Recovering riparian plant communities with wolves in northern yellowstone

Beschta, R. L., and W. J. Ripple. 2010. Recovering riparian plant communities with wolves in northern yellowstone, U.S.A. Restoration Ecology 18 (3): 380-9.

Ripple and Beschta are well-known for advancing this 'trophic cascade' idea; they've published a parallel paper on cougars, deer, and oak trees in the Yosemite Valley. The principle is that by restoring a top predator, you suppress an herbivore, which in turn releases the plants they were in turn suppressing. What I like about this paper as an addition to the others we've read is that so far we've heard a lot about restoring vegetation or abiotic processes (referred to as a "bottom-up" approach), and these authors tend to talk about restoring the interactions involving top predators (a "top-down" approach). I think this is a nice shift in thinking, as is the change in emphasis to animals rather than plants. The point that animals may need restoring but can themselves be part of the restoration process is valuable. In addition, the role of the top predator can conceptually be taken up by humans or fire, so understanding that role in restoration is important. Finally, the sociological impact of reintroducing top predators is significant and could provide a lot of fuel for discussion in terms of the social and political side of restoration.

Figure: a slide from Mary Power's Population and Community Biology class, Fall 2008, Integrative Biology 153. It describes the concept of whether vegetation should be suppressed or released depending on how many layers there are above it on the food chain. Trophic cascades are related to this concept.