Climate change, evolution, and what happens when researchers are also friends

IMAGE: This is an illustration of an eco-evolutionary feedback loop perpetuated by evolution of carbon cycling traits, in response to climate change.

Image credit: 
Grey Monroe et al./Colorado State University

What happens when six graduate students in different fields, who happen to be friends, put their heads together on an emerging issue in climate change?

They get published in a major journal.

The Colorado State University researchers, whose studies cut across three colleges, three departments and the Graduate Degree Program in Ecology, urge more of this type of collaboration in a new paper in Trends in Ecology and Evolution. Their paper, which addresses how climate change is affecting the evolution of organisms, underscores the need for evolutionary, ecosystem and climate scientists to work together to better understand eco-evolutionary feedback dynamics. They pose the question of whether evolution of plants, animals and other organisms altered by climate change will ultimately help, or hurt, the planet's current warming trend.

Evolutionary biologist Grey Monroe, lead author and a student in the Graduate Degree Program in Ecology, said the idea for the paper came from a course called Ecosystem Ecology, taught by biology professor Joe von Fischer. In a final paper for the course, Monroe explored evolution's impact on broad ecosystem processes like nitrogen and carbon cycling. Wanting to learn more, he approached other graduate students with similar interests for help fleshing out ideas.

"Ultimately, we were all interested in understanding the role evolution might play in shaping the future of carbon cycling, and how it might affect atmospheric carbon dioxide and climate change," Monroe said.

Colleen Webb, director of the Graduate Degree Program in Ecology and professor in biology, noted that it is highly unusual for graduate students to publish without a faculty member as a co-author. The paper's novel approach and dissemination by a major ecological journal speaks to the CSU graduate experience, she said.

The paper is a comprehensive literature review that explains, via synthesized analysis of published research, how evolution interacts with the environment and how it affects the global carbon cycle. The carbon cycle is the constant movement of carbon through various ecosystems. For example, atmospheric carbon dioxide is absorbed by plants through photosynthesis. Some of that carbon is deposited into the soil through the plants' roots, or animals eat the plants and exhale the carbon dioxide back into the atmosphere

For many decades, humans have inserted themselves into these natural processes by adding excess carbon dioxide into ecosystems through agriculture, burning fossil fuels, and other activities; thus the era we live in is known as the "Anthropocene," or the geological age dominated by human activity.

In their paper, the researchers delved into the idea that climate change in the Anthropocene is directly affecting natural selection. As global temperatures increase, precipitation patterns change, oceans acidify, and all those changes work together to alter selection pressures on many organisms, sometimes over just one or two generations.

Their paper points to the possibility that these altered states of evolution could either accelerate or mediate climate change through a feedback loop. For example, if plants evolve larger root systems in response to prolonged drought, they may deposit more carbon into the soil, thus increasing rates of carbon sequestration.

As another example, scientists have studied selection pressures exhibited by phytoplankton - photosynthetic algae that deposit carbon into ocean bottoms. In some cases, these algae evolve higher photosynthetic rates in response to climate change-induced pressures. They also evolve traits that make them sink more quickly to the ocean floor, pointing to a net increase of ocean carbon flux.

"There is a growing interest in eco-evolutionary feedback loops," Monroe said. "Our paper fits into this conceptual framework. We feel there is room for research in this area, to provide more empirical consideration for how evolution will affect the future trajectory of atmospheric carbon."

After all, the carbon cycle is dominated by organisms, and photosynthesis globally moves 20 times more carbon than humans do.

"That was one of the reasons we felt that the magnitude of evolutionary changes could be significant," Monroe said.

Credit: 
Colorado State University