“What these sorts of analyses have not paid attention to is what we call the indirect multiplier effects,” Schmitz says. “And these indirect effects can be quite huge – and disproportionate to the biomass of the species that are instigating the change.”
In the paper, “Animating the Carbon Cycle,” a team of 15 authors from 12 universities, research organizations and government agencies cites numerous cases where animals have triggered profound impacts on the carbon cycle at local and regional levels.
In one case, an unprecedented loss of trees triggered by the pine beetle outbreak in western North America has decreased the net carbon balance on a scale comparable to British Columbia’s current fossil fuel emissions.
And in East Africa, scientists found that a decline in wildebeest populations in the Serengeti-Mara grassland-savanna system decades ago allowed organic matter to accumulate, which eventually fueled wildfires across 80 percent of the ecosystem annually, releasing carbon from the plants and the soil.
“These are examples where the animals’ largest effects are not direct ones,” Schmitz says. “But because of their presence they mitigate or mediate ecosystem processes that then can have these ramifying effects.”
“We hope this article will inspire scientists and managers to include animals when thinking of local and regional carbon budgets,” said Peter A. Raymond
, a professor of ecosystem ecology at the Yale School of Forestry & Environmental Studies.