Effects of gray wolf-induced trophic cascades on ecosystem carbon cycling

It is predicted that predator-induced trophic cascades could have important impacts on ecosystem carbon cycling. Yet the magnitude and direction of predator impacts on carbon cycling have not been widely quantified for terrestrial ecosystems. Here, we report on analyses of the potential for gray wolves to have cascading impacts on ecosystem carbon cycling. Our goal is to provide reasonable first approximations of their potential role in this fundamental ecosystem process. We find that gray wolves could lead to an increase in net ecosystem productivity (NEP) of 24.0-52.0 g C·m−2·yr−1 in Isle Royale's boreal forest, and a decrease in NEP of 30.03-102.88 g C·m−2·yr−1 in Yellowstone's grasslands. If such gray wolf impacts scale up to the broader North American boreal and grassland gray wolf range, these estimates suggest a potential for the indirect effects of wolves on yearly carbon fluxes to be on the same order of magnitude as the fossil fuel emissions of 6-20 million passenger cars per year. While considerable heterogeneity and uncertainty in gray wolf effects is likely to exist over both time and space, our results suggest that it may be worth examining in more detail the potential significance of the indirect effects of top predators on terrestrial ecosystem carbon using more systematic landscape-scale sampling in locations with and without wolves.