How will populations respond to climate change?
There is now plentiful evidence that climate change is affecting ecosystems, often together with other human-driven environmental change. Some species adapt, because they are flexible enough to survive different environments. Others can migrate to more suitable locations (cold-adapted fish are swimming north, for example).
But many species cannot do either. And an ecosystem as a whole cannot simply up sticks to a more suitable location. The speed of change is thus threatening to disrupt countless existing ecosystems.
Some species, particularly ‘generalists’ that are not too fussy about their surroundings, may thrive. Invasive species, moving away from natural enemies such as herbivores, predators, pathogens or parasites, may also do well.
Climate change can be expected to affect certain animals because of their known dependence on a specific climate (though it’s important to remember that some of these changes could also result from climate variability).
A reduction in the extent and thickness of sea ice in the Arctic threatens polar bears. In the southern range of the polar bear’s habitat, sea ice melts earlier in the spring and forms later in the autumn, shortening the period when bears can hunt seals and fish and restore their body fat and fitness. This is a particular problem for pregnant or nursing bears and their cubs.
Tropical insects appear to be at the limits of their thermal tolerance. They may be highly vulnerable to climate change, more so than their temperate relatives.
Climate change may also have an impact on animals; for example, for many species of reptile the sex of their offspring is dependent on temperature. Below incubation temperatures of 28°C map turtles produce only male offspring; higher than 30°C and only females are born. Even now, single-sex nests are common.Lead image:
Ary A Hoffmann, Melbourne University, Australia