higher spatial level, also the composition and structure of the landscape mosaic, influences biotic processes and hence species richness. In this exploratory study we investigated if plant species diversity could be correlated with landscape structure and complexity indices which were based on Landsat Thematic Mapper satellite imagery. Plant species data were derived from the km resolution Flora Database of Flanders (i.e. northern Belgium). Plant species number within the km grid cells was positively correlated with most of the landscape diversity indices whereas landscape fragmentation indices only affected the group of the threatened species. We found a gradient of increasing species richness beginning from the rural areas of Flanders over the suburban towards the urban areas. This gradient was mostly due to the higher number of alien plant species, warmth indicators and threatened species in urbanised areas. We conclude that, at least in the studied region, the effects of landscape changes on plant species diversity can be monitored and predicted on a large scale and over long periods of time using land cover data. Bottleneck in this kind of analyses remains the reliability of the land cover data and the availability and reliability of the biological data.
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Human-driven ecosystem simplification has highlighted questions about how the number of species in an ecosystem influences its functioning. Although biodiversity is now known to affect ecosystem productivity, its effects on stability are debated. Here we present a long-term experimental field test of the diversity–stability hypothesis. During a decade of data collection in an experiment that directly controlled the number of perennial prairie species, growing-season climate varied considerably, causing year-to-year variation in abundances of plant species and in ecosystem productivity. We found that greater numbers of plant species led to greater temporal stability of ecosystem annual aboveground plant production. In particular, the decadal temporal stability of the ecosystem, whether measured with intervals of two, five or ten years, was significantly greater at higher plant diversity and tended to increase as plots matured. Ecosystem stability was also positively dependent on root mass, which is a measure of perenniating biomass. Temporal stability of the ecosystem increased with diversity, despite a lower temporal stability of individual species, because of both portfolio (statistical averaging) and overyielding effects. However, we found no evidence of a covariance effect. Our results indicate that the reliable, efficient and sustainable supply of some foods (for example, livestock fodder), biofuels and ecosystem services can be enhanced by the use of biodiversity.
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Human-driven ecosystem simplification has highlighted questions about how the number of species in an ecosystem influences its functioning. Although biodiversity is now known to affect ecosystem productivity, its effects on stability are debated. Here we present a long-term experimental field test of the diversity–stability hypothesis. During a decade of data collection in an experiment that directly controlled the number of perennial prairie species, growing-season climate varied considerably, causing year-to-year variation in abundances of plant species and in ecosystem productivity. We found that greater numbers of plant species led to greater temporal stability of ecosystem annual aboveground plant production. In particular, the decadal temporal stability of the ecosystem, whether measured with intervals of two, five or ten years, was significantly greater at higher plant diversity and tended to increase as plots matured. Ecosystem stability was also positively dependent on root mass, which is a measure of perenniating biomass. Temporal stability of the ecosystem increased with diversity, despite a lower temporal stability of individual species, because of both portfolio (statistical averaging) and overyielding effects. However, we found no evidence of a covariance effect. Our results indicate that the reliable, efficient and sustainable supply of some foods (for example, livestock fodder), biofuels and ecosystem services can be enhanced by the use of biodiversity.
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AbstractI challenge (1) the assumption that habitat patches are natural units of measurement for species richness, and (2) the assumption of distinct effects of habitat patch size and isolation on species richness. I propose a simpler view of the relationship between habitat distribution and species richness, the ‘habitat amount hypothesis’, and I suggest ways of testing it. The habitat amount hypothesis posits that, for habitat patches in a matrix of non‐habitat, the patch size effect and the patch isolation effect are driven mainly by a single underlying process, the sample area effect. The hypothesis predicts that species richness in equal‐sized sample sites should increase with the total amount of habitat in the ‘local landscape’ of the sample site, where the local landscape is the area within an appropriate distance of the sample site. It also predicts that species richness in a sample site is independent of the area of the particular patch in which the sample site is located (its ‘local patch’), except insofar as the area of that patch contributes to the amount of habitat in the local landscape of the sample site. The habitat amount hypothesis replaces two predictor variables, patch size and isolation, with a single predictor variable, habitat amount, when species richness is analysed for equal‐sized sample sites rather than for unequal‐sized habitat patches. Studies to test the hypothesis should ensure that ‘habitat’ is correctly defined, and the spatial extent of the local landscape is appropriate, for the species group under consideration. If supported, the habitat amount hypothesis would mean that to predict the relationship between habitat distribution and species richness: (1) distinguishing between patch‐scale and landscape‐scale habitat effects is unnecessary; (2) distinguishing between patch size effects and patch isolation effects is unnecessary; (3) considering habitat configuration independent of habitat amount is unnecessary; and (4) delineating discrete habitat patches is unnecessary.
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A meaningful interpretation of landscape metrics is possible only when the limitations of each measure are fully understood, the range of attainable values is known, and the user is aware of potential shifts in the range of values due to characteristics of landscape patches. To examine the behavior of landscape metrics, we generated artificial landscapes that mimicked fragmentation processes while controlling the size and shape of patches in the landscape and the mode of disturbance growth. We developed nine series of increasingly fragmented landscapes and used these to investigate the behavior of edge density, contagion, mean nearest neighbor distance, mean proximity index, perimeter-area fractal dimension, and mass fractal dimension. We found that most of the measures were highly correlated, especially contagion and edge density, which had a near-perfect inverse correspondence. Many of the measures were linearly-associated with increasing disturbance until the proportion of disturbance on the landscape was approximately 0.40, with non-linear associations at higher proportions. None of the measures was able to differentiate between landscape patterns characterized by dispersed versus aggregated patches. The highest attainable value of each measure was altered by either patch size or shape, and in some cases, by both attributes. We summarize our findings by discussing the utility of each metric.
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Historical data on landuse changes are important for interpreting the current status of natural systems such as forests. Analyses of road network dynamics can be particularly useful as network expansion is often a precursor to and an indicator of increased human activity. Legal protection is often seen as the most viable option available for protecting natural forests; but over the past decade, its effectiveness has been questioned. We assessed the impact of roads and the designation of a forest reserve on deforestation and forest fragmentation in a tropical moist forest, Cockpit Country, Jamaica, from 1942 to 2010. Specifically, we classified multi-temporal images (black and white aerial photographs, IKONOS and GeoEye images) using an object based image analysis and we included a vector of digitized roads for each year of assessment during the classification process. We then conducted a fragmentation analysis of the classified images and assessed the relationship between road density and several fragmentation metrics over time, and the spatial influence of the reserves (presence/absence) and roads (Euclidean distance from roads) on deforestation and several fragmentation metrics using generalized linear models.
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Species-rich semi-natural grasslands have rapidly declined and become fragmented in Northern Europe due to ceased traditional agricultural practices and animal husbandry. Restoration actions have been introduced in many places to improve the habitat conditions and increase the area to prevent any further losses of their ecological values. However, given the limited resources and long time span needed for successful restoration, it is essential to target activities on sites having a suitable initial state and where the effects of restoration are most beneficial for the habitat network. In this paper we present a conceptual framework for evaluating the restoration potential of partially overgrown and selectively managed semi-natural grasslands in a moderately transformed agricultural environment in south-western Finland. On the basis of the spatio-temporal landscape trajectory analysis, we construct potential restoration scenarios based on expected semi-natural grassland characteristics that are derived from land productivity, detected grassland continuum, and date of overgrowth. These scenarios are evaluated using landscape metrics, their feasibility is discussed and the effects of potential restoration are compared to the present extent of open semi-natural grasslands. Our results show that landscape trajectory analysis and scenario construction can be valuable tools for the restoration planning of semi-natural grasslands with limited resources. The approach should therefore be considered as an essential tool to find the most optimal restoration sites and to pre-evaluate the effects.
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Edge effect is a key process influencing populations and communities, particularly in fragmented landscapes. A general analytical framework has been proposed to quantify the strength of the edge effects (extent and magnitude); however, factors determining the later remain poorly explored. Using a continuous approach we explore the response of dung beetle species and assemblages to ecotones which differ in environmental dissimilarity in the Southern Atlantic forest of Argentina. Using baited pitfall traps and automatic sensors, we estimated dung beetle abundance, microclimatic conditions and vegetation structure along five different forest-plantations transects. At the assemblages level, the majority of species showed either edge avoidance or preference; however, the response depended on the environmental dissimilarity between habitats (plantation and native forest) and varied from a neutral response on mature plantations (low contrast ecotone) to edge avoidance on recent ones (high contrast ecotone). At the species level, the degree of habitat specialization explains the differential response of species to edge effects; more specialized species showed stronger edge response while generalist species showed softer or neutral responses. Environmental dissimilarity between confronted habitats and species specialization explain the quantitative component of edge effects on species and assemblages. Functional groups (rollers and tunnellers) often showed opposite responses to edge effects. At the landscape level, functional connectivity of forest fragments is probably drastically reduced by high contrasts matrices (such as recent plantations) for native forest species, whereas soft ecotones (such as native forest-mature plantations) maintained functional connectivity. These results are particularly relevant on highly fragmented landscapes, such as the Atlantic forest, where edge effect is probably one the most important mechanisms affecting native species and communities.
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The KwaNibela Peninsula is situated in the northernmost region of Lake St Lucia in KwaZulu-Natal. It is covered by forest patches of either Sand Forest or Coastal Forest within the Maputaland Coastal Vegetation. The area and the forests are heavily used by inhabitants of the region. The current and historical distributions of the forest patches were mapped to determine the changes in their cover (area) and character since 1937. A series of seven aerial photos, dating from 1937, 1960, 1969, 1979, 1990, 2002, to 2008 were used to quantify changes in land-cover type. The land-cover types were classified into core forest, regrowth forest and open areas (open woodland and anthropogenically altered land) and the percentages of each cover type were compared across years to determine the overall vegetation change, as well as the direction of change. Characteristic species were recorded at different stages of forest succession throughout the study area and are presented as supplementary information. The ratios of these land-cover types are shown to shift in both directions, with core forest ultimately expanding and open areas contracting slightly between 1937 and 2001. The nature of the land-cover types has changed significantly, with increasing fragmentation of both the core forest and open areas. This information has important implications for understanding forest dynamics in a changing environment, with shifting disturbance-recovery processes.
Article
Land cover/land use (LCLU) transitions and landscape changes were mapped and interpreted in a deltaic Natura 2000 habitat site in northern Greece. Multi-temporal maps created over a period of about 65 years and based on panchromatic aerial photographs and high spatial resolution satellite data, helped to assess LCLU transformations. These changes were associated with human interference and major socio-economic processes occurring in the area during the study period. In 1945, forests and wetlands dominated the delta area, occupying 63% of the total land cover. Subsequently, these land cover types severely reduced in coverage, and agricultural areas dominated the landscape as a result of policies introduced to accommodate the settlement of refugees from Asia Minor. This transition increased landscape fragmentation in 1960. Due to relative increase of swap changes, the landscape became less heterogeneous in 1992. Finally, in 2002, agricultural areas exhibit a small decrease in coverage having converted back to natural areas following the introduction of EU Common Agricultural Policy. About 77% of the deltaic ecosystem experienced LCLU changes during the first period of the analysis (1945–1960). Almost two thirds of this change is attributed to intercategorical transitions, while the rest is related to swap changes. During the second period of the analysis (1960–1992), half the study area was transformed due to net and swap changes. Finally, in the third, most recent time period (1992–2002), 85% of the landscape showed persistence while net changes were twice as frequent as swap changes. Human interference was the key factor beyond the landscape transformations and intercategorical transitions observed in the delta. During the previous century natural habitats were pressured by major socio-economic processes that transformed their composition and structure. Assessing these changes is critical to develop area-specific policies that minimize negative influences and provide a framework for restoring habitats to their natural conditions.
Article
The coastal grasslands in north-eastern South Africa are a severely threatened vegetation type rich in plant species, particularly forbs. Many of the forbs have underground storage organs which allow them to resprout rapidly after fires. A significant portion of this land was placed under commercial pine afforestation in the 1950s. The pine plantations have since been removed starting 17 years ago and restored to grasslands within a conservation area. We assessed the effects of plantations on grassland plant diversity and functional trait composition by sampling 64 circular quadrats of 5 m radius distributed equally in restored versus natural grasslands. The difference in plant diversity was dramatic with the natural grassland supporting 221 species of which 163 were forbs compared with 144 and only 73 forb species in restored grasslands. Major differences in species composition were recorded, especially for forb species. Natural grasslands were dominated by resprouters (130 species) but these were rare in the restored grasslands (36 species). Differences in plant species response to fire were also evident for the two grassland states. In contrast to coastal forest restoration studies in the same area which have shown near linear increases in woody species with time, restored grasslands showed no increase in forb species richness with increasing time since clear-felling of pines. Our results indicate that current methods for restoring these grasslands are inadequate and that restoring grasslands may be a lot harder than previously thought. Considerable effort should be made in conserving what is left of natural grasslands.
Article
For some species of forest-breeding birds, productivity is much higher in large forest fragments than in small forest fragments and is higher than the level needed to replace individuals within the fragment (sources). Thus large forest fragments potentially provide excess individuals to neighboring small fragments where productivity is much lower and not adequate for replacement (sinks). We used occurrence data and distances between putative sources and sinks for four species of forest birds with this pattern of demography in large and small forest fragments to predict occupancy in small fragments. For the Ovenbird ( Seiurus aurocapilla), Wood Thrush ( Hylocichla mustelina), Veery (Catharus fuscescens), and Rose-breasted Grosbeak (Pheucticus ludovicianus), distance from large woodlots was a significant predictor of occurrence in small woodlots. Distance from large woodlots did not predict occupancy of Red-eyed Vireos ( Vireo olivaceus), a species with no apparent difference in productivity in relation to fragment size. Neither vegetation features nor area of the small woodlots adequately explained patterns of occupancy for any species. These results suggest that maintenance of large, productive forest fragments benefit regional occurrence of forest-breeding birds by providing individuals to neighboring small woodlots. Limited reproduction in these small woodlots means that they may act as a reservoir for excess individuals in the case of catastrophic events that result in vacancies in source woodlots. Conservation and sound forest management of small forests should be directed particularly toward those closer to large regional forests.
Article
Long-term grassy woodland researchers explain how restoration of grassy ecosystems can be improved through an understanding of their key natural patterns and processes, and the ways these change during degradation.
Article
Summary • Biodiversity conservation of grasslands in the face of transformation and global climate change will depend mainly on rangelands because of insufficient conservation areas in regions suited to agriculture. Transformed vegetation (pastures, crops and plantations) is not expected to conserve much biodiversity. This study examined the impact of land use on the plant diversity and community composition of the southern Drakensberg grasslands in South Africa, which are threatened with complete transformation to pastures, crops and plantations. • The main land uses in this high rainfall region are: ranching or dairy production under private tenure using indigenous grassland, pastures (Eragrostis curvula, kikuyu and ryegrass) and maize; plantation forestry; communal tenure (maize and rangelands); and conservation. • Plant diversity and composition were assessed using Whittaker plots. Transformed cover types were depauperate in species and ranged from kikuyu (1·4 species m−2) and ryegrass (2·9), to pine plantation (3·1), E. curvula pasture (3·1), commercial maize (3·2) and communal maize (7·8). With the exception of pine plantations, these communities supported mostly exotic (50 of 70 species) or ruderal indigenous species and made little contribution to plant species conservation. Abandoned communal cropland reverted to an indigenous grassland almost devoid of exotic species within c. 20 years. • It was predicted that frequently cultivated sites (maize and ryegrass) would support less diversity than long-lived pastures (kikuyu and E. curvula). This was contradicted by the relatively high species diversity of communal maize fields, which was attributed to a lack of herbicides, and the depauperate communities of kikuyu and of E. curvula pasture, which were attributed, respectively, to a dense growth form and a severe mowing regime. • Pine plantations harboured fourfold more indigenous species per plot (27) than other transformed types. Species were mostly shade-tolerant grassland relics that had persisted for 12 years since planting, and some forest colonizers. Indigenous species were unlikely to be maintained because of aggressive invasion by the exotic Rubus cuneifolius and severe disturbance associated with tree harvest and replanting. • The richness of indigenous grasslands was expected to differ in response to grazing pressure but they differed only in composition. Grasslands were dominated by grasses, despite the richness of herbaceous species. The dominance of Themeda triandra was reduced under livestock grazing in favour of more grazing-tolerant species. Exotic species were inconspicuous except for the dicotyledon Richardia brasiliensis, a subdominant under communal grazing. • Southern Drakensberg grasslands are probably now stocked with livestock six- to 35-fold higher than during pre-settlement times. A grassland protected for c. 50 years supported twofold greater richness (101 species plot−1) than grazed grasslands, suggesting that a 150-year history of increased mammalian grazing had already reduced plant diversity. • Synthesis and applications. Land acquisition is costly, thus conservation of plant diversity in the southern Drakensberg requires a policy that inhibits transformation of rangelands. This can be achieved by enhancing their economic viability without changing the vegetation composition. Their inherent value must be recognized, such as for water production. The viability of commercial ranches can be improved by increasing their size. Conservation efforts need to be focused on plant taxa that only occur on unprotected rangelands. Journal of Applied Ecology (2005) doi: 10.1111/j.1365-2664.2005.01065.x
Article
The Mediterranean area is one of the most significantly altered hotspots on Earth, since it has been intensively affected by human activity for millennia. As a result, only 4.7% of its primary vegetation remained unaltered and the landscape has been repeatedly transformed. In this paper, we aimed at detecting both the direction and the rate of landscape change focusing on the effects of human activity on the environmental heterogeneity of the Mediterranean landscape under study. In particular, we carried out an analysis of landscape changes occurred in a Mediterranean area from 1954 to 2000, by means of a comparative examination of a historical and a recent land use map. Land use changes have been quantified by landscape metrics coupled with topographical information. Results underline: i) a general homogenisation of the landscape, ii) modification of the arrangements for exploitation of the territory, particularly in the plain areas, iii) a trend of recovery of the territory by the forest to the detriment of semi-natural and agricultural areas in hilly and mountain parts. The analysis of the complex phenomena related to land use changes can be a useful tool to define effective strategies for natural resources management and biodiversity conservation.
Article
The ability to predict which areas of conservation importance are most vulnerable to transformation and to rank the relative damage that transforming land uses could cause to biodiversity are important components of an effective and realistic conservation planning process. We used the South African grassland biome as a case study to illustrate the assessment of vulnerability to land-use transformation through the construction of a “threat map.” We identified the dominant transforming land uses and created suitability models based on area appropriateness for each. Land uses were scored according to their expected relative impacts on biodiversity, with a framework that included compositional, structural, and functional components. This information, once combined, resulted in a map that highlighted the areas most vulnerable to transformation in terms of the likelihood of their transformation and the impact on their biodiversity. We propose that such an analysis of the threat of transformation, in combination with species-representation approaches, will aid the integration of conservation planning theory and decision making. This approach can be applied at any scale and in any region with a robustness and accuracy dependent on data quality, resultant suitability models, and comprehension of how land uses affect an area's biodiversity.
Article
It is important to understand the relative effects of landscape habitat loss, habitat fragmentation, and matrix quality on biodiversity, so that potential management options can be appropriately ranked. However, their effects and relative importance may change with the size of the landscape considered because the multiple (and potentially conflicting) ecological processes that are influenced by landscape structure occur at different spatial scales (e.g. dispersal, predation, foraging). We estimated the relative effects of habitat loss, habitat fragmentation, and matrix quality (measured as the amount of forest, the proportion of forest area contained in large core forests, and the density of roads respectively) on fragmentation-sensitive forest birds in southern Ontario, Canada using a range of landscape sizes (0.8–310 km2). We used three complementary statistical approaches to estimate relative effects of these correlated landscape factors – 1) multiple regression, 2) information theoretic (AIC) estimates of the most parsimonious model, and 3) multi-model inference to average effects across all supported models. We controlled for spatial autocorrelation, local habitat, roadside sampling bias, time of day, season, habitat heterogeneity, and the interaction between the effects of habitat amount and fragmentation. We found that relative effects of habitat amount and fragmentation were scale dependent; habitat amount had a consistently positive effect that was consistent over more than two orders of magnitude in landscape area (~1–300 km2). In contrast, the effects of habitat fragmentation depended on the size of the landscape considered. Indeed, for veery Catharus fuscescens, habitat fragmentation had positive effects at one scale and negative effects at another. The effects of matrix quality were generally weak and changed little with scale. For the number of fragmentation sensitive species and the presence of veery, habitat amount was most important in large landscapes and habitat fragmentation in small landscapes but for the presence of ovenbird Seiurus aurocapilla, habitat amount was most important at all scales.
Article
While studies have found that bat abundance is positively related to the amount of forest cover in a landscape, the effects of forest fragmentation (breaking apart of forest, independent of amount) are less certain, with some indirect evidence for positive effects of fragmentation. However, in most of these studies, the variables used to quantify fragmentation are confounded with forest amount, making it difficult to interpret the results. The purpose of this study was to examine how forest amount and forest fragmentation independently affect bat abundance. We conducted acoustic bat surveys at the centers of 22 landscapes throughout eastern Ontario, Canada, where landscapes were chosen to avoid a correlation between forest amount and forest fragmentation (number of patches) at multiple spatial scales, while simultaneously controlling for other variables that could affect bat activity. We found that the effects of forest amount on bat relative abundance were mixed across species (positive for Lasiurus borealis, negative for Perimyotis subflavus and Lasionycteris noctivagans). When there was evidence for an effect of forest fragmentation, independent of forest amount, on bat relative abundance, the effect was positive (Myotis septentrionalis, Myotis lucifugus and Lasiurus borealis). We suggest that the mechanism driving the positive responses to fragmentation is higher landscape complementation in more fragmented landscapes; that is, increased access to both foraging and roosting sites for these bat species. We conclude that fragmented landscapes that maximize complementation between roosting and foraging sites should support a higher diversity and abundance of bats. KeywordsLandscape structure–Landscape composition–Landscape configuration–Spatial heterogeneity–Habitat loss–Habitat fragmentation–Resource proximity–Multi-scale analysis–Inter-patch movement–Chiroptera
Article
Landscapes are constantly changing, both ecologically and culturally, and the vectors of change occur over many time scales. In order to plan landscapes, they must be understood within their spatial and temporal contexts. This paper argues that the inevitable dynamism in a landscape requires planning to explain and to deal with change. However, planning has been slow to do this, in part because it is inadequately equipped to analyze both rapid change and gradual evolution. A landscape history exposes the evolutionary patterns of a specific landscape by revealing its ecological stages, cultural periods, and keystone processes. Such a history can be a valuable tool as it has the potential to improve description, prediction, and prescription in landscape planning.In proposing landscape history as a tool for planning, I specifically address four questions. Why is this tool needed in landscape planning? What form should landscape history take? What are the obstacles to acquiring good landscape histories? And, what are the potential benefits of using history in landscape planning? To illustrate this proposition, I draw from an example of landscape history developed for Long Pond, Pennsylvania.
Article
A multi-scale, object-based analysis of a Quickbird satellite image has been carried out to delineate forest vegetation polygons in a natural forest in Northern Greece. Following a multi-resolution segmentation, a classification tree was developed and compared using a nearest neighbour classifier for the assignment of image segments to classes. Additionally, texture images derived from local indicators of spatial association were calculated and used to improve the classification.The best results were obtained when texture images were considered in the classification sequence, however, the accuracy of the final map did not exceed 80%. The classification tree yielded better results than the nearest neighbour algorithm. Overall, the object-based classification approach presented both advantages and limitations, which have to be considered prior to its operational use in mapping Mediterranean forest ecosystems.
Article
The estimation of the road edge effect is useful to understand changes induced by the road network on ecosystems. Road networks on islands may break ecosystem integrity through microclimate edge effects, which are known to be associated with disturbances to animal and plant communities. Road edge effects have been scarcely studied on oceanic islands. In this paper we studied road edge effects on microclimate and canopy structure in laurel and pine forests in Tenerife (Canary Islands). We assessed depth of road edge effect for temperature at four vertical layers (soil, litter and air at 5 cm and 1.3 m above ground), light intensity, canopy cover and height, in transects running from narrow (6–7 m width) asphalt roads and dust trails to 100 m to the interior of both forests. We used an ANOVA procedure with Helmert difference contrasts to identify the distances along transects over which edge effects were significant. We detected significant gradients for most parameters but they were consistently narrow both within and between forests. In the laurel forest, we detected highly significant gradients for soil temperature, light, and canopy cover and height in both asphalt and unpaved roads. In the pine forest, we detected a highly significant gradient for soil temperature at asphalt roads, and a significant light gradient for both asphalt and unpaved roads. From the road edge to the forest interior, significant temperature changes persisted for only 3 m, light variation persisted for 6 m, and canopy cover and height changed significantly within the first 10 m. Asphalt roads and dust trails revealed different patterns of variation for temperature between edge and interior. No differences were found between the two types of roads in edge-interior trends for light or canopy structure. The abruptness of microclimate and canopy gradients was slightly higher in the laurel forest than in the pine forest, caused by a higher edge contrast in the former. The depth of the road edge effect found in laurel and pine forests was small, but it could have cumulative effects on forest microclimate and forest associated biota at the island scale. Such changes deserve attention by local road managers for planning and design purposes.
Article
Roads and topography can determine patterns of land use and distribution of forest cover, particularly in tropical regions. We evaluated how road density, land use, and topography affected forest fragmentation, deforestation and forest regrowth in a Brazilian Atlantic Forest region near the city of São Paulo. We mapped roads and land use/land cover for three years (1962, 1981 and 2000) from historical aerial photographs, and summarized the distribution of roads, land use/land cover and topography within a grid of 94 non-overlapping 100 ha squares. We used generalized least squares regression models for data analysis. Our models showed that forest fragmentation and deforestation depended on topography, land use and road density, whereas forest regrowth depended primarily on land use. However, the relationships between these variables and forest dynamics changed in the two studied periods; land use and slope were the strongest predictors from 1962 to 1981, and past (1962) road density and land use were the strongest predictors for the following period (1981–2000). Roads had the strongest relationship with deforestation and forest fragmentation when the expansions of agriculture and buildings were limited to already deforested areas, and when there was a rapid expansion of development, under influence of São Paulo city. Furthermore, the past (1962) road network was more important than the recent road network (1981) when explaining forest dynamics between 1981 and 2000, suggesting a long-term effect of roads. Roads are permanent scars on the landscape and facilitate deforestation and forest fragmentation due to increased accessibility and land valorization, which control land-use and land-cover dynamics. Topography directly affected deforestation, agriculture and road expansion, mainly between 1962 and 1981. Forest are thus in peril where there are more roads, and long-term conservation strategies should consider ways to mitigate roads as permanent landscape features and drivers facilitators of deforestation and forest fragmentation.
Article
Given the potentially negative effects of forest fragmentation on biodiversity, governments and management agencies have sought generic landscape measures of forest fragmentation to monitor changes in forest cover—measures that also may be informative for decisions relating to changes in biodiversity. In this paper, we discuss issues relating to the evaluation of landscape surrogate measures and their usefulness as ecological indicators. We illustrate some of these points by a detailed examination of statistical relationships among several target responses (defined as the occurrence of particular species), and a selection of landscape surrogate measures in two forest regions of southeastern Australia.There was no evidence in our data that surrogate landscape measures have generic applicability for the conservation of large sets of species. Although landscape surrogates may be useful where the aim is to quantify current landscape patterns from a human perspective or to monitor the extent and rate of change in that pattern over time, they may not have biological and statistical significance for particular elements of the biota. There is a need for a clear definition of units and measures, a need to be aware of redundancy among potential surrogates, and a need for the establishment of a framework for rigorously evaluating ecological indicators.