The pros and cons of going organic
Lower yields would mean more greenhouse gases, research suggests. Richard A Lovett reports.
Although organic agriculture has many environmental benefits – including healthier soils, reduced pollution and enhanced biodiversity – a global switch to it would not help offset global warming, agricultural researchers say.
Instead, it would have the opposite effect: releasing more, not less, planet-warming greenhouse gases into the air.
The problem, says Laurence Smith, an agroecologist at Royal Agricultural University, Reading, UK, is that organic farming produces lower yields than conventional farming. That means that under present methods, a large-scale conversion to it could only be achieved by increasing the total amount of cultivated land.
In a study published in the journal Nature Communications, Smith’s team calculated the effect of a 100% conversion to organic farming in England and Wales.
The good news was that because it is less energy-intensive, organic farming would reduce the amount of greenhouse gases emitted per tonne of crops by about 20%, largely by eliminating the use of commercial nitrogen fertilisers, which are very energy-intensive to manufacture.
But this same switch means it must rely on lower-key methods to supply nitrogen, such as crop rotation or manure. “There’d be about a 40% drop in production,” Smith says.
That would have to be made up for with imports.
And that is the rub, Smith says, because it would require large increases in land devoted to crops in other parts of the world. These increases would, among other things, require ploughing up grasslands that now sequester large amounts of carbon in their plants and soils.
Worse, it would also require growing crops on lands that could be used to suck carbon dioxide out of the air via reforestation.
The result, Smith says, is that the amount of greenhouse gases going into the air from farming would increase by 20-70%.
In other words, says co-author Guy Kirk, a soil scientist at Cranfield University, UK, environmental efforts in one part of the world can backfire if they produce opposing effects elsewhere. “That is the message from our paper, that you’ve got to look at this globally.”
Ann Bartuska, a senior advisor with Resources for the Future in the US, finds the new study interesting. “It raises a very valid point about the tradeoffs,” she says.
But she thinks it’s also a limited “snapshot” of organic agriculture production today, specifically in the UK, constrained by the fact agricultural practices are constantly changing. “We don’t know what innovations might occur down the road,” she says.
For example, she adds, US farmers are increasingly engaging in double cropping – a process in which two crops are grown per year.
The first crop, she says, is the traditional one, “whatever that might be – corn, soybeans, strawberries. The second tends to be something like alfalfa, or some other crop that adds nutrients and carbon into the soil.”
Another innovation, she says, is a movement toward urban agriculture, especially for produce like fruits and vegetables. “That’s on the cusp of being incredibly important,” she says.
Kirk adds that there are also efficiencies to be found by learning how to reduce waste and to increase “yield gaps” – the difference between production levels that can potentially be achieved and those that actually are achieved.
“Closing that gap will contribute a lot to conserving the amount of land that’s required,” he says.