Twenty-eighth Report Adapting Institutions to Climate Change Cm ...

BIODIVERSITY
SUMMARY OF THE IMPACTS OF CLIMATE CHANGE ON ECOSYSTEMS FROM
THE STERN REVIEW 50
“Ecosystems will be highly sensitive to climate change. For many species, the rate of warming
will be too rapid to withstand. Many species will have to migrate across fragmented landscapes
to stay within their ‘climate envelope’ (at rates that many will not be able to achieve). Migration
becomes more difficult with faster rates of warming. In some cases, the ‘climate envelope’ of a
species may move beyond reach, for example moving above the tops of mountains or beyond
coastlines. Conservation reserves may find their local climate becoming less amenable to the
native species.”
Climate envelopes and their consequences
2.83 A ‘climate envelope’ describes the range of climatic conditions within which an organism can
survive and reproduce. Climate envelopes are conceptual, multidimensional spaces, with axes
defined by the key climatic variables directly or indirectly influencing survival or reproduction in
a particular species – for example average, winter minimum and summer maximum temperatures,
frost-free days, rainfall patterns and so on. The concept applies equally to terrestrial, freshwater
and marine organisms, although the key climatic variables may be very different.
2.84 The geographic range of any particular species will be strongly, but not uniquely, determined by its
climate envelope. Whereas no species can survive for long in a hostile environment, a species may
not occur everywhere across geographic areas with a suitable climate. 51 For example, barriers to
dispersal (mountain chains or open ocean) may prevent a species reaching all potentially suitable
areas; competition with other species may exclude them, as may diseases or natural enemies;
and overexploitation by humans may eliminate species from climatically suitable regions. Still
others may be absent because important habitat features are missing or otherwise unsuitable
– for instance, the underlying geology might be wrong or a key food species might be absent.
Nevertheless, climate envelopes are an important, but by no means the sole, determinant of
species’ distributions. 52
2.85
2.86
As the Earth’s climate changes, so each species’ characteristic climate envelope will shift geographically.
Studies on European breeding birds53 and on a sample of 32 European species (including
breeding birds, insects, bats and plants) from a variety of different habitats54 analysed shifts in
the geographic distributions of species’ climate envelopes in Britain and Europe under various
climate change scenarios in the late 21st century. For example, the centroids of the current and
potential (based on their climate envelope) breeding distributions of 430 species of breeding
birds are predicted to move an average of 545 km north-eastwards across Europe, but with huge
variations in both direction and distance; the largest movement is nearly 2,500 km, and the climate
envelopes of individual species settle across all points of the compass. 55 The climate envelopes
of some species, both birds and plants, may disappear completely from the UK, or even Europe,
whereas those for other species are projected to increase in size. 56 In general, the climate envelopes
of most species of birds are likely to be smaller than now by about 20%. 57
If climate change makes parts (or all) of a species’ current geographic distribution increasingly
inhospitable and ultimately uninhabitable, there are three things that might result: the species
might evolve to keep pace with the change, it might move (migrate) to stay within its climatic
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Chapter 2