Bird conservation in fragmented Mediterranean forests of Spain: effects of geographical location, habitat and landscape degradation

The effects of habitat fragmentation on forest bird assemblages were analysed in 214 holm oak (Quercus ilex) remnants spread across the northern and southern plateaux of central Spain. Bird richness was highly dependent on fragment area for all species regardless of isolation, and barely affected by habitat traits. Geographical location was associated with high differences in richness of bird assemblages, which included 17 species exclusive to northern remnants and one exclusive to southern remnants. This supports the hypothesis that habitat suitability deteriorates sharply from north to south for forest birds in Spain. The species-area relationships of bird assemblages sampled in fragmented forests along a broad continental gradient (from Norway to southern Spain) showed that true forest birds only nest in woodlands >100 ha in southern Spain, whereas the full complement of forest species occurs in much smaller fragments in central-western Europe. Loss of species that are particularly sensitive to habitat fragmentation accounts for these differences between dry Spanish and mesic European woodlands. These results are explained by the low habitat suitability of Spanish woodlands, associated with the restrictive conditions for plant regeneration in the Mediterranean climate and long-standing human usage. There is, therefore, a particular need to develop management strategies that conserve birds, and probably other forest organisms, in Mediterranean regions by preventing habitat deterioration and decreases in fragment size, and by conserving all woods >100 ha.     

Small mammals in agricultural landscapes of Prince Edward Island (Canada): Effects of habitat characteristics at three different spatial scales

We examined the influence of habitat characteristics at the microhabitat, macrohabitat, and landscape spatial scales on small mammals occurring in 12 forest patches within four agricultural landscapes of Prince Edward Island (Canada). Landscape features were important determinants of small mammal variables at all levels, but especially at the community level, whereas microhabitat characteristics tended to influence small mammals at the population level. Macrohabitat characteristics had only minor effects on small mammals occurring in our study sites. Species richness was most strongly influenced by patch area, reaching a threshold at forest patches of roughly 8-10 ha. The proportions of both forest and hedgerow cover within 400 m from the study site were also significant determinants of small mammals species diversity, possibly reflecting their ability to perceive suitable habitats, forage in areas outside the forest patches, and/or disperse in agricultural landscapes. At least one small mammal species (Napaeozapus insignis) benefitted from the presence of agricultural fields at distances up to 1000 m. Tamias striatus benefitted from the presence of hedgerow cover within 400 m from forest patches, possibly allowing them to move between forest patches. Clearly, the maintenance of forest patches of 8-10 ha and of forest cover within 400 m from them is fundamental for the conservation of small mammals inhabiting agricultural landscapes on the Island. Conservation strategies should also consider the establishment of more effective regulations to prevent and/or reduce hedgerow removal on Prince Edward Island.     

Habitat fragmentation alters the structure of dung beetle communities in the Atlantic Forest

Habitat loss and fragmentation have turned into the most important threats to biodiversity and ecosystem function worldwide. Here we investigate the effects of habitat fragmentation and drastic changes in tree communities on dung beetle richness and community structure. This study was carried out in a severely fragmented 670-km² forest landscape of the Atlantic Forest of north-eastern Brazil. Sampling was carried out in 19 forest fragments between September 2007 and March 2008 with the use of pitfall traps and flight interception traps. A total of 5893 individuals and 30 species of dung beetle were collected. Fragment area and isolation were the most significant explanatory variables for predictable and conspicuous changes in dung beetle species richness. Smaller and isolated fragments presented lower number of species, but fragments with lower tree species richness and lower proportion of shade-tolerant species were also considerably impoverished in terms of dung beetle species richness. The body mass of dung beetles were explained by fragment area and the percentage of emergent trees with smaller and less stratified fragments being dominated by small-bodied dung beetles. An ordination analysis segregated dung beetle communities between small fragments (<100 ha) and the control area. Seventy-seven percent of the species were recorded in the control area and 22% of all species were unique to this habitat. Our findings indicate that large fragments in the Atlantic Forest appear to consist in a sort of irreplaceable habitats for particular groups of dung beetle species, as well as for the integrity of their communities.     

Landscape-level thresholds of habitat cover for woodland-dependent birds

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.     

The severe decline of butterflies on western German calcareous grasslands during the last 30 years: A conservation problem

Butterflies and burnet moths are a suitable model species group with which to analyse the general decline of invertebrate biodiversity over the last few decades. In this study, we analysed which ecological groups of butterflies and burnet moths are most affected and how the recent modifications of the landscape have influenced them. Therefore, we studied the species composition of seven calcareous grassland remnants in south-western Germany in 1972 and 2001. We observed a strong change in the community composition and a severe decline in species richness. In general, the incidence of the autochthonous non-ubiquitous species declined by more than 50%, whereas ubiquitous species showed no significant difference in numbers during this period. Especially affected by the decline were those species which need structured habitats, those which are poor dispersers, species which need habitat sizes of 16 ha and more, monophagous species, K strategists and Red Data Book species. Most probably, either habitat outside the reserves is affecting dynamics within the reserves or loss of habitat outside the protected areas has reduced the overall area and connectivity of habitat for some species, increasing extinction rates and reducing colonisation rates in metapopulations. We conclude that these negative trends can only be stopped or even reversed if the landscape structure is made less hostile for species with conservation interest.     

How much do site age, habitat structure and spatial isolation influence the restoration of rainforest beetle species assemblages?

Reforestation has been suggested as a way to mitigate the effects of tropical rain forest loss. However, factors influencing the successful colonisation of biota into newly created rainforest are poorly understood. We assessed beetle species assemblages with flight interception traps, in sites undergoing rainforest restoration across the largely cleared landscape of the Atherton Tablelands in north-eastern Queensland, Australia. There were two levels of site age (2-4 years and 6-17 years) and two distances from intact rainforest (adjacent and >0.9 km), with six sites in each treatment, together with six reference sites in each of pasture and small rainforest remnants (n = 36 sites). Multivariate metrics were used to assess the restored sites’ relative similarity to pasture and rainforest, in terms of both physical habitat structure and beetle species composition within ten family groups. Older restoration sites were structurally most similar to rainforest. Older sites and those adjacent to rainforest had a more rainforest-like beetle species composition (without significant interaction). However, even the closer and older sites had a substantially lower abundance and richness of rainforest-associated beetles than did rainforest. Age effects were generally stronger than distance effects, with the latter appearing to be entirely driven by rare rainforest species. Beetle assemblage similarity to rainforest was more strongly correlated with structural similarity to rainforest than with age, except within older sites. The use of revegetation techniques which lead to more rainforest-like structural conditions appears to be of over-riding importance in catalysing the rapid acquisition of volant rainforest beetle assemblages in the initial stages of restoration.     

Detrimental effects of peat mining on amphibian abundance and species richness in bogs

Peat bogs of eastern North America are increasingly being mined for peat, which results in the extensive draining of these systems. First, I quantified the effects of peat mining on amphibian species richness and abundance in bog remnants adjacent to mining activity and unmined bogs. I then investigated amphibian occurrence patterns in bog remnants relative to the distance to the mined edge, after accounting for microhabitat and distance to landscape elements. The response of amphibians to peat mining varied across taxa. For instance, amphibian species richness, total amphibian captures (all spp. combined), as well as those of green frogs (Rana clamitans) were greater in unmined bogs than in bog remnants. Wood frogs (Rana sylvatica) were most abundant in unmined bogs in areas far from bog ponds, as well as in unmined bogs in areas near shrub patches. After accounting for microhabitat and landscape variables, American toads (Bufo americanus) in bog remnants were most abundant close to mined edges, whereas the other species did not respond to the proximity of mined edges. Peat mining negatively impacts amphibians occurring in bog remnants. The response of amphibians to peat mining is similar to the one of birds and plants, but differs with small mammals. Maintaining a complex mosaic of bog ponds, shrub and forest patches might help mitigate peat mining effects on amphibian patterns of abundance.     

Plant communities at the periphery of the Atlantic rain forest: Rare-species bias and its risks for conservation

Initiatives that establish species rarity as an indicator of conservation priority might be biased if they disregard important evolutionary and adaptive processes taking place in lower diversity communities and ecotones. Conservation policies regarding the Atlantic forest strongly emphasize the core formation (i.e. the rainforest stricto sensu) rather than the marginal habitats (e.g. restingas, swamps, and high altitude campos) and species that are rare/endemic. To discuss this issue I revisit a hypothesis I have forwarded in 2002 that postulates that plant colonization of habitats marginal to the Atlantic rain forests of the State of Rio de Janeiro was largely related to terrestrial nurse plants that originally, in the rainforest habitat, were canopy plants such as epiphytes or hemi-epiphytes. Adaptations to water and nutrient restrictions, typical of life in the canopy, granted success to such plants upon migration to sandy, swampy or rocky substrates in neighbouring areas. Many such species, then, behaved as nurse plants and favoured colonization of these more extreme habitats by a number of other rainforest species. I now review recent evidence that corroborate this hypothesis, while examining the nature of such nurse plants. In all marginal habitats, nurse plants are often highly abundant locally and have high ecophysiological vigour, while both widespread and endemic species are found among them. Thus, nursing effect, local abundance, and ecophysiological performance are not related to species geographic distribution or to their spectrum of habitat preference. Paradoxically, several abundant nurse plant species have low Darwinian fitness. These studies provoke two reflections. First, the Atlantic forest sensu lato, i.e. the core formation plus the peripheral ones, should be treated collectively as a biodiversity hotspot, rather than the core rainforest formation alone. Second, widespread or common species play important functional roles in such marginal habitats and, despite their ubiquity, ecologically they might be less fit than rare/endemic ones at the local level due, for instance, to current constraints to sexual reproduction. Thus, they should also be targeted as conservation priorities.     

Conservation value of forest fragments to Palaeotropical bats

Forested landscapes in Southeast Asia are becoming increasingly fragmented, making this region a conservation and research priority. Despite its importance, few empirical studies of effects of fragmentation on biodiversity have been undertaken in the region, limiting our ability to inform land-use regimes at a time of increased pressure on forests. We estimated the biodiversity value of forest fragments in peninsular Malaysia by studying fragmentation impacts on insectivorous bat species that vary in dependence of forest. We sampled bats at seven continuous forest sites and 27 forest fragments, and tested the influence of fragment isolation and area on the abundance, species richness, diversity, composition and nestedness of assemblages, and the abundance of the ten most common species. Overall, isolation was a poor predictor of these variables. Conversely, forest area was positively related with abundance and species richness of cavity/foliage-roosting bats, but not for that of cave-roosting or edge/open space foraging species. The smallest of fragments (<150 ha) were more variable in species composition than larger fragments or continuous forest, and larger fragments retained substantial bat diversity, comparable to continuous forest. Some fragments exhibited higher bat abundance and species richness than continuous forest, though declines might occur in the future because of time lags in the manifestation of fragmentation effects. Our findings suggest that fragments >300 ha contribute substantially to landscape-level bat diversity, and that small fragments also have some value. However, large tracts are needed to support rare, forest specialist species and should be the conservation priority in landscape-level planning. Species that roost in tree cavities or foliage may be more vulnerable to habitat fragmentation than those that roost in caves.     

Drastic erosion in functional attributes of tree assemblages in Atlantic forest fragments of northeastern Brazil

The long-term dynamics of plant communities remain poorly understood in isolated tropical forest fragments. Here we test the hypothesis that tropical tree assemblages in both small forest fragments and along forest edges of very large fragments are functionally much more similar to stands of secondary growth (5-65-yr old) than to core primary forest patches. The study was carried out in a severely fragmented landscape of the Brazilian Atlantic forest. Nine functional attributes of tree assemblages were quantified by sampling all trees (DBH ? 10 cm) within 75 plots of 0.1 ha distributed in four forest habitats: small forest fragments (3.4-79.6 ha), forest edges, second-growth patches, and primary forest interior areas within a large forest fragment (3500 ha). These habitats were markedly different in terms of tree species richness, and in the proportion of pioneer, large-seeded, and emergent species. Age of second-growth stands explained between 31.4% and 88.2% of the variation in the functional attributes of tree assemblages in this habitat. As expected, most traits associated with forest edges and small forest fragments fell within the range shown by early (<25-yr old) and intermediate-aged secondary forest stands (25-45-yr old). In contrast to habitat type, tree assemblage attributes were not affected by vegetation type, soil type and the spatial location of plots. An ordination analysis documented a striking floristic drift in edge-affected habitats. Our results suggest that conservation policy guidelines will fail to protect aging, hyper-fragmented landscapes from drastic impoverishment if the remaining forest patches are heavily dominated by edge habitat.     

Do frugivorous birds assist rainforest succession in weed dominated oldfield regrowth of subtropical Australia?

Exotic plants often form the first woody vegetation that grows on abandoned farmland. If this vegetation attracts vertebrate frugivores which disperse the seeds of native plants, then native plants may recruit to such oldfield sites. However, there is debate about the extent to which exotic vegetation assists or suppresses the regeneration of native plants, and about its effects on faunal biodiversity. These issues were investigated in subtropical eastern Australia, where rainforests were cleared for agriculture in the 19th century, and where regrowth dominated by camphor laurel (Cinnamomum camphora, an exotic, fleshy-fruited tree) has become common on former agricultural land. The study assessed the assemblages of frugivorous birds, and the recruitment of rainforest plants, at 24 patches of camphor laurel regrowth. The patches were used by nearly all frugivorous birds associated with subtropical rainforest. Many of these birds (16 of 34 species) are considered to have a medium to high potential to disperse the seeds of rainforest plants, and eight of these were abundant and widespread in regrowth patches. Of 208 recorded plant species, 181 were native to local rainforest. The ratio of native to exotic species was higher amongst tree recruits than adult trees, both for numbers of species and individuals. Among native tree recruits, 79% of 75 species, and 93% of 1928 individuals, were potentially dispersed by birds. These recruits included many late-successional species, and there were relatively more individuals of late-successional, bird-dispersed native species amongst recruits than adult trees. The species richness, but not the abundance, of both frugivorous birds and of bird-dispersed rainforest trees decreased with distance from major rainforest remnants. Camphor laurel regrowth provides habitat for rainforest birds and creates conditions suitable for the regeneration of native rainforest plants on abandoned farmland. Careful management of regrowth dominated by fleshy-fruited exotic invasive trees can provide an opportunity for broadscale reforestation in extensively-cleared landscapes.     

The importance of forest area and configuration relative to local habitat factors for conserving forest mammals: A case study of koalas in Queensland, Australia

The loss and fragmentation of forest habitats by human land use are recognised as important factors influencing the decline of forest-dependent fauna. Mammal species that are dependent upon forest habitats are particularly sensitive to habitat loss and fragmentation because they have highly specific habitat requirements, and in many cases have limited ability to move through and utilise the land use matrix. We addressed this problem using a case study of the koala (Phascolarctos cinereus) surveyed in a fragmented rural-urban landscape in southeast Queensland, Australia. We applied a logistic modelling and hierarchical partitioning analysis to determine the importance of forest area and its configuration relative to site (local) and patch-level habitat variables. After taking into account spatial autocorrelation and the year of survey, we found koala occurrence increased with the area of all forest habitats, habitat patch size and the proportion of primary Eucalyptus tree species; and decreased with mean nearest neighbour distance between forest patches, the density of forest patches, and the density of sealed roads. The difference between the effect of habitat area and configuration was not as strong as theory predicts, with the configuration of remnant forest becoming increasingly important as the area of forest habitat declines. We conclude that the area of forest, its configuration across the landscape, as well as the land use matrix, are important determinants of koala occurrence, and that habitat configuration should not be overlooked in the conservation of forest-dependent mammals, such as the koala. We highlight the implications of these findings for koala conservation.     

Relative effects of fragment size and connectivity on bird community in the Atlantic Rain Forest: Implications for conservation

It is known that large fragment sizes and high connectivity levels are key components for maintaining species in fragments; however, their relative effects are poorly understood, especially in tropical areas. In order to test these effects, we built models for explaining understory birds occurrence in a fragmented Atlantic Rain Forest landscape with intermediate habitat cover (3%). Data from over 9000 mist-net hours from 17 fragments differing in size (2-175 ha) and connectivity (considering corridor linkages and distance to nearby fragments) were ranked under a model selection approach. A total 1293 individuals of 62 species were recorded. Species richness, abundance and compositional variation were mainly affected by connectivity indices that consider the capacity of species to use corridors and/or to cross short distances up to 30 m through the matrix. Bird functional groups were differently affected by area and connectivity: while terrestrial insectivores, omnivores and frugivores were affected by both area and connectivity, the other groups (understory insectivores, nectarivores, and others) were affected only by connectivity. In the studied landscape, well connected fragments can sustain an elevated number of species and individuals. Connectivity gives the opportunity for individuals to use multiple fragments, reducing the influence of fragment size. While preserving large fragments is a conservation target worldwide and should continue to be, our results indicated that connectivity between fragments can enhance the area functionally connected and is beneficial to all functional groups and therefore should be a conservation priority.     

Structure of the advanced regeneration community in tropical rain forest fragments of Los Tuxtlas, Mexico

We characterized the tree seedling community within seven forest fragments of different size (3-640 ha) at Los Tuxtlas, Mexico. We considered individual density, species richness, diversity, composition and functional group (shade tolerant, non-pioneer-light demander and pioneer species). We recorded 8038 individuals, belonging to 128 species and 40 morphospecies. Overall, shade-tolerant species had the highest density and diversity followed by non-pioneer-light demanders and pioneer species. Mean individual density per plot was not related to fragment size, but mean species richness per plot, total observed species richness and diversity were inversely related to fragment size, with the smallest fragments having the highest values. Species composition comparisons highlighted low similarity among fragments. Furthermore, larger fragments shared more species with the smallest fragments than between each other. Our results show that the largest fragments do not always hold the highest species richness; that small fragments comprise of high seedling species diversity, and represent a high regeneration potential for tree native species in the study landscape.     

Determinants of native avian richness in suburban remnant vegetation: Implications for conservation planning

While urban areas are increasingly recognized as having potential value for biodiversity conservation, the relationship between biodiversity and the structure and configuration of the urban landscape is poorly understood. In this study we surveyed birds in 39 remnant patches of native vegetation of various sizes (range 1-107 ha) embedded in the suburban matrix in Melbourne, Australia. The total richness of species within remnants was strongly associated with the size of remnants. Remnant-reliant species displayed a much stronger response to remnant area than matrix-tolerant species indicating the importance of large remnants in maintaining representative bird assemblages. Large remnants are important for other ecological groups of species including migratory species, ground foraging birds and canopy foraging birds. Other landscape (e.g. amount of riparian vegetation) and structural components (e.g. shrub cover) of remnants have a lesser role in determining the richness of individual remnants. This research provides conservation managers and planners with a hierarchical process to reserve design and management in order to conserve the highest richness of native species within urban areas. First of all, conservation efforts should preferentially focus on the retention of larger remnants of native vegetation. Second, where possible, riparian vegetation should be included within reserves or, where it is already present, should be carefully managed to ensure its integrity. Third, efforts should be focused at maintaining appropriate habitat and vegetation structure and complexity.     

Probable consequences of high female mortality for speckled warblers living in habitat remnants

The effects of habitat fragmentation on the Australian avifauna have been widespread with species richness and abundance declining with reduced remnant size and habitat quality and increased habitat isolation. The speckled warbler, Chthonicola sagittata is one species from the highly fragmented temperate woodlands of eastern Australia that has declined across its range and populations that remain appear to be patchily distributed in habitat remnants. Specific causes of decline are unknown but several aspects of its biology make the species particularly vulnerable to decline in fragmented landscapes. Here, we analyse survey data (presence/absence) of speckled warblers in a large sample of habitat remnants from three regions to identify patterns of occupancy. We explore the effects of patch size on extinction risk using population viability analyses (PVA) and detailed demographic data from a behavioural study of individuals in the Australian Capital Territory, south-eastern Australia. Patch size was a strong predictor of the persistence of speckled warblers in habitat remnants. High density populations had higher probabilities of persisting, and inclusion of an Allee effect during drought decreased the probability of persistence. In the absence of an Allee effect, only high density populations in patches greater than 300 ha and low density populations in patches greater than700 ha had more than an 80% probability of persisting over 100 years. The accelerating decrease in population persistence below approximately 200-400 ha suggests that small populations were particularly vulnerable to stochastic demographic and environmental events. Adult female mortality was the single most important factor in driving population extinction. Our PVA model predictions matched the survey data for the Australian Capital Territory region remarkably well, but failed to predict occupancy rates in remnants in other regions. Differences in occupancy patterns between regions may, however, have resulted from inbreeding depression. This study demonstrates both the strengths and limitations of PVA analysis. PVA can predict occupancy patterns with reasonable accuracy, given good demographic data, but data for one region cannot be used universally for all regions. We highlight the need for studies of demography in different regions to interpret regional patterns of occupancy and to identify mechanisms of decline in remnant habitat.     

Geographic information system (GIS) predictions of past, present habitat distribution and areas for re-introduction of the endangered subtropical rainforest shrub Triunia robusta (Proteaceae) from south-east Queensland Australia

The endangered Australian subtropical rainforest understorey shrub Triunia robusta, is restricted to the south-east Queensland region of Australia. The potential pre-clearing and current distribution of the species was modelled by relating species presence at recorded locations to correlated abiotic and biotic factors, which in combination, were then used as a surrogate for predicting distribution of the species habitat over its known range. From a defined study area of 330,000 ha, output of geographic areas likely to contain T. robusta habitat at three levels of probability were generated for pre-clearing vegetation, and vegetation classified as remnant in 1999. Potential pre-clearing distribution was compared with potential current distribution to ascertain the likely impact of clearing of native vegetation on the extent, pattern, and contiguity of T. robusta habitat. For pre-clearing vegetation, a total area of 45,480 ha was identified as potential T. robusta habitat. For vegetation classified as 1999 remnant, 13,440 ha were identified, representing an overall reduction of 70% in potential habitat for T. robusta. The model was partially validated, with T. robusta found at six new locations. Allowing for errors from spatial mismatching, five of the sites were located within habitat patches predicted by the model. A number of local areas containing high densities of predicted habitat patches were identified to guide searches for unrecorded populations. Strategically located areas linking known populations containing suitable or potentially suitable habitat that may be available for introduction of new populations were identified. The results indicate that the species former centre of range was in lowland areas adjacent to the north arm of the Maroochy River. Clearing and fragmentation of T. robusta habitat is the most likely cause of the apparent decline in distribution and abundance of the species.     

Waterfowl-habitat associations during winter in an urban North Atlantic estuary

Coastal habitats near urban centres in North Atlantic estuaries often support substantial numbers of wintering waterfowl, but little is known of the effects of landscape setting and urbanisation on habitat use. We conducted surveys of waterfowl at 32 wintering sites in Narragansett Bay, Rhode Island, to identify characteristics that may influence habitat use. Sites were chosen along a gradient of urbanisation and reflected the dominant habitat types used by waterfowl in the Bay. Mean waterfowl abundance was 206.7 ± 209.5 birds per site, and sites in the inner part of the estuary had higher overall waterfowl abundances (r² = 0.40, p = 0.021). Species richness ranged from 3.2 to 13.0 and decreased with increasing hunting activity (r² = 0.36, p = 0.040). Hunting activity and habitat characteristics (e.g., latitude, shoreline configuration, prey density) explained 13-27% of the variation in waterfowl abundance and species richness among sites, but landscape characteristics (e.g., surrounding residential development, vegetated land, or wetland surrounding the sites and the extent of wetland edge) explained an additional 1-26%. The landscape characteristics extent of adjacent residential development and vegetated upland were the most common variables entering into the models; most species were more abundant at sites with more adjacent vegetated upland and less adjacent residential development. Our results suggest that landscape setting may be influencing the distribution of wintering waterfowl, and should be considered when developing strategies for the conservation for these species in urban North Atlantic estuaries.     

A meta-analysis of fauna and flora species richness and abundance in plantations and pasture lands

We conducted a systematic global review of differences between timber plantations and pasture lands in terms of animal and plant species richness and abundance, and assessed the results using meta-analysis techniques. Our principal aim was to test the hypothesis that plantations contain higher species richness or abundance than pasture. Of the 1967 studies of potential relevance, 66 provided biological monitoring information and 36 met the requirements for meta-analyses. Sufficient data were available for meta-analyses to be conducted comparing the species richness and abundance of plantations and pasture lands for five taxonomic groups: plants, invertebrates, reptiles/amphibians, mammals, and birds. Within each taxon there was considerable variation in the difference between species richness and abundance between plantations and pasture lands. Birds and reptile/amphibians exhibited significantly higher species richness, and mammals exhibited significantly higher abundance, in plantations than in pasture lands which lacked remnant vegetation. Reptile/amphibian species richness was significantly higher in plantations in general. No significant differences in species richness were found for mammals, plants, or invertebrates, and no significant differences in abundance were found for birds, reptiles/amphibians, invertebrates, or plants. It is only within the presence of taxonomic caveats (i.e. reptiles/amphibians), or specific landscape features (i.e. absence of remnant vegetation within pasture), that it can be concluded that plantations support higher species richness or abundance than pasture land. We emphasize that caution is warranted when making general statements about the inherent biodiversity value of diverse and broadly-defined land-uses.     

The role of forest structure, fragment size and corridors in maintaining small mammal abundance and diversity in an Atlantic forest landscape

Using the abundance and distribution of small mammals at 26 sites in an Atlantic forest landscape, we investigated how species abundance and alpha and beta diversity are affected by fragment size and the presence of corridors. To account for the variability in forest structure among fragments, we described and minimized the influence of foliage density and stratification on small mammal data. Sites were distributed among three categories of fragment size and in continuous forest. For small and medium-sized categories, we considered isolated fragments and fragments connected by corridors to larger remnants. Small mammal abundance and alpha and beta diversity were regressed against site scores from the first axis of a Principal Component Analysis on forest structure variables. Residuals were used in analyses of variance to compare fragment size and connectivity categories. Forest structure influenced total abundance and abundance of some species individually, but not the diversity of small mammal communities. Total abundance and alpha diversity were lower in small and medium-sized fragments than in large fragments and continuous forest, and in isolated compared to connected fragments. Three species were less common, but none was more abundant in smaller fragments. At least one species was more abundant in connected compared to isolated fragments. Beta diversity showed an opposite relationship to fragment size and corridors, increasing in small and isolated fragments. Results highlight the importance of secondary forest for the conservation of tropical fauna, the hyper-dynamism of small isolated fragments and the potential of corridors to buffer habitat fragmentation effects in tropical landscapes.