By Richard Black
Environment correspondent, BBC News website, Nairobi
Some of the world's most spectacular migratory animals will be severely affected by climate change, according to a new United Nations report.
Marine species are threatened by climate change, the report says
The UN Environment Programme (Unep) says that rising temperatures spell extinction for some mobile species.
Turtles are particularly affected, the report finds, with rising temperatures changing the ratio of males to females.
But it says conservation measures targeted at key areas can protect even migratory animals.
By definition, migrating species must depend on several different ecosystems.
Birds may fly from one continent to another, perhaps stopping at feeding grounds on the way. Whales and turtles cover vast tracts of ocean.
The UN Convention on Migratory Species (CMS), which co-produced the report with Unep and the UK government, says that changes in any one of the locations which these animals use can be serious.
"Obviously these species have developed these [migration] patterns over millennia, and obviously they can develop more," said CMS executive director Robert Hepworth.
"But the emphasis is that it's taken millennia. We're dealing with climate change that's likely to be drastic over the next 25 to 50 years; it's most unlikely that these species can adapt fast enough," he told BBC News.
Among the animals most hit by rising temperatures are turtles.
Scientists have found that at higher temperatures, some turtles produce far more female eggs than male. In parts of peninsula Malaysia, nesting sites are producing only females, the report says.
The authors also cite evidence that some turtles become more prone to cancer as the waters warm, perhaps because infectious organisms can thrive.
With birds, the main issue is climate-related damage to critical habitat, at either end of the migration routes or at stopping places.
About one-fifth of bird species covered by the CMS are threatened by climate-related impacts including rising sea levels, coastal erosion and more vigorous storms, the report concludes.
Apart from turtles, species picked out as particularly vulnerable include:
- the North Atlantic right whale, whose main food of plankton is disturbed by shifting ocean currents
- several bird species in the Caribbean, which may literally be blown off course during migration by more intense spring storms
- the white-beaked dolphin, which is out-competed by other dolphin species in warmer waters
- the Baikal teal, whose habitat is threatened by drought
"We have some cases where a temperature rise will condemn a species to extinction," commented Unep executive director, Achim Steiner.
Adapt and survive
The report is not entirely gloomy. Even with major climatic changes, conserving vulnerable habitats can still help migrating species to recover.
"Migratory species need better and quicker delivery of conservation measures," said Dr Hepworth.
"We have to work more efficiently to step up programmes at national and international level."
And some species are apparently adapting. Fin and bowhead whales in the Arctic are changing their feeding behaviour, finding new grounds and new species to eat.
The report suggests researching ways of helping others to adapt faster.
In a two-week meeting dominated by talk of issues such as carbon markets, stabilisation wedges and the adaptation of human societies, this was a sobering reminder that climate change threatens to bring big changes to the natural world too.