“When you trample on it, you’re resetting a clock that’s been running for a long time to zero,” said Finger-Higgens, whose latest findings on bioshell degradation were published last month in NASA. “So now the system has to fix itself.”
Finger-Higgins prefers to keep quiet about the exact location of her research site in order to keep her plot from being damaged. But the supposedly immaculate desert crust, with the white fungus peeking through, wasn’t as healthy as expected, she said. Something is not right—not only in the Colorado Plateau (which flows into the four U.S. states: Utah, Colorado, Arizona, and New Mexico), but everywhere else as well.
In some ways, deserts are the forgotten landscapes of climate change. This is all the more incredible considering that drylands cover about 40% of the Earth’s land surface and feed about 2 billion people, while biocrusts cover 12% of the Earth’s surface. However, the Finger-Higgins study suggests that even without human intervention, “warming may partially offset decades of protection from disturbance, with biocrust communities reaching an important tipping point.” “Refers to the moment when ecosystems can only experience more stress before they fundamentally change.
Finger-Higgens said rising temperatures and drought meant we could be “going in circles”. From 1967 to 1996, nitrogen-fixing lichens appeared to stabilize at 19% of biocrust coverage, but then declined from this constant to 5% in 2019. It shows that the caloric upper limit of biocrusts was not fully known until recently. “
Bala Chowdhury, a soil ecologist and assistant professor at Dartmouth College who was not involved in the study, agrees. Even if humans take a proactive approach to how their physical presence affects the landscape, “biological crusts are also affected by global climate change,” she said.
Of course, even long-term observational studies struggle to eliminate all possible confounding factors, which is why scientists have also taken experimental steps to simulate biological crusts in a warming world.
For example, between 2005 and 2014, a team used infrared heat lamps to heat a piece of crust on the Colorado Plateau by 2-4 degrees Celsius. They also found that warming led to a reduction in moss and lichen compared to unaltered land.
Then there’s a 2018 study that analyzed data from more than 500 publications and estimated that biocrusts “will decrease by about 25-40% over 65 years due to anthropogenic climate change and land-use intensification.”
Compared to these experimental studies, the Finger-Higgens “paper offers more realism,” Bowker said. It shows “things that unfold over a long period of time in a natural ecosystem”.
So, does it really matter to peel off the crust of the desert? If you’ve been in the American Southwest for a while, you know it’s windy and storm systems can sweep across the land. Biocrust acts as a protective layer—a glue that holds soil together. Biocrusts are sometimes called ecosystem engineers, Chowdhury said, likening them to the ability of beavers to alter landscapes.