Because of the dual pressures of climate change and habitat loss, scientists estimate that somewhere between 15 and 40 percent of the planet’s species are headed for extinction by 2050 (and some projections go even higher). The good news is that there are things we can do to minimize the loss in biodiversity over future decades, even if warming due to increasing greenhouse gases goes unchecked.
Fossil evidence and biological observations have revealed that populations of plants, insects, and animals can shift to different elevations, or move north or south, to follow changing temperatures as the climate warms and cools. But over the past couple hundred years, humans have altered much of the natural landscape, turning it into a virtual minefield for would-be climate migrants. To get from one livable location to another, many populations that could once have moved easily would now have to cross large areas of uninhabitable farmland or urban land or dangerous barriers like highways or cities.
One solution proposed by conservationists is to reconnect those patches of habitat. The idea is to link protected lands so that plants and animals can travel safely to more hospitable places. Creating these links can cost a lot of money and require complex management and coordination by farmers and other landowners. But biologists and ecologists estimate that those dispersal routes could prevent the extinction of thousands of species. It’s not just a theoretical idea: such corridors are already being established in many parts of the world. In the United States and Canada, for example, conservationists are working to create a safe corridor all the way from Yellowstone National Park to the Yukon Territory, more than a thousand miles away.
While such habitat networks could potentially help reduce the loss of biodiversity in coming decades, they can’t save populations that are poor dispersers, too isolated from other potential habitats, or already under serious pressure from climate change. The Florida torreya, a coniferous tree found only in one tiny ravine in Florida, is already a victim of all of these circumstances. Like other land plants, this tree can shift its range only as far as its seeds are dispersed—maybe two or three hundred yards—from one generation to the next. But scientists estimate that climate zones will shift toward higher latitudes at an average of almost six hundred yards (one-third of a mile) per year over the next century.
The Florida torreya is unlikely to keep up. Even if it could, the tree doesn’t just need favorable temperatures. It also needs specific conditions for survival, including plenty of shade and moist soil—conditions that don’t exist anywhere close by its current habitat. To try to save the Florida torreya, a group of activists has been transplanting seedlings to new locations in places like the mountains of North Carolina. This idea, called assisted migration, is gaining ground with many ecologists and conservation biologists. But critics argue that it would be too costly and too risky to do for large numbers of species, especially since no one can be totally sure whether, or under what conditions, it will work and what kinds of negative consequences it might have on ecosystems that receive these climate migrants.
Of course, while both methods of helping species migrate could soften the damage of climate change to biodiversity in coming decades, the most effective solution would also include trying to limit emissions of planet-warming greenhouse gases and slow the destruction of habitat from activities like the clear-cutting of forests.