Species Richness In Landscapes Research Articles

The landscape ecological view of vertebrate species richness in urban areas across biogeographic realms

Understanding how the spatial arrangement of remnant green spaces in cities complements biodiversity provides an opportunity for synergy between urban development and biological conservation. However, the geography of urbanization is shifting from Europe and North America to Asia and Africa, and more research is needed for fast-growing regions. To understand how shifting urbanization shapes biodiversity patterns, we analyzed the contribution of landscape factors in explaining vertebrate species richness in urban areas across biogeographic realms. We used variation partitioning to quantify and compare the relative importance of landscape factors (composition and configuration) and environmental factors (climate, elevation, and latitude) in explaining vertebrate species richness in landscapes with at least a million inhabitants across biogeographic realms. Our results pointed out that in the Indo-Malayan, the Afrotropical, and the Neotropical realm (on average of 16.46%) and China and India (11.88%), the influence of landscape factors on vertebrate species richness are significantly higher than that of the Palearctic and Nearctic realms (6.48%). Our findings outline the importance of landscape composition and configuration in shaping biodiversity patterns in regions with fast urban growth during the next two decades, such as Africa, Latin America, and Southeastern Asia. We suggest improving land governance and urban planning to construct eco-friendly landscape structures to mitigate biodiversity loss due to urbanization.

Partitioning of arthropod species diversity in temperate meadows, wildflower areas and pastures

To counteract the rapidly ongoing species decline in modern agroecosystems, most European countries have developed and adopted agri-environment schemes. The efficiency of these schemes, however, ranges from successful to nearly ineffective. To estimate the efficiency of the Swiss agri-environment scheme in particular, we investigated the contribution of extensively managed pastures and meadows and wildflower areas to beetle, heteropteran bug and spider diversity. Extensively managed meadows were shown to contribute most to landscape-scale richness (highest species richness for beetles and bugs), followed by wildflower areas (bugs). Meadows harboured approximately twice as many beetle species unique to this habitat type than wildflower areas and pastures. Bug species unique to a specific habitat type were similar between meadows and wildflower areas, but much lower (approximately 30%) in pastures. To increase beetle species richness, extensively managed meadows should be represented more often in the landscape because meadows harboured the highest number of species and most uniquely found species. To increase species richness of true bugs, both meadows and wildflower areas should be represented more often in the landscape because they harboured more species and more uniquely found species compared to pastures. Across arthropod taxa and habitat types, β diversity was more important for γ diversity than α diversity, indicating that distinctiveness, rather than within-site diversity, was key in determining the contribution of sites to γ (landscape) diversity. This substantiates the argument that increasing the number of sites is efficient to increase landscape species richness. The turnover component of β diversity was far more important than the nestedness component for all arthropod taxa and habitat types and accounted for 79.0% to 95.4% of total β diversity. In conclusion, extensively managed meadows and wildflower areas should be particularly promoted by the Swiss agri-environment scheme, as they contributed more to landscape species richness and species uniqueness than pastures.

Modeling the Evolution of Aquatic Organisms in Dynamic River Basins

AbstractRivers are conduits for aquatic organisms and host an exceptional number of species. Over geologic time, rivers and the aquatic organisms that live in them are subject to changes in topography that can alter where rivers flow. Differences in erosion rates across drainage divides cause some river basins to grow and others to shrink. Occasionally, rivers are abruptly rerouted by river captures that create both new dispersal corridors and barriers for aquatic organisms. These changes in habitat connectivity can lead to the evolution of new species, which has prompted suggestions that river captures may be a mechanism to produce high freshwater biodiversity. We test this hypothesis by building a model, Bio‐SLANT (Biodiversity on Simulated LAndscapes using Neutral Theory). Bio‐SLANT couples a computational landscape model that simulates river basin reorganization to a macroevolutionary model that simulates the dispersal, speciation, and extinction of organisms. We first show that modeled basin area exerts a primary control on within‐basin species richness due to the species‐area relationship. We then describe the effects of drainage area exchange between river basins. River capture increases species richness, but only temporarily, whereas elevated rates of speciation and extinction provide a persistent biological record of river network reorganization. When river captures are frequent, speciation rates increase more than extinction rates, resulting in a positive diversification rate under most of the biological parameters tested. We explore the implications of our results for species richness in landscapes with basins of different relative sizes and for diversification in tectonically active and inactive settings.

Degradation of Ecosystem Services and Deforestation in Landscapes With and Without Incentive-Based Forest Conservation in the Ecuadorian Amazon

Anthropogenic activities such as logging or forest conversion into agricultural lands are affecting Ecuadorian Amazon forests. To foster private and communal conservation activities an economic incentive-based conservation program (IFC) called Socio Bosque was established. Existing analyses related to conservation strategies are mainly focused on deforestation; while degradation and the role of IFC to safeguard ecosystem services are still scarce. Further on, there is a lack of landscape-level studies taking into account potential side effects of IFC on different forest types. Therefore we assessed ecosystem services (carbon stocks, timber volume) and species richness in landscapes with and without IFC. Additionally, we evaluated potential side-effects of IFC in adjacent forest types; hypothesizing potential leakage effects of IFC. Finally, we tested if deforestation rates decreased after IFC implementation. Forest inventories were conducted in 72 plots across eight landscapes in the Ecuadorian Central Amazon with and without IFC. Plots were randomly selected within three forest types (old-growth, logged and successional forests). In each plot all individuals with a diameter at breast height greater than 10 cm were measured. Old-growth forests in general showed higher carbon stocks, timber volume and species richness, and no significant differences between old-growth forests in IFC and non-IFC landscapes were found. Logged forests had 32% less above-ground carbon (AGC) and timber volume in comparison to old-growth forests. Surprisingly, logged forests near IFC presented higher AGC stocks than logged forests in non-IFC landscapes, indicating positive side-effects of IFC. Successional forests contain 56% to 64% of AGC, total carbon and timber volume, in comparison to old-growth forests, and 82% to 87% in comparison to logged forests. Therefore, successional forests could play an important role for restoration and should receive more attention in national climate change policies. Finally, after IFC implementation deforestation rate decreased on parish level. Our study presents scientific evidence of IFC contribution to conserving ecosystem services and species richness. In addition IFC could help indirectly to reduce degradation effects attributed to logging, indicating potential compatibility of conservation aims with forest activities at a landscape level.

Habitat amount, not patch size and isolation, drives species richness of macro‐moth communities in countryside landscapes

AbstractAimOur aim was to test whether species richness patterns are best explained by the effect of the total amount of habitat within the landscape, or instead by a combination of patch size and patch isolation effects. To this end, we jointly contrast the habitat amount hypothesis and countryside biogeography with patch size and isolation concepts from island biogeography.LocationThree multi‐habitat landscapes in Peneda‐Gerês National Park, NW Portugal.TaxonMacro‐moths (Lepidoptera).MethodsLight‐trapping using a semi‐nested design at 84 fixed sites which were each repeatedly sampled six times.ResultsAutocovariate models show that sampling sites with a higher number of forest and meadow macro‐moth species (alpha diversity) were surrounded by a higher amount of forest and meadow habitat, respectively within a 160 and 320 m radius (scale of effect). These top‐ranked models, containing only habitat amount as a significant variable, had lower Akaike's information criteria (AIC) than models (only) containing patch size and/or isolation. Complementary to this, the countryside species–area relationship (SAR) model outperforms the classic SAR model, so that the effective area of habitat explains landscape species richness (gamma diversity) across spatial scales (beta diversity) better than the classic SAR. Specifically, we show that forest macro‐moths have a higher spatial turnover than meadow macro‐moths and that, on average, there are more species in forest than in meadow habitat.Main conclusionsThe habitat amount hypothesis predicts alpha species richness in multi‐habitat landscapes better than do patch size and isolation while the countryside SAR predicts beta and gamma diversity better than the classic SAR. We suggest that evidence is mounting to revise the application of the classical approaches of island biogeography and metapopulation theory to conservation biogeography.

Landscape‐specific thresholds in the relationship between species richness and natural land cover

Abstract Thresholds in the relationship between species richness and natural land cover can inform landscape‐level vegetation protection and restoration targets. However, landscapes differ considerably in composition and other environmental attributes. If the effect of natural land cover on species richness depends on (i.e., interacts with) these attributes, and this affects the value of thresholds in this relationship, such dependencies must be considered when using thresholds to guide landscape management. We hypothesized that the amount of natural land cover at which a threshold occurs would differ in predictable ways with particular anthropogenic, abiotic, and biotic attributes of landscapes. To test this, we related woodland bird species richness in 251 landscapes, each 100 km2, to natural land cover in south‐east Australia. We compared the fit of exponential and threshold models of the richness–natural land cover relationship, focussing on the extent of natural land cover at which thresholds presented among landscapes that differed in matrix land use intensity, heterogeneity, productivity, and the prevalence of strong biotic interactors. We used linear mixed modelling to examine how interactions between natural land cover and the various landscape attributes affected the fit of models of species richness. Threshold models of the richness–natural land cover relationship were always a better fit than exponential models. Threshold values did not vary consistently with specific landscape attributes, with the exception of landscapes that were classified by the prevalence of strong biotic interactors (hypercompetitive native birds of the genus Manorina). Natural land cover had a more positive effect on species richness in landscapes when Manorina prevalence was higher. This positive interaction provided the biggest improvement in explanatory power of models of species richness. Synthesis and applications. While we detected an interaction between Manorina prevalence and the area of natural land cover, generalities relating to the underlying nature of thresholds in the richness–natural land cover relationship remain elusive. Complex interactions, relating to various landscape attributes and associated ecological processes, likely underpin variation in threshold values. Until these complexities are better understood, the use of thresholds for informing landscape management and conservation target setting should be approached with caution.

Spatial relationship between biodiversity and geodiversity across a gradient of land-use intensity in high-latitude landscapes

‘Conserving Nature’s stage’ has been advanced as an important conservation principle because of known links between biodiversity and abiotic environmental diversity, especially in sensitive high-latitude environments and at the landscape scale. However these links have not been examined across gradients of human impact on the landscape. To (1) analyze the relationships between land-use intensity and both landscape-scale biodiversity and geodiversity, and (2) assess the contributions of geodiversity, climate and spatial variables to explaining vascular plant species richness in landscapes of low, moderate and high human impact. We used generalized additive models (GAMs) to analyze relationships between land-use intensity and both geodiversity (geological, geomorphological and hydrological richness) and plant species richness in 6191 1-km2 grid squares across Finland. We used linear regression-based variation partitioning (VP) to assess contributions of climate, geodiversity and spatial variable groups to accounting for spatial variation in species richness. In GAMs, geodiversity correlated negatively, and plant species richness positively, with land-use intensity. Both relationships were non-linear. In VP, geodiversity best accounted for species richness in areas of moderate to high human impact. These overall contributions were mainly due to variation explained jointly with climate, which dominated the models. Independent geodiversity contributions were highest in pristine environments, but low throughout. Human action increases biodiversity but may reduce geodiversity, at landscape scale in high-latitude environments. Better understanding of the connections between biodiversity and abiotic environment along changing land-use gradients is essential in developing sustainable measures to conserve biodiversity under global change.

An empirical investigation of why species-area relationships overestimate species losses.

It is generally assumed that, when natural habitat is converted to human-dominated land cover, such habitat is lost to its native species. Most literature assumes that species richness should vary as a function of remaining natural area, following the well-known species-area relationship (i.e., classic SAR). However, classic SARs have consistently overestimated species losses resulting from conversion of natural forested land cover to human-dominated landscapes. Moreover, richness is sometimes a peaked function of remaining natural habitat. Recent studies propose modified SAR models based on species' utilization of multiple habitat types, yet none fully explain a peaked species-area relationship. Here, we evaluate the responses of total avian richness, forest bird richness, and open-habitat bird richness to remaining natural land cover within 991 quadrats, each 100 km2, across southern Ontario, Canada. Total bird species richness peaks at roughly 50% natural land cover. Richness of forest birds varies as a classic power function of forested area. In contrast, richness of birds that prefer open habitats does not increase monotonically with either natural- or human-dominated land cover. Richness of open-habitat species can be predicted when we partition human-dominated land cover into an "available human-dominated" component and "lost" habitat. Disiinguishing three land-cover types (natural, available human-dominated, and lost) can thus permit accurate predictions of species richness in landscapes with differing levels of natural habitat conversion.

Broad‐scale patterns in plant diversity vary between land uses in a variegated temperate Australian agricultural landscape

AbstractPlant diversity is threatened in many agricultural landscapes. Our understanding of patterns of plant diversity in these landscapes is mainly based on small‐scale (<1000 m2) observations of species richness. However, such observations are insufficient for detecting the spatial heterogeneity of vegetation composition. In a case‐study farm on the North‐West Slopes of New South Wales, Australia, we observed species richness at four scales (quadrat, patch, land use and landscape) across five land uses (grazed and ungrazed woodlands, native pastures, roadsides and crops). We applied two landscape ecological models to assess the contribution of these land uses to landscape species richness: (i) additive partitioning of diversity at multiple spatial scales, and (ii) a measure of habitat specificity – the effective number of species that a patch contributes to landscape species richness. Native pastures had less variation between patches than grazed and ungrazed woodlands, and hence were less species‐rich at the landscape scale, despite having similar richness to woodlands at the quadrat and patch scale. Habitat specificity was significantly higher for ungrazed woodland patches than all other land uses. Our results showed that in this landscape, ungrazed woodland patches had a higher contribution than the grazed land uses to landscape species richness. These results have implications for the conservation management of this landscape, and highlighted the need for greater consensus on the influence of different land uses on landscape patterns of plant diversity.

Quantifying habitat‐specific contributions to insect diversity in agricultural mosaic landscapes

Abstract Agricultural intensification often leads to loss and fragmentation of natural and semi‐natural habitats. As a consequence, biodiversity in intensively managed agro‐ecosystems is often lower than in agricultural landscapes with greater natural and semi‐natural land cover. Different types of semi‐natural habitat may support specific species assemblages thereby increasing landscape‐level biodiversity, but this has seldom been tested, especially for insects that have different functional roles in agro‐ecosystems. Here, we quantified these habitat‐specific contributions by surveying species richness and composition of wild bees, true bugs and ground beetles and compared them among different types of semi‐natural habitats within two differently structured agricultural landscapes in Switzerland. We found high shares of habitat specific species and habitat types within landscapes to differ up to fourfold in their specificity (i.e. their contribution to the total landscape species richness). Using statistical null models for habitat specificity and multiplicative beta diversity, we identified habitats that contributed more or less than expected by chance to the overall species diversity at the landscape level. The observed degree of complementarity among habitats highlights the importance of habitat diversity for insect species richness and potentially ecosystem functioning in agricultural landscapes. By helping to understand better the habitat‐specific contributions to insect diversity in agricultural areas, our results will facilitate targeted conservation measures and sustainable landscape planning. Yet, qualitative differences in habitat specificity and separation of habitat‐specific communities observed between landscapes should be explored further in future studies of multiple landscapes.

The Effects of Landscape Variables on the Species-Area Relationship during Late-Stage Habitat Fragmentation

Few studies have focused explicitly on the later stages of the fragmentation process, or “late-stage fragmentation”, during which habitat area and patch number decrease simultaneously. This lack of attention is despite the fact that many of the anthropogenically fragmented habitats around the world are, or soon will be, in late-stage fragmentation. Understanding the ecological processes and patterns that occur in late-stage fragmentation is critical to protect the species richness in these fragments. We investigated plant species composition on 152 islands in the Thousand Island Lake, China. A random sampling method was used to create simulated fragmented landscapes with different total habitat areas and numbers of patches mimicking the process of late-stage fragmentation. The response of the landscape-scale species-area relationship (LSAR) to fragmentation per se was investigated, and the contribution of inter-specific differences in the responses to late-stage fragmentation was tested. We found that the loss of species at small areas was compensated for by the effects of fragmentation per se, i.e., there were weak area effects on species richness in landscapes due to many patches with irregular shapes and high variation in size. The study also illustrated the importance of inter-specific differences for responses to fragmentation in that the LSARs of rare and common species were differently influenced by the effects of fragmentation per se. In conclusion, our analyses at the landscape scale demonstrate the significant influences of fragmentation per se on area effects and the importance of inter-specific differences for responses to fragmentation in late-stage fragmentation. These findings add to our understanding of the effects of habitat fragmentation on species diversity.

Landscape context affects the relationship between local and landscape species richness of butterflies in semi‐natural habitats

Local species richness of butterflies can be expected to benefit from both local habitat properties as well as the availability of suitable habitats and source populations in the surrounding landscape. Whether local species richness is dependent on local or landscape factors can be assessed by examining the relationship between local and landscape species richness. Here we studied how local species richness is related to landscape‐level species richness in landscapes differing in agricultural intensity. The relationship was linear for field boundaries in intensively cultivated landscapes and non‐linear in less‐intensively cultivated landscapes. In landscapes containing semi‐natural grasslands (on average 4% of overall land‐use), the relationship was non‐linear for field boundaries, but linear when considering local species richness of the grasslands themselves. These results show that local factors are more important than landscape factors in determining local species richness in landscapes which contained semi‐natural grasslands. Local species richness was limited by landscape factors in intensively cultivated landscapes. This interpretation was supported by the relationship between local species richness and landscape‐scale average mobility and generalist percentage of butterfly assemblages. We conclude that the management of field boundary habitat quality for butterflies is expected to be most effective in landscapes with semi‐natural grasslands, the species composition of which in turn is dependent on the regional occurrence of grasslands. Based on our results, managing non‐crop habitats for the conservation of habitat specialists and species with poor mobility will be most efficient in regions where patches of semi‐natural grasslands occur.

Colonization of central European abandoned fields by dry grassland species depends on the species richness of the source habitats: a new approach for measuring habitat isolation

Abandoned fields are perceived as potential habitats for species of threatened semi-natural dry grasslands. However, information is lacking regarding how the spontaneous colonization of abandoned fields depends on the broader spatial context. We recorded the occurrence of 87 target species in 46 abandoned fields and 339 dry grasslands. We tested the effect of the isolation of abandoned fields from source grasslands on the number of dry grassland species occurring in abandoned fields either with or without habitat characteristics being used as covariates. The isolation of the fields was calculated using the distance and area (IA) or distance and species richness (IS) of source habitats. IS always explained the number of grassland species in the abandoned fields better than IA. The effect of isolation became smaller or even non-significant with the inclusion of covariates; it also changed with the method used for measuring distance (edge-to-edge or center-to-center), and it was lower when other abandoned fields were considered as additional source habitats. The different performance of the two isolation measures can be explained by the weak species–area relationship in the grasslands, indicating differences in their habitat quality. Species richness is a better proxy of habitat importance in terms of propagule source than habitat area, and the new isolation measure is therefore suitable for studying the effects of landscape structure on species richness in landscapes presenting a weak species–area relationship, such as areas exhibiting pronounced effects of land-use history. Inclusion of habitat characteristics as covariates may considerably alter conclusions regarding the effect of isolation, which might actually be overestimated when assessed separately.

Value of an urban habitat for the native Mediterranean avifauna

Mediterranean landscapes resulted from complex land uses that produced a mosaic of extensive crops, grasslands, scrublands and scattered woodlands. During the twentieth century the decrease in traditional agriculture triggered a decrease in open habitats and an increase in forests. In the meantime urban centres grew dramatically. Both spread of forest and urban areas have been suspected to participate in the decline of typical Mediterranean bird species and, in general, to cause faunal loss. However, modern cities offer a variety of landscape types and, in the Mediterranean, their value for native bird species has been little assessed. We compared the bird communities from an urban landscape, including built up and natural or semi natural units within the limits of the city of Montpellier, to the bird communities from non-urban habitats (cropland, grassland and woodland) located nearby but away from direct urban influence. Fifty four percent of the bird species recorded in the non-urban habitats also occurred in the urban landscape. On average, estimated species richness in the urban landscape was similar to values obtained for non-urban habitats. Within the urban landscape species richness was lowest in the dense historical centre and highest in the residential areas. The residential areas and urban woods were suitable habitats for most generalist species but also for several more specialized species recorded in the non-urban habitats. Some species actually reached their highest observation frequency in the urban landscape. Urban landscape was least favourable to the same farmland and open-habitat specialists that have been negatively affected by agricultural abandonment in the region. Finally, five of the species common in the urban landscape had an unfavorable conservation status in 2004 in the EU. This study emphasizes that Mediterranean urban areas have the potential to host a diverse native bird community. Finding ways to improve their carrying capacity for the local avifauna might be a worthwhile objective for animal conservation.

Effects of topographic variability on the scaling of plant species richness in gradient dominated landscapes

It is commonly assumed that variation in abiotic site conditions influences the number of niches, which in turn affects the potential species richness in an area. Based on theoretical considerations, abiotic variation is often used as an estimator of species richness at broad scales, while at finer landscape scales the diversity of habitat types is used. However, habitat estimators assume the landscape to be composed of discrete, homogeneous patches with sharp boundaries, and such a concept is hard to apply in gradient‐dominated landscapes. The aim of this study was therefore to investigate the influence of topographic variability (TV) on species richness at the landscape level (gamma (γ) diversity) and on its components (alpha (α) and beta (β) diversity) at microsite and habitat group levels. Using floristic data from 12 “landscapes” of 1 km2 we investigated the influence on diversity components of two simple and one complex measures of TV. While the standard deviation (SD) of altitude explained a high proportion of the variation in γ diversity (linear regression model, R2=0.63), the complex measure, SD of solar radiation explained it even better (R2=0.82). There were strong effects of TV on α and β diversity components at the microsite level, but only marginal increases of the diversity components at the habitat level. Further analyses revealed that the missing increase of the habitat level components was caused by differences between habitat groups and that only grassland diversity components increased significantly with TV. We conclude that TV at a landscape scale has strong effects on niche or microsite diversity and is an appropriate estimator of relative species richness in landscapes that are topographically heterogeneous and gradient dominated.

How landscape structure, land‐use intensity and habitat diversity affect components of total arthropod diversity in agricultural landscapes

Summary Agricultural intensification poses a serious threat to biodiversity as a consequence of increased land‐use intensity, decreased landscape heterogeneity and reduced habitat diversity. Although there is interest in the preservation of total species richness of an agricultural landscape (γ diversity), the effects of intensification have been assessed primarily by species richness at a local scale (α diversity). This ignores species richness between local communities (β diversity), which is an important component of total species richness. In this study, measures of land‐use intensity, landscape structure and habitat diversity were related to γ, α and β diversity of wild bees (Apoidea), carabid beetles (Carabidae), hoverflies (Syrphidae), true bugs (Heteroptera) and spiders (Araneae) within 16 local communities in 24 temperate European agricultural landscapes. The total landscape species richness of all groups was most strongly affected by increased proximity of semi‐natural habitat patches. Bees also decreased in landscapes with a high intensity of farmland management, demonstrating additive effects of both factors. Separating total species diversity into components, the decrease in total species richness could be attributed primarily to a decrease in species diversity between local communities. Species richness of the local communities of all investigated groups decreased with increasing land‐use intensity and, in the case of spiders, decreasing proximity of the semi‐natural habitat patches. The effect of increased habitat diversity appeared to be of secondary importance to total species richness but caused a shift in the relative contribution of α and β diversity towards the latter. Synthesis and applications. This study demonstrates that the effects of agricultural change operate at a landscape level and that examining species diversity at a local level fails to explain the total species richness of an agricultural landscape. The coincidence of patterns of β diversity with those of γ diversity emphasizes that such information is of crucial importance for the implementation and evaluation of restoration programmes aiming to restore sustainable countryside diversity. As local extinction processes in highly fragmented landscapes shape biodiversity, priority should be given to the conservation of diverse agricultural landscape remnants in Europe.

Quantifying determinants contributing to plant species richness in mosaic landscapes: a single- and multi-patch perspective

Despite good theoretical knowledge about determinants of plant species richness in mosaic landscapes, validations based on complete surveys are scarce. We conducted a case study in a highly fragmented, traditional agricultural landscape. In 199 patches of 20 representative multi-patch-plots (MPPs, 1 ha) we recorded a total of 371 plant species. In addition to an additive partitioning of species diversity at the (a) patch- and (b) MPP-scale, we adopted the recently proposed ‘specificity’ measure to quantify the contribution of a spatial subunit to landscape species richness (subunit-to-landscape-contribution, SLC). SLC-values were calculated at both scales with respect to various spatial extents. General regression models were used to quantify the relative importance of hypothesis-driven determinants for species richness and SLC-values.

Interacting effects of landscape context and habitat quality on flower visiting insects in agricultural landscapes

Summary Landscape context and habitat quality may have pronounced effects on the diversity of flower visiting insects. We investigated whether the effects of landscape context and habitat quality on flower visiting insects interact in agricultural landscapes in the Netherlands. Landscape context was expressed as the area of semi-natural habitats or the density of linear landscape features, and was quantified at spatial scales ranging from 250 to 2000 m. Habitat quality was determined as flower abundance. Species richness and abundance of hoverflies and bees were determined along 16 stream banks experiencing similar environmental conditions but situated in areas with contrasting landscape context. Only flower abundance and the area of semi-natural habitats within 500–1000 m were significantly related to species richness of hoverflies and bees and these factors had interacting effects on both species groups. Our results suggest that the regional area of semi-natural habitats had a positive effect on hoverfly species richness when flower abundance was relatively high, but not when flower abundance was low. Moreover, flower abundance had positive effects on hoverfly species richness only in areas with relatively many semi-natural habitats. Contrastingly, flower abundance had a more positive effect on bee species richness in landscapes with few semi-natural habitats compared to landscapes with more semi-natural habitats. Our results suggest that the importance of landscape context for the species richness of flower visiting insects depends upon the quality of the habitat patches.

Contribution of live fences to the ecological integrity of agricultural landscapes

Live fences are conspicuous features of agricultural landscapes across Central America but there is remarkably little information about their abundance, distribution, and function. Here we present a detailed analysis of: (1) the abundance, composition, structure and distribution of live fences in four contrasting cattle-producing areas of Costa Rica and Nicaragua; (2) the management of live fences by farmers; and (3) the ecological roles of live fences in providing habitat, resources and connectivity for wildlife. Data on botanical composition and structure are complemented by documentation of local knowledge about live fences and associated management practices, as well as an assessment of fauna that utilize them. Live fences were common, occurring on between 49% and 89% of cattle farms, with an overall mean of 0.14 ± 0.01 km ha−1 of farm land and almost 20 fences per farm. They were generally short (164.3 ± 5.4 m), narrow (3.76 ± 0.03 m) and densely planted (323.1 ± 8.6 trees km−1), consisting primarily of planted trees. The mean tree species richness for individual fences in each landscape was low (from 1.4 to 7.5 species per fence), but landscape species richness was higher (from 27 to 85 species, with over 70 species in three out of four sites). A total of 161 tree and palm species were recorded in the live fences across the four sites. The abundance, tree species composition and structure of live fences varied across farms and landscapes, reflecting differences in environmental conditions and management strategies. In all landscapes the main productive roles of live fences were to divide pastures and serve as barriers to animal movement, although they were also sources of fodder, firewood, timber and fruit. The main ecological roles were to provide habitats and resources for animal species and structural connectivity of woody habitat across the agricultural landscape. More than 160 species of birds, bats, dung beetles and butterflies were recorded visiting them. Their value for biodiversity conservation depended on their species composition, structural diversity and arrangement within the landscape, all of which were heavily influenced by management currently undertaken by farmers in pursuit of production rather than conservation goals. Live fences are important features of agricultural landscapes that merit much greater attention in sustainable land management strategies and need to be an explicit element in regulations and incentives that aim to enhance the ecological integrity of rural landscapes in Central America.

Landscape‐dependent distribution of northern forest birds in winter

We evaluated the effects of landscape structure, along a broad gradient of deforestation (forest cover 8–88%, 500‐m radius), on the spatial distribution of forest birds exposed to winter climatic conditions, in Quebec, Canada. Concurrently, we conducted an experiment to determine if these effects would persist if an unlimited source of energy, provided by food‐supplementation, became available. We analyzed these effects at the population level, using count data of black‐capped chickadees Poecile atricapillus, but also at the community level, referring to species richness. In one of the two years of the study, before food‐supplementation began (November), “forest integrity” (a composite of forest cover and edge density) was positively associated with chickadee abundance and species richness. Each year, forest integrity was also positively associated with chickadee abundance and species richness in landscapes that were supplemented (December–February). However, in control landscapes, during the food‐supplementation period, chickadee abundance and species richness tended to decrease with an increase in forest integrity. We argue that the more forested control landscapes facilitated winter emigration of juveniles and transient birds. Conversely, our results further suggest that, in the highly deforested and fragmented control landscapes, birds became “gap‐locked” when rigorous winter climatic conditions exacerbated already existing movement constraints.