Cascading social-ecological costs and benefits triggered by a recovering keystone predator

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Science  12 Jun 2020:
Vol. 368, Issue 6496, pp. 1243-1247
DOI: 10.1126/science.aay5342

The benefits of ecosystem restoration

Human activities have fundamentally altered many ecosystems. Recent successful restoration efforts have led to healthier ecosystems, but this has led to a disruption in economies dependent on the altered state of the system. One of the best-known trophic cascades is the sea otter–kelp forest system, wherein recovery of once extirpated sea otters is bringing back biodiverse and healthy kelp forests but reducing the abundance of harvested shellfish. Gregr et al. looked at the costs and benefits of this shift and found that for key trade-offs, the value of kelp forest–associated features such as tourism, fin fish fisheries, and carbon capture outweighed the losses to economies (see the Perspective by Estes and Carswell). Thus, ecosystem recovery can benefit both ecosystems and economies.

Science, this issue p. 1243; see also p. 1178


Predator recovery often leads to ecosystem change that can trigger conflicts with more recently established human activities. In the eastern North Pacific, recovering sea otters are transforming coastal systems by reducing populations of benthic invertebrates and releasing kelp forests from grazing pressure. These changes threaten established shellfish fisheries and modify a variety of other ecosystem services. The diverse social and economic consequences of this trophic cascade are unknown, particularly across large regions. We developed and applied a trophic model to predict these impacts on four ecosystem services. Results suggest that sea otter presence yields 37% more total ecosystem biomass annually, increasing the value of finfish [+9.4 million Canadian dollars (CA$)], carbon sequestration (+2.2 million CA$), and ecotourism (+42.0 million CA$). To the extent that these benefits are realized, they will exceed the annual loss to invertebrate fisheries (−$7.3 million CA$). Recovery of keystone predators thus not only restores ecosystems but can also affect a range of social, economic, and ecological benefits for associated communities.

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