Ask A Scientist© Environmental Science Archive

Author:     amj
Text:       Why are the rain forests being burnt?

Response #: 1 of 2
Author:     woodford
Text:       I understand that the rain forests are being burnt in order to 
provide short term farm/grazing land for squatters. By short term I mean that 
the burnt land provides a farming/grazing resource only for a few years and 
then it cannot be used anymore. It takes decades for the forest growth to 
return to the burned area, while all the other places are being burned out to 
provide another year or two of useful land.

Response #: 2 of 2
Author:     Don Libby
Text:       Good question. There are many reasons. Woodford responded that it 
is for n short term farm/grazing land for squatters". It is true that rain 
forests are being burnt for farming and grazing land. This practice has been 
common for thousands of years and is not necessarily harmful. Small groups of 
indigenous people can survive indefinitely by clearing and burning a small 
area, planting a garden, and then moving on after a few years when the soil 
fertility declines to the point where plants do not grow well. These small 
plots cultivated by "swidden" horticulturists recover to original wild 
vegetation within a few years, and are not a threat to the long-term viability 
of the rain forest ecosystem. However, the last few decades have seen a 
different kind of "slash-and-burn" agriculture taking place: commercial cattle 
herders will clear huge tracts of forest in order to allow grasses and shrubs
to grow for animal fodder. The cattle are grazed for a few years and then 
taken to market and sold for a profit. The practice is very profitable because 
forest land is cheap, and sometimes governments of tropical countries just 
give it away. However, tropical soils are very poor and cannot sustain growth 
for more than a few years without the rain forest cover to recycle nutrients 
rapidly. When a large area is cleared, the wild forest around the edges cannot 
reclaim the whole area very quickly so large clearings take longer to recover 
than small plots. If all the wild forest is cleared, the land may never again 
be productive.