Bushmeat, Fisheries, and How It’s all One Planet
There’s a great study by Brashares et al. in the journal Science that reminds this ocean conservationist that we need healthy terrestrial ecosystems in order to have healthy marine ecosystems, and vice versa.
The article uses 30 years of data on the bushmeat trade in Ghana and to show that years of poor fish supply coincided with increased hunting in nature reserves and sharp declines in biomass of 41 wildlife species.
In short, if there isn’t enough fish, coastal populations in West Africa have to depend on their terrestrial ecosystems more for food.
Quoting:
In support of the prediction that annual standing biomass of large mammals would be linked positively with the annual supply of marine and freshwater fish, we found that changes in annual biomass of terrestrial mammals from 1970 to 1998 were closely related to annual per capita fish supply. Years with a lower-than-average supply of fish had higher-than-average declines in mammal biomass, and vice versa. In contrast, fish supply and wildlife declines were unrelated to other potential explanatory factors, including annual rainfall, land and water temperatures, political cycles, oil prices,
and gross national product.
The fish data came from the FAO, which I found interesting. The FAO database of fish landings is generally lacking good data (or any data for that matter) on inshore and freshwater fisheries. I would have liked more work on cleaning this up.
The biomass data was obtained through about 700 walking counts of nature reserves in Ghana.
This simple study was backed up by a few additional analyses. The one I found most interesting was a review of fish and bushmeat availability and prices in 12 local markets over four years. Again quoting:
[I]f annual variation in fish supply and bushmeat hunting are linked causally, we would expect that the availability of bushmeat in local markets would be related negatively to the supply of fish. In support of this prediction, we found that monthly supply of fish in 12 local markets in northern, central, and eastern Ghana from 1999 to 2003 was related negatively to the volume of bushmeat sold in these markets. In addition, the price of fish sold in markets was closely and negatively related to local fish supply and positively related to the volume of bushmeat sold. The strong negative correlation between fish price and quantity sold, combined with the positive correlation between fish price and bushmeat sales, is consistent with the idea that variation in fish supply drove bushmeat sales. Comparing monthly fish price in markets with the bushmeat sales in the following month yielded even stronger correlations, again suggesting that bushmeat sales were driven by fish availability and price more so than the reverse case. These results show a substitution of wildlife for fish at the local scale.
That’s a great use of economics.
The big takeaway for me is that terrestrial and marine conservationists should talk more with each and even collaborate on integrated projects.
—
Brashares, J. (2004). Bushmeat Hunting, Wildlife Declines, and Fish Supply in West Africa Science, 306 (5699), 1180-1183 DOI: 10.1126/science.1102425