Predators play an overlooked role in ecosystem restoration • Earth.com

In the quest to restore degraded ecosystems through revegetation, a new study highlights a critical oversight in most restoration projects: the failure to manage herbivorous herbivores.

The study, which analyzed nearly 2,600 restoration efforts across ecosystems, found that while many projects focus on removing competing plant species, only 10% address the threat herbivores pose to young plants.

Protect young plants

Professor Brian Silliman, an expert in marine conservation biology at Duke University, emphasized the vulnerability of young plants.

“While most projects took steps to exclude competing plant species, only 10% took steps to control or temporarily exclude herbivores, despite the fact that in the early stages these plants resemble lollipops – irresistible little treats for grazers ,” says Silliman.

He explained that by not protecting plants in their early stages, conservationists are missing out on major opportunities to significantly accelerate recovery, improve outcomes and reduce costs.

“Our analysis of the projects studied shows that introducing predators to control herbivore populations or erecting barriers to keep them at bay until plantings become more established and less vulnerable can increase plant regrowth by an average of 89% .”

Increased grazing pressure

The international research team, consisting of experts from twenty universities and institutions, published their findings in the journal Science.

Co-led by Qiang He of Fudan University and his collaborator Changlin Xu, the study highlights the urgency of this problem in the context of climate change, especially in warmer, drier regions where the impact on herbivores is most pronounced.

The decline of top predators, such as wolves, lions and sharks, which have historically kept herbivore numbers in check, is seen as a key factor contributing to increased grazing pressure. This imbalance, Silliman suggests, indirectly hinders vegetation expansion.

Natural predation

The researchers call for a paradigm shift in restoration practices and advocate the use of natural predation as a cost-effective and efficient method to boost plant diversity and ecosystem recovery.

According to Silliman, the approach is like a “new gardening trick” with the potential to double vegetation yield.

Once a plant is established, its herbivores are also essential, he added. “Plants only need a short break from being eaten before they can start forming ecosystems again. Once established, herbivores are critical to maintaining the diversity and functioning of the plant ecosystem.”

Study implications

“If we want more plants, we have to let in more predators or restore their populations,” Silliman says. “Indeed, the decline of large predators, such as wolves, lions and sharks, which normally keep herbivore populations in check, is likely an important indirect cause of the high grazing pressure.”

“Conventional restoration slows our losses, but it doesn’t expand vegetation in many places, and climate change could make that even more difficult.”

This new insight into ecosystem restoration provides a compelling argument for reevaluating current methods and embracing a more holistic approach that takes both predators and prey into account.

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