Science
Nature & environment

Trees on farms absorb a lot of CO2

Trees on farmland sequester a lot more CO2 worldwide than we have hitherto assumed. This conclusion was drawn by Wageningen researcher Meine van Noordwijk and colleagues in an article in Nature.
Albert Sikkema

Agriculture is responsible for about 24 percent of the greenhouse effect in the world, according to figures from the IPCC climate panel. This is due to the felling of tropical rain forests for farmland. The climate models are based on the assumption that only negligible levels of CO2 sequestration occur on farmland. This assumption turns out to be wrong.

An international research team including Meine van Noordwijk of the Plant Production Systems group collected data about the number of trees on agricultural land. The researchers found that 40 percent of the world’s farmland has more than 10 percent tree cover. This wealth of trees raises the CO2 sequestration taking place on agricultural land from 5 to 20 tons of carbon per hectare. That represents the absorption of 0.75 gigatons of CO2 per year. By way of comparison: the conversion of rain forest into farmland leads to CO2 emissions of 0.85 per year.

Increase

The researchers notice increased interest in agroforestry and climate-smart agriculture around the world. As the extent of the world’s rain forests continued to decrease over recent years, the amount of farmland with more than 10 percent tree cover grew in countries such as China, India, Brazil and Indonesia.

The trees on agricultural land not only sequester carbon but also ensure reduced wind erosion, higher humidity and milder temperatures. These kinds of improvement in the microclimate motivate farmers to plant and maintain trees on their farms, explains Van Noordwijk.

Up to now trees on agricultural land have not featured in government climate adaption programmes. It is time to change this, say these researchers, because agroforestry systems can temper climate change.

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