Lichens Are in an Evolutionary Race Against Climate Change

The symbiotic organisms could need more than a million years to adapt to just 1 degree Celsius of warming, a new study suggests

Image of splotchy green and blue lichen growing on the surface of a rock
Lichens produce oxygen, trap moisture, and serve as food and shelter to other organisms. Baac3nes via Getty Images

The planet may be warming too quickly for tiny organisms called lichens to adapt, according to new research. 

Lichens are widespread plant-like organisms often seen growing on rocks, trees, and buildings. They’re easily confused with mosses at first glance, but aren’t plants. Lichens are actually two organisms working together: a fungus and either alga or cyanobacterium. The fungus shapes most of the lichen's physical characteristics, while their photosynthetic partner provides food for the fungus.

"When you see a lichen, you're basically looking at all fungal tissue, with some algal cells hidden away and protected inside," says study author Matthew Nelsen, an evolutionary biologist at Chicago’s Field Museum, in a statement. "Loosely speaking, it's like a greenhouse—the fungus creates a more hospitable environment for the algae."

Some lichens look hair-like, while others are curly, branching, or flat. From pale green to dark red, they range in color depending on their algal partner. Lichens are a diverse and widespread organism, with around 17,000 species covering around seven percent of the world’s surface. They play a key ecological role by churning out oxygen, trapping moisture, and serving as food and shelter to other organisms.

Scientists have long known that lichens grow at a staggeringly slow rate. Some are thousands of years old and grow just millimeters each year. Now, new research published in Frontiers in Microbiology suggests lichens are struggling to keep up with the changing climate.

To investigate how lichens were adapting to a warming planet, Nelsen and his colleagues at the Field Museum in Chicago focused on a single genus of algae, Trebouxia, which is found in about 7,000 species of lichen.

“It really puts it in perspective that this is quite a lot of diversity these algae are responsible for maintaining,” Nelsen tells Jake Buehler for New Scientist.

The team then looked at the climate in different locations where the algae live around the world and used a database of Trebouxia genes to find out which forms of the algae were evolutionary older than others, reports CNN’s Ashley Strickland. That allowed Nelson and his team to estimate how quickly the algae—and in turn, the lichen—adapted to past changes in their environment.

Their work revealed that lichens are slow to adapt to a changing climate and would likely need around one million years to cope with a temperate increase of one degree Celsius. With a predicted global temperate rise of one degree Celsius to four degrees Celsius by the end of the century, lichens may not be able to keep up.

"I was shocked," says Nelsen in a statement. "I should have known better from the other papers I've read, but I was disturbed to see it. It's so close to home, on a group of organisms near and dear to my heart."

The research team suspects that lichens that depend on Trebouxia will disappear from where they’re currently found. But that doesn’t mean they’re headed for extinction. Nelson thinks those lichens may migrate to new, more hospitable regions of the globe, and there is no telling what ecological effect that might have.

“[Lichens] are going to have to shift their distribution,” says Nelsen to New Scientist. “They’re going to have to disperse to roll with the punches.”

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