Since the soot discovery in 1985, other researchers have found independent evidence of fires, some of which in particular supports the burning of trees. An impact in Central America could start fires in both North and South America. It is also possible, however, that the impact only started local fires, and that more widespread fires on a global scale were ignited only after forests had died in the darkness and dried out. The movement of dust through the atmosphere would cause frictional heating and the build-up of static electricity, increasing the rate of lightning strikes and therefore forest fires. The injection of black soot into the atmosphere along with the dust from the impactor would have made worse any darkening and cooling caused by the dust alone.
Fires also produce mutagens, pyrotoxins and heat.
Also a product of combustion is CO2, which would have contributed to a greenhouse effect. Earth is continually bombarded by debris from space, most of it dust-sized. The larger the object, the less chance there is of it hitting Earth, since larger objects occur less frequently in space. For example, it is estimated that the Earth gets hit by tons of dust-sized particles every year. It has been about 15 million years since the last impact of that size.