Climate change impacts - Climate Change: A Very Short Introduction - page 91

Biodiversity
The current loss of biodiversity around the world is due to human activity including defor-
estation, agriculture, urbanization, and mineral exploitation. Extinction rates are currently
100‒1,000 times higher than the background natural rate and climate change will exacer-
bate this decline. The IPCC 2014 impact report lists the following species as those most at
risk from climate change: the mountain gorilla in Africa; amphibians that live in the cloud
forests of the neotropics; the spectacled bear of the Andes; forest birds of Tanzania; the
'resplendent quetzal' bird in Central America; the Bengal tiger, and other species found
only in the Sundarban wetlands; rainfall-sensitive plants found only in the Cape Floral
Kingdom of South Africa; and polar bears and penguins near the poles. The primary reason
for the threat to these species is that they are unable to migrate in response to climate
change because of their particular geographical location or the encroachment of human
activity, particularly farming and urbanization. An example of the former is the cloud
forests of the neotropics: as climate changes, this particular climatic zone will migrate up
the mountainside until the point where there is no more mountain left.
One example of an ecosystem under threat is the coral reefs. Coral reefs are a valuable eco-
nomic resource for fisheries, recreation, tourism, and coastal protection. Some estimate that
the global cost of losing the coral reefs runs into hundreds of billions of dollars each year.
In addition, reefs are one of the largest global stores of marine biodiversity. The last few
years have seen unprecedented declines in the health of coral reefs. In 1998, El Niño was
associated with record sea-surface temperatures and associated coral bleaching, which is
when the coral expels the algae that live within it that are necessary to its survival (see Box
2 ) . In some regions, as much as 70 per cent of the coral may have died in a single season.
There has also been an upsurge in the variety, incidence, and virulence of coral disease in
recent years, with major die-offs in Florida and much of the Caribbean region. In addition,
increasing atmospheric carbon dioxide concentrations could decrease the calcification rates
of the reef-building corals, resulting in weaker skeletons, reduced growth rates, and in-
creased vulnerability to erosion. Model results suggest these effects would be most severe
at the current margins of coral reef distribution.