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| Figure 3: Disproportionate impacts of human harvesting the largest individuals and the largest species in a community first. Such harvesting causes local declines in abundance of the largest individuals, inducing population-scale downsizing and many population-scale impacts. This decline often proceeds to local extinction of populations of large-sized species. Replicated across regions, this local extinction often progresses to global extinction, such that large body size is a leading predictor of global extinction risk.
Megafauna images courtesy of Fiona A. Reid.
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ABSTRACT
Anthropocene defaunation, the global extinction of faunal species and populations and the decline in abundance of individuals within populations, has been predominantly documented in terrestrial ecosystems, but indicators suggest defaunation has been more severe in freshwater ecosystems. Marine defaunation is in a more incipient stage, yet pronounced effects are already apparent and its rapid acceleration seems likely. Defaunation now impacts the planet's wildlife with profound cascading consequences, ranging from local to global coextinctions of interacting species to the loss of ecological services critical for humanity. Slowing defaunation will require aggressively reducing animal overexploitation and habitat destruction; mitigating climate disruption; and stabilizing the impacts of human population growth and uneven resource consumption. Given its omnipresence, defaunation should receive status of major global environmental change and should be addressed with the same urgency as deforestation, pollution, and climatic change. Global action is needed to prevent defaunation's current trajectory from catalyzing the planet's sixth major extinction.
Keywords: animal conservation, defaunation cascades, animal overexploitation, terrestrial fauna, marine fauna, freshwater fauna
Hillary S. Young, Douglas J. McCauley, Mauro Galetti and Rodolfo Dirzo. 2016. Patterns, Causes, and Consequences of Anthropocene Defaunation. Annual Review of Ecology, Evolution, and Systematics. 47; 333-358. DOI: 10.1146/annurev-ecolsys-112414-054142
