Mediterranean forest bird communities and the role of landscape heterogeneity in space and time
... Wildlife in cities depends on the maintenance of uses and human activities whose socioeconomic viability and social acceptance should be taken into account. The so-called socioecological ap-proach to conservation (Mace 2014;Díaz, Demissew, et al. 2015), which integrates ecological and socioeconomic goals into management plans, is starting to be applied in agricultural and forestry settings with promising results (Fischer et al. 2012;Campos et al. 2013;Díaz and Concepción 2016;Brotons et al. 2018). Expanding this approach to urban systems requires sampling and analytical frameworks to diagnose causes of wildlife population changes, protocols to derive management proposals aimed at counteracting causes, and scientific monitoring of the performance of management actions to improve them following the principles of adaptive management (Díaz and Concepción 2016). ...
We human beings are becoming urban citizens. More and more people spend their lives in urban environments, so that the conservation and improvement of urban biodiversity is an increasingly hot topic. On the one hand, as cities grow bigger and more populated they can become more hostile for some birds, but cities can also be safer than the surrounding rural environment for others. On the other hand, factors affecting negatively or positively wild birds may also influence human’s health, either directly (e.g. pollution) or indirectly (enjoying wildlife diversity could contribute to improve our wellbeing). We review current state of knowledge on factors determining the abundance, diversity and health of urban birds, and derive methods for diagnosing what factors are acting in each particular case. Diagnoses are essential to design effective and efficient ways to manage urban bird diversity and improve it adaptively. We also address whether factors affecting birds could affect citizenship directly, so that urban birds can be used as indicators for healthy urban environments. Investigating and improving urban bird life can also improve human wellbeing through people’s involvement on citizen science programs. Monitoring approaches taken by both authorities and NGOs are still too general and badly designed, but collaboration among scientist, volunteers and authorities will contribute to make them effective. Improving citizen involvement will in turn contribute to improve urban bird diversity, closing a win-win loop for both people and wildlife wellbeing.
... This is the case of, for example, the shift from dehesas to dehesas + afforestation, which has been shown to improve number of species and species mobility (i.e. birds and mammals) (Sánchez-Oliver et al. 2015;Brotons et al. 2018). Other species that rely on woody vegetation (e.g., insects) are likely to require more specialised habitat conditions (for example, using a subset of woody vegetation or grasslands) and/or having special movement requirements that our resistance model does not take into account (e.g., roads are barriers to movement). ...
One of the research issues considered in landscape ecology is the fragmentation of landscapes, which is characterised by a great heterogeneity of land uses and shapes. The objective of this study was to investigate changes in landscape fragmentation and connectivity associated with the afforestation on agricultural land in two locations in southern Spain that was promoted by an EU scheme between 1990 and 2018. This was done using the Andalusia Land Cover Databases (1990 and 2018), along with the combination of two approaches with which to determinate the variation of fragmentation (Patch Analyst-ARCgis and LDTtool) and ecosystem connectivity (Graphab software). Afforestation on agricultural land represented significant change in land use in the two locations (Andevalo, Quercus ilex and Q. suber, 22,313.25 ha) and Guadix (Pinus halepensis, 2532.68 ha). Changes in fragmentation metrics reflected that landscape fragmentation increased as a consequence of afforestation, and a significate decrease in mean patch size (MPS) and mean patch edge (MPE) was observed over time in both locations in most land uses. Furthermore, afforestation increased connectivity for forest species, which was reflected in higher values of connectivity metrics (probability of connectivity and flux). The presence of low-cost pathways connecting patches suggested a reduction in the gap-crossing distance between forests, although the increase on fragmentation of forest patches there where an increase in forest connectivity that revealed favourable relationship between afforestation and landscape connectivity functions. The European Community policies aimed at the afforestation of marginal agricultural land could, therefore, play an important role in improving the ecological functions of agricultural landscapes.
Quarrying activities cause profound modifications on ecosystems, such as removal of vegetation cover, biodiversity loss and depletion of ecosystem services. Ecological restoration stands as a solution to revert such effects. Concomitantly, awareness is currently being given on ecosystem services and ecological processes to evaluate restoration efficiency.
The objective of the study was to assess restoration success in a quarry subjected to restoration practices for the last 40 years involving the plantation of native Mediterranean vegetation and the non-native Aleppo pine Pinus halepensis. The study was carried out by assessing the effectiveness of seed dispersal service provided by birds in the restored quarry by comparing this service to neighbouring natural (shrubland) and other semi-natural areas (oak-pine mixed open and Aleppo pine forest) present at the landscape. For this purpose, we explored bird composition structure and seed dispersal networks using point counts and faecal samples of mist-netted birds. We also collected vegetation structure data and explored its effect on bird community composition.
Our results showed that bird abundance in the restored quarry was significantly lower, and its bird community was compositionally different than natural shrubland and semi-natural areas. For instance, seed-dispersing birds, woody and shrub/ground foragers and partially migrators were the most affected groups at the restored area. Bird community composition and their traits were likely driven by vegetation characteristics, with higher native vegetation cover and fruit richness promoting higher bird abundance and Aleppo pine cover negatively influencing seed-dispersing birds. Concurrently, seed dispersal network in the restored quarry was less complex than in other areas.
Seed dispersal services in the restored quarry were below the reported values for neighbouring natural and semi-natural areas and are likely driven by the low abundance of seed-dispersing birds. We consider that the causes affecting this group's low abundance can be related to revegetation measures favouring Aleppo pine, combined with a shallow soil depth and poor soil quality, which may have constrained native vegetation development.
We conclude that seed dispersal services at the quarry are depleted, which may suggest a low restoration success concerning ecosystem functioning. Our results strengthen that quarry revegetation with non-native species must be avoided, since it alters bird community composition, and consequently, affects seed dispersal service provided by birds.
A four year study of the impact of fire on different types of Mediterranean vegetation has been carried out in the Eastern part of the Pyrenean range (Département des Pyrénées-Orientales, France).
Following fire, a number of transient plant species colonize the open ground, while the original vegetation regenerates from stumps, rhizomes or buried seeds. This results in an increase in species richness of the vegetation at this stage.
The time necessary for the bird communities to reach their pre-fire species composition and population levels differs in Cork-oak and Holm-oak forests. This takes three years in the first case, but is much slower in the second vegetation type. Bird-species richness is higher in the burned maquis during the second and third years following the fire.
The population densities of small mammal species, particularly that of Apodemus sylvaticus, can be higher in all burned areas during the second and third post-fire years, but population structures (age and sex ratios) are different.
Changes in the physical structure of the above-ground vegetation following the fire is apparently the major factor influencing the bird community, whereas the small mammal community is more influenced by modification of the litter and the subsequent changes in food and shelter availability.
Too many roads
Roads have done much to help humanity spread across the planet and maintain global movement and trade. However, roads also damage wild areas and rapidly contribute to habitat degradation and species loss. Ibisch et al. cataloged the world's roads. Though most of the world is not covered by roads, it is fragmented by them, with only 7% of land patches created by roads being greater than 100 km ² . Furthermore, environmental protection of roadless areas is insufficient, which could lead to further degradation of the world's remaining wildernesses.
Science , this issue p. 1423
The EU Common Agricultural Policy (CAP) has tried to counteract negative impacts of intensive agriculture on biodiversity and associated ecosystem services mostly by means of voluntary agri-environment schemes (AES). More recently, direct payments to farmers have been linked to the application of greening measures derived from previous AES experiences. AES and greening measures (CAP greening hereafter) have become the main farmland conservation tools in Europe due to large budgets and extensive application. Effectiveness of greening measures (i.e. differences in biodiversity or ecosystem service measurements that can be attributed to the application of such measures) has not yet been evaluated thoroughly, whereas evaluations of AES effectiveness—although still not systematically incorporated into policy design—have lead to the conclusion that AES generally increase farmland biodiversity at the field scale with effect sizes that depend on the surrounding landscape. On the basis of knowledge gaps derived from available AES evaluations, we
29 develop a five-stage hierarchical decision-making proposal to improve the effectiveness of CAP greening. Effectiveness is difficult to predict because non-linear relationships between diversity and land-use intensity at both field and landscape scales constrain and modulate it. Besides, relationships vary regionally and among target species, species groups and ecosystem services. Hence, regional targeting, landscape-scale thinking, and learning processes linked to systematic evaluations are key elements in any decision-making procedure aimed at improving this effectiveness. Ideas and guidelines developed here will help to develop regionally adapted measures aimed at overcoming constraints to CAP greening effectiveness and improving farmland conservation policies.
Fire, a frequent phenomenon in Mediterranean landscapes, is a major ecological disturbance in terrestrial ecosystems. We hypothesized that bird communities undergo greater seasonal changes in burnt areas than in unbumt ones. Using the point-count method we assessed bird species composition and abundance in three zones (unbumt, burnt in 1982, and burnt in 1994) during the breeding and wintering seasons of 1997 and 1998.
From the breeding to the wintering seasons, burnt zones showed an increase in forest species, whereas the bird community of the unbumt zone remained stable in the gradient open-forest species. Moreover, the seasonal turnover of communities was higher in burnt zones than in the unbumt ones, although this did not imply that the former varied in richness through the year. The pattern of bird abundance in the unbumt zone was similar during the two study years, in contrast with that of burnt zones, suggesting higher annual cyclicity in resource availability in unbumt areas. These findings suggest that fire increases the seasonal variability of bird communities.
There is a longstanding debate regarding the need for ecology to develop consistent terminology. On one hand, consistent terminology would aid in synthesizing results between studies and ease communication of results. On the other hand, there is no proof that standardizing terminology is necessary and it could limit the scope of research in certain fields. This article is the first to provide evidence that terminology can influence results of ecological studies. We find that researchers are classifying ‘woodland birds’ inconsistently because of their research aims and linguistic uncertainty. Importantly, we show that these inconsistencies introduce a systematic bias to results. We argue that using inconsistent terms can bias the results of studies, thereby harming the field of ecology, because scientific progress relies on the ability to synthesize information from multiple studies.
Farmland birds are reported to decrease strongly in numbers throughout Europe over the last 30 years.
Agricultural land abandonment is considered amongst the main drivers for the negative population trends.
This process has been studied widely in Western Europe but the evidence for Central and Eastern Europe
is limited. We examined the differences in the bird community structure among several secondary succession
stages after land abandonment (since the 1940s) in central Bulgaria. Our results demonstrated
that avian species richness and diversity decreased with the secondary succession, while no significant
difference in the overall bird abundance was observed. The shifts in bird community pattern were mainly
related to grassland specialists, which decreased in species richness, diversity and abundance along the
succession gradient. Birds of European Conservation Concern were also negatively affected by the woody
vegetation overgrowth. We think that in order to stop and reverse the loss of farmland bird diversity in the
low-productive mountainous regions of Bulgaria, the rural sustainable development should be reinforced
by implementation of agri-environmental and other policy measures that encourage effectively smallscale
extensive farming.
In extensive low input farming and in agroforestry systems, the importance for biodiversity of managed productive fields with respect to unmanaged marginal habitats that occupy a low proportion of farm surface, is still poorly understood, contrasting with the well-known key importance of marginal habitats in intensive systems. We analyzed the importance of open and wood pastures and marginal habitats for species richness of Iberian dehesas in Central-Western Spain. We sampled 155 plots classified into 9 general habitat categories: wood pastures (n = 41 plots); open pastures dominated by annual plants (n = 11), by perennial plants (n = 15) and co-dominated by annuals and perennial plants (n = 16); shrublands (n = 19); agricultural crops (n = 12); herbaceous strips (n = 10); woody strips (n = 11); and water bodies (n = 10). In each plot we measured the abundance and species richness of four taxonomic groups: vascular plants, bees, spiders, and earthworms. We detected 431 plant species (37 ± 2.5 CI95 in 100 m2 on average), 60 bee species (3.1 ± 1.1 in 600 m2), 128 spider species (7.4 ± 1.2 in 1.5 m2) and 18 earthworm species (2.5 ± 1.0 in 0.27 m2) in 145 sampling plots. Wood pastures supported fewer species of spiders and earthworms at the plot level, but more plants and earthworm species at the landscape level than open pastures. The low proportion of shared species among habitats and among plots within each habitat type, and the high proportion of species found in unique plots or habitats indicated that every habitat contributes to farm biodiversity. Overall, our extensive survey confirms the hypothesis that the high diversity of dehesas depends on the coexistence within farms of a wide mosaic of habitats, including marginal habitats, which seemed to harbor a disproportionately high number of species as compared to their small extent. Results support policy measures for the maintenance of farm keystone structures such as linear features, small wood/shrub patches and ponds, and reveal that these measures should not be exclusively applied to more intensive farming systems.
Major conservation efforts in human-dominated systems, such as farmland, have focused on the establishment of subsidies and compensation promoting low-impact management practices to reverse the impacts of conservation threats in the short term (reactive approaches). In this study, we discuss how a different way of framing conservation policy (proactive approaches)could lead to fundamentally different long-term conservation outcomes. We define proactive approaches as those not necessarily including measures directly addressing the threats affecting biodiversity, but promoting transitions from current scenarios in which species are threatened to new states in which the threat is no longer present. We illustrate reactive and proactive approaches using as a case study two contrasting conservation frameworks for a vulnerable farmland bird, the Montagu's harrier (Circus pygargus) in north-eastern Spain. This example shows that reactive approaches can lead to “conservation traps”, which we defined as situations where the application of biologically-focused actions in response to conservation problems results in an unsustainable need to perpetuate the implementation of those actions. Our aim is to offer a fresh perspective on biodiversity conservation in human-dominated systems and to stimulate alternative, more holistic approaches in conservation promoting transitions to new states not requiring long-term active and costly conservation action.This article is protected by copyright. All rights reserved.
Climate, land use and fire are strong determinants of plant diversity, potentially resulting in local extinctions, including rare endemic and economically valuable species. While climate and land use are decisive for vegetation composition and thus the species pool, fire disturbance can lead to landscape fragmentation, affecting the provisioning of important ecosystem services such as timber and raw natural resources. We use multi-proxy palaeoecological data with high taxonomic and temporal resolution across an environmental gradient to assess the long-term impact of major climate shifts, land use and fire disturbance on past vegetation openness and plant diversity (evenness and richness). Evenness of taxa is inferred by calculating the probability of interspecific encounter (PIE) of pollen and spores and species richness by palynological richness (PRI). To account for evenness distortions of PRI, we developed a new palaeodiversity measure, which is evenness-detrended palynological richness (DE-PRI). Reconstructed species richness increases from north to south regardless of time, mirroring the biodiversity increase across the gradient from temperate deciduous to subtropical evergreen vegetation. Climatic changes after the end of the last ice age contributed to biodiversity dynamics, usually by promoting species richness and evenness in response to warming. The data reveal that the promotion of diverse open-land ecosystems increased when human disturbance became determinant, while forests became less diverse. Our results imply that the today's biodiversity has been shaped by anthropogenic forcing over the millennia. Future management strategies aiming at a successful conservation of biodiversity should therefore consider the millennia-lasting role of anthropogenic fire and human activities.
asserine bird communities of Iberian dehesas: a review.--- The Iberian dehesas are a man--made habitat composed of scattered oaks (Quercus spp.) and extensive grass cover occupying three million ha in south-- western Iberia. This paper compares the structure of the passerine bird communities in this region with other bird assemblages of Iberian woodlands. Although forest bird numbers in the southern half of the Iberian peninsula are decreasing, the dehesas show the highest richness in breeding birds, seemingly as the result of the increased presence of border and open--habitat birds. A low intra--habitat turnover of species was observed in the dehesas, with birds recorded at a sampling point accounting for a high percentage of the total richness of the community. This can be related to the low spatial patchiness of this habitat. In winter, the dehesas continued to maintain many bird species, but showed bird densities similar to other woodlands. This pattern, as well as the scarcity of some common forest passerines during the breeding period, could result from the removal of the shrub layer typical of Mediterranean woodlands.
Forest cover has increased world-wide over the last decade despite continuous forest fragmentation. However, a lack of long-term demographic data hinders our understanding of the spatial dynamics of colonization in remnant populations inhabiting recently protected areas or set-aside rural lands.We investigated the population expansion of the Phoenician juniper (Juniperus phoenicea subsp. turbinata), which is an endozoochorous Mediterranean tree species inhabiting landscapes that have been managed for many centuries. By combining the photointerpretation of aerial photos that have been taken over the last 50 years with in situ sampling and spatial analyses of replicated plots, we estimated the population growth over the chronosequence; identified hotspots, coldspots and outliers of regeneration; and assessed the roles of key environmental factors in driving demographic expansion patterns, including elevation, initial density and distance to remnant forests.Ecological factors leading to seed limitation, such as initial plant density, are expected to drive colonization patterns at the early stages. Factors mediating the competition for limiting resources, such as water availability, would prevail at later stages of expansion. We further expect that nucleated colonization patterns emerge driven by vertebrate seed dispersal.The photointerpretation of aerial images in combination with in situ measurements has yielded reliable density data. Overall, our results show a marked demographic expansion during the first decade followed by a period of steady and heterogeneous population growth with signs of local population decline. We found evidence of nucleated establishment patterns as expected for an endozoochorous species. Hotspots and outliers of regeneration emerged throughout the study chronosequence, whereas coldspots of regeneration only appeared at advanced colonization stages. Factors influencing dispersal limitation had contrasting effects at different colonization stages, and the initial density influenced population growth at various spatial scales.Synthesis. The photointerpretation of aerial images shows that the influence of dispersal limitation versus factors mediating competitive responses changes throughout colonization stages. Whereas dispersal limitation is the main factor influencing colonization at early stages, competition for local resources controls population growth at later stages. Therefore, long-term studies are required to capture the overall combined influence of key ecological factors in shaping long-term spatial demographic trends.
Understanding how fire weather danger indices changed in the past and how
such changes affected forest fire activity is important in a changing
climate. We used the Canadian Fire Weather Index (FWI), calculated from two
reanalysis data sets, ERA-40 and ERA Interim, to examine the temporal
variation of forest fire danger in Europe in 1960–2012. Additionally, we
used national forest fire statistics from Greece, Spain and Finland to
examine the relationship between fire danger and fires. There is no obvious
trend in fire danger for the time period covered by ERA-40 (1960–1999),
whereas for the period 1980–2012 covered by ERA Interim, the mean FWI shows
an increasing trend for southern and eastern Europe which is significant at the
99% confidence level. The cross correlations calculated at the national level
in Greece, Spain and Finland between total area burned and mean FWI of the
current season is of the order of 0.6, demonstrating the extent to which the current
fire-season weather can explain forest fires. To summarize, fire risk is
multifaceted, and while climate is a major determinant, other factors can
contribute to it, either positively or negatively.
Intra- and interspecific spatially contagious seed dispersal has far-reaching implications for plant recruitment, distribution, and community assemblage. However, logistical and analytical limitations have curtailed our understanding concerning the mechanisms and resulting spatial patterns of contagious seed dispersal in most systems and, especially, in complex seed-disperser networks. We investigated mechanisms of seed aggregation using techniques of spatial point pattern analysis and extensive data sets on mutispecific endozoochorous seed rain generated by five frugivorous mammals in three Mediterranean shrublands over two seasons. Our novel analytical approach revealed three hierarchical and complementary mechanisms of seed aggregation acting at different levels (fecal samples, seeds, pairs of seed species) and spatial scales. First, the three local guilds of frugivores tended to deliver their feces highly aggregated at small and intermediate spatial scales, and the overall pattern of fecal delivery could be described well by a nested double-cluster Thomas process. Second, once the strong observed fecal aggregation was accounted for, the distribution of mammal feces containing seeds was clustered within the pattern of all feces (i.e., with and without seeds), and the density of fecal samples containing seeds was higher than expected around other feces containing seeds in two out of the three studied seed-disperser networks. Finally, at a finer level, mark correlation analyses revealed that for some plant species pairs, the number of dispersed seeds was positively associated either at small or large spatial scales. Despite the relatively invariant patterning of nested double-clustering, some attributes of endozoochorous seed rain (e.g., intensity, scales of aggregation) were variable among study sites due to changes in the ecological context in which seeds and their dispersers interact. Our investigation disentangles for the first time the hierarchy of synergic mechanisms of spatially contagious seed dispersal at a range of spatial scales in complex seed-disperser networks, thus providing a robust and widely applicable framework for future studies.
Evolutionary molecular studies of island radiations may lead to insights in the role of vicariance, founder events, population size and drift in the processes of population differentiation. We evaluate the degree of population genetic differentiation and fixation of the Canary Islands blue tit subspecies complex using microsatellite markers and aim to get insights in the population history using coalescence based methods. The Canary Island populations were strongly genetically differentiated and had reduced diversity with pronounced fixation including many private alleles. In population structure models, the relationship between the central island populations (La Gomera, Tenerife and Gran Canaria) and El Hierro was difficult to disentangle whereas the two European populations showed consistent clustering, the two eastern islands (Fuerteventura and Lanzarote) and Morocco weak clustering, and La Palma a consistent unique lineage. Coalescence based models suggested that the European mainland forms an outgroup to the Afrocanarian population, a split between the western island group (La Palma and El Hierro) and the central island group, and recent splits between the three central islands, and between the two eastern islands and Morocco, respectively. It is clear that strong genetic drift and low level of concurrent gene flow among populations have shaped complex allelic patterns of fixation and skewed frequencies over the archipelago. However, understanding the population history remains challenging; in particular, the pattern of extreme divergence with low genetic diversity and yet unique genetic material in the Canary Island system requires an explanation. A potential scenario is population contractions of a historically large and genetically variable Afrocanarian population, with vicariance and drift following in the wake. The suggestion from sequence-based analyses of a Pleistocene extinction of a substantial part of North Africa and a Pleistocene/Holocene eastward re-colonisation of western North Africa from the Canaries remains possible.
Forests hold a significant proportion of global biodiversity and terrestrial carbon stocks and are at the forefront of human-induced global change. The dynamics and distribution of forest vegetation determines the habitat for other organisms, and regulates the delivery of ecosystem services, including carbon storage. Presenting recent research across temperate and tropical ecosystems, this volume synthesises the numerous ways that forests are responding to global change and includes perspectives on: • the role of forests in the global carbon and energy budgets • historical patterns of forest change and diversification • contemporary mechanisms of community assembly and implications of underlying drivers of global change • the ways in which forests supply ecosystem services that support human lives. The chapters represent case studies drawn from the authors' expertise, highlighting exciting new research and providing information that will be valuable to academics, students, researchers and practitioners with an interest in this field.
Plants are able to compensate for loss of tissue due to herbivores at a variety of spatial and temporal scales, masking detrimental effects of herbivory on plant fitness at these scales. The stressing effect of herbivory could also produce instability in the development of plant modules, and measures of such instability may reflect the fitness consequences of herbivory if instability is related to components of plant fitness. We analyse the relationships between herbivory, developmental instability and produc-tion of female flowers and fruits of holm oak Quercus ilex trees by means of herbivore removal experiments. Removal of leaf herbivores reduced herbivory rates at the tree level, but had no effect on mean production of female flowers or mature fruits, whereas herbivory tended to enhance flower production and had no effect on fruit abortion at the shoot level. Differences in herbivory levels between shoots of the same branch did not affect the size and fluctuating asymmetry of intact leaves. These results indicate compensation for herbivory at the tree level and over-compensation at the shoot level in terms of allocation of resources to female flower production. Removal of insect herbivores produced an increase in the mean developmental instability of leaves at the tree level in the year following the insecticide treatment, and there was a direct relationship between herbivory rates in the current year and leaf fluctuating asymmetry the following year irrespective of herbivore removal treatment. Finally, the production of pistillate flowers and fruits by trees was inversely related to the mean fluctuating asymmetry of leaves growing the same year. Leaf fluctuating asymmetry was thus an estimator of the stressing effects of herbivory on adult trees, an effect that was delayed to the following year. As leaf fluctuating asymmetry was also related to tree fecundity, asymmetry levels provided a sensitive measure of plant performance under conditions of compensatory responses to herbivory.
Land abandonment is a widespread phenomenon in agricultural systems, especially in former communist countries of Eastern and South-eastern Europe. Moreover, Croatia was affected by acts of war which enhanced the depopulation of marginal areas impelling further land abandonment. Agricultural landscapes in Croatia are highly parcelled with various proportions of forest habitats due to traditional smallholder farming systems. Secondary successions as a consequence of land abandonment affect farmland birds that are among the most endangered bird species in Europe. We examined bird communities along a habitat gradient in heterogeneous agricultural landscapes. We used the share of woody vegetation cover as a proxy measure for land abandonment that we classified in four classes. Our results showed no significant Shannon Wiener Index differences of bird communities along the land abandonment gradient. However, there were differences in abundances when we examined bird guilds such as farmland, forest and "other" birds separately. However, the conservation value of each of the four land abandonment classes did not show significant differences. We extracted single bird species such as the Yellowhammer (Emberiza citrinella), Red-backed Shrike (Lanius collurio), Song Thrush (Turdus philomelos) and European Robin (Erithacus rubecula) as potential indicator species for the four examined land abandonment levels. With these four species we successfully modelled the distribution of the recorded bird assemblages at the plot level along the four vegetation succession stages. We emphasized the need to develop new and integrative land use management concepts for areas affected by land abandonment in order to formulate sound conservation policy.
Agricultural land abandonment is one of the main drivers of land use change, leading to various responses of farmland ecological communities. In an effort to better understand the effect of agricultural land abandonment on passerine bird communities, we sampled 20 randomly selected sites [1 km x 1 km] in remote Greek mountains, reflecting an abandonment gradient, in terms of forest encroachment. We sampled 169 plots using the point count method of fixed distance (47 passerine species), and we investigated bird diversity and community structure turnover along the gradient. We found that grazing intensity has a beneficial effect hampering forest encroachment that follows progressively land abandonment. Habitat composition changes gradually with forests developing at the expense of open meadows and heterogeneous grasslands. Forest encroachment has a significant negative effect on bird diversity and species richness, affecting in particular typical farmland and Mediterranean shrubland species. Birds form five distinct ecological clusters after land abandonment: species mostly found in pinewoods and cavity-dwelling species, species that prefer open forests forest edges or ecotones, species that prefer shrubland or open habitats with scattered woody vegetation, Mediterranean farmland birds that prefer semi-open habitats with hedges and/or woodlots and generalist forest-dwelling or shrubland species. We extracted a set of 22 species well representing the above ecological communities, as a new monitoring tool for agricultural land use change and conservation. We suggest that the maintenance of rural mosaics should be included in the priorities of agricultural policy for farmland bird diversity conservation.
Mediterranean landscapes are suffering two opposing forces leading to large-scale changes in species distribution: land abandonment of less productive areas and an increase in wildfire impact. Here, we test the hypothesis that fires occurred in recent decades drive the pattern of expansion of early-successional, open-habitat bird species by aiding in the process of colonisation of newly burnt areas. The study was carried out in Catalonia (NE Spain). We selected 44 burnt sites occurring between 2000 and 2005 to model colonisation patterns under different assumptions of potential colonisers’ sources and evaluated the colonisation estimates with empirical data on six bird species especially collected for this purpose. We first defined three landscape scenarios serving as surrogates of potential colonisers’ sources: open-habitats created by fire, shrublands and farmlands. Then, we used a parameter derived from a functional connectivity metric to estimate species colonization dynamics on the selected sites by each particular scenario. Finally, we evaluated our colonisation estimates with the species occurrence in the studied locations by using generalized linear mixed models. The occurrence of the focal species on the newly burnt sites was significantly related to the connectivity patterns described by both the recent fire history and the other open-habitat types generated by a different type of disturbance. We suggest that land use changes in recent decades have produced a shift in the relative importance of habitats acting as reservoirs for open-habitat bird species dynamics in Mediterranean areas. Before the middle of the twentieth century species’ reservoirs were probably constituted by relatively static open habitats (grassland and farmland), whereas afterwards they likely consist of a shifting mosaic of habitat patches where fire plays a key role as connectivity provider and largely contributes to the maintenance of species persistence.
This chapter (the pdf partly reproduces the text) illustrates the main trends of interlaced forces acting on the development of the Mediterranean landscape during the Holocene. The mosaic of habitats distributed in the Mediterranean basin has been continuously transformed by climatic changes occurring at a global scale during the early, mid and late Holocene. In the meantime, the environment has been exploited and the landscape shaped by different civilizations. Climate changes and human activities are observed through the lens of pollen found in terrestrial and marine sediment cores and in archaeological layers. Joint actions of increasing dryness, climate oscillations, and human impact are hard to disentangle, and this becomes particularly true after the mid-Holocene onset of Bronze Age cultures. Regional differences and similarities are reported for eastern, central and western Mediterranean, and for northern Africa and Sahara. The mixing of cultures accelerated the exchanges of ideas, technologies, raw materials and people along the coasts of this ‘great lake’, making the different civilizations linked between them as one network of regions belonging to the ‘Mediterranean culture’.
Oak woodlands have offered a welcoming environment for human
activities for tens of thousands of years, but how that history has unfolded has
many variations. The long-time collaboration that led to this book ran into complications
arising from the different meanings attached to many a term, including
struggles over the most appropriate title, settling on common units of measurement
and area, quantifying the woodland’s extent in Spain and California, and even in
deciding how many oaks constitute a woodland. Defining with anything
approaching international precision such terms as oak woodlands, oak woodland
ranches, and wooded dehesas is nuanced, and is compounded by distinctions in
culture and language. But our efforts to dovetail one inscrutable system with
another may offer insight into the relationship of humans with environments long
occupied and modified, as further shaped by location, history, and opportunity. In
15 chapters we offer a comparison of conservation and management on California
oak woodland ranches and in the dehesas of Spain, including economic, institutional,
ecological, spatial, and geographical aspects, from how to raise an Iberian
pig to what we can learn about oak woodlands with remote sensing.
High biodiversity in Spanish and California woodlands is due to the intermixing of habitat types and habitat elements. Dehesa management in Spain creates a mosaic of vegetation that includes trees, shrubs, and grasslands. Maintaining this diversity requires control of invasive shrubs, but sustaining the woodlands calls for periodic management to permit an encroachment of shrubs that foster oak regeneration. Californian oak woodlands are also high in biodiversity, but have been managed far less intensively, largely for acorns and game in the pre-contact period and for livestock grazing and game in current times. Shrub invasion is slower and less common than in Spain. The impacts of livestock on oak regeneration seems to vary across California’s very heterogeneous climatic and soil conditions. Just as biodiversity supports the multifunctional dehesa economy, the possibilities of income generation from biodiversity may be crucial to the sustenance of California oak woodland ranches, reducing conversion to intensive agriculture and urbanization.
Agricultural decline may pose an important threat to mountain biodiversity but it also constitutes a driving force of socio-economic transformation. The aim of this study is to investigate the implications of alternative agricultural policy scenarios on the sustainable development of Greek mountain areas using a case study approach (Zagori region, Greece). Two agricultural policy scenarios were explored and assessed against a list of sustainability objectives. Causal relationships among drivers of changes and sustainability objectives were explored using Network Analysis. Our analysis has shown that agricultural liberalisation is expected to have devastating effects on the development of the area and it was strongly opposed as an alternative future by the local stakeholders. The analysis of the driver's causal relationship has also revealed that in order to ensure the sustainable development of the area it is necessary to sustain low input extensive farming, to promote mild tourism development and to enhance the operational efficiency of the National Park. Moreover, in order to reconcile agricultural decline, biodiversity and sustainable development, policy-management recommendations must be drawn at multiple administrative levels and complementary policy interventions within and between levels are required. It is thus, important that EU agricultural policies are complemented by national-regional interventions in order to regulate the fragile balance between agriculture and tourism. Finally, this study has shown that the combination of scenario analysis and sustainability assessment can provide an efficient tool to inform management strategies for sustainable development.
Capsule Following recent introduction in Spain, Red‐billed Leiothrix have the potential to attain a wide distribution in Catalonia and probably in other parts of Europe.Aim To investigate past, present and potential distribution of this exotic species in Catalonia (northeast Iberian Peninsula).Methods We collected data on the species’ occurrence over the period 1992–2008 and used information obtained in other regions where it has previously established to produce hypotheses about the ecological processes that affect its population increase and range expansion. We then generated fine‐grained distribution maps covering the entire region for the periods 1992–2001 and 2002–2008, and for the species’ potential range according to its specific habitat requirements.Results Since being first detected in the wild in the Collserola Park, near the city of Barcelona, Red‐billed Leiothrix have expanded to neighbouring forested areas. The wild population is currently in a phase of exponential growth and, according to our habitat suitability model, the species’ potential distribution in Catalonia might be 36 times greater than at present.Conclusion Our results suggest that the Red‐billed Leiothrix has the potential to attain a widespread distribution over large regions of Europe in the near future. However, we discuss several factors that might affect these predictions.
Climate changes have profound effects on the distribution of numerous plant and animal species. However, whether and how different taxonomic groups are able to track climate changes at large spatial scales is still unclear. Here, we measure and compare the climatic debt accumulated by bird and butterfly communities at a European scale over two decades (1990-2008). We quantified the yearly change in community composition in response to climate change for 9,490 bird and 2,130 butterfly communities distributed across Europe. We show that changes in community composition are rapid but different between birds and butterflies and equivalent to a 37 and 114ĝ€‰km northward shift in bird and butterfly communities, respectively. We further found that, during the same period, the northward shift in temperature in Europe was even faster, so that the climatic debts of birds and butterflies correspond to a 212 and 135ĝ€‰km lag behind climate. Our results indicate both that birds and butterflies do not keep up with temperature increase and the accumulation of different climatic debts for these groups at national and continental scales.
Mediterranean forests are highly resilient to fires, showing a rapid recovery after disturbance. However, in some cases direct tree regeneration fails leading to radical changes in landscape composition. In this study, we evaluated the impact of landscape changes on the conservation value of bird species using the new landscape mosaic arising from non-direct regeneration after a fire. We used data from a large fire that occurred in central Catalonia (NE Spain) in 1998. The fire affected about 26,000 ha of a land mosaic mainly covered by Black Pine Pinus nigra forests and farmland dominated by cereal crops. We used line transects to estimate bird abundance and gathered information on dominant vegetation covers and landscape variables. Redundancy analysis (RDA) and generalized linear models were used to explore how the measured environmental variables explain bird species abundance and to analyze how post-fire heterogeneity in vegetation affected the conservation value of the bird community. Factors describing the main patterns in the post-fire landscape explained up to 31.2% of the total variability in bird community composition and described three main groups of bird species sharing similar ecological requirements. Additionally, 71% of the studied species significantly responded to one of the first three vegetation gradients distinguished in the study area. Finally, the conservation value of the bird community significantly decreased in areas dominated by Q. humilis resprouters and significantly increased in shrubland areas. Overall, our results suggest that large fires affecting non-direct regenerating forest types lead to a new and radically different mosaic landscape offering new opportunities to species with unfavourable European conservation status.
Teasing out how species respond to human-induced environmental changes has become a priority for addressing the challenges posed by the need to conserve biodiversity. Although land abandonment is widespread, the threat it can represent to biodiversity remains poorly understood. To address this issue, we used data from eight long-term studies in a region with widespread land abandonment that has been identified as a biodiversity hotspot, the north-west Mediterranean Basin. We conducted a multi-site analysis of how changes in species occurrence were affected by species' attributes (habitat preference, habitat breadth, migration strategy and latitudinal distribution). The analysis revealed a nested pattern in the effect of species attributes. Woodland and shrubland species showed the strongest increase, whereas no change in overall occurrence patterns was detected in farmland species. Residents increased significantly, especially those with a northern distribution, whereas migrants decreased significantly, especially farmland species with a narrow habitat breadth. Changes in species occurrence were also related to initial landscape composition, with larger increases in initially woodland or mixed landscapes. Woodland species increased in all landscape types, shrubland species increased only in mixed landscapes, and farmland species decreased more, although not significantly, in farmland landscapes. Our results strongly support the hypothesis that large-scale habitat changes associated mainly with land abandonment are impacting bird community patterns in the Mediterranean region. Negative effects seem to be recorded mostly for migrants in farmland landscapes, suggesting that declines in these species are likely to be caused by a variety of mechanisms interacting with habitat change in the breeding region.
Fire is an integral part of many ecosystems, including the Mediterranean ones. However, in recent decades the general trend in number of fires and surface burnt in European Mediterranean areas has increased spectacularly. This increase is due to: (a) land-use changes (rural depopulation is increasing land abandonment and consequently, fuel accumulation); and, (b) climatic warming (which is reducing fuel humidity and increasing fire risk and fire spread). The main effects of fire on soils are: loss of nutrients during burning and increased risk of erosion after burning. The latter is in fact related to the regeneration traits of the previous vegetation and to the environmental conditions. The principal regeneration traits of plants are: capacity to resprout after fire and fire-stimulation of the establishment of new individuals. These two traits give a possible combination of four functional types from the point of view of regeneration after fire, and different relative proportions of these plant types may determine the post-fire regeneration and erosion risk. Field observations in Spain show better regeneration in limestone bedrock type than in marls, and in north-facing slopes than in south-facing ones. Models of vegetation dynamics can be built from the knowledge of plant traits and may help us in predicting post-fire vegetation and long-term vegetation changes under recurrent fires.
In view of the massive change in the area of distribution of many world biota across classical biogeographical realms, and of the drastic restructuring of the biotic components of numerous ecosystems, the Scientific Committee on Problems of the Environment (SCOPE) decided at its general Assembly in Ottawa, Canada, in 1982 to launch a project on the 'Ecology of Biological Invasions'. Several regional meetings were subsequently organized within the framework of SCOPE, in order to single out the peculiarities of the invasions that took place in each region, the behaviour of their invasive species and the invasibility of their ecosystems. Most noteworthy among such workshops were one in Australia in August 1984, one concerning North America and Hawaii in October 1984, and one dealing with southern Africa in November 1985. A leitmotiv of these workshops was that most of the invasive species to those regions were emanating from Europe and the Mediterranean Basin, inadvertently or intentionally introduced by man. It was therefore considered as a timely endeavour to organize the next regional meeting in relation to this region. The workshop on 'Biological Invasions in Europe and the Mediterranean Basin' was held in Montpellier, France, 21 to 23 May 1986, thanks to the financial support of SCOPE and of the A.W. Mellon Foundation, and the logistic facilities of the Centre National de la Recherche Scientifique (C.N .R.S.).
The Mediterranean region has been shaped by human activity and maintained by traditional practices of land use for centuries. This has affected the distribution of plants and the landscape, which can be considered as part of the European cultural landscape. This book details the rapid changes that have taken place in the vegetation of the Mediterranean in the last half-century, a period in which major socio-economic development greatly affected the cultural and physical landscape.
The populations of farmland birds in Europe declined markedly during the last quarter of the 20th century, representing a severe threat to biodiversity. Here, we assess whether declines in the populations and ranges of farmland birds across Europe reflect differences in agricultural intensity, which arise largely through differences in political history. Population and range changes were modelled in terms of a number of indices of agricultural intensity. Population declines and range contractions were significantly greater in countries with more intensive agriculture, and significantly higher in the European Union (EU) than in former communist countries. Cereal yield alone explained over 30% of the variation in population trends. The results suggest that recent trends in agriculture have had deleterious and measurable effects on bird populations on a continental scale. We predict that the introduction of EU agricultural policies into former communist countries hoping to accede to the EU in the near future will result in significant declines in the important bird populations there.
Disturbances from wind, bark beetles, and wildfires have increased in Europe's forests throughout the 20(th) century (1). Climatic changes were identified as a main driver behind this increase (2), yet how the expected continuation of climate change will affect Europe's forest disturbance regime remains unresolved. Increasing disturbances could strongly impact the forest carbon budget (3,4), and are hypothesized to contribute to the recently observed carbon sink saturation in Europe's forests (5). Here we show that forest disturbance damage in Europe has continued to increase in the first decade of the 21(st) century. Based on an ensemble of climate change scenarios we find that damage from wind, bark beetles, and forest fires is likely to increase further in coming decades, and estimate the rate of increase to +0.91·10(6) m(3) of timber per year until 2030. We show that this intensification can offset the effect of management strategies aiming to increase the forest carbon sink, and calculate the disturbance-related reduction of the carbon storage potential in Europe's forests to be 503.4 Tg C in 2021-2030. Our results highlight the considerable carbon cycle feedbacks of changing disturbance regimes, and underline that future forest policy and management will require a stronger focus on disturbance risk and resilience.
Diversity patterns in eastern Nearctic and western Palaearctic temperate and boreal breeding assemblages of forest birds are compared. Several spatial scales of diversity were considered. First, the number of forest passerine species present in continental and regional (200 X 200 km(2)) pools were counted; secondly, average dissimilarities between breeding assemblages of passerine birds within a forest type (pine dominated forests) on a continent wide scale are calculated to assess the compositional variation among regional pools on each continent. Thirdly, the between-habitat diversity was assessed by comparing census results from two different forests types within regions. Finally, within-habitat diversity was measured by estimating the number of species present in standard samples from Nearctic and Palaearctic forests. Breeding assemblages of passerine birds of the eastern Nearctic region are more diverse than those of the western Palaearctic region on several spatial scales. First, there are more forest bird species in continental and in most regional species pools. Secondly, Neartic regional species pools are not only richer but also structurally more variable as revealed by a larger dissimilarity among Nearctic than Palaearctic pine forest bird assemblages. Thirdly, dissimilarity in bird community structure between two forest types is larger in the Nearctics, indicating a higher between-habitat diversity there. However, local breeding bird assemblages are about equally rich in species on both continents. The results match well with knowledge of the differences between the two continents in the history of avifaunas and vegetation formations. The results imply that conservation strategies should be uniquely tailored to local communities, taking into account the ecological characteristics of the species.
Fruit availability and its relation to bird abundance at different spatio-temporal scales were examined in olive orchards in southern Spain. Because olive abundance in orchards can be manipulated, this system provides an opportunity to examine the link between populations of fruit-eating birds and fruiting plants in much more detail than possible in natural systems. Olive availability varied in space and time as a result of differences in olive yield and in ripening and harvesting rates. The most abundant frugivorous birds in the orchards (Sylvia atricapilla and Turdus philomelos) were frequently able to track olive availability on both local and regional scales. S. atricapilla showed a response to even small-scale harvesting of olives by humans, distributing itself preferentially in unharvested patches. The ability of both species to track fruit availability may explain their high abundance. Other less abundant frugivores (Erithacus rubecula and S. melanocephala) showed less capacity to track olive availability. I suggest that their inability to respond to rapidly changing patterns of olive abundance may partially account for their scarcity in olive orchards. Olive orchards play an important role in maintaining frugivorous bird populations in the Mediterranean area. My data suggest that a key reason for this is great spatial and temporal variability in the availability of olives in orchards, which result in a widely scattered but temporally continuous availability of olives. The capacity of some frugivorous species to track complex spatio-temporal patterns of fruit availability was, I hypothesize, a pre-adaptive feature that allow them to flourish in the highly modified habitat of southern Spain.
1. The forested habitats in a large part of the Mediterranean semi-arid climates of Spain are dominated by Aleppo pine forests, most of which are managed plantations. Despite this, the effects of changes in the structure and composition of vegetation on birds are unknown. The work reported here was an attempt to detect the relationships between vegetation characteristics and the bird species that inhabit these forests. 2. The point-count method was used to estimate the presence of bird species and their abundance in Aleppo pine plantations In wrater and spring. Four perpendicular 15-m transects were traced in each counting station to estimate the size and density of pines, the cover of main species in understorey vegetation and its height. Correspondence analysis was used to find the most important variables in the composition of bird communities, as well as in understorey composition and vertical structure. 3. The composition of bird communities at forest sites was better explained by understorey characteristics than by tree-layer variables. Bird species composition was related to understorey composition in both seasons. 4. A significant linear regression model was found relating bird species richness during the breeding season to understorey composition, in particular variation in Quercus ilex and Q. coccifera cover. No significant model could be found for bird species richness in wrater. 5. The probability of finding a bird species at a given site within pine plantations was modelled using logistic regression. 6. Maintenance or introduction of Q. ilex in the understorey of Aleppo pine plantations would increase the diversity of breeding bird communities and would also improve habitat quality for forest bird species with limited distribution in semi-arid climates. On the other hand, a reduction in pine density would have little effect on these bird communities provided that an appropriate understorey was conserved.
AimMediterranean terrestrial ecosystems serve as reference laboratories for the investigation of global change because of their transitional climate, the high spatiotemporal variability of their environmental conditions, a rich and unique biodiversity and a wide range of socio-economic conditions. As scientific development and environmental pressures increase, it is increasingly necessary to evaluate recent progress and to challenge research priorities in the face of global change. LocationMediterranean terrestrial ecosystems. Methods
This article revisits the research priorities proposed in a 1998 assessment. ResultsA new set of research priorities is proposed: (1) to establish the role of the landscape mosaic on fire-spread; (2) to further research the combined effect of different drivers on pest expansion; (3) to address the interaction between drivers of global change and recent forest management practices; (4) to obtain more realistic information on the impacts of global change and ecosystem services; (5) to assess forest mortality events associated with climatic extremes; (6) to focus global change research on identifying and managing vulnerable areas; (7) to use the functional traits concept to study resilience after disturbance; (8) to study the relationship between genotypic and phenotypic diversity as a source of forest resilience; (9) to understand the balance between C storage and water resources; (10) to analyse the interplay between landscape-scale processes and biodiversity conservation; (11) to refine models by including interactions between drivers and socio-economic contexts; (12) to understand forest-atmosphere feedbacks; (13) to represent key mechanisms linking plant hydraulics with landscape hydrology. Main conclusions(1) The interactive nature of different global change drivers remains poorly understood. (2) There is a critical need for the rapid development of regional- and global-scale models that are more tightly connected with large-scale experiments, data networks and management practice. (3) More attention should be directed to drought-related forest decline and the current relevance of historical land use.
Investigations on vertebrate seed dispersal systems in the Mediterranean show that extremely efficient plant-disperser mutualisms do not require, and thus are not evidence for, mutual evolutionary adjustments of participants. Current Mediterranean dispersal systems have apparently been shaped by means of 1. trophic and behavioral adaptations of birds morphologically preadapted to pre-existing plant resources, and 2. disperser-mediated processes of habitat-shaping occurring at an ecological time scale. These processes depend on differential recruitment of plant species as a function of disperser preferences, rather than on adjustments based on evolutionary processes. On the plant side, there is a prevalence of historical and phylogenetic effects, which reflects a series of ecological limitations inherent to the interactions between plants and dispersal agents that constrain plant adaptation to dispersers. To test adaptive hypotheses and explanations, future investigations on Mediterranean plant-disperser systems should concentrate more on the animal than on the plant side of the interaction.
Concern over the impact of invaders on biodiversity and on the functioning of ecosystems has generated a rising tide of comparative analyses aiming to unveil the factors that shape the success of introduced species across different regions. One limitation of these studies is that they often compare geographically rather than ecologically defined regions. We propose an approach that can help address this limitation: comparison of invasions across convergent ecosystems that share similar climates. We compared avian invasions in five convergent mediterranean climate systems around the globe. Based on a database of 180 introductions representing 121 avian species, we found that the proportion of bird species successfully established was high in all mediterranean systems (more than 40% for all five regions). Species differed in their likelihood to become established, although success was not higher for those originating from mediterranean systems than for those from nonmediterranean regions. Controlling for this taxonomic effect with generalized linear mixed models, species introduced into mediterranean islands did not show higher establishment success than those introduced to the mainland. Susceptibility to avian invaders, however, differed substantially among the different mediterranean regions. The probability that a species will become established was highest in the Mediterranean Basin and lowest in mediterranean Australia and the South African Cape. Our results suggest that many of the birds recently introduced into mediterranean systems, and especially into the Mediterranean Basin, have a high potential to establish self-sustaining populations. This finding has important implications for conservation in these biologically diverse hotspots.
Fire is a key mechanism creating and maintaining habitat heterogeneity in Mediter- ranean landscapes by turning continuous woody landscapes into mosaics of forests and shrublands. Due to the long historical role of fires in the Mediterranean, we hypothesised a moderate negative effect of this type of perturbation on forest bird distribution at a landscape level. We conducted point bird censuses in Aleppo pine forest patches surrounded by burnt shrublands and studied the relationships between three ecological groups of bird species (forest canopy species, forest understorey species, and ubiquitous species) and the features of local habitat, whole patch and surrounding landscape. We used a multi-scale approach to assess the effects of landscape variables at increasing spatial scales on point bird richness. Regarding local habitat components, canopy species were positively associated with tall pines while understorey species with the cover of shrubs and plants from holm-oak forests. Forest birds were positively related to patch size and irregular forest shapes, that is, with high perimeter/size ratios. Thus, these species did not seem to perceive edges as low quality but rather favourable microhabitats. We did not detect any negative effect of isolation or cover of woodlands in the landscape on the presence of forest species after local habitat factors had been accounted for. Finally, only local habitat factors entered the model for ubiquitous species. We suggest that mosaic-like landscapes shaped by fires in the Mediterranean basin are not strongly associated with negative effects fragmentation on forest birds other than those related with habitat loss.