The two ecologists that contributed to understanding how human activity harms ecosystems, recognized with the Frontiers of Knowledge Award

Working independently, Likens and Scheffer have, says the jury, contributed to understanding and finding solutions for “gradual, abrupt and potentially irreversible ecosystem change” in response to pollution and other ecological threats.

The work of the American and Dutch ecologists is today instrumental in informing decisions on how to confront pollution risks, and policies to manage ecosystems safely, and even successfully restore them after serious deterioration.

The work done by Gene Likens, a professor at the Cary Institute of Ecosystem Studies in New York, “was instrumental to develop effective policies to reduce the acid rain problem,” according to the prize jury.  His discovery, published in 1974, paved the way for measures like the Clean Air Act Amendment of 1990, “with great impact on environmental law and clean-energy research.”

“Acid rain is a serious environmental problem that affects water, soil, forests ….” Likens explains. “In the United States we have achieved a notable reduction in the main compound causing acid rain, and the acidity of rain and snow has decreased by 80%. But acid rain has been falling for many years, which has made the soil far more sensitive to other impacts.”

Saving marshes, tropical forests and coral reefs

Marten Scheffer, a professor at Wageningen University in the Netherlands, helped to identify the risk of an ecosystem suffering abrupt change, and how such transitions could be avoided.

His studies can serve to anticipate the consequences of global climate change, and to prime specific ecosystems – like the Doñana marshes and other wetlands – to cope when they appear.  His first contribution was to confirm the reality of those critical ecosystem transitions known as “tipping points” (turning points and also, potentially, points of no return).  The Dutch scientist uncovered the first empirical evidence in the early 1990s in shallow lakes in different parts of Europe, where lakes had turned murky due to an excess of nutrients from agricultural fertilizers,

Scheffer was able to prove that reducing these pollutant inputs failed to restore them to their previous state.  The deteriorated ecosystem had transitioned to a new equilibrium, and was in need of “shock therapy,” as he described it: no less drastic a measure in this case than extracting all the fish.

This remedy is still practiced today, even in large lakes – with nets, he explains, several kilometers long – and marks a radical break with the strategies previously attempted.

Scheffer declares himself “especially happy” about the practical utility of his findings, not just for the recovery of lakes, but also other ecosystems poised to reach their own tipping points, such as tropical forests and coral reefs.

“In some instances, it is sometimes possible to harness natural phenomena, like El Niño, to help restore degraded forests”

For instance, his work showed that it is sometimes possible to harness natural phenomena, like El Niño, to help restore degraded forests:  the current provides humidity and its arrival marks the best time to withdraw livestock and initiate successful reforestation.

In one of his latest works, a 2015 paper published in Science, he applies his ecosystem model to the wetlands of Doñana, with suggestions on how to improve their resilience to climate change.  This Spanish National Park is threatened by several tipping points; a particular trigger being the cyanobacteria toxins increasingly present due to both rising temperatures and higher concentrations of nitrogenous and phosphorus waste from the fertilizers used on nearby strawberry crops.   With the prospect of hotter weather ahead, the strategy should be to reduce such nutrient inputs.

The next step in Scheffer’s research was to look for reliable indicators as to whether ecosystems are heading for “catastrophic and potentially irreversible change,” as the citation puts it.

“What we do is try to determine how far we are from a tipping point,” Scheffer explains.  “In practice, this gives you a measure of an ecosystem’s ability to recover from a perturbation.”