Climate change is predicted to become a major threat to biodiversity in the 21st century, but accurate predictions and effective solutions have proved difficult to formulate. Alarming predictions have come from a rather narrow methodological base, but a new, integrated science of climate-change biodiversity assessment is emerging, based on multiple sources and approaches. Drawing on evidence from paleoecological observations, recent phenological and microevolutionary responses, experiments, and computational models, we review the insights that different approaches bring to anticipating and managing the biodiversity consequences of climate change, including the extent of species' natural resilience. We introduce a framework that uses information from different sources to identify vulnerability and to support the design of conservation responses. Although much of the information reviewed is on species, our framework and conclusions are also applicable to ecosystems, habitats, ecological communities, and genetic diversity, whether terrestrial, marine, or fresh water.

Beyond Predictions: Biodiversity Conservation in a Changing Climate

The effects of climate change on biodiversity are increasingly well documented, and many methods have been developed to assess species' vulnerability to climatic changes, both ongoing and projected in the coming decades. To minimize global biodiversity losses, conservationists need to identify those species that are likely to be most vulnerable to the impacts of climate change. In this Review, we summarize different currencies used for assessing species' climate change vulnerability. We describe three main approaches used to derive these currencies (correlative, mechanistic and trait-based), and their associated data requirements, spatial and temporal scales of application and modelling methods. We identify strengths and weaknesses of the approaches and highlight the sources of uncertainty inherent in each method that limit projection reliability. Finally, we provide guidance for conservation practitioners in selecting the most appropriate approach(es) for their planning needs and highlight priority areas for further assessments.

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Assessing species' vulnerability to climate change

Recent advances in the ecology of food webs underscore the importance of detritus and indirect predator–prey effects. However, most research considers detritus as an invariable pool and predation as the only interaction between carnivores and prey. Carrion consumption, scavenging, is a type of detrital feeding that should have widespread consequences for the structure and stability of food webs. Providing access to high-quality resources, facultative scavenging is a ubiquitous and phylogenetically widespread strategy. In this review, we argue that scavenging is underestimated by 16-fold in food-web research, producing inflated predation rates and underestimated indirect effects. Furthermore, more energy is generally transferred per link via scavenging than predation. Thus, future food-web research should consider scavenging, especially in light of how major global changes can affect scavengers.

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Scavenging: how carnivores and carrion structure communities.

Projected effects of climate change on animal distributions primarily focus on consequences of temperature and largely ignore impacts of altered precipitation. While much evidence supports temperature-driven range shifts, there is substantial heterogeneity in species' responses that remains poorly understood. We resampled breeding ranges of birds across three elevational transects in the Sierra Nevada Mountains, USA, that were extensively surveyed in the early 20th century. Presence–absence comparisons were made at 77 sites and occupancy models were used to separate significant range shifts from artifacts of false absences. Over the past century, rising temperature pushed species upslope while increased precipitation pulled them downslope, resulting in range shifts that were heterogeneous within species and among regions. While 84% of species shifted their elevational distribution, only 51% of upper or lower range boundary shifts were upslope. By comparison, 82% of range shifts were in a direction predicted by changes in either temperature or precipitation. Species were significantly more likely to shift elevational ranges than their ecological counterparts if they had small clutch sizes, defended all-purpose territories, and were year-round residents, results that were in opposition to a priori predictions from dispersal-related hypotheses. Our results illustrate the complex interplay between species-specific and region-specific factors that structure patterns of breeding range change over long time periods. Future projections of increasing temperature and highly variable precipitation regimes create a strong potential for heterogeneous responses by species at range margins.

The push and pull of climate change causes heterogeneous shifts in avian elevational ranges

The topics assessed in this chapter were last assessed by the IPCC in 2007, principally in WGII AR4 Chapters 3 (Kundzewicz et al., 2007) and 4 (Fischlin et al., 2007), but also in WGII AR4 Sections 1.3.4 and 1.3.5 (Rosenzweig et al., 2007). The WGII AR4 SPM stated “Observational evidence from all continents and most oceans shows that many natural systems are being affected by regional climate changes, particularly temperature increases,” though they noted that documentation of observed changes in tropical regions and the Southern Hemisphere was sparse (Rosenzweig et al., 2007). Fischlin et al. (2007) found that 20 to 30% of the plant and animal species that had been assessed to that time were considered to be at increased risk of extinction if the global average temperature increase exceeds 2°C to 3°C above the preindustrial level with medium confidence, and that substantial changes in structure and functioning of terrestrial, marine, and other aquatic ecosystems are very likely under that degree of warming and associated atmospheric CO2 concentration. No time scale was associated with these findings. The carbon stocks in terrestrial ecosystems were considered to be at high risk from climate change and land use change. The report warned that the capacity of ecosystems to adapt naturally to the combined effect of climate change and other stressors is likely to be exceeded if greenhouse gas (GHG) emission continued at or above the then-current rate.

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Terrestrial and Inland Water Systems

One consequence of climate change is an increasing mismatch between timing of food requirements and food availability. Such a mismatch is primarily expected in avian long-distance migrants because of their complex annual cycle, and in habitats with a seasonal food peak. Here we show that insectivorous long-distance migrant species in The Netherlands declined strongly (1984–2004) in forests, a habitat characterized by a short spring food peak, but that they did not decline in less seasonal marshes. Also, within generalist long-distance migrant species, populations declined more strongly in forests than in marshes. Forest-inhabiting migrant species arriving latest in spring declined most sharply, probably because their mismatch with the peak in food supply is greatest. Residents and short-distance migrants had non-declining populations in both habitats, suggesting that habitat quality did not deteriorate. Habitat-related differences in trends were most probably caused by climate change because at a European scale, long-distance migrants in forests declined more severely in western Europe, where springs have become considerably warmer, when compared with northern Europe, where temperatures during spring arrival and breeding have increased less. Our results suggest that trophic mismatches may have become a major cause for population declines in long-distance migrants in highly seasonal habitats.

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Avian population consequences of climate change are most severe for long-distance migrants in seasonal habitats

El principal objectiu del programa de seguiment d’ocells reproductors d’Holanda (BMP) es avaluar els canvis de mida poblacional de les especies reproductores comunes i escasses en aquest pais. Tot i que aquest programa de seguiment disposa d’un gran nombre de punts de mostreig, les tendencies poden estar esbiaixades perque els punts no estan igualment distribuits en el pais. En aquest article es presenta un procediment d’estratificacio i ponderacio a posteriori per corregir aquesta desigualtat en la presa de dades. Els indexs i les tendencies es van calcular primerament per a un nombre d’especies especifiques d’estrats (combinacions de regio, tipus principal d’habitat i categoria de densitat d’ocells). Posteriorment, els indexs per estrat van ser ponderats per les mides poblacionals (tal com es despren d’un conjunt de dades d’atles que van ser extrets de forma independent) i esforc de mostreig per estrat. El procediment te un petit pero substancial efecte sobre les tendencies nacionals, tendencies que, en general, solen ser menys conservadores (es mes facil trobar diferencies significatives). S’espera que per a la majoria de les especies reproductores el procediment impliqui una suficient i substancial millora de les tendencies i, per tant, es continuara amb el BMP en els proxims anys.

Monitoratge d’espècies nidificants comunes i escasses a Holanda: aplicació dels procediments d’estratificació i ponderació per obtenir tendències poblacionals menys esbiaixades

Arco J. van Strien

Papers

Avian population consequences of climate change are most severe for long-distance migrants in seasonal habitats

Monitoratge d’espècies nidificants comunes i escasses a Holanda: aplicació dels procediments d’estratificació i ponderació per obtenir tendències poblacionals menys esbiaixades