FIRES

Forest fires in the Amazon and other rainforests are frequent today because of the intentional ignition and accidental spread of fire from nearby pasturelands and agricultural fields, and the increased susceptibility to burning of degraded and logged over forests. Every year, during the burning season, thousands of fires are set by land speculators, ranchers, plantation owners, and peasants to clear bush and forest. The number of fires set each month during this period is mind-boggling. In Brazil alone, satellite pictures reveal that in July 1994, 8,503 fires were apparent and in August 1994 61,000 fires were burning. In July 1995, 39,900 fires were detected (a 369% increase) while through the first 15 days of August 1995, 72,200 fires were visible (a projected 137% increase).

Usually the first time a fire penetrates virgin forest is does little more than consume the dry leaf litter and kill some seedlings as it slowly moves along the forest floor, flames only a few inches in height. However, in passing, the fire sets the path for recurrent fires and subsequent forest loss. Once burned forests are twice as likely to be deforested as unburned forests largely because the initial fires - however small - thins out the canopy, allowing more dessicating sunlight to reach the forest floor. Previously burned forests, in addition to having more combustible material, are also often adjacent to fire-maintained pastures and therefore are frequently exposed to sources of ignition. Subsequent fires burn with increased velocity and intensity and cause higher tree mortality. Fires intervals of less than 20 years may eliminate all trees in the forest stand.

Under "normal" rainfall and humidity conditions most of these fires are extinguished by the arrival of the rainy season or monsoon. Usually virgin forests serve as a sort of humid barrier which prevents the spread of agricultural fires (Woods Hole Research Center 1998). However, under dry conditions - such as those of an el Niño year - fires can spread from pastures and fields into primary forest. 90% of burning in the Brazilian Amazon occurs in el Niño years.

The unusually strong El Niño of 1997-98 contributed to massive forest fires. In the Amazon, humidity in the Basin was 45-55% lower than usual and the Woods Hole Research Center estimated that 400,000 square kilometers of forest could go up in smoke during the burning season.

In early 1998, some of these fears materialized as 13,200 square miles (34,000 square km) of Roraima state in Northern Brazil burned. The fires, started by subsistence farmers, spread rapidly across the dry savanna and advanced into rainforest usually too humid to burn. As many as 3800 square miles (10,000 sq km) of intact rainforest were damaged or destroyed by these fires. The government firefighting efforts had virtually no effect and it was only freak heavy showers that extinguished the flames.

Besides destroying the rainforest ecosystem and killing wildlife, these fires create other environmental problems. The "burnings" release thousands of tons of carbon into the atmosphere and the smoke produced causes local airport closings and hospitalizations for smoke inhalation. These fires are significant sources of greenhouse gases. For example, in a four month period (July-October) in 1987, about 19,300 square miles (50,000 sq. km) of Brazilian Amazon were burned in the states of Parˆ, Rondonia, Matto Grosso, and Acre. The burning produced carbon dioxide containing more than 500 million tons of carbon, 44 million tons of carbon monoxide, and millions of tons of other particles and nitrogen oxides.

Rains Impacted by Smoke?

The tropical forest fires that have made headlines as of late will only worsen as more forest is degraded and the area of previously burned area expands. A recent study by IMAZON (the Institute for Man and Nature in the Amazon) found that for every acre burned or cleared that shows up on satellite, at least one acre burns undetected under the forest canopy. These leaf litter fires can burn for months with warm temperatures and little rain and subsequent fires in these previously burned are more intense and destructive.

WWF declared 1997 "The year the world caught fire" not only for the widespread fires in the Brazilian Amazon, but also for the devastating fires in Indonesia and Africa. Fires set by peasants for clearing scrub and forest scorched large areas in Africa where logging roads opened up previously inaccessible regions.