Modelling multi-species response to landscape dynamics: mosaic cycles support urban biodiversity

The importance of the spatial as well as the temporal structure of habitat patches for urban biodiversity has been recognised, but rarely quantified. In dynamic environments the rate of habitat destruction and recreation (i.e. the landscape turnover rate), the minimum amount of potential habitat, its spatial configuration as well as the environmental conditions determining habitat quality are crucial factors for species occurrence. We analysed species responses to environmental parameters and to the spatio-temporal configuration of urban brownfield habitats in a multi-species approach (37 plant and 43 insect species). Species presence/absence data and soil parameters, site age, vegetation structure and landscape context were recorded by random stratified sampling at 133 study plots in industrial areas in the city of Bremen (Germany). Based on the field data, we predicted species occurrences by species distribution models using a multi-model inference approach. Predicted species communities were driven by successional age both at the scale of a single building lot and at the landscape scale. Minimum average succession time of brownfield habitats required to support all and especially regionally rare species depended on the proportion of available open space; the larger the potential habitat area the faster the acceptable turnover. Most plant, grasshopper, and leafhopper species modelled could be maintained at an intermediate turnover rate (mean age of 10–15 years) and a proportion of open sites of at least 40%. Our modelling approach provides the opportunity of inferring optimal spatio-temporal landscape configurations for urban conservation management from patch scale species-environment relationships. The results indicate that urban planning should incorporate land use dynamics into the management of urban biodiversity. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Modeling scale-dependent landscape pattern,dispersal, and connectivity from the perspective of the organism

Understanding the impacts of habitat fragmentation on dispersal is an important issue in landscape and conservation ecology. Here I examine the effects of fine- to broad-scale patterns in landscape structure on dispersal success of organisms with differing life-history traits. An individual-based model was used to simulate dispersal of amphibian-like species whose movements were driven by land cover and moisture conditions. To systematically control spatial pattern, a landscape model was created by merging simulated land cover maps with synthetic topographic surfaces. Landscapes varied in topographic roughness and spatial contagion in agriculture and urban land cover. Simulations included three different species types that varied in their maximum potential dispersal distances by 1-, 2-, or 4-fold. Two sets of simulations addressed effects of varying aspects of landscape structure on dispersal success. In the first set of simulations, which incorporated variable distances between breeding patches, dispersal success was lowest for all species types when anthropogenic cover was patchily distributed. In the second set, with interpatch distances held constant as landscape composition varied, dispersal success decreased as anthropogenic cover became spatially contagious. Both sets revealed strong main effects of species characteristics, interpatch distances and landscape composition on dispersal success; furthermore, scale-dependent patterns in land cover and moisture gradients had a stronger effect on longer- than shorter-ranging species types. Taken together, these simulations suggest that heuristic conservation strategies could potentially be developed based on important but limited life history information.     

An integrative approach for analysing landscape dynamics in diverse cultivated and natural mountain areas

Our landscape can be regarded as a development process that is affected and subsequently shaped by a series of different environmental and human-induced factors. However, to date, concrete data about the impact of each of these factors are still missing. One key reason for this is that methods of acquisition and evaluation of these factors inherently have differences, thereby preventing meaningful comparative analyses. This study presents an integrative methodical approach that bridges many of these gaps. Our approach also has the advantages of being generally applicable while delivering easily interpretable results that also allow comparisons between diverse geographical regions. The indicators used enable all major features of landscape change, e.g. changes in land use, landscape structuring, habitat settings, and urban sprawl, to be accurately monitored and provide high-quality realistic results that were validated in our study site, South Tyrol (North Italy). Indicators were selected for both their further subdivision, e.g. monocrops and different features of mixed crops, and their easy to ascertain hierarchically structured feature classification, e.g. land cover. Furthermore, our use of ecoregions enables better comparison of aspects of landscape development for geographical regions having diverse socio-economic and ecological conditions. Our methodical approach can be used as a basis not only for creating landscape change scenarios, but also for determining the environmental and human-induced factors involved and being able to list them in order of importance. Further the detected striking difference between the mapped land-use data and the official census data suggests a validation of the methodical approach in context of the national agriculture census.     

Effects of land use on population presence and genetic structure of an amphibian in an agricultural landscape

Context

Species distributions are a function of an individual’s ability to disperse to and colonize habitat patches. These processes depend upon landscape configuration and composition.

Objectives

Using Blanchard’s cricket frogs (Acris blanchardi), we assessed which land cover types were predictive of (1) presence at three spatial scales (pond-shed, 500 and 2500 m) and (2) genetic structure. We predicted that forested, urban, and road land covers would negatively affect cricket frogs. We also predicted that agricultural, field, and aquatic land covers would positively affect cricket frogs.

Methods

We surveyed for cricket frogs at 28 sites in southwestern Ohio, USA to determine presence across different habitats and analyze genetic structure among populations. For our first objective, we examined if land use (crop, field, forest, and urban habitat) and landscape features (ponds, streams, and roads) explained presence; for our second objective, we assessed whether these land cover types explained genetic distance between populations.

Results

Land cover did not have a strong influence on cricket frog presence. However, multiple competing models suggested effects of roads, streams, and land use. We found genetic structuring: populations were grouped into five major clusters and nine finer-scale clusters. Highways were predictive of increased genetic distance.

Conclusions

By combining a focal-patch study with landscape genetics, our study suggests that major roads and waterways are key features affecting species distributions in agricultural landscapes. We demonstrate that cricket frogs may respond to landscape features at larger spatial scales, and that presence and movement may be affected by different environmental factors.

     

Spatial resilience: integrating landscape ecology,resilience, and sustainability

Landscape ecology has a high potential to contribute to sustainability in the interactions of people and nature. Landscape ecologists have already made considerable progress towards a more general understanding of the relevance of spatial variation for ecosystems. Incorporating the complexities of societies and economies into landscape ecology analyses will, however, require a broader framework for thinking about spatial elements of complexity. An exciting recent development is to explicitly try to integrate landscape ecology and ideas about resilience in social–ecological systems through the concept of spatial resilience. Spatial resilience focuses on the importance of location, connectivity, and context for resilience, based on the idea that spatial variation in patterns and processes at different scales both impacts and is impacted by local system resilience. I first introduce and define the concepts of resilience and spatial resilience and then discuss some of their potential contributions to the further interdisciplinary integration of landscape ecology, complexity theory, and sustainability science. Complexity theorists have argued that many complex phenomena, such as symmetry-breaking and selection, share common underlying mechanisms regardless of system type (physical, social, ecological, or economic). Similarities in the consequences of social exclusion and habitat fragmentation provide an informative example. There are many strong parallels between pattern–process interactions in social and ecological systems, respectively, and a number of general spatial principles and mechanisms are emerging that have relevance across many different kinds of system. Landscape ecologists, with their background in spatially explicit pattern–process analysis, are well placed to contribute to this emerging research agenda.     

Integrating landscape ecology and conservation physiology

The need to understand how anthropogenic landscape alteration affects fauna populations has never been more pressing. The importance of developing an understanding of the processes behind local extinction is widely acknowledged, but inference from spatial patterns of fauna distribution continues to dominate. However, this approach is limited in its ability to generate strong predictions about future distributions and local extinctions, especially when population-level responses to landscape alteration are subject to long time lags. We review the potential for indices of physiological stress and condition to contribute to understanding of how landscape pattern affects species persistence. Such measures can indicate habitat quality from the perspective of the individual animal, and can reveal environmental stressors before their negative consequences begin to manifest at a population level. Spatial patterns of chronic stress may therefore yield valuable insight into how landscape alteration influences species. We propose that the emerging disciplines of conservation physiology and macrophysiology have much to offer spatial ecology, and have great potential to reveal the physiological pathways through which habitat alteration affects fauna populations and their persistence in fragmented landscapes.     

城市密集区域鸟类群落结构与生境关系分析

鸟类多样性作为城市生态化程度的表征,已被广泛应用于世界各地的城市环境评价因子。城市扩张带来城市景观格局的改变,同时也将改变城市野生动物的栖息环境。城市密集区中绿地系统作为鸟类在城市栖息、游憩的场所,其自然状态已被人工选择取代,这无疑影响着鸟类的多样性、物种数、丰富度、优势度等群落结构特征。成都市青龙场鸟类观测数据显示鸟类群落结构与不同生境间存在密切联系,这种联系为城市生态化建设中的合理规划与布局提供了参考,更期望城市野生动物的栖息地保护能够得到更多的社会关注。     

Spatial correlates of amphibian use of constructed wetlands in an urban landscape

Many amphibian species rely on both aquatic and terrestrial habitats to complete their life cycles. Therefore, processes operating both within the aquatic breeding habitat, and in the surrounding uplands may influence species distributions and community composition. Moreover, changes in land use adjacent to breeding site may degrade aquatic habitats. To assess land use effects on pond-breeding amphibian assemblages, we investigated relationships between land use, breeding habitat conditions, and breeding amphibian use of constructed wetlands in urban environments of the Baltimore metropolitan area, USA. Forest and impervious surface associations with species richness and occurrence occurred at spatial scales ranging from 50 to 1,000 m, with strongest relationships at 500 m. Forest and impervious surface cover within 1,000 m of ponds were also related to water and sediment quality, which in turn were capable of explaining a proportion of the observed variation in species richness and occurrence. Taken together, our results suggest that forest and other land covers within relatively proximal distances to ponds (i.e., within 50–1,000 m) may be influencing species richness directly via the provisioning of upland habitat, and indirectly via influences on within pond habitat quality. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Quantifying the landscape influence on plant invasions in Mediterranean coastal habitats

Landscape pattern might be an important determinant of non-native plant invasions because it encompasses components influencing the availability of non-native plant propagules and disturbance regimes. We aimed at exploring the relative role of patch and landscape characteristics, compared to those of habitat type and regional human influence on non-native plant species richness. For this purpose, we identified all non-native plant species in 295 patches of four coastal habitat types across three administrative regions in NE Spain differing in the degree of human influence. For each patch, we calculated several variables reflecting habitat patch geometry (size and shape), landscape composition (distribution of land-cover categories) and landscape configuration (arrangement of patches). The last two groups of variables were calculated at five different spatial extents. Landscape composition was by far the most important group of variables associated with non-native species richness. Natural areas close to diverse and urban landscapes had a high number of non-native species while surrounding agricultural areas could buffer this effect. Regional human influence was also strongly associated with non-native species richness while habitat type was the least important factor. Differences in sensitivity of landscape variables across spatial extents proved relevant, with 100 m being the most influential extent for most variables. These results suggest that landscape characteristics should be considered for performing explicit spatial risk analyses of plant invasions. Consequently, the management of invaded habitats should focus not only at the stand scale but also at the highly influential neighbouring landscape. Prior to incorporate landscape characteristics into management decisions, sensitivity analyses should be taken into account to avoid inconsistent variables.     

Pond density as a determinant of aquatic species richness in an urban landscape

Green spaces within urban areas provide services and benefits to human populations and habitat for a variety of species. Freshwater, in the form of rivers, canals, lakes, reservoirs and ponds, is an important component of urban greenspaces. This paper focuses on ponds; and specifically ponds within urban areas. This work is timely as during 2008 ponds were designated, in the UK, as habitats of national conservation importance. Yet, while farmland ponds have received considerable attention, there has been little work on the ecology and landscape ecology of urban ponds. Ecological data was collected from 37 ponds in the Borough of Halton (northwest England) over a period of 2 years (2005–2006). The median species richness in these ponds was 28 invertebrate species and 10 macrophyte species. A highly significant correlation was observed between pond density and species richness. The relationship between the richness of different taxa varied according to scale; becoming more significant within pond clusters than within a single pond. These findings have significance for those involved in planning and managing urban environments, further strengthening the need for functional ecological connectivity in urban areas. With pressure to increase infill development, and thus raise housing density, a greater understanding of the affect of urban design on pond ecology will be of importance to urban planners and ecologists alike.     

Effects of landscape composition and connectivity on the distribution of an endangered parrot in agricultural landscapes

The extent and connectivity of individual habitat types strongly affects the distribution and abundance of organisms. However, little is known of how the level of connectivity and the interactions between different habitat types influences the distribution of species. Here, we used the geographically restricted and endangered regent parrot Polytelis anthopeplus monarchoides as a case study to examine the importance of composition and connectivity between different elements in 39 complex landscape mosaics (each 10 km radius). We compiled a database of 674 regent parrot nesting records, regional vegetation maps and measures of multipath connectivity between core vegetation types under different scenarios of resistance to movement provided by landscape elements. The occurrence of regent parrot nests was strongly affected by landscape composition, being positively related to the extent Eucalyptus camaldulensis riverine forest, but negatively related to the extent of semi-arid woodlands dominated by Eucalyptus largiflorens. Connectivity between E. camaldulensis forest (principal nesting habitat) and mallee (preferred feeding habitat) was a strong predictor of nest locations. Our study shows that the suitability of fragmented agricultural landscapes for supporting species can be greatly affected by connectivity and interactions between preferred and non-preferred habitats. For species that require complementary habitats such as the regent parrot, conservation management activities may be ineffective if they simply focus on a single core habitat type or the impacts of human land uses without regard to the interrelationships among landscape elements. While increasing the amount of primary preferred habitat should remain a cornerstone goal, increasing the extent and improving connectivity with alternative landscape elements also should be priority management objectives.     

Quantifying landscape connectivity through the use of connectivity response curves

Habitat connectivity is an essential component of biodiversity conservation. Simulated landscapes were manipulated to quantify the impact of changes to the amount, fragmentation and dispersion of habitat on a widely applied landscape connectivity metric, the probability of connectivity index. Index results for different landscape scenarios were plotted against the dispersal distances used for their calculation to create connectivity response curves for each scenario. Understanding index response to controlled changes in landscape structure at a range of spatial scales can be used to give context to comparison of alternative landscape management scenarios. Increased amounts of habitat, decreased fragmentation and decreased inter-patch distances resulted in increased connectivity index values. Connectivity response curves demonstrated increases in assessed connectivity for scenarios with continuous corridors or “stepping stone” connectors. The sensitivity of connectivity response curves to controlled changes in landscape structure indicate that this approach is able to detect and distinguish between different types of landscape changes, but that delineation of habitat and method of quantifying dispersal probability incorporate assumptions that must be recognized when interpreting results to guide landscape management. Representing landscape connectivity in this manner allows for the impacts of alternative landscape management strategies to be compared visually through comparative plots, or statistically through the parameters that describe connectivity response curves.     

The effects of future urban development on habitat fragmentation in the Santa Monica Mountains

A site suitability model of urban development was created for the Santa Monica Mountains in southern California, USA, to project to what degree future development might fragment the natural habitat. The purpose was to help prioritize land acquisition for the Santa Monica Mountains National Recreation Area and examine to what extent projected urban development would affect distinct vegetation classes. The model included both environmental constraints (slope angle), and spatial factors related to urban planning (proximity to roads and existing development, proposed development, and areas zoned for development). It implemented a stochastic component; areas projected to have high development potential in the suitability model were randomly selected for development. Ownership tracts were used as the spatial unit of development in order to give the model spatial realism and not arbitrarily `develop' grid cells. Using different assumptions and parameters, the model projected the pattern of development from 5 to 25 years hence (based on recent development rates in the area). While <25% of the remaining natural landscape is removed under these scenarios, up to 30% of core (interior) habitat area is lost and edge length between natural vegetation and development increases as much as 45%. Measures of landscape shape complexity increased with area developed and number of patches of natural habitat increased four- to nine-fold, depending upon model parameters. This increase in fragmentation occurs because of the existing patterns of land ownership, where private (`developable') land is interspersed with preserved park lands.     

Landscape cohesion: an index for the conservation potential of landscapes for biodiversity

In urbanising landscapes, planning for sustainable biodiversity occurs in a context of multifunctional land use. Important conditions for species persistence are habitat quality, the amount and configuration of habitat and the permeability of the landscape matrix. For planning purposes, these determinants should be integrated into simple indicators for spatial conditions of persistence probability. We propose a framework of three related indices. The cohesion index is based on the ecology of metapopulations in a habitat network. We discuss how an indicator for species persistence in such a network could be developed. To translate this network index into an area index, we propose the concept of spatial cohesion. Habitat cohesion and spatial cohesion are defined and measured for single species or, at best, for species profiles. Since species differ in their perception of the same landscape, different species will rate different values of these indices for the same landscape. Because landscapes are rarely planned for single species, we further propose the index of landscape cohesion, which integrates the spatial cohesion indices of different species. Indices based on these concepts can be built into GIS tools for landscape assessment. We illustrate different applications of these indices, and emphasise the distinction between ecological and political decisions in developing and applying such tools. This revised version was published online in August 2006 with corrections to the Cover Date.     

Measuring urban habitat fragmentation: an example from the Black Country,UK

The processes of urbanisation have left a fragmented mosaic of habitat patches of varying size, shape and character with the result that from location to location the number and quality of contacts between patches varies considerably. Traditional measurements of this habitat fragmentation, and its converse, connectivity, have rarely looked at the landscape as a whole but instead have simplified it to specific landscape subsets, or else have looked at area-to-area relationships through generalising the landscape into homogeneous pixels or grids. In this paper the character of the whole landscape is examined at scales appropriate to the spatial variability of the urban environment. Using a direct measurement of patch-to-patch contact all contacts between all patches are examined and the relationship between all contiguous and connecting habitats is quantified. This is further refined to look at connections between patches of different quality, a measure that highlights the adverse effects of urbanisation as a whole on landscape connections between quality habitats.     

Incorporating landscape diversity into greenway alignment planning

As an important factor of scenic quality and biodiversity along a greenway, landscape diversity has yet to receive as much attention as it deserves. In the practice of greenway alignment planning, it usually gives way to the primary consideration of land suitability. In this article, we aim to make up this missing link. Upon the new concepts and measurement of linear landscape diversity and cellular landscape diversity, we proposed greenway potential index incorporating land suitability and landscape diversity. The greenway potential index was combined with connectivity analysis to connect path between a future greenway’s origin and destination that meets both land suitability and landscape diversity requirements. Specially, with Wuchang (Wuhan City, China) as a case study area, we proposed three greenway alignment planning scenarios respectively according to the criteria of suitability, diversity and the synthesis of them. Markedly differences were revealed between the results of suitability greenways and diversity greenways. The results indicate that the tripartite model we proposed is capable of planning a connecting path between a future greenway’s origin and destination that not only meets land suitability requirements for greenway construction, but also incorporates as many landscape types of significant difference as possible.     

Soil occupation efficiency and landscape conservation in four Mediterranean urban regions

This study investigates the relationship between soil sealing and landscape conservation in four Mediterranean regions (Athens, Barcelona, Lisbon, Rome) characterized by different patterns of urban expansion. Per-capita sealed land, a landscape conservation index and selected territorial variables were considered into a multivariate exploratory framework aimed at assessing the correlation between land-use efficiency (based on the degree of soil sealing per-capita) and the quality of suburban landscape. A population density gradient with intensity of sealed land decreasing with the distance from the central city was observed in compact urban regions such as Athens and Barcelona. A mixed urban gradient was observed in Rome and Lisbon. In all the considered cities the spatial distribution of per-capita sealed land was not correlated with the urban gradient indicating that land consumption follows place-specific patterns irrespective of landscape quality. These findings suggest that urban containment and landscape conservation are policy targets requiring environmental measures irrespective of the prevailing morphology of the urban region (compact vs dispersed). In this context, green infrastructure planning is a promising tool for landscape conservation and the containment of soil sealing within fragile and dynamic contexts such as the wildland-urban interface.     

Impacts of road corridors on urban landscape pattern: a gradient analysis with changing grain size in Shanghai, China

Urbanization is one of the most important driving forces for land use and land cover change. Quantifying urban landscape pattern and its change is fundamental for monitoring and assessing ecological and socioeconomic consequences of urbanization. As the largest city in the country, Shanghai is now the fastest growing city in China. Using land use data set of 2002 and combining gradient analysis with landscape metrics, we analyzed landscape pattern of Shanghai with increasing grain size to study the impacts of road corridors on urban landscape pattern. Landscape metrics were computed along a 51×9 km² transect cutting across Shanghai with a moving window. The results showed that the urban landscape pattern of Shanghai was greatly changed when road corridors were merged with urban patches and the variation of patch density would alter when grain size changed. As a linear land use type, road corridors exhibited a different spatial signature comparing with other land use types and distinctive behavior with increasing grain size. Merging road and urban patches resulted in a sharp reduction in patch density, mainly caused by segmentation of roads corridors. The results suggested that grain size around 7.5 m might be optimal for urban landscape analysis. Landscape patch density is significantly correlated with road percent coverage and the most important effect of road corridors in urban landscape is increased habitat fragmentation.