Over the past five years, Indonesia’s palm oil production rose by 13.4% and exports by 16.2% a year. This dramatic increase was largely stimulated by the rising demand for biofuels, particularly among the European Union member countries. “From a European perspective, replacing fossil fuels with biofuels is an attractive way of reducing carbon emissions,” explains World Agroforestry Centre scientist, Meine van Noordwijk, “but there can be considerable environmental costs in countries where biofuels are produced.”

There has been a heated debate about the pros and cons of palm oil production in Indonesia. On the one hand, the industry has made some bold claims about the environmental benefits of establishing palm oil plantations; indeed, the Indonesian Palm Oil Commission has even stated that plantations consume more carbon dioxide, and release more oxygen, than tropical forests. Environmental groups, in contrast, point out that vast areas of native forests have been cleared to make way for plantations, and that this has led to serious loss of biodiversity and high emissions of carbon dioxide, the main gas implicated in global warming.

To get to the bottom of the matter, van Noordwijk and his colleagues conducted a pilot study on the carbon footprint of palm oil production. Focusing on two areas in Sumatra and Kalimantan, they developed a relatively simple method to calculate the carbon budget of palm oil development, taking into account land clearance prior to establishing plantations, the balance of carbon emissions and carbon absorption during the life of the plantations, and the transport and processing of palm oil.

A key finding was that palm oil plantations store around 40 tonnes of carbon per hectare over their 25-year lifespan. In contrast, logged-over tropical forests, large areas of which have been cleared to make way for palm oil plantations in Indonesia, can store 70–200 tonnes of carbon per hectare. Pristine tropical forests can store double this amount.

The implications are clear. Conversion of forests to palm oil plantations should only be considered on land where above-ground carbon stocks are less than 40 tonnes per hectare; in other words, on grasslands or heavily degraded scrubland. Conversion of areas with high carbon stocks will lead to a net loss of carbon, with the draining of peat soils leading to particularly high losses. The researchers also suggest that palm oil companies should set aside specific areas for conservation, thus providing the twin benefit of sequestering carbon and enhancing biodiversity.

From the outset, the World Agroforestry Centre was determined to prove that it was independent, and subservient to neither palm oil companies nor the environmental lobby. “I believe we’ve managed to do that,” says scientist, Sonya Dewi. “I also think that we have convinced most people in the industry that palm oil development does have a significant environmental cost when it involves the clearance of carbon-rich forests. At the same time, we have provided evidence that palm oil development is not, per se, a bad thing, contrary to what some environmentalists claim.”

Yunnan’s drought – sorting fact from fiction

During the past half century, Yunnan province, in south-west China, has become progressively warmer and experienced an increase in extreme climatic events. However, nothing prepared its inhabitants for the recent drought. Between September 2009 and May 2010, the province received 60% less rainfall than normal. Over 8 million people – a fifth of the population – suffered from a shortage of drinking water and initial estimates for crop losses were set at US$ 2.5 billion.

Environmentalists were quick to point the finger of blame. Some claimed that the drought was caused by the large number of dams which had been constructed on the Mekong River and its tributaries. “That simply wasn’t the case,” explains Jianchu Xu, an ecologist with the World Agroforestry Centre. “The dams regulate streamflow, but they don’t have any impact on the regional climate.”

Other environmental groups claimed that the drought had been caused by widespread tree planting, particularly of eucalyptus. For many years, the Chinese government has been planting around 4 million hectares of fast-growing trees annually, most on dry and marginal lands. “It is true that tree-planting programmes can have an impact on the local hydrology, but they cannot be blamed for major events such as the Yunnan drought,” says Xu, drawing on research conducted in Yunnan’s Kejie watershed.

Over a 40-year period, the area under forest in the watershed increased by over 22%, largely at the expense of grassland, although there were significant transfers from cropland, barren land and human settlement. The research found that afforestation and reforestation had led to an increase in evapotranspiration – the process by which trees take water from the soil and release it into the atmosphere – and a decrease in surface water and stream flow, especially during the wet season. On the positive side, the forests had increased water flow during the dry season.

These and other research findings show that tree-planting programmes can influence the local hydrology, but there is nothing to suggest that they are responsible for the recent drought in Yunnan province. Nor is there any evidence that the Yunnan drought, a once-in-a-century event, was caused by global warming.