Saturday, December 01, 2007

Burn baby, burn

Yadvinder Malhi and his colleagues have published an overview paper, Climate Change, Deforestation, and the Fate of the Amazon, drawing on work from their valuable conference earlier this year (which I mentioned in my third caveat here).

Some of the introductory faclets are likely to be familiar: Amazonia hosts about a quarter of the world’s terrestrial species. Some may be less so. For example, Amazonia accounts for about 15% of global terrestrial photosynthesis, and its forests been a significant and continuous part of earth system functioning since the Cretaceous.

Predicted temperature changes more than a little dramatic:
In recent decades the rate of warming in Amazonia has been about 0.25 °C per decade. Under mid-range GHG emission scenarios, temperatures are projected to rise 3.3 °C (range 1.8–5.1 oC) this century, slightly more in the interior in the dry season, or by up to 8 °C if significant forest dieback affects regional biophysical properties. At the end of the last glacial period, Amazonia warmed at only ~0.1 °C per century.
But there are scraps that suggest that not all is necessarily unmitigated gloom. For example:
There is mounting evidence …that intact Amazonian forests are more resilient (though not invulnerable) to climatic drying than is currently represented in vegetation-climate models...The probability of significantly enhanced drought under mid-range greenhouse gas emissions scenarios ranges from > 60% in the southeast to <20% in the west.
The authors sketch a climate reslience plan, which includes:
1. Keep the total extent of deforestation safely below possible climatic threshold values (about 30–40% cleared), in a matrix that includes large protected areas with limited fragmentation, and managed landscapes (…).
2. Control fire use through both education and regulation, probably for net economic benefit (…).
3. Maintain broad species migration corridors in ecotonal areas that are most likely to show early signals of climate impacts (…).
4. Conserve river corridors to act as humid refugia and migration corridors for terrestrial ecosystems, sedimentation buffers, and as refugia for aquatic systems (…).
5. Keep the core northwest Amazon largely intact as a biological refuge that hosts the highest biodiversity and is the least vulnerable to climatic drying (…).
They ask whether such a plan is feasible. ‘Recent developments suggest the good governance is achievable’...[but] particular, new financial incentives are needed to act as a countervailing force to the economic pressures for deforestation.’

No comments: