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Lichens cannot adapt as fast as Earth's temperature is changing

Lichens are composite organisms consisting of algae living among the filaments of various species of fungi in symbiotic relationships. While the fungi are providing the physical structure, the algae use photosynthesis to supply the necessary nutrients.

Lichens grow everywhere, from the Arctic tundra to the bark of trees in common backyards, and play a large variety of important ecologic roles, from creating oxygen to serving as food for reindeer and other animals.

A new study led by the Field Museum in Chicago has characterized these algae’s preferred climates and found that their ability to change climatic preferences happens very slowly, during millions of years. This means that they will likely be severely impacted by the rapid climate change the Earth is currently experiencing, and face – together with the lichens they are a part of – an increased risk of extinction.

In order to determine how much time it took algae to change under evolutionary pressures in the past, the scientists created family trees showing how different algae are related to each other, and calibrated it by using age estimates from previous work. Moreover, by comparing the DNA-based relationships of different species of modern algae to one another and looking at the environments in which they lived, they identified the climatic preferences of various species of algae.

By performing a series of statistical analyses on the data they collected, the researchers found that it could take hundreds of thousands, or even millions of years, for these algae to adapt to the temperature changes that we will witness over the course of this century.

“I was shocked,” said study lead author Matthew Nelsen, a research scientist at the Field Museum. “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.”  

According to Nelsen, losing lichens could have profound effects on their ecosystems.  “Lichens are the dominant vegetation on 7 percent of the Earth’s surface. They play roles in ecosystem hydrology by retaining moisture. They also play roles in carbon and nitrogen cycling, and some of them are used by animals for food or nesting materials.”

The research results are an important step forward in predicting climate change’s effects, and an incentive to take this phenomenon seriously and work toward systemic changes to mitigate its worse effects.

The study is published in the journal Frontiers in Microbiology.

By Andrei Ionescu, Staff Writer

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