Press Release

(click for pictures and maps about Indonesia's fires)

Fires associated with the El Niño/Southern Oscillation climate event devastated huge areas of tropical rainforest in 1997-98. A detailed satellite-based survey of the damage caused to forests in Indonesia, the country with the largest remaining rainforest area in Asia, reveals that over 5.2 million hectares including 2.6 Mio ha of forests burned in East Kalimantan alone. This is much more than previously thought and could spell trouble. If current land use policies continue unchanged, the prospects are that forest fires, boosted by future El Niños, could lead to an irrevocable loss of important forest resources within a matter of years.

This research was based on the application of advanced satellite image processing technologies using a combination of radar and optical satellite imagery. It is the first to successfully identify fire damages using ERS-Radar satellite imagery on a very large area of tropical rainforest. The new technology allows to map burn scars, fire impact and deforestation even when cloud and haze hamper conventional optical satellites. We demonstrated that radar microwave satellites such as ERS are a powerful instrument for disaster management and resource mapping in tropical regions. A detailed spatial analysis of fire impact was done by a combined evaluation of results from the remote sensing survey, data from field studies and official planning data in a geographic information system (GIS).

During active burning and the months after the fires, clouds and haze severely hampered or made impossible a damage assessment by the means of conventional earth observation satellites. We therefore chose to base a damage assessment study on the interpretation of images acquired by the European radar satellite ERS-2. Radar has the capacity to penetrate clouds and haze, thus enabling observation of the earth’s surface even during difficult meteorological conditions. Through application of change detection methods on artificial images composed of radar images acquired before, during and after the fires we were able to discriminate different levels of fire damage on an area of 5.2 Mio ha. We also discriminated simple land-use classes from radar images and were thus able to give a precise estimate of 2.6 Mio ha of forested land affected by the fires.

Using Landsat satellite images to evaluate impact of logging

A subset of the area was studied in detail with the help of a the only cloud-free images available for the time of the fires. With this images, it was possible to discriminate closed forest from forests degraded by logging. An overlay with the data retrieved from the radar-based fire map showed that more forests opened up by logging activities burned and that these forests were hit harder by the fires than closed forests.

Intense ground checks were done during several journeys inland and through aerial surveys with low-flying aeroplanes. The tracks of these surveys were recorded using the global positioning system (GPS) and integrated into a Geographic Information System.

In one 30.000 ha-concession affected by fire a detailed ground inventory recorded damage levels for the whole concession. Again, it could be shown that the recently logged areas were more severely affected than closed forest areas.

The fires left millions of trees dead, but unburned. These provide fuel for future fires that could even be more devastating. Continued heavy impact logging and large scale conversion of forested areas to plantations may additionally increase the risk of future fires. A revision of land use policies and increased fire prevention activities are therefore called for.

In 1997–98, fires associated with an exceptional drought caused by the El Niño/Southern Oscillation (ENSO) devastated large areas of tropical rain forests worldwide. Evidence suggests that in tropical rainforest environments selective logging may lead to an increased susceptibility of forests to fire. We investigated whether this was true in the Indonesian fires, the largest fire disaster ever observed. We performed a multiscale analysis using coarse- and high-resolution optical and radar satellite imagery assisted by ground and aerial surveys to assess the extent of the fire-damaged area and the effect on vegetation in East Kalimantan on the island of Borneo. A total of 5.2 0.3 million hectares including 2.6 million hectares of forest was burned with varying degrees of damage. Forest fires primarily affected recently logged forests; primary forests or those logged long ago were less affected. These results support the hypothesis of positive feedback between logging and fire occurrence. The fires severely damaged the remaining forests and significantly increased the risk of recurrent fire disasters by leaving huge amounts of dead flammable wood.