BURNING OF VEGETATION. a coninon practice in the tropics, releases soot and several gases, particularly carbon dioxide (Cor), carbon monoxide (CO), hydro- carbons, nitric oxide (NO) and nitrogen dioxide (NO2). This and other human activities- such as the burning of fossil fuels- account to a great extent for dramatic increases over the past two centuries, In the atmospheric concentrations of many trace gases. These Increases are giving rise to such environmental perturbation as acid deposition, urban smog and depletion of the stratospheric ozone layer that absorbs damaging ultraviolet radiation. Warm lag of the planet is also expected, from the buildup of green house gases that trap infrared radiation.