杏吧原创

Why we can’t tell the wood from the trees

FORESTS are dwindling much more slowly than they were 10 years ago, the UN鈥檚
Food and Agriculture Organization told Forestry officials from around the world
in Rome this week. But critics say the FAO鈥檚 numbers are misleading.

The FAO has assessed the world鈥檚 forests every 10 years since 1950 and its
Global Forest Resources Assessment 2000, published this week, suggests that the
rate of total global forest loss has slowed since 1990, from 11 million to 9
million hectares a year.

But Emily Matthews of the World Resources Institute, a think tank based in
Washington DC, disputes the figures. The FAO has combined supposed increases in
forest area in Europe, North America and Australia with continuing losses in the
tropics. But Matthews says poor data from Canada and Russia, in particular, and
a change in the definition of 鈥渇orest鈥 have led to huge apparent increases.
Parts of the Australian outback, which Australia itself classifies as desert, as
well as scrubland and tundra, have all been counted.

Some apparent tropical gains stem from increasing tree plantations,
especially in Asia, says Matthews. The FAO says remote sensing shows that
natural tropical forests are losing 鈥渙nly鈥 13.5 million hectares per year. But
Matthews says the FAO鈥檚 own more detailed data show that in fact the loss is 17
per cent faster.

Matthews says better forest data is needed to resolve such questions. She
suggests that 鈥渁 global, wall-to-wall high-resolution imagery dataset鈥 from
remote sensing satellites such as the US Landsat could provide a more accurate
deforestation analysis for the 1990s.

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