Deforestation, fires and unhealthy air quality in Singapore

Poor air quality in Singapore is back in the news again this week. In the last few days, the Pollutant Standards Index in Singapore reached 148 meaning that the air quality was “very unhealthy”. Unlike most cities in the world, this poor air quality is not caused by cars or industry but by forest fires.

By Dominick Spracklen – University of Leeds.

Deforestation fire
Hundreds of fires burning across Indonesia emit large amounts of smoke into the atmosphere. This smoke is blown north by prevailing winds causing the unhealthy haze in Singapore, as well as many cities in Indonesia and Malaysia. Research has shown that forest fires in Indonesia can cause several thousand premature deaths in the region each year through poor air quality.

Most of the fires in Indonesia are not natural – they are lit by people as an easy method to clear trees and vegetation from the land and prepare the land for agriculture. Satellites show that most of the fires occur in southern Kalimantan and central and southern Sumatra and research has demonstrated that it is these fires that cause most of the air quality problems. However, until recently it wasn’t known what land-use activities in Indonesia were actually responsible for most of the fires.

In Indonesia the government has allocated large areas of forest land, known as concessions, to companies for oil palm, timber and selective logging. Oil palm concessions produce palm oil; timber concessions grow Acacia and Eucalyptus to produce pulp and paper; natural forest logging concessions are managed for selective logging of trees to produce round wood or plywood.

A recent study by Miriam Marlier and colleagues compares the amount of fire occurring on these industrial concessions to areas of land outside concessions. They find that one third of population exposure to smoke across Equatorial Asia is caused by fires in oil palm and timber concessions. This highlights the role played by concessions in poor air quality, but also demonstrates that a substantial fraction of air pollution is actually due to fires occurring outside concession boundaries.

A very important finding of this study is that logging concessions – areas of natural forest allocated by the government for selective extraction of timber – have very few fires and contribute little to air quality degradation. Marlier and colleagues found that oil palm and timber concessions cause more than ten times the smoke pollution compared to that of logging concessions. This means that logging concessions contribute an important, but largely unrecognised, ecosystem service — the provision of clean air across Equatorial Asia.

Once a logging company has extracted the best trees from a particular logging concession, the value of the land is much reduced and the logging concession is liable for reclassification as an oil palm or timber concession. After reclassification, companies then clear any remaining trees, often by setting fire to the vegetation, then plant oil palm or timber species. We argue that the scarcity of fire on logging concessions presents a persuasive reason to protect logged forests and prevent reclassification of these areas into oil palm or timber concessions.

This research adds to considerable existing evidence showing that protection of logged forests is an important component of tropical forest conservation.