Ecologists and conservation biologists have repeatedly sounded the alarm about the global decline of apex predators. Yet despite major efforts to recover some of the world’s most charismatic megafauna, restoration practitioners have had limited success. Recovery of apex predators is critical because they provide fundamental services such as disease regulation, the maintenance of biodiversity, and carbon sequestration. A new publication in Science Advances by members of the Ocean Tipping Points team at NCEAS provides key recommendations to address this problem.
Stier et al. examined empirical studies of successful and failed recovery efforts from around the world to understand what factors encourage or impede progress in the recovery of apex predators. The authors recommend that recovery strategies should be tailored based on how apex predators are connected to their surrounding ecosystems. The success of techniques, like supplementing resources or culling mid-level predators that compete with apex predators, would be dependent on the context in which apex predators exist in their ecosystem. They also recommend that managers should consider the key role of timing in apex predator recovery. This is particularly relevant when an apex predator strongly competes with mid-level predators, as these species often skyrocket in abundance following apex predator declines.
“The ‘when’ is just as important as ‘what’ with respect to timing predator recoveries. This means designing adaptive sequences of management strategies that embrace key environmental and species interactions as they emerge.”
– Adrian Stier, UCSB's Department of Ecology, Evolution, and Marine Biology
and NCEAS researcher for the Ocean Tipping Points team
While over-exploitation and poaching are the most prevalent causes for the decline of these top predators, other human influences can interact with the slow life history characteristics of these species. Pollution, bioaccumulation of toxic contaminants, and chronic stress of anthropogenic noise could continue to affect apex predator populations for decades even after harvesting or poaching is managed or stopped altogether. Stier et al. suggest that the future of apex predator restoration will therefore require compromise among multiple stakeholders who develop policies that adapt to constantly changing social-ecological systems.
Towards Apex Predator Recoveries
A. C. Stier, J.F. Samhouri, M. Novak, K. N. Marshall, E. J. Ward, R. D. Holt, & P.S. Levin. Science Advances, 27 May 2016, Vol. 2, Issue 5, DOI: 10.1126/sciadv.1501769
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Photo credit: Johnny Armstrong