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.

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Brashares, J. (2004). Bushmeat Hunting, Wildlife Declines, and Fish Supply in West Africa Science, 306 (5699), 1180-1183 DOI: 10.1126/science.1102425