Projected Impacts of Climate and Land-Use Change on the Global Diversity of Birds

Walter Jetz,David S Wilcove,Andrew P Dobson,Georgina M Mace

doi:10.1371/journal.pbio.0050157

Abstract

Over the past few decades, land-use and climate change have led to substantial range contractions and species extinctions. Even more dramatic changes to global land cover are projected for this century. We used the Millennium Ecosystem Assessment scenarios to evaluate the exposure of all 8,750 land bird species to projected land-cover changes due to climate and land-use change. For this first baseline assessment, we assumed stationary geographic ranges that may overestimate actual losses in geographic range. Even under environmentally benign scenarios, at least 400 species are projected to suffer >50% range reductions by the year 2050 (over 900 by the year 2100). Although expected climate change effects at high latitudes are significant, species most at risk are predominantly narrow-ranged and endemic to the tropics, where projected range contractions are driven by anthropogenic land conversions. Most of these species are currently not recognized as imperiled. The causes, magnitude and geographic patterns of potential range loss vary across socioeconomic scenarios, but all scenarios (even the most environmentally benign ones) result in large declines of many species. Whereas climate change will severely affect biodiversity, in the near future, land-use change in tropical countries may lead to yet greater species loss. A vastly expanded reserve network in the tropics, coupled with more ambitious goals to reduce climate change, will be needed to minimize global extinctions.

Highlights

Accelerated climate change and the destruction of natural habitats through direct human activities are two of the greatest threats to terrestrial biodiversity
Habitat specialists may be affected by habitat changes finer than those registered by the available land-cover categorization, which would cause us to underestimate climate change impacts for these species
While refined range maps were used in this analysis, not all parts of the current and projected range will be fully occupied; this will inevitably result in an underestimation of the impact of environmental change for a significant proportion of species, those with specialized niches and heterogeneous distributions across their current geographic range

Summary

Introduction

Accelerated climate change and the destruction of natural habitats through direct human activities are two of the greatest threats to terrestrial biodiversity. We integrated the exposure of species to climate and land-use change through the combined effects of these drivers on global land cover and explored the resulting reductions in range size and possible extinctions within the world’s 8,750 terrestrial bird species. For this first global assessment, we used the simplifying yet transparent assumption of stationary geographic ranges, which allows us to quantify risk in terms of the projected vegetation changes across a species’ current range. This assumption yields worst-case projections and a number of factors could modify the local details and timeline of our projections, we think the general picture that emerges is robust: a clear and striking geographic disjunction between the relative impacts of future habitat loss and climate change on global avian diversity

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Discussion

Conclusion