Does offsetting work?

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Huge numbers of offsetting schemes have started up. Planting trees is the predominant offsetting mechanism. Trees are the only proven method we currently have for actively removing carbon dioxide from the air. Does it really work?

There are a number of issues to consider with this offset method:

• Native monocultures and non-native forests are not good for our ecosystem. So unless the carbon company are planting a mix of native woodland species, they could be causing more problems than they are solving.
• On a positive front, native trees provide habitat for native plants and animals. They also assist with combating soil salinity and preventing erosion.
• Unless well managed, there is no guarantee that the trees in the forests will survive long enough to offset your carbon. Trees are susceptible to death through fire, disease and illegal felling.
• The Kyoto Protocol only requires the tree to last for 30 years anyway (approximately 1 tonne of carbon is taken out of the atmosphere in 30 years). If you do offset with trees, it's better if the organisation guarantees the tree's protection for 100 years.
• Planting trees in the most northerly or southerly areas of the planet has a net warming effect because the carbon dioxide absorbed is more than cancelled out by the increased absorption of incoming radiation.
• Planting trees in tropical areas has a net cooling effect because they grow fast and tall and so absorb carbon more quickly than temperate trees. Tropical trees also lose a lot of water through their leaves which creates cooling cloud cover that counteracts the warming effects of the radiation that they absorb.
• There is no clear scientific consensus on tree planting in temperate areas. It is possible that it is warming neutral.

So, planting tress is only beneficial in certain regions.

Ironically, we are paying to offset our carbon by planting trees whilst at the same time we are cutting down large swathes of rainforest: more than 25% of global carbon emissions come from tropical deforestation.

However, there is sometimes a drawback to offsetting via such green technologies – the offsetting money sometimes goes into projects that would have been government funded anyway. So in these cases there is no gain as the project would have gone ahead regardless.

There are no industry standards in the offsetting market so you need to look carefully at the small print to check that your money is being effectively used to soak up carbon. If you are using offsetting schemes, you should look for the Gold Verified Emission Reduction (VER).