资源环境科技发展态势分析平台

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BEFORE humans came along with their polished axes and (much later) sawmills, there were as many as 6 trillion trees on this planet. Today there are roughly half that number, with their loss continuing apace in many developing countries. In the Amazon, deforestation has recently surged, after a decade of stability, to make room for cattle ranching and soybeans.

Even in the developed world, where efforts are being made to replant forests, urban trees are often viewed as a nuisance. Dead branches must be cut back and pavements broken by sprawling roots repaired. Trees block valuable views, shade flower beds and drop detritus on cars. Surely there is no harm in chopping down this one or that?

It probably bears repeating that our survival depends on trees. Along with other land plants, trees supply around half of the oxygen entering our atmosphere (ocean organisms like phytoplankton account for the rest). They also suck up carbon dioxide from the atmosphere. There are plenty of less obvious benefits too, such as the way tree canopies save us energy by shading buildings in summer and diverting away cold winds in winter.

In the world of Dr Seuss there is an angry orange creature called the Lorax who speaks up on behalf of trees. In reality, however unpalatable it may sound, we need an argument that goes beyond fine words.

Enter a branch of economics just for trees: “treeconomics”. Cities all over the world are having their trees valued, and the balance sheet of their benefits makes impressive reading (see “Treeconomics: How to put a fair price tag on urban forests”). These valuations can teach us which species to plant to provide the largest possible benefits. But more importantly, they may help us treat every tree with the respect it deserves.

This article appeared in print under the headline “The giving trees”