Ellen Phiddian
Cosmos science journalist
A study has found that nearly half of land cleared in Indonesia is left idle for more than 5 years.
Indonesia has lost 25% of its old-growth forest since 1990, and while much of it has been converted to other use like palm oil, US and Indonesian researchers have found that 44% of cleared lands stay unused for at least half a decade.
The study is published in Proceedings of the National Academy of Sciences.
“Old-growth tropical forests are an extremely valuable resource, both locally and globally,” says Diana Parker, a postdoctoral associate at the department of geographical sciences in the University of Maryland, US.
“The fact that such a large area of old-growth forest has been cleared then left empty is surprising.”
The researchers used satellite data to track forest coverage in Indonesia from 1991 to 2020.
They found that while 7.8 million hectares of cleared forest had been planted with oil palm plantations by 2020, 8.8 million hectares of land remained unused.
Many researchers have speculated that forest fires are the primary source of land clearing.
But this study found that, while fires were a major source of deforestation, 54% of the land had been cleared mechanically.
“Forest fires can be either intentional or accidental,” says Parker.
“Mechanical clearing, however, is not only intentional but can be time consuming and costly. Once we realised that more than half of idle areas were not created by fires, it led to a new question: why would people expend so much effort to clear forests then leave the land empty?”
Nor was timber demand a major driver: most of the forests were selectively logged prior to clearing, and cleared land tended to be more expensive than uncleared land.
Instead, the researchers believe this land clearing is related to palm oil speculation. Palm oil, which is extracted from oil palm trees that only grow in the tropics, is a very common food ingredient, as well as being used in cosmetic, biofuel, and other industries. Planting of the lucrative crop has been heavily criticised because of its link with deforestation.
While other uses, like other tree plantations, were started straight after deforestation in an area, a majority of oil palm plantations were delayed by at least a year.
“About 80% of mechanically cleared idle land that was converted to a productive use became a palm oil plantation,” says Parker.
The researchers suggest that land banking and speculation in the palm oil industry, alongside possible failed palm oil plantations, could be a significant cause of this apparently pointless deforestation.
“The satellite imagery can’t tell us exactly how idle land creation and the palm oil industry are linked, but the land use trends suggest a relationship,” says Parker.
“In some cases, companies or individuals may intend to sell deforested land but are waiting for land prices to rise. Or they may plan to develop the land later, holding it as part of their land bank.
“In other cases, young seedlings may have died before they could be detected in satellite imagery, or conflicts with communities or other concession holders could have delayed planting.”
The researchers say there is reason to be optimistic about this. The study, which covered 1991 to 2020, found that deforestation rates were at their slowest in 2017-20, at the end of the study period. The already cleared land may be a driver of this.
“Indonesia is one of the few tropical forest countries that has been able to successfully slow deforestation,” says senior author Matthew Hansen, a professor at the University of Maryland.
“Given how much idle land is currently available, Indonesia could stop clearing forests altogether while still increasing palm oil production.”
