Humans disrupt relationships in nature, study finds

Humans are changing relationships between species in fundamental ways.

In nature, species interact with each other on a daily basis. It is known that certain species, like plants and the mycorrhizal fungi that live in their roots, benefit from each other through the sharing of nutrients. But human activities are interfering with and, in some cases, disrupting these interactions, according to FIU researchers.

“Healthy nutrient exchange relationships between species help maintain ecosystem function and biodiversity,” said Andrew Shantz, a biological sciences Ph.D. student at FIU and lead author of the study. “Given the importance of these relationships and the scale at which humans are altering the planet, it is critical to understand how global change will influence these partnerships.”

The plant on the left has a network of mycorrhizal fungi around the roots, while the one on the right does not. The fungi forms a mutually beneficial relationship with the plant, ts resistance to drought and disease. In exchange, the plant feeds the fungi liquid carbon to generate more nutrients. Photo by soilcarboniscool.org.

A new study published in Ecology Letters found that when excess amounts of nutrients, like phosphorous and nitrogen, are introduced to an environment, the costs and benefits of sharing nutrients change. As plants and algae enjoy the benefits of the excess nutrients, they stop sharing as many resources with the animals, fungi, and bacteria that they normally partner with, causing declines in the growth of these organisms. This breakdown of the mutually beneficial interactions was found in both land and water environments across the world.

More than 80 percent of plant species partake in nutrient exchange relationships, while in marine environments these relationships sustain important foundation species, like sponges and corals. A healthy nutrient exchange relationship not only promotes food security, but it also improves a species’ tolerance to toxins, disease and extreme conditions such as drought.

“Most people think of climate change as the greatest modification to the planet’s natural processes, but people often overlook nutrient loading and the impact we’ve had on the world’s nutrient cycles,” Shantz said. “I hope our study helps draw attention to the widespread consequences of nutrient pollution and will improve management and remediation strategies.”