The UN’s definition of a forest may not be adequate enough to underpin a robust carbon market in avoided deforestation envisaged under the emerging REDD initiative, the results of a new study suggest. The study by Nophea Sasaki and Francis E. Putz has been published in the journal Conservation Letters and considers the differences in carbon stocks in forests of different densities.

The UN climate change convention (UNFCCC) offers a very flexible definition of a forest as an area of land at least 0.05 to 1 hectare, and at least 10 to 30 per cent covered by tree canopy. Trees must also have the potential to reach a minimum height of 2 to 5 metres. It is open to nations to set their own limits within these wide ranges, creating the potential for significant inconsistency in forest treatment around the world.

Worse still, the researchers say that overall these benchmarks are too low and should be raised. A natural forest typically has higher coverage than these ranges. They warn that exploitative foresters could log a substantial volume of mature trees within a natural forest and leave a severely degraded forest still meeting the UN standard.

REDD is envisaged to establish a payment mechanism to prevent both total deforestation and partial deforestation, or degradation, of natural forest. But the loose UN forest definition could undermine prevention of degradation. It could allow foresters to claim carbon credits for protecting a forest, yet still log a substantial proportion of its trees. With those trees could go up to 40 per cent of the carbon stored in forest, Sasaki and Putz say, much of it released to the atmosphere and producing a very poor result for the climate.

Strict carbon verification standards have been established that go a long way to ensuring that carbon credits generated from forestry projects reflect real and measurable carbon storage and emission reductions. But forest degradation is much harder to monitor than total deforestation, which may allow less reputable loggers to claim the full carbon market value for forest preservation yet still get away with selective harvesting of the biggest trees.

The study authors say the UN forest definition should be tightened to establish a minimum threshold for canopy cover of 40 per cent and a minimum tree height of 5 metres. There should also be tighter rules for natural forests than plantations, they argue.
 
Nature.com 19/8/09, Mongabay.com 20/8/09