Guest essay by Eric Worrall
Snow hares – fluffy, cute, less likely to eat you than a Polar Bear. The ideal candidate for the next green icon, except for their distressing lack of rarity, and their unfortunate ability to adapt to changes in their environment.
Can Evolution Save Snow Hares From Climate Change?
Species go extinct unless they can adapt to changes to their environment. And while the climate change caused by humans is often viewed as a future threat to wildlife, it’s already having a measurable impact on species today.
One potential casualty of climate change is the snowshoe hare. A close relative of rabbits, the hare’s hind feet (its ‘snowshoes’) have a large surface area to stop it sinking into snow. It also has another adaptation for life in North America: the animal’s brown summer coat turns white in winter, providing camouflage to hide it from predators.
“This is one of the most direct demonstrations of mortality costs for a wild species facing climate change,” [L Scott] Mills said in a press release. And while snowshoe hares aren’t currently endangered, the biologists predict that the higher death rate will lead to a significant drop in population levels by the end of the century.
But the chances of extinction can be minimized by a conservation strategy called ‘evolutionary rescue’: if a population is made-up of a large variety of individuals, it will have a deep gene pool, maximizing the likelihood that at least some individuals carry a genetic variant that would help them to survive and reproduce. This would enable a population to adapt through natural selection. For hares, this means individuals with genes that make them molt at times which match snow cover (it’s unknown whether they would be able to adapt in time).
The abstract of Scott’s study;
Anthropogenic climate change has created myriad stressors that threaten to cause local extinctions if wild populations fail to adapt to novel conditions. We studied individual and population-level fitness costs of a climate change-induced stressor: camouflage mismatch in seasonally colour molting species confronting decreasing snow cover duration. Based on field measurements of radiocollared snowshoe hares, we found strong selection on coat colour molt phenology, such that animals mismatched with the colour of their background experienced weekly survival decreases up to 7%. In the absence of adaptive response, we show that these mortality costs would result in strong population-level declines by the end of the century. However, natural selection acting on wide individual variation in molt phenology might enable evolutionary adaptation to camouflage mismatch. We conclude that evolutionary rescue will be critical for hares and other colour molting species to keep up with climate change.
The main thrust of Scott’s point seems to be the need for a healthy, diverse population. But imagine if Scott’s findings apply to other species? Could it be possible, that species are capable of adapting to altered conditions, through natural selection, and that a couple of degrees of global warming isn’t quite the catastrophic threat we’ve been led to believe?