The ecological consequences of biodiversity loss have aroused considerable interest and controversy during the past decade. Major advances have been made in describing the relationship between species diversity and ecosystem processes, in identifying functionally important species, and in revealing underlying mechanisms. There is, however, uncertainty as to how results obtained in recent experiments scale up to landscape and regional levels and generalize across ecosystem types and processes. Larger numbers of species are probably needed to reduce temporal variability in ecosystem processes in changing environments. A major future challenge is to determine how biodiversity dynamics, ecosystem processes, and abiotic factors interact.

Summary 1.We examined the empirical relationship between predator-prey body size ratio and interaction strength in the Ythan Estuary food web. 2. We have refined a previously published version of the food web and explored how size-based predatory effects might affect food web dynamics. To do so, we used four predatory species Crangon crangon (Linnaeus), Carcinus maenas (Linnaeus), Pomatoschistus microps (Krøyer) and Platichthys flesus (Linnaeus) and one common prey species Corophium volutator (Pallas) from the food web. 3. All predators and prey were sorted into small, medium and large size classes and placed into mesocosms in all possible pairwise combinations of size and species identity to determine per capita effects of predators on prey ( a ij ). 4. Using Lotka-Volterra dynamics the empirical body size relationships obtained from these experiments and other relationships already available for the Ythan Estuary, we parameterized a food web model for this system. The local stability properties of the resulting food web models were then determined. 5. We found that by choosing interaction strengths using an empirically defined scaling law, the resulting food web models are always dynamically stable, despite the residual uncertainties in the modelling approach. This contrasts with the statistical expectation that random webs with random parameters have a vanishingly improbable chance of stability. 6. The patterning of predator and prey body sizes in real ecosystems affects the arrangement of interaction strengths, which in turn determines food web stability.

Revealing the consequences of species extinctions for ecosystem function has been a chief research goal and has been accompanied by enthusiastic debate. Studies carried out predominantly in terrestrial grassland and soil ecosystems have demonstrated that as the number of species in assembled communities increases, so too do certain ecosystem processes, such as productivity, whereas others such as decomposition can remain unaffected. Diversity can influence aspects of ecosystem function, but questions remain as to how generic the patterns observed are, and whether they are the product of diversity, as such, or of the functional roles and traits that characterize species in ecological systems. Here we demonstrate variable diversity effects for species representative of marine coastal systems at both global and regional scales. We provide evidence for an increase in complementary resource use as diversity increases and show strong evidence for diversity effects in naturally assembled communities at a regional scale. The variability among individual species responses is consistent with a positive but idiosyncratic pattern of ecosystem function with increased diversity.

Climate change is real. The wrangling debates are over, and we now need to move onto a predictive ecology that will allow managers of landscapes and policy makers to adapt to the likely changes in biodiversity over the coming decades. There is ample evidence that ecological responses are already occurring at the individual species (population) level. The challenge is how to synthesize the growing list of such observations with a coherent body of theory that will enable us to predict where and when changes will occur, what the consequences might be for the conservation and sustainable use of biodiversity and what we might do practically in order to maintain those systems in as good condition as possible. It is thus necessary to investigate the effects of climate change at the ecosystem level and to consider novel emergent ecosystems composed of new species assemblages arising from differential rates of range shifts of species. Here, we present current knowledge on the effects of climate change on biotic interactions and ecosystem services supply, and summarize the papers included in this volume. We discuss how resilient ecosystems are in the face of the multiple components that characterize climate change, and suggest which current ecological theories may be used as a starting point to predict ecosystem-level effects of climate change.Keywords: climate change; ecosystem services; biotic interactions; biodiversity; ecological networks; resilience CLIMATE CHANGE IMPACTS BEYOND INDIVIDUAL SPECIESClimate change is real. It is expected to be the major threat to biodiversity and one of the main factors affecting human health and well-being over the coming decades (Thomas et al. 2004;ME Assessment 2005; Schröter et al. 2005;Pimm 2009). Recent studies suggest CO 2 concentrations are over the safe boundary beyond which the risk of irreversible climate change is extremely high, such as the loss of major ice sheets, accelerated sea-level rise and abrupt changes in ecosystems, including agrosystems (Rockström et al. 2009).There is ample evidence that ecological responses are already occurring. First, data on many taxa in the Northern Hemisphere show a consistent trend of northward or westward expansion of species ranges and altitudinal shifts (Parmesan et al. 1999;Thomas et al. 2001;Walther et al. 2002;Walther 2010). Second, globally rising temperatures trigger spring advancement of phenology (Root et al. 2003;Edwards & Richardson 2004;Parmesan 2006). And third, reduction in body size owing to warming is generalized in aquatic systems (Daufresne et al. 2009;Moran et al. 2010). At the individual species (population) level, much progress has been made in the area of range shifts and effects on population dynamics. But scaling from populations through to communities, let alone ecosystems, will be challenging (Kareiva et al. 1993;Schmitz et al. 2003;Tylianakis et al. 2008;Berg et al. 2010;Fenton & Spencer 2010). The population responses of many species to climate change are unlikely to be simply additive and their combinational...