Conservationists, ecologist Mark Schwartz wrote nearly three decades ago, faced a looming conundrum: Many species would likely be unable to keep up with the projected pace of climate change and could face extinction as a result. This didn’t pose “an insurmountable conservation problem,” he wrote — people could help species reach places with suitable physical and biological conditions. They might carry endangered animals to habitats cut off by mountains, rivers, or human barriers, for example, or plant endangered trees or shrubs higher up mountain slopes or farther north.
In one sense, these would be ordinary actions. People had been moving species around the world for thousands of years, as farmers and horticulturalists, and out of simple curiosity. But long experience had given conservationists reason to be cautious about taking such actions themselves, Schwartz wrote. The salvation of one species could mean the destruction of another.