Oil palm plantations threaten quality of water: Study

The clearing of tropical forests to plant oil palm trees leaves an adverse impact on the quality of water, finds a study.

The process releases massive amounts of carbon dioxide, a greenhouse gas that is fuelling climate change and significantly erodes water quality, the researchers said.

"Although we had previously documented carbon emissions from oil palm plantation, we were stunned at how profoundly these plantations alter freshwater ecosystems for decades," said Lisa M. Curran, professor of ecological anthropology at Stanford University in the US.

Land clearing, plantation management (including fertiliser and pesticide application) and processing of oil palm fruits to make crude palm oil can all send sediment, nutrients and other harmful substances into streams that run through plantations, the study noted.

Vegetation removal along stream banks destroys plant life that stream organisms depend on for sustenance and shade.

For the study, researchers focused on small streams flowing through oil palm plantations, smallholder agriculture and forests in and around Gunung Palung National Park in Indonesia.

They found that water temperatures in streams draining recently cleared plantations were almost four degrees Celsius (more than seven degrees Fahrenheit) warmer than forest streams. Sediment concentrations were up to 550 times more.

They also recorded a spike in stream metabolism - the rate at which a stream consumes oxygen and an important measure of a stream's health - during a drought.

The findings suggest that converting logged forests and diverse smallholder agricultural lands to oil palm plantations may be almost as harmful to stream ecosystems as clearing intact forests.

The new study appeared in the Journal of Geophysical Research: Biogeosciences.