Showing papers by "Chris D. Thomas published in 2010"

Climate, climate change and range boundaries

Abstract: Aim A major issue in ecology, biogeography, conservation biology and invasion biology is the extent to which climate, and hence climate change, contributes to the positions of species’ range boundaries. Thirty years of rapid climate warming provides an excellent opportunity to test the hypothesis that climate acts as a major constraint on range boundaries, treating anthropogenic climate change as a large-scale experiment. Location UK and global data, and literature. Methods This article analyses the frequencies with which species have responded to climate change by shifting their range boundaries. It does not consider abundance or other changes. Results For the majority of species, boundaries shifted in a direction that is concordant with being a response to climate change; 84% of all species have expanded in a polewards direction as the climate has warmed (for the best data available), which represents an excess of 68% of species after taking account of the fact that some species may shift in this direction for non-climatic reasons. Other data sets also show an excess of animal range boundaries expanding in the expected direction. Main conclusions Climate is likely to contribute to the majority of terrestrial and freshwater range boundaries. This generalization excludes species that are endemic to specific islands, lakes, rivers and geological outcrops, although these local endemics are not immune from the effects of climate change. The observed shifts associated with recent climate change are likely to have been brought about through both direct and indirect (changes to species’ interactions) effects of climate; indirect effects are discussed in relation to laboratory experiments and invasive species. Recent observations of range boundary shifts are consistent with the hypothesis that climate contributes to, but is not the sole determinant of, the position of the range boundaries of the majority of terrestrial animal species.

The impact of proxy‐based methods on mapping the distribution of ecosystem services

Abstract: An increasing number of studies are examining the distribution and congruence of ecosystem services, often with the goal of identifying areas that will provide multiple ecosystem service 'hotspots'. However, there is a paucity of data on most ecosystem services, so proxies (e.g. estimates of a service for a particular land cover type) are frequently used to map their distribution. To date, there has been little attempt to quantify the effects of using proxies on distribution maps of ecosystem services, despite the potentially large errors associated with such data sets. 2. Here, we provide the first study examining the effects of using proxies on ecosystem service maps and the degree of spatial congruence of these maps with primary data, using England as a case study. 3. We show that land cover based proxies provide a poor fit to primary data surfaces for biodiversity, recreation and carbon storage, and that correlations between ecosystem services change depending on whether primary or proxy data are used for the analyses. 4. The poor fit of proxies to primary data was also evident when we selected hotspots of single ecosystem services, and consistency between raw and modelled surfaces was extremely low when considering the locations that were coincident hotspots for multiple services. 5. Synthesis and applications. Proxies may be suitable for identifying broad-scale trends in ecosystem services, but even relatively good proxies are likely to be unsuitable for identifying hotspots or priority areas for multiple services

Heterogeneous landscapes promote population stability

Abstract: Habitat heterogeneity is often suggested as being important for the stability of populations, and promoted as a means to aid the conservation of species, but the evidence for such an assumption is poor. Here we show that heterogeneous landscapes that contain a variety of suitable habitat types are associated with more stable population dynamics for 35 British butterfly species from 166 sites. In addition, topographic heterogeneity may also promote stability. Our results were robust to different measures of population variability, differences in mean abundance among sites, and to the spatial scale (radius 1-5 km around the centres of sites) at which landscapes were analysed. Responses to landscape heterogeneity differed among species; for more mobile 'wider-countryside' species, habitat heterogeneity at larger landscape scales had the strongest effect on population dynamics. We suggest that heterogeneous landscapes offer a greater range of resources and microclimates, which can buffer populations against climatic variation and generate more stable population dynamics.

Comparing organic farming and land sparing: optimizing yield and butterfly populations at a landscape scale.

Abstract: Organic farming aims to be wildlife-friendly, but it may not benefit wildlife overall if much greater areas are needed to produce a given quantity of food. We measured the density and species richness of butterflies on organic farms, conventional farms and grassland nature reserves in 16 landscapes. Organic farms supported a higher density of butterflies than conventional farms, but a lower density than reserves. Using our data, we predict the optimal land-use strategy to maintain yield whilst maximizing butterfly abundance under different scenarios. Farming conventionally and sparing land as nature reserves is better for butterflies when the organic yield per hectare falls below 87% of conventional yield. However, if the spared land is simply extra field margins, organic farming is optimal whenever organic yields are over 35% of conventional yields. The optimal balance of land sparing and wildlife-friendly farming to maintain production and biodiversity will differ between landscapes.

The identification of priority policy options for UK nature conservation

Abstract: 1. The conservation of biodiversity depends upon both policy and regulatory frameworks. Here, we identify priority policy developments that would support conservation in the UK in the light of technological developments, changes in knowledge or environmental change. 2. A team of seven representatives from governmental organizations, 17 from non-governmental organizations and six academics provided an assessment of the priority issues. The representatives consulted widely and identified a long-list of 117 issues. 3. Following voting and discussion during a 2-day meeting, these were reduced to a final list of 25 issues and their potential policy options and research needs were identified. Many of the policies related to recent changes in approaches to conservation, such as increased interest in ecosystem services, adaptation to climate change and landscape ecology. 4. We anticipate that this paper will be useful for policy makers, nature conservation delivery agencies, the research community and conservation policy advocates. 5. Although many of the options have global significance, we suggest that other countries consider an equivalent exercise. We recommend that such an exercise be carried out in the UK at regular intervals, say every 5 years, to explore how biodiversity conservation can best be supported by linked policy development and research in a changing world. 6. Synthesis and applications. Opportunities for policy development were prioritized and for each of the top 25 we identified the current context, policy options and research questions. These largely addressed new issues relating to developing topics such as ecosystem services, landscape planning and nanotechnology. We envisage that this will largely be used by researchers wishing to make a contribution to potential policy debates.

Linking habitat use to range expansion rates in fragmented landscapes: a metapopulation approach

Abstract: Temperature increases because of climate change are expected to cause expansions at the high latitude margins of species distributions, but, in practice, fragmented landscapes act as barriers to colonization for most species. Understanding how species distributions will shift in response to climate change therefore requires techniques that incorporate the combined effects of climate and landscape-scale habitat availability on colonization rates. We use a metapopulation model (Incidence Function Model, IFM) to test effects of fine-scale habitat use on patterns and rates of range expansion by the butterfly Hesperia comma. At its northern range margin in Britain, this species has increased its breadth of microhabitat use because of climate warming, leading to increased colonization rates. We validated the IFM by reconstructing expansions in five habitat networks between 1982 and 2000, before using it to predict metapopulation dynamics over 100 yr, for three scenarios based on observed changes to habitat use. We define the scenarios as ‘‘cold-world’’ (only hot, south-facing 1502508 hillsides are deemed warm enough), ‘‘warm-world’’ in which 1003008 hillsides can be populated, and ‘‘hot-world’’, where the background climate is warm enough to enable use of all aspects (as increasingly observed). In the simulations, increased habitat availability in the hot-world scenario led to faster range expansion rates, and to long-term differences in distribution size and pattern. Thus, fine-scale changes in the distribution of suitable microclimates led to landscape-scale changes in population size and colonization rate, resulting in coarse-scale changes to the species distribution. Despite use of a wider range of habitats associated with climate change, H. comma is still expected to occupy a small fraction of available habitat in 100 yr. The research shows that metapopulation models represent a potential framework to identify barriers to range expansion, and to predict the effects of environmental change or conservation interventions on species distributions and persistence.

Representation of ecosystem services by tiered conservation strategies

Abstract: In human-dominated regions, protected areas are complemented by other conservation strategies (e.g., restrictive zoning, incentive payments) to maintain biodiversity and other ecosystem services. These strategies are often not mutually exclusive, with many areas covered by multiple (tiered) management strategies. However, it is not known whether tiering increases (or decreases) representation of ecosystem services. Here, we compare the representation of four ecosystem services by areas protected by both tiered and single conservation strategies (protected areas, restrictive zoning, and incentive payments to landowners) in a human-dominated region (England). Tiering always coincided with the highest levels of stored carbon, sometimes coincided with high biodiversity and agricultural production, but never coincided with high recreational value. We also show that tiering is common in England and biased towards upland areas. Future evaluations of the effectiveness of conservation strategies should consider the degree of overlap of the different strategies fully to understand which are most effective.