US study claims intensive farms 'slow climate change'

Intensive farming has slowed down the rate of climate change in the last 50 years, a US study has claimed.

The Carnegie Institute for Science report, published in the Proceedings of the National Academy of Sciences journal, said ‘the Green Revolution’ of the late 20th century increased crop yields worldwide and helped feed the growing global population.

The Green Revolution is a term used to describe the spread of the new technologies in the latter half of the last century. This included the development of high-yielding varieties of cereal grains, the expansion of irrigation infrastructure, and the distribution of hybridised seeds, synthetic fertilisers, and pesticides to farmers.

Researchers estimate that since 1961, higher yields per acre have avoided the release of nearly 600b tonnes of carbon dioxide into the atmosphere.

Study co-author Steven Davis said: "That’s about 20 years of fossil fuel burning at present rates. Our results dispel the notion that industrial agricultural with its petrochemicals are inherently worse for the climate than a more ‘old-fashioned’ way of doing things."

Scientists also found that although the various inputs to modern farms require more energy and greenhouse gas (GHG) emissions per unit of food output, crop yields have increased by 135%, reducing the amount of crop land needed to produce the same amount of food compared to more less intensive methods.

Without these advances, the conversion of vast natural areas to agriculture would have caused much more GHGs, which is the equivalent of nearly 600b tonnes of CO2 since 1961, the report concluded.

Davis added: "Converting a forest or some scrubland to an agricultural area causes a lot of natural carbon in that ecosystem to be oxidized and lost to the atmosphere. What our study shows is that these indirect impacts from converting land to agriculture outweigh the direct emissions that come from the modern, intensive style of agriculture."

The report authors claimed they have also calculated the benefits of investing in agricultural research as a strategy for reducing GHG emissions. They estimate that since 1961 agricultural research has averted CO2 emissions at a cost of about $4 per tonnes of CO2.

The potential for emissions reduction compares favourably with other strategies, researchers added. They claimed agricultural advances have prevented about 13b tonnes of CO2 emissions each year, much more than the estimated 1.8b tonnes obtainable by improvements in energy supply or the estimated 1.7b from improved transportation systems.

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