Conservation

Over-hunting affects species and ecosystems in different ways. Bushmeat hunting can lead to declines and local/global extirpation of certain species if harvests are higher than the natural population growth of hunted species can accommodate, taking into account the potential dispersal mechanisms. The direct impacts on hunted species might have indirect and long-term impacts on ecosystems as a whole. However, hunting does not always lead to defaunation and some species might benefit from hunting if conducted in a sustainable way.

What are the impacts of overhunting on species and which species are the most affected?

‘Defaunation’ is often cited as the most evident impact of over-hunting. Examples of defaunation are numerous across the world, yet the relative contribution of hunting versus other drivers such as climate change, habitat alteration (i.e., land-use changes, destruction, fragmentation), and impacts of invasive species, makes it difficult to attribute causation to hunting alone.

What are the long term impacts of defaunation on ecosystems?

Defaunation may have the potential to impact not only targeted species but the ecosystem more broadly. In many ecosystems, the larger vertebrate fauna, especially frugivorous birds, primates, ungulates, and mammalian carnivores, have been extirpated or reduced in number. As these large animals vanish, so do the ecological interactions and processes they generate such as ecosystem engineering, herbivory, seed predation, and dispersal. Defaunation might unleash trophic cascades that derail ecological processes, resulting in changes in community composition and loss of diversity. ‘Keystone species’, or organisms with high community importance are groups whose loss is expected to have a disproportionate impact on ecosystems compared to the loss of other species. Local extinction of predators can trigger large changes in prey populations, which in turn could alter browsing or grazing to the point where large regime shifts may happen.

Does hunting always lead to defaunation?

Hunting does not always necessarily lead to defaunation, particularly if conducted in a sustainable way. Sustainable hunting refers to hunting practices that allow for the hunted population to maintain sustainable levels in the long term in a way that hunting can continue to provide the cultural, nutritional, economic and ecological services to future generations. Species are impacted by hunting pressure to different extents. How populations respond to harvest can vary greatly depending on their social structure, reproductive strategies, dispersal patterns and intactness of habitats.

What are the direct or indirect drivers of defaunation?

Wildlife populations worldwide are affected by a variety of direct and underlying drivers that may influence the sustainability of bushmeat use. The direct drivers with higher impact on wildlife are habitat loss and degradation, increased hunting pressure (through increased demand for bushmeat, new hunting technologies, etc), and disturbances related to extraction activities (timber industry, mining, oil). Underlying drivers, such as conflict and war, human demography, climate change, may not cause direct change on bushmeat species, but may act indirectly to contribute to change in bushmeat use. Identifying drivers and, where possible, quantifying their impact, facilitates the design and development of appropriate management guidelines for extractive use.

Further reading

Lindsey, P.A., Balme, G., Becker, M., Begg, C., Bento, C., Bocchino, C., Dickman, A., Diggle, R., Eves, H., Henschel, P., Lewis, D., Marnewick, K., Mattheus, J., McNutt, W., McRobb, R., Midlane, N., Milanzi, J., Morley, R., Murphree, M., Phadima, J., Purchase, G., Rentsch, D., Roche, C., Shaw, J., van der Westhuizen, H., van Vliet, N. & Zisadza-Gandiwa, P. 2013. The bushmeat trade in African savannas: impacts, drivers, and possible solutions. Biological Conservation, 160, 80–96.

Nasi, R., Brown, D., Wilkie, D., Bennett, E., Tutin, C., van Tol, G. & Christophersen, T. 2008. Conservation and use of wildlife-based resources: the bushmeat crisis. Technical Series No. 33. Montreal, Canada, Secretariat of the Convention on Biological Diversity; Bogor, Indonesia, Center for International Forestry Research (available at www.cbd.int/doc/publications/cbd-ts-33-en.pdf).

Nasi, R., Taber, A. & van Vliet, N. 2011. Empty forests, empty stomachs? Bushmeat and livelihoods in the Congo and Amazon Basins. International Forestry Review, 13(3): 355–368.

van Vliet, N., Nasi, R., Abernethy, K., Fargeot, C., Kümpel, N., Ndong Obiang, A.M. & Ringuet, S. 2012. The role of wildlife for food security in Central Africa: a threat to biodiversity? In C. de Wasseige, P. de Marcken, N. Bayol, F. Hiol Hiol, Ph. Mayaux, B. Desclée, R. Nasi, A. Billand, P. Defourny & R. Eba’a, eds. The forests of the Congo Basin – State of the forest 2010, pp. 123–126. Luxembourg, Office des publications de l’Union Européenne.