Statistical Jungle

by Julie Walsh on January 8, 2008

As if the nonsense written about ‘global warming’ were not bad enough, that over the supposed retreat of tropical forests has tended to be even worse.

Luckily, there are some brave and meticulous scholars who seek the truth. One of my former colleagues, Dr Alan Grainger, Senior Lecturer in Geography at the University of Leeds, is one such, and an internationally-renowned expert on tropical deforestation, having studied the issue in great depth since 1978. He has now produced a major study, ‘Difficulties in tracking the long-term global trend in tropical forest area’, published in the Proceedings of the US National Academy of Sciences [see for full details: ‘No convincing evidence for decline in tropical forest’, EurekaAlert, January 7].

Dr. Grainger states: “The errors and inconsistencies I have discovered in the area data raise too many questions to provide convincing support for the accepted picture of tropical forest decline over the last 40 years. Scientists all over the world who have used these data to make predictions of species extinctions and the role of forests in global climate change will find it helpful to revisit their findings in the light of my study.”

As EurekaAlert points out:

“Dr Grainger first examined data published every 10 years by the United Nations Food and Agriculture Organization (FAO) since 1980. These cover all forest in the humid and dry tropics and appear to indicate decline. FAO’s Global Forest Resources Assessment 2000, for example, showed that all tropical forest area fell from 1,926 million hectares to 1,799 million hectares between 1990 and 2000. Ten years earlier, however, FAO’s previous report said that tropical forest area fell from 1,910 million ha to 1,756 million ha for the same 90 countries between 1980 and 1990.

‘Owing to corrections to the earlier study, the 1990s’ trend was just like a ‘re-run’ of that in the 1980s,’ said Dr Grainger. ‘The errors involved in making estimates for forest area could easily be of the same order as the forest area reported cleared in the previous 10 years. Even if you take enormous care, as FAO does, I argue that large errors are inevitable if you produce global estimates by aggregating national statistics from many countries. This has important implications for the many scientists who rely on FAO data.’”

This time round, Grainger found no evidence for decline since the early 1970s. Indeed, while his own estimate in 1983 of tropical moist forest area in 1980 was 1,081 million hectares, the latest satellite data led to an estimate of 1,181 million hectares for the same 63 countries in 2000 – a small increase.

Although one should rightly be cautious about this putative small increase in area (as Grainger is himself), all this indicates that the apparent decline in tropical moist forest area is being offset by natural reforestation at a higher rate than previously thought.

Now let me stress, so that nobody tries to dismiss this important study out-of-hand: Alan Grainger is an excellent, main-stream researcher, and I respect his opinion completely.

So, yet again, we have clear scientific evidence of the yawning gap between reality and Green myth-making, this time in relation to tropical forests. This is perhaps not so surprising when it comes to ‘tropical rain forests’ per se, which are largely a Western, or Northern, construction of knowledge.

In this respect, you may like to read my own piece, ‘Jungles of the Mind: the Invention of the Tropical Rain Forest’, which was first published in History Today Vol. 51, May 2001, pages 38 – 44. This is available to read online here [premium web content] or in a very basic version for university students here.

Grainger has done us all a service, because the figures for tropical forest decline are used unquestioningly in so many studies, including those on climate change.

I would ask everybody who reads this blog to ensure the very widest reporting of Grainger’s new study. Thank you.


Please visit Philip's new blog, 'Global Warming Politics: a Hot Topic Blog' at:

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