Can predators have a big impact on carbon emissions calculations?

Abstract

Models suggest that predators and even biodiversity in general play a potentially significant role in carbon sequestration. But whether such results buttress conservation arguments remains a matter of debate. Gray wolves lie at the heart of vigorous debate about the costs and benefits of conservation. But they also might inform another ongoing debate: the pace and projections for atmospheric CO2 accumulation in a warming world. Wolf kills may indirectly affect woody-plant abundance by having an impact on the number of plant-eating prey. Here, a wolf at Jasper National Park in Alberta, Canada, stands over an elk carcass. Image courtesy of Mark Bradley (Boreal Nature Photos). Ecologists are venturing into a new field of inquiry as they attempt to estimate how populations of predators affect atmospheric carbon levels. It turns out that losing wildlife could mean losing an important mechanism of carbon sequestration. Wolves and other predators generally affect carbon sequestration indirectly, by controlling the abundance of plants. For instance, when a wolf kills a moose, the moose no longer consumes woody plants, thus indirectly increasing woody plant abundance (1). Carbon accumulated in a plant remains sequestered throughout the plant’s lifetime and perhaps longer if it ultimately turns into coal or oil (2). In another well studied example, sea otters, by controlling the sea urchin population, indirectly allow for more carbon-storing kelp, a food source for the urchins (3). And predation is not the only way that animals mediate carbon storage. Ecologists recently found that the amount of diversity in an ecosystem is itself linked to increased amounts of carbon storage (4). The result of such dynamics, say those conducting these studies: an estimated tens of millions of metric tons of carbon stored. These carbon-storage calculations, though, represent extrapolations of baseline densities observed in modern times and applied …