There’s a big outcry about the destruction of various forests - the Amazon being the biggest, but also forests in Malaysia and Indonesia.
One of complaints is that this destoys the CO[sub]2[/sub] fixing in the area. But is this actually true? Does the replacement farmland fix a lesser or greater amount of CO[sub]2[/sub]?
I’m fully aware of other benefits of forests - habitat, preventing erosion, etc, but I’d like to ignore them for this thread.
The question isn’t so much carbon fixation, it’s carbon storage. Obviously when you burn or otherwise destroy forests, you are converting the carbon that was locked up in their wood into carbon dioxide, contributing to the amount in the atmosphere. There is not nearly the same amount of biomass present in grassland.
If you converted all the wood into houses or furniture, you would still be storing much of the carbon. However, much of the forest is simply being burned to make way for agriculture, or sometimes for short-term uses such as paper pulp, which doesn’t provide long-term storage. And even if you are using the trees for timber, much of the biomass of the original forest will end up being converted to carbon dioxide as waste wood, etc.
And to elaborate a little more, under normal conditions most tropical forests are not thought to be either a source or a sink for CO2. That is, the amount of carbon they fix is balanced by respiration and decomposition, so that there is no net gain. (Some boreal forests and other ecosystems accumulate carbon in the soil, because the rate of fixation exceeds decomposition plus respiration. But decomposition is so fast in tropical forests little organic material can accumulate in the soil.)
A major unanswered question is whether this situation may change in the face of global climate change. Some scientists have speculated that warming tempertures and increased CO2 will increase growth rates and carbon fixation in tropical forests so that they will become net carbon sinks and provide a negative feedback for increased atmospheric carbon. Others think that the rate of carbon fixation will plateau at high tempertures before respiration and decomposition rates do, making tropical forests a net carbon source and accelerating the problem.