Tree-planting, intended to help draw down carbon dioxide from the atmosphere, has become a synonym (同义词) for climate action. In our constant focus on trees, we've developed a fixed understanding: Trees absorb carbon dioxide, end of story. The reality is that trees don't grow well alone. They exist within complex communities, helped along by each other as well as the animals they coexist with. The woodland isn't nature's only carbon sink: Grasslands and oceans also help reduce the carbon level and rely on a healthy amount of biodiversity.
That's what the paper, published in Nature, wants to get across. Co-author Oswald J. Schmitz, a professor of ecology at Yale University, said trees might not be able to do their carbon-uptake job efficiently without the right animals in their ecosystem. That's because animals animate the carbon cycle through their behavior and roles in the ecosystem. He added that the very presence of wild animals could cause feedback effects that change the ecosystem's capacity to absorb, release, or transport carbon.
In Serengeti, for instance, the sharp decline in wildebeest (角马) population s during the mid-20th century allowed grass to grow wildly, eventually promoting wildfires that consumed 80 percent of the ecosystem annually and led to a net release of carbon dioxide into the atmosphere. When disease management and bans on illegal hunting helped animal populations recover, a greater share of the carbon stored in plants was consumed by wildebeest and released as waste, keeping it in the system and restoring the grassland as a carbon sink.
Researchers rarely consider wildlife conservation as a strategy to increase an ecosystem's carbon storage capacity, said Schmitz. "They think that animals either aren't important enough or that you can't take up carbon and conserve animals at the same time," he said. "Our message is that you can and should. It can be a win-win for both biodiversity conservation and carbon uptake." We need a full picture-with both trees and animals-to explore nature's full potential.
