Fire is integral to life in much of Africa. As predictable as the rainy and dry seasons, fire sweeps across the continent in a wave that moves north to south following the seasons. In early June, Africa’s fires were concentrated in central Africa. Lightning-ignited fire is part of the natural ecology, but for thousands of years it has also been a tool used by mankind to clear land for new growth, return nutrients to the soil, make charcoal for cooking and fuel, clear debris, and hunt. It is primarily human activity that leads to intense burning in a region during the fire season.
While the fires themselves may not be harmful, they cloud the skies with smoke, which contains both soot and ozone-forming gases like nitrogen oxides, carbon monoxide, and hydrocarbons. This image shows high concentrations of carbon monoxide over the Democratic Republic of the Congo as observed by the Measurements Of Pollution In The Troposphere (MOPITT) instrument aboard NASA’s Terra satellite between June 1 and June 8, 2008. The dark orange and red tones of the image indicate that carbon monoxide levels were generally high throughout the region, but the highest concentrations of the gas were over central Africa, where the fire season was in full swing. Areas that were cloudy throughout the eight-day period are gray.
Carbon monoxide is produced by incomplete combustion during biomass burning, and this makes it a good tracer of pollution in smoke. When exposed to sunlight and heat, carbon monoxide, nitrogen oxides, and hydrocarbons combine to form ground-level ozone, a gas that can cause respiratory disease, destroy lung tissue, and damage plants.