Put another way: Cactus species could be suffering from sublethal effects of drought—the lack of water may not kill them immediately but still interfere with their reproduction. And without procreation, populations shrink. In the Sonoran Desert, for example, the iconic, towering saguaro is reproducing less frequently during prolonged droughts, because they’re not always flowering.
Part of the problem is that while desert ecosystems may look tough and hardened overall, they’re in fact quite fragile. “They don’t recover quickly once they are disturbed, or once they are degraded, just because there’s so little water and such higher temperatures,” said Marcos Robles, the Nature Conservancy’s lead scientist in Arizona, who wasn’t involved in the research. “It takes multiple decades to recover, and in some cases, they don’t recover.”
Now drought is compounding with other stressors, like habitat loss and poaching, to drive cactus species to the brink. On the opposite end of the spectrum, too much water from rising seas has led to the local extinction of the Key Largo tree cactus in Florida. Higher nighttime temperatures are a problem, too, since that’s when saguaro and other cacti respire to avoid water loss. “If the nighttime temperatures are very high, they can’t do it,” said Rod Haenni, president of the nonprofit Cactus and Succulent Society of America, who wasn’t involved in the paper. “Then if you water on top of that, the plants just rot.”
Still, some cactus species may persist by picking up and leaving. Well, not individual plants, but populations could creep into areas with climates that more closely match what the species adapted to all those millennia ago. A similar thing is happening in the Arctic, actually, where some plants are marching farther north in “search” of increasingly agreeable weather and more water.
In the end, the purpose of this sort of research is to better inform where conservation professionals might concentrate their efforts. They can’t stop droughts, of course, but they can evacuate enough cacti to establish populations in botanical gardens, where they can be cared for as the climate grows more unrecognizable to even the hardiest desert vegetation. Species can even be reintroduced to the wild in some cases, so long as drought and high temperatures don’t remain a threat to a population.
Governments, too, need to protect the lands where cacti are threatened, Haenni said. This new research, he added, could make that happen. “Hopefully, it’ll wake people up,” Haenni said. “But the problem is that a lot of the governments involved are indifferent to this. There are a lot of people in the countries who are not indifferent, but they’re not running the governments.”
This story originally appeared on Grist and is part of the Climate Desk collaboration.