Bushmeat Links Land and Sea
How Fluctuations in Ocean Fisheries Can Affect Wildlife Conservation
Nov 8, 2008
A challenge for resource management is to establish defensible linkages between ecological and socio-economic systems, especially over large geographic scales. It is not enough to show correlation, effective management requires establishing the underlying mechanisms of observed changes. Unfortunately, the data required to support such analyses rarely exist; however, one example from the African nation of Ghana provides stunning insight into the connection between human and natural systems.
Bushmeat is an Economically Important but Ecologically Unsound Source of Protein
In Ghana, as in many developing countries in tropical regions, trade in ‘bushmeat’, the meat of wild terrestrial animals, is an economically important, but ecologically unsound source of protein. As the human populations of these countries grow, hunting pressure increases on dwindling wildlife populations, even those in nature reserves. To ensure effective wildlife conservation, it is imperative to understand the ecological and socioeconomic mechanisms that drive the increased consumption of bushmeat.
This is what J.S. Brashares and his colleagues achieved. They compared wildlife data, painstakingly collected over many years in the nature reserves of Ghana, to fish catch data and were able to establish a socioeconomic ‘bushmeat’ link between trends in the abundance of wildlife and fish (J.S. Brashares, P. Arcese, M.K. Sam, P.B. Coppolillo, A.R E. Sinclair and A. Balmford. 2004. Bushmeat Hunting, Wildlife Declines, and Fish Supply in West Africa. Science 306: 1180 – 1183.)
The “Protein Limitation Hypothesis” Versus the “Nonessential Good Hypothesis”
The researchers examined support for two hypotheses: 1) the “protein limitation hypothesis” where the consumption of bushmeat varies with the availability of other sources of protein, like fish, or 2) the “bushmeat is a nonessential good” hypothesis, perhaps only consumed as a delicacy and in proportion to the size of the human population. The two hypotheses suggest different approaches to conservation.
The former could include a suite of measures to both protect wildlife, but also increase the availability of other sources of protein to decrease reliance on bushmeat, while the latter might focus conservation resources more narrowly on the increased protection of existing reserves.
The Correlation Between Temporal Patterns of Fish Catch and Wildlife Biomass
Their first clue for an ocean-land connection was the close correspondence between the patterns of annual biomass estimates for terrestrial mammals and that of annual fish supply, a correspondence unrelated to other potential explanatory factors like rainfall, temperature, or select economic indicators (e.g., the price of oil). This finding suggested some kind of a connection between wildlife and fish abundance, but three additional pieces of evidence helped explain its cause.
Fewer Fish Increase Costs and Reduce Employment Causing Increased Hunting for Bushmeat
First, more hunters were seen in nature reserves during years when the fish supply was low and this increase was linked to accelerated declines in wildlife. Second, when fish were scarce in local markets, and thus more expensive, bushmeat became more prevalent.
Finally, the researchers found that the strongest link between changes in fish supply and wildlife populations occurred in nature reserves near the coast. This is because most of the population of Ghana lives within 100Km of the coast and fish are both a primary source of protein and major source of employment and income. Poor fish harvests lead to lower employment and increased household reliance on bushmeat for both income and food.
Economic Development, Food Security, and Conservation of Biological Diversity are Closely Linked
Taken together, these results support the "protein limitation hypothesis" over the “nonessential good hypothesis" which suggests that funding to increase economic development, food security, and wildlife conservation are closely linked, at least in Ghana.
Furthermore, by establishing the mechanisms driving the increased hunting and consumption of bushmeat in Ghana, and thus the pressure on wildlife populations, the researchers could make specific management recommendations for reducing pressure on wild sources of marine and terrestrial protein.
Their recommendations targeting marine sources of protein include limiting commercial fishing by heavily subsidized foreign fleets in West African waters and increasing the protection of fish stocks from illegal, or ‘pirate’ fishing fleets. Their recommendations targeting terrestrial sources of protein include building up regional livestock and agriculture to decrease hunting pressure on wildlife populations, while increasing the size, number and protection of wildlife reserves.
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