Last week Antarctica outdid itself, and not in a good way, setting a high for its warmest temperature ever recorded: 65 degrees Fahrenheit. If the first thought that popped into your head is that balmy weather certainly can’t be good for the continent’s ice, you’d be right. But the heat is also a problem for the tiny creatures that teem across Antarctica.

Antarctica has a reputation as a wasteland where no trees grow and where few large animals roam, save for penguins and seals. But step into the Martian-like dry valleys and you’ll be treading on a bustling community of tiny organisms, like nematode worms and ultra-hardy water bears and mites.

“Really, that's the charismatic megafauna of continental Antarctica,” says evolutionary ecologist Byron Adams of Brigham Young University, who is currently surveying life on the continent. “The lions and tigers of the dry valleys are these microscopic animals at the very top of the food chain.” They’re species that are found nowhere else on Earth, feeding on bacteria, and, at times, on one another. If it gets too cold, they can slip into a sort of suspended animation—the water bear in particular is famous for its ability to dry out and reanimate years later.

But they may be ill-prepared for what’s coming, and indeed, what’s already here. Antarctica has two possible futures, as Adams and other scientists see it. One is business as usual but more extreme: Antarctica remains Mars-like in its barrenness and dryness, only these qualities get turned up to 11. The other possibility is that it becomes hotter, yet also wetter. It would be much like South America’s Patagonia region is now: a place with not a tremendous amount of vegetation but more biocrusts like lichen and mosses, the “living skin” of the planet. “I think most scientists probably favor the wetter, warmer, greener hypothesis,” Adams says.

That may sound like an impending diversification of Antarctica’s relatively simple ecosystems, but, in reality, it may be more like homogenization. Ecologically speaking, the continent is a segregated place: With water locked up in frozen lakes and rivers—some of which don’t thaw for decades—bodies of solid water don’t often melt, flow, and converge. That means the microbial communities that live in, say, liquid water below surface ice are unique, having gathered and established ecological relationships in isolation.

But now rivers, lakes, and subsurface ice are thawing and flowing and beginning to converge. “You start to see these features starting to become more and more connected, so that the biota are moving more easily between them,” says Adams. They exchange nutrients, too, eliciting a biological response. “The soil animals that are highly adapted to these super harsh conditions—cold, dry, salty—their numbers are going down, and their distributions are starting to shrink a little bit.”

Adams knows this because he’s doing controlled experiments in Antarctica’s dry valleys. He sets aside plots of land and periodically samples them, sorting out all the species, even counting the number of males, females, and offspring. Other plots he manipulates by adding nutrients or water to test how the ecosystems might morph in a warming world. “It kind of looks like a little garden,” Adams says. “The helicopter pilots here call us ‘worm herders.’ We've got worm farms out there.”

Things aren’t looking good for one particular nematode, Scottnema lindsayae, the most abundant animal on the continent. It loves Antarctica’s typically harsh conditions but is seeing its preferred habitats shrink as the climate grows milder and the landscape fills with melted ice water. The water bears, on the other hand, tend to like warmer, wetter habitats, where more food grows in the form of algae and cyanobacteria. Indeed, the tiny bears are already increasing in abundance.