In the pursuit of restoring degraded ecosystems through re-vegetation, a new study highlights a critical oversight in most restoration projects – the failure to manage plant-eating herbivores.
The survey, which analyzed nearly 2,600 restoration efforts across various ecosystems, revealed that while many projects focus on removing competing plant species, only a mere 10% address the threat posed by herbivores to young plants.
Professor Brian Silliman, an expert in marine conservation biology at Duke University, emphasized the vulnerability of young plants.
“While most of the 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 are like lollipops – irresistible little treats for grazers,” said Silliman.
He explained that by not protecting plants in their early states, conservationists are missing out on great opportunity to significantly speed restoration, improve its outcomes, and lower its costs.
“Our analysis of the surveyed projects shows that introducing predators to keep herbivore populations in check or installing barriers to keep them at bay until plantings become more established and less vulnerable, can increase plant re-growth by 89% on average.”
The international research team, including experts from 20 universities and institutions, published their findings in the journal Science.
Co-led by Qiang He of Fudan University and his associate Changlin Xu, the study highlights the urgency of this issue in the context of climate change, especially in warmer, drier regions where herbivore impact is most pronounced.
The decline of apex predators, such as wolves, lions, and sharks, which historically have kept herbivore numbers in check, is identified as a key factor contributing to increased grazing pressure. This imbalance, Silliman suggests, indirectly hinders the expansion of vegetation.
The researchers are calling for a paradigm shift in restoration practices, advocating for 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 yields.
Once a plant is established, the herbivores are essential too, he added. “Plants just need a small break from being eaten to get restarted making ecosystems. Once they establish, herbivores are key to maintaining plant ecosystem diversity and function.”
“If we want more plants, we have to let more predators in or restore their populations,” said Silliman. “Indeed, the decline of large predators, like wolves, lions, and sharks, that normally keep herbivore populations in check, is likely an important indirect cause of high grazing pressures.”
“Conventional restoration is slowing our losses, but it’s not expanding vegetation in many places, and climate change could make that even more difficult.”
This new insight into ecosystem restoration presents a compelling argument for reevaluating current methods and embracing a more holistic approach that accounts for both the predators and prey.
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