Rainforests Slip Into Cycle of Destruction

As large tracts of Indonesia’s forest land go up in flames for the second time in five years, scientists are warning that the world’s rainforests risk becoming caught in a reinforcing cycle of destruction that could make them difficult to save. Research in recent years has shown that the very nature of rainforests—from Southeast Asia to the Amazon—is changing as a result of extensive clearing for farms, pastureland and other use, making them much more vulnerable to further destruction. “All the mechanisms essentially feed into a positive feedback loop,” said William Laurance, a research professor at James Cook University in Australia. “More fire begets more fires, more degradation begets more degradation.” Deforested land dries out quickly in the sun and wind. Fires, both naturally occurring and man-made, can spread more easily from this degraded landscape into the adjoining forest.

There is another problem too. Clearing foliage reduces evapotranspiration, the process by which the forest releases water vapour into the atmosphere—which accounts for around a third of the rainfall in a rainforest like the Amazon, according to Dominick Spracklen, a professor at the University of Leeds who studies the link between rainforest and rainfall. The reduction in water vapour decreases rainfall and extends dry seasons, making the forest more vulnerable to fire—and the fires more difficult to control. Last year, Thomas Lovejoy, a professor at George Mason University, and Carlos Nobre, a Brazilian scientist, wrote in an editorial in academic journal Science Advances that parts of the Amazon system could hit a tipping point and “flip to non-forest ecosystems” when deforestation reaches around 20% to 25%, given the added challenge of climate change. Around 17% of the Amazon rainforest has been lost over the past half-century, according to the World Wildlife Fund.

Indonesia’s rainforests, which are smaller than the Amazon, are already greatly diminished. Industrial agriculture expanded aggressively over the past few decades, making the country the world’s largest producer of palm oil. There is evidence that rainforest destruction has already changed weather patterns extensively. Researchers found that by 2010, 70% of forest area on the Indonesian island of Sumatra had been converted for plantations and other purposes. Temperatures in the island’s Jambi province were nearly 2 degrees Fahrenheit higher in 2015 than 2000, a study found—an increase, researchers linked to heavy deforestation there. Forest fires were once rare in heavily forested parts of the island, such as Riau, near Singapore, but in recent years have occurred almost annually, say, scientists. On the nearby island of Borneo, mainly controlled by Indonesia and Malaysia, forestland declined by 30% in less than four decades leading up to 2010, making parts of the island hotter and more susceptible to fires. A recent study found that rainfall there had decreased by around 20% since the 1950s and that deforested areas in the lowlands were around 3 degrees Fahrenheit warmer than forested areas. Scientists say climatic changes like these could have contributed to this year’s fires. A preliminary analysis by David Gaveau, a scientist who is an associate at Indonesia’s Center for International Forestry Research, found that many were started on degraded former forest land, now covered by fern and scrub, and spread from those dry areas into the rainforest. “These fires today are legacy of past peat swamp forest destruction,” said Mr Gaveau. “In a sense, you could say that the tipping point has been reached.”

Concerns about Southeast Asia’s forests have spurred global campaigns against palm oil, found in products from soap and candy to biofuels and mainly produced in Indonesia and neighbouring Malaysia. A European Union regulation published this year will phase out subsidies to palm-oil-derived fuels that aren’t certified as sustainable, beginning in 2024. The governments of Indonesia and Malaysia have spoken out against the regulation, with Malaysia saying it will effectively ban palm-oil biofuel in the EU. Jakarta says it is taking steps to improve forest conditions. In 2016 the government launched programs to restore peat swamp forests, which are naturally occurring waterlogged forests with spongy peat soil. But that is a long, complex and costly process. The swamp forests of Borneo are crisscrossed by drainage canals to make it easier to burn and clear for agriculture. To restore their swampy nature requires backfilling the canals with compacted peat soil. Nazir Foead, the Head of Indonesia’s Peatland Restoration Agency, said he was summoned to a meeting in August by the country’s president, Joko Widodo. The leader said local officials who failed to stop fires would be replaced. Mr Foead said Mr Widodo’s concerns were justified, but that during dry seasons as intense as the current one, it was a huge task to prevent fires from sparking and spreading. “We fully realize that the weather can get more and more extreme and that the forest could be more and more vulnerable to fires,” he said.

The picture for the Amazon and the Congo Basin rainforests could be yet direr. Indonesia’s rainforests are on islands and closer to the ocean than their counterparts in South America and Africa, which means they are less reliant on rainfall from evaporated forest moisture. “You can say it’s the canary in the coal mine,” said Douglas Sheil, a professor at the Norwegian University of Life Sciences. “If this is happening in Borneo, that’s scary.”

Credit: Jon Emont for The Wall Street Journal, 15 October 2019.