An interesting, frightening and and at the same time, potentially hopeful, paper has just appeared in the latest issue of Proceedings of the Royal Society B.
Co-authored by a previously highlighted Conservation Scholar Georgina Mace, the paper by Boakes and colleagues entitled Extreme contagion in global habitat clearance is probably one of the strongest bits of evidence to save intact habitat complexes.
Yes, yes – save things so you don’t destroy biodiversity. What’s new about that? Well, Boakes and colleagues’ paper shows at a global scale that over the last 300+ years, the chance of a patch of forest or grassland being converted to agriculture depends strongly on whether its neighbouring patch has already been cleared. In other words, once you start to hack away at natural habitats, people have a tendency to assume that it’s perfectly acceptable to do the same on their own patch.
The authors reprojected the History Database of the Global Environment to ~ a 50 x 50 grid and examined habitat conversion from 1700 to the present (in 50-year increments). Using some rather simple contagion statistics, they came up with the startling result that conversion probability is strongly dependent on whether an adjacent cell has already been converted.
What I found particularly frightening was the result that:
“A quarter of the world’s forest and half its grassland has been converted to agriculture since 1700.”
and from a personal perspective, the highest grassland conversion rates have happened in Australasia (the highest forest conversion rates have been in the Indo-Malay and Nearctic realms).
What are the implications for conservation? In my opinion, this relatively simple analysis and result confirms even more strongly that saving intact, large tracts of forest and grassland is essential for long-term biodiversity conservation. Cutting up the forest into smaller bits not only compromises biodiversity via fragmentation, it ends up speeding the entire process of full-scale ecosystem degradation.
‘Get ‘em protected while they’re still unaffected’.
Boakes, E., Mace, G., McGowan, P., & Fuller, R. (2009). Extreme contagion in global habitat clearance Proceedings of the Royal Society B: Biological Sciences, 277 (1684), 1081-1085 DOI: 10.1098/rspb.2009.1771