The study reveals that expanding production of palm oil – a common ingredient in processed foods and confectionery products – is driving the destruction of carbon-rich tropical forests in Borneo, leading to huge releases of carbon dioxide into the atmosphere.
Writing in Nature Climate Change, US-based researchers from Stanford and Yale universities suggest that the vast deforestation occurring during the development of oil palm plantations in Indonesian Borneo "is becoming a globally significant source of carbon dioxide emissions."
The researchers said the sustainable production of palm oil will require re-evaluation of awarded oil palm plantation leases located on forested lands – around 80% of which are currently unconverted.
Led by Professor Lisa Curran from Stanford, the authors explained that a technique combining field measurements with high-resolution satellite image was used to evaluate carbon emissions for lands targeted for palm oil plantations.
The team used this classification to generate the first comprehensive maps of oil palm plantation expansion in Borneo (also known as Kalimantan) from 1990 to 2010. The team then quantified the types of land that have been cleared for oil palm plantations, and worked out the carbon emissions and sequestration from oil palm agriculture.
"A major breakthrough occurred when we were able to discern not only forests and non-forested lands, but also logged forests, as well as mosaics of rice fields, rubber stands, fruit gardens and mature secondary forests used by smallholder farmers for their livelihoods," said Kimberly Carlson, a Yale doctoral student and lead author of the study.
"With this information, we were able to develop robust carbon bookkeeping accounts to quantify carbon emissions from oil palm development."
Curran and her team said the findings show that allocated oil palm leases “represent a critical yet undocumented source of deforestation and carbon emissions.”
Curran and her colleagues had initially gathered oil palm land lease records during interviews with local and regional governmental agencies. These records identified locations that have received approval and are allocated to oil palm producers.
They revealed that the total allocated leases spanned about 120,000 square kilometres – an area slightly smaller than Greece. Most leases in the study occupied more than 100 square kilometres – an area slightly larger than Manhattan, the team said.
However the researchers said that around 80% of these leases remained unplanted in 2010.
Using the information from the leases – in combination with land cover maps – the team then estimated the future land-clearing and carbon emissions for already approved but not yet cleared plantations.
The team found that if all of these leases were developed, more than a third of Kalimantan's lowlands would be planted with oil palm by 2020. They said this planned expansion is projected to contribute more than 558 million metric tons of carbon dioxide to the atmosphere in that time.
"These plantation leases are an unprecedented 'grand-scale experiment' replacing forests with exotic palm monocultures," said Curran.
"We may see tipping points in forest conversion where critical biophysical functions are disrupted, leaving the region increasingly vulnerable to droughts, fires and floods."
Source: Nature Climate Change
Published online ahead of print, doi: 10.1038/nclimate1702
“Carbon emissions from forest conversion by Kalimantan oil palm plantations”
Authors: Kimberly Carlson, Lisa Curran, Gregory Asner, Alice McDonald Pittman, Simon Trigg, J. Marion Adeney