Fire's role in global warming studied

September 27, 1999
Web posted at: 4:49 p.m. EDT (2049 GMT)

This low intensity fire will burn only the grassy fuels and the fine woody litter producing little inert charcoal. A hot fire is more likely to kill trees and generate a large amount of charcoal, adding more to the greenhouse effect.

Scientists from 12 countries are monitoring the contribution fires make to greenhouse gas emissions as well as the impact fires have when they destroy trees that soak up carbon dioxide.

The project, named The World Fire Web, is using satellite images to map and monitor the extent of fires across two-thirds of the Earth. Each participating country is responsible for monitoring a particular area and the results will be shared over the Internet to produce daily global fire maps.

"Fires make a significant contribution to the greenhouse effect - perhaps accounting for 40 percent of annual global greenhouse gas emissions," said Dr. Dean Graetz of the Australian Commonwealth Scientific and Industrial Research Organization (CSIRO) Earth Observation Center. Unlike fossil fuel emissions, at this stage comparatively little is known about where fires occur and how much carbon they release, according to Graetz.

Burning vegetation and trees contribute to the release of carbon dioxide into the atmosphere directly through emissions of gases and aerosols from the fires and indirectly through the impact fire activity has on the forest ecosystem and its ability to store carbon.

The European Commission Global Vegetation Monitoring Unit(GVM) is coordinating the effort. By the end of the year, the World Fire Web network should have an almost global coverage of fires.

The objectives of GVM are to document the evolution of global fire activity, develop detection procedures to identify and characterize fire events and to also create a global fire information system. As of April 1999, the countries involved in the World Fire Web are Vietnam, Brazil, Australia, Italy, Dakar (Senegal), Thailand, Venezuela, Argentina, Canada, Russian Federation, Central African Republic and Botswana.

This satellite image of Australia's Top End shows land, water and plumes of smoke from fires. Daily images such as this can calculate and convert the total area and the weight of grassy fuel into the emissions of carbon dioxide.

The World Fire Web's global fire maps show where most of the world's fires are occurring. "Africa is the burning continent," said Graetz. "Followed by South America, Southeast Asia and Australia."

CSIRO plays two roles in the project. Its Earth Observation Center is in charge of tracking fires throughout Australia, New Guinea and parts of Indonesia. Secondly, they are working to help correlate what the satellite images portray with what is actually happening on the ground. This information is crucial for all of the project's participants.

"The satellite images used in the project are continuously processed, most semi-automatically by computers, to detect 'hot spots', or probable locations of current fires," said Graetz. "But the most difficult task, not just for us, but for all of the project, is to train the computer to automatically recognize and measure burnt areas, while ignoring cloud shadows and other distractions."

To help train computers to measure the burned areas, Graetz and his colleagues from CSIRO and the GVM have spent the last few months studying fires in Australia's Northern Territory Kakadu National Park.

The tropical belt of Australia where Kakadu National Park is located experiences widespread human-caused fires every year during the dry season which typically begins in April.

"Over this year's dry season in Kakadu, we've been making measurements from the ground and from aircraft of fires lit by the park rangers. Back in the laboratory, these measurements, along with satellite images, are helping us develop more accurate methods of detecting burnt areas," said Graetz.

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