We heard this week that
a quarter of all mammals are threatened with extinction.One of those, the polar bear, made headlines earlier this year for being the first animal to be listed on the US Endangered Species Act, because of its vulnerability to climate change.
This begs the question: aren't all species vulnerable to climate change? Why protect the polar bear but not the ringed seal?
This is the question that a huge endeavour led by the World Conservation Union (IUCN) is attempting to answer. Its first results were presented in Barcelona, Spain, on Wednesday.
The verdict is bleak: of 17,000 assessed species, over 7000 could become threatened with extinction because of climate change. Read the report (PDF)
"Climate change is already happening, but conservation decision-makers currently have very little guidance on which species are going to be the worst affected," says Wendy Foden, who led the efforts. Yet, "Climate change is going to affect everything we do in terms of conservation," adds Jean-Christophe Vié, deputy head of the species programme at the IUCN.
In order to assess which species need protection first, experts working with the IUCN have spent the past few years reviewing 17,000 species of birds, amphibians and warm-water corals to assess how susceptible they are to climate change.
Life history traits
They first had to decide what made a species likely to suffer from the effects of climate change.
For instance, a frog called the spotted snout-burrower (Hemisus guttatus), relies on the rain to kick off a season of explosive breeding each year. If the rains change, or fail, the species may not survive.
A hummingbird, the black-breasted puffleg (Eriocnemis nigrivestis) lives in the forest atop two mountains in north-west Ecuador. As temperatures rise around it, it will eventually be unable to climb any higher in search of cooler habitats.
The experts identified 90 such "life history traits" – essential elements of a species' behaviour or lifestyle – that were likely to be affected by a change in their local climate. These included:
- Requirements for a specialised habitat: some amphibians depend on a stream or pond, so if that dries out there is no way they can survive;
- Specific environmental tolerances: many corals cannot survive if the water temperature or pH exceeds a certain threshold;
- Dependence on environmental cues: many species depend on changes in day length or rainfall to start breeding;
- Dependence on interactions with other species: without prey a specialised predator cannot survive; lichen depend on trees, and many plants on their pollinators;
- Ability to disperse: as their historical habitats become increasingly hostile, species will need to move to new territories but may not be able to do so if there is something – a body of water, perhaps – in their way.
Foden's team then determined which of the 90 life traits each of the 17,000 species had. The study included all known amphibian and bird species, as well as all reef-building corals that are found in warm waters.
"We looked at these three groups because we know their global distribution," explains Vié. This meant the team could map all susceptible species within those groups and see where in the world biodiversity is most at risk of climate change.
Scary research
They could also compare their new maps to existing maps showing where species are threatened by other factors such as deforestation and poaching. "Honestly, it is quite scary research," says Vié.
Half of all amphibians, one-third of all birds and over two-thirds of assessed corals are susceptible to climate change.
Within each group, some species are more likely to suffer. Among the birds, all albatross and penguin species were deemed susceptible. Herons, egrets, ospreys, kites, hawks and eagles, on the other hand, are less so.
Ultimately, the real threat to a species depends not just on whether or not it is susceptible to climate change, but also on whether it inhabits a region that is likely to change with global warming. Efforts to use regional climate change models to map out this overlap are already underway in some parts of the world (see Climate maps offer wildlife hope of sanctuary).
Conservationists may then have to apply their creativity to finding new ways of protecting species. "Protected areas are fixed pieces of land or sea," Vié, "but the new threats – shifting diseases, rising temperatures, changing rainfall – do not stop at the edge of protected areas."
Debates are raging within the conservation community over what protection methods are reasonable.
The last remaining members of some species may have to be removed from the wild and housed in artificially-controlled environments – this has already happened with some species of frogs threatened by the chytrid fungus. In situations where species are not able to move to more clement habitats, they may need a helping hand (see Threatened species 'need help' finding cooler homes).
Threatened ecosystems, threatened economies
Disappearing animals may not seem so important compared with the threat of water shortages and lethal heat waves, but Vié points out how the welfare of biodiversity and humans is intrinsically linked. "If you lose coral reefs, hundreds of millions of people will be affected – they will have no food, no income from tourism."
He says one outcome of the mapping exercise could be to anticipate what regions are going to need humanitarian aid in future.
Climate Change - Want to know more about global warming – the science, impacts and political debate? Visit our continually updated special report.
Endangered species - Learn more about the conservation battle in our comprehensive special report.
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