Climate change is generally considered bad for people, earth’s biomes, and, of course, polar bears. But as the climate warms will all critters suffer? Will they all be affected the same way? No. In addition to the losers who slowly fizzle out under the oppressive heat, there will be winners who benefit from warming.
An animal’s response to climate change depends largely on two things: the amount of warming in a habitat and the physiological limits of the animal. It has been shown pretty convincingly that animals closer to the equator are more sensitive to warming than animals farther north. I know what you are thinking, “but tropical animals are hot all the time, they should be used to it.” I thought the same thing, but how it works is that since they are hot all the time, they live close to their thermal limits. So for animals in hot places, a little more heat pushes them over the edge.
Therefore the biological effects of climate change are expected to vary geographically, particularly for ectothermic animals such as insects. Elsa Youngsteadt and other folks in the lab took a road trip to test the hypothesis that insects at high latitudes, where it is cold, should generally benefit from warming whereas insects at low latitudes should have mixed responses: some should benefit, but others should be pushed over their thermal limits.
In a brilliant new paper Elsa reports her findings from this trip. The team sampled insects from street trees in the hottest and coolest parts of four cities–Raleigh, Baltimore, Queens, and Boston–taking advantage of the urban heat island effect as a natural warming experiment.
In the lowest latitude city, Raleigh, some taxa became more abundant with warming while others declined. This suggests that, although some species benefited from warming, just as many species suffered. In the coldest and highest latitude city, Boston, most insect groups were unaffected or became more abundant, suggesting that warming was good for most species living in a frigid northern metropolis. Just as predicted! This doesn’t happen very often.
It seems good that not all taxa tank in Raleigh–but the fact that some benefit and others decline could be ecologically disruptive, too: Maybe a parasitoid and its host respond differently, or a predator and its prey. This sort of mismatch could lead to extinction of higher trophic levels if the prey does poorly, or herbivore outbreaks if the predator fails.
I’ll warn you upfront, this paper is dense and there are probably a lot of new concepts packed in that most people will need time to unpack. However, capturing the response of a whole community to a couple degrees of warming is novel and worth the read. Think about the responses of your favorite organisms. Not just in cities but across the globe.