Press release: Deforestation linked to palm oil production is making Indonesia warmer

Nr. 211/2017 - 25.10.2017

Göttingen experts on bioclimatology report effects on temperatures after changes in land use

(pug) In the past decades, large areas of forest in Sumatra, Indonesia have been replaced by cash crops like oil palm plantations and rubber. Now a team of scientists led by the University of Göttingen found out that these changes in land use increase temperatures in the region. The added warming could affect plants and animals and make parts of the country more vulnerable to wildfires. The results are reported in the European Geosciences Union journal Biogeosciences.

Palm oil is the most widely used vegetable oil in the world, appearing in the ingredients’ list of many con-sumer goods, from chocolate to soap. Indonesia, the world’s largest producer of palm oil, has seen large swathes of rainforest cleared away and replaced by oil palm plantations. The island of Sumatra has had the highest loss of native rainforest in all of Indonesia. In the framework of the Collaborative Research Centre “Ecological and Socioeconomic Functions of Tropical Lowland Rainforest Transformation Systems (Sumatra, Indonesia)” of the University of Göttingen the research team, led by Clifton Sabajo and Alexander Knohl, now found out that the expansion of oil palm and other cash crops in Sumatra has made the region warmer. “The land use change does not only impact biodiversity and stored carbon, but also has a surface warming effect, adding to climate change,” says Knohl, a professor in bioclimatology.

The team studied differences in surface temperature for various types of land cover, such as forests, clear-cut land, and cash crops, in the Jambi province of Sumatra. They used satellite data collected be-tween 2000 and 2015 as well as data collected on the ground. They found that clear-cut land was up to 10 degrees Celsius warmer than forests. “Clear-cut land is the phase after forest has cleared away and before the start of commercial plantations or farming,” says Sabajo, a PhD student and the lead author of the study.

Mature palm oil plantations were about 0.8 degrees Celsius warmer than forests, while young palm oil plan-tations were 6 degrees Celsius warmer. “Young palm oil plantations have fewer and smaller leaves and an open canopy, thus they transpire less water. Also, the soil receives more solar radiation and dries out faster,” explains Sabajo. Mature palm oil plantations, which are older than 5 years, have a closed canopy and larger and more abundant leaves, which results in a cooler ground compared to a young plantation. The coldest surface temperatures they found in forests mainly because of evaporative cooling, which is similar to the process that cools us down when we sweat.

Overall, the average mid-morning surface temperature in the Jambi province increased by 1.05 degrees Celsius between 2000 and 2015. Some of this warming is a result of climate change, but some is a direct consequence of the changes in land use. “We compared the average land-surface temperature increase in the province with a site that was covered by forest over the entire period and that can be considered as a control, unaffected by direct land-use change. The land-surface temperature of the forest sites only in-creased by 0.45 degrees Celsius, suggesting that at least 0.6 degrees Celsius of the 1.05 degrees Celsius increase is due to land-use change,” says Knohl.

To the scientists, the strong warming effect in the Jambi province may serve as an indication of future changes in land-surface temperature for other regions of Indonesia that will undergo land transformations towards oil palm plantations. “Land surface temperature is an important part of the microclimate, which shapes habitat conditions for plants and animals,” says Knohl. “The observed warming may affect ecosys-tems in many ways. Current land-use developments in Indonesia need to carefully evaluate and consider all aspects of environmental and socio-economic consequences.”

Original paper: Sabajo, C. R., le Maire, G., June, T., Meijide, A., Roupsard, O., and Knohl, A.: Expansion of oil palm and other cash crops causes an increase of the land surface temperature in the Jambi province in Indonesia, Biogeosciences, 14, 4619–4635, https://doi.org/10.5194/bg-14-4619-2017, 2017

Contact:
Prof. Dr. Alexander Knohl and Clifton Sabajo
University of Göttingen
Faculty of Forest Sciences and Forest Ecology – Bioclimatology
Büsgenweg 2, D-37077 Göttingen
Phone: +49 551 39-33682 and 39-12114
Mail: aknohl@uni-goettingen.de and csabajo@uni-goettingen.de
Web: www.uni-goettingen.de/en/67076.html