As the Earth’s climate changes, a significant number of plant and animal species are moving to new places, which is equivalent to what researchers in 2017 called “a universal redistribution of life on Earth.”
A new review article in the journal Biology of global change looks at the northward march of a variety of tropical species in North America, from mangroves to Burmese pythons. The authors, led by Michael Osland, an ecologist with the US Geological Survey, focus on “tropical-temperate transition zones” – places where occasional severe frost restricts the range of tropical plants and animals.
“These extreme freezing events play a very important role in controlling the northern limits of a wide range of cold-sensitive tropical organisms,” Osland says. As winters continue to warm thanks to human-caused climate change, this boundary becomes more porous and some of these creatures move north, producing an ecosystem shift researchers call “tropicalization.”
“Changes in winter conditions are one of the main, if not the main, drivers of evolutionary distributions,” said co-author Caroline Williams, associate professor of integrative biology at UC Berkeley. declaration. “For the vast majority of organisms, if they freeze, they die,” but as extreme cold spells become less frequent, “this allows tropical species to take hold more and more.”
For some of these species, such as sea turtles, mangroves and manatees, the ability to migrate north could be seen as beneficial, Osland notes. For others, like the burmese python or mosquitoes carrying viruses harmful to humans, there are “more complex issues that we will have to tackle”.
Of course, “how species will adapt to climate change is highly variable,” says Osland.
Examples highlighted in the study include mangroves, coastal wetland trees whose germinated seeds, or propagules, are released in ocean currents; mangroves (although threatened in another way) have been heading north for some time, with a complicated table implications for other species. The review also examines the changing range of the buffalo, a type of grass that is new to the Southwest and may increase the risk of wildfires there, as well as the potential expansion of l range of forest insects like the southern pine beetle and migrating butterflies. , which may extend northward.
“This is an important review that brings together, in one place, the underlying reasons why many tropical species are only found in the tropics, and how this may change with climate change,” Camille writes. Parmesan, an ecologist at the University of Plymouth, in an email to Popular Science. Parmesan says that the destabilization of the polar vortex induced by climate change, which some scientists think could be the source of extremely cold weather events like the one we saw recently in Texas – adds complexity to any forecast.
“We can see waves of tropical species moving north for about ten years, then they are all killed down to their historic borders” by a blast of arctic air.
For Osland, the main takeaway from the review is that just north of these tropical-temperate transition zones, life will change.
“Some species are very resilient and able to adapt, and mangroves are a very good example of that,” he says. But that’s not the case for the others, who might not be able to keep up. “Some species will be able to make long leaps north, and some won’t even be able to move at all.”