Using 30 years worth of census data collected monthly by rangers in six nature reserves in Ghana, the researchers have found a direct link between fish supply and the demand for bushmeat in Ghanaian villages. Bushmeat is any wild species taken from public land and sold for consumption.
The group's findings will be published in November 12 issue of the journal Science.
More than half of Ghana's 20 million people reside within 100 km of the coast, where fish are the primary source of dietary protein and income.
Looking at data for the years 1970 to 1998, researchers found that in 14 local food markets, when fish supply was limited or its price increased, residents substituted bushmeat as an alternate source of affordable protein and the number of bushmeat hunters observed by rangers in parks increased. Overall, the wildlife harvest has contributed to a 76 per cent decline in the biomass of 41 species of mammals in parks since 1970.
The bushmeat trade in Ghana is estimated conservatively at 400,000 tons per year. Species affected include several species of antelope, carnivores and small primates.
During the same period, trawl surveys conducted in the Gulf of Guinea, off Ghana's coast, since 1970 along with other regional stock assessments, estimate that fish biomass in nearshore and offshore waters has declined by at least 50 per cent. In the same period, there has been a threefold increase in human populations in the region.
"We've suspected this link exists but this is the first time we've been able to demonstrate it," says Arcese, an associate professor in UBC's forestry faculty.
"Everyone is familiar in a colloquial way with the effects on wildlife in Africa, but to demonstrate the links between human demands for protein and the decline of wildlife resources in a statistical way has not been done before because the data hasn't been available. We've been able to do this study because of the long history of ranger surveys in Ghana."
The researchers suspect the decline in the availability of fish at local Ghanaian markets is linked to heavy overfishing in the Gulf of Guinea. UBC fisheries professor Daniel Pauly and others have identified the Gulf as one of the most overfished areas of the world, and now at risk of collapse.
Declines in fish stocks in waters off West Africa have coincided with more than ten-fold increases in regional fish harvests by foreign and domestic fleets since 1950. The European Union has consistently had the largest foreign presence off West Africa, with EU fish harvests there increasing by a factor of 20 from 1950 to 2001.
Arcese says the results support arguments that he, Sinclair and other biologists and agricultural economists have made for over a decade that urgent measures are needed to develop local sources of cheap protein alternatives to offset demand for wildlife harvest.
But, he adds, until the larger issue of international fish export agreements, increased populations and increased demand for food is addressed, local-level efforts to prevent the extinction of wildlife species will be very difficult.
"Many conservationists in Africa have been focusing on small-scale interaction of people near parks and say the solution lies in local development projects for local people," Arcese says. "It's an ethical and good approach, but if the larger problem of wildlife decline is mainly a result of large-scale economic policies and pressures that cause the over-exploitation of natural resources, including marine fishes, then small-scale development projects that sometimes encourage the reliance of local people on wildlife harvest are unlikely to have a positive impact on the rate of wildlife decline."
To interview Peter Arcese, Anthony Sinclair or Daniel Pauly, contact Michelle Cook at the UBC Public Affairs Office. Tel: 604-822-2048 or cell: 604-818-5685.
UBC radio and TV studio are available free of charge for interviews. Please contact Michelle Cook to make arrangements.