Rain forest depletion leaves it looking like Swiss cheese

By Jan-Uwe Ronneburger Nov 22, 2005, 16:35 GMT

Buenos Aires - The amount of Brazil's rain forest that is already destroyed or badly damaged is twice as large as previously estimated, according to a study conducted by U.S. and Brazilian researchers.

The researchers arrived at the conclusion after using new high- resolution satellite images that reveal new information about logging activities. The data is helping scientists evaluate the effects of 'selective logging', which is when loggers seek to take only the commercially prized trees, said the researchers' report, which appeared last month in the magazine Science.

'The forest looks like Swiss cheese,' said the report's co-author, Michael Keller of the U.S. Forest Service. 'We expected to see large areas of logging. But the extent to which logging penetrates deep into the frontier is much more dramatic than we anticipated.'

The researchers' article said selective logging poses a far bigger threat to the Earth's largest tropical forest than previously thought.

Greg Asner, an ecologist at the Carnegie Institution's Department of Global Ecology in Palo Alto, California, was quoted at National Geographic's website as saying loggers have practiaed selective logging for years, but the activity has been largely hidden by the rain forest canopy.

The new high-resolution satellite image technology can penetrate the upper layers of forest leaves. Until now, satellites were only useful in detecting swathes that were completely cleared.

Though the goal of selective logging is to take only the high- value trees, other nearby trees and ground cover often are lost or damaged in the process. The lack of monitoring makes the situation even worse for the condition the forest is left in. Too many trees are chopped down, and many small trees and ground cover also are destroyed.

Between 20 per cent and 30 per cent of the rain forest's canopy already has been lost, resulting in the rain forest becoming warmer, dryer and more susceptible to fire because sunshine can reach the forest floor. The sunlight also puts the forest's unique vegetation and animals under greater stress.

There is a more careful way to carry out selective logging that lessens the impact on the rain forest, Keller said. Trees that are to be chopped down have to be drawn into maps to plan the felling so that trees near the selected ones are damaged as little as possible. The trees are cut so that when they fall they take down as few other trees as possible. Careful planning also makes it possible to keep the damage caused by heavy equipment used to remove trees to a minimum.

Following these simple rules can reduce by half the collateral damage caused by selective felling, said Keller.

The new awareness of how rapidly the rainforest is being lost first came to light in May. The Brazilian Ministry of the Environment cited data released by Brazil's National Institute for Space Research on satellite images taken from August 2003 until August 2004 showing that 26,130 square kilometres of rain forest had been destroyed in the period.

The report, however, took into account only areas that were completely cleared. Combined, the areas were about half the size of Switzerland, an increase of 6 per cent compared with the previous year.

'We are surprised. No one expected these numbers,' said Environment Minister Marina Silva.

Brazil loses a stretch of rainforest equal to the size of seven football fields every minute, said Michael Evers of the environmental protection organization World Wildlife Fund in Germany. The Brazilian government is partly to blame for the deforestation, Evers said, because it favours the enlargement of grazing areas for cattle and it doesn't put up a strong fight against illegal logging and the exploitation of workers.

The Brazilian government created the Amazon Protection Area Programme in 2002, which set a goal of creating at least 50 million hectares of protected territory. The WWF considers this far too little to stop deforestation and demands that the benefits of the rain forest be realized without its destruction.