Scientific Alliance Newsletter - October 24th, 2008

Much has been made by others of the importance of environmental goals relative to financial ones, and economic analyses have been produced to justify this stance. But how much credence can we give to these? Assessing the worth of ecosystems is in itself a worthwhile goal; how else is expenditure on environmental projects to be prioritised against alternative uses of the money? The problem is always to establish a fair value.

Assumptions are everything. In the case of forests, a large part of this notional value relates to carbon sequestration: the capture of atmospheric carbon dioxide in the wood of the trees and the organic matter in the soil. Estimates of the carbon content of established forests, together with a projection for the value of carbon set by emissions trading systems gives a value per hectare. Multiply this by the number of hectares lost each year, and we have a value for this service provided by forests.

This economic analysis tells us that it is cost effective to pay up to the calculated value of the forest to prevent its destruction. But how valid is this? The implicit assumption in such calculations is that the cleared land then has no value, while the forest itself has a steady, ongoing value. However, taking the example of carbon sequestration alone, it is clear that such capture is not permanent, but part of a continuing cycle. As forests mature, they reach a state of equilibrium, with old trees dying and releasing their carbon into the atmosphere as they rot on the forest floor, and new trees taking their place, growing rapidly and themselves tying up atmospheric carbon.

However, if areas of forest are cleared, the timber continues to act a reservoir of carbon if it is used for construction: all the carbon is released only if the wood is burned. Most likely the cleared area is itself then used to grow crops, which will also sequester carbon. If the poor tropical soil is soon exhausted and the forest allowed to regenerate, rapidly growing trees are a greater annual carbon sink than mature trees.

But we also need to look at the broader picture: as tropical forests are to some extent shrinking, the area of temperate forests is increasing. Looking at the broader picture may give a different perspective. Although we are (rightly) concerned about the recent and current loss of tropical forest, in earlier times the area of temperate woodland declined dramatically as mankind increasingly turned to farming and the population grew. The point is that it is relatively easy to place a value on the loss of something such as woodland, but more difficult to value what might replace it. Certainly there is no indication that the loss of European forests, regrettable though that may be on one level, has had any detrimental effect on the lives of humans, and many plant and animal species have thrived, while others have declined. Read more here.