Peak Farmland Is an Ecological Imperative

Along with rapidly reducing greenhouse gas emissions, reaching 'peak farmland' is probably the world's most important environmental objective. However, it is far less well-known, and is not advocated as a target to my knowledge by any major environmental organization. The reason for this is doubtless because most of the agricultural policies long advocated by the green movement would serve to take us further away from peak farmland rather than towards it.

It should be fairly obvious why peaking farmland expansion is important. Biodiversity loss ranks alongside climate change as an existential threat to the Earth's ecological systems, and conversion of land to agriculture and the resultant loss of habitat is in turn the greatest single threat to biodiversity. There is no prospect of sparing large areas of wilderness from the curse of the plough without halting the conversion of nature to human-oriented agriculture.

It's either peak farmland or zero rainforest: our choice.

And it is not just biodiversity on the line. When a team of scientists led by Johan Rockstrom in 2009 proposed a set of 'planetary boundaries' for avoiding damaging interference in the operations of the Earth system, they noted that majority of these proposed boundaries were significantly affected by farming: biodiversity, climate, nitrogen, water use, and so on. Making farming sustainable is therefore critical for planetary health in a wider sense than just climate or wildlife.

Unfortunately, ideology—most clearly in the religion of organic and the cult of the 'natural'—serves mainly to obscure what needs to be done to achieve peak farmland. Organic farming has some direct soil and ecological benefits, but these are far outweighed by the fact that yields are significantly lower than in conventional systems: more farmland must therefore be brought into cultivation to produce the same overall harvest of food. There is a robust scientific consensus about this finding, which is supported by numerous meta-reviews.

One recent innovation might have served to make organic agriculture viable—the harnessing of the power of biology, via crop genetics, as a disruptive technology to replace external inputs from agrochemicals. However, organic believers at an early stage decided that genetic engineering was an 'unnatural' technological innovation and therefore should be ruled out a priori. Ever since, various organic enthusiasts have tried to stop any cultivation of genetically modified crops elsewhere on the supposed basis that these crops might 'contaminate' their supposedly pure and natural (but lower-yielding) harvest.

Genetic engineering can be thought of as biological precision agriculture. A single DNA sequence can be added to the genome of a crop to confer resistance to insect pests or fungal infections. This means, all other things remaining equal, that the insecticides or fungicides that would otherwise have been sprayed to protect the crop are no longer necessary. Drought tolerance as a trait can reduce the need for irrigation, while nitrogen efficiency can reduce fertilizer inputs. It was an epochal mistake for the organic movement to reject this technology. In a rational world, GMOs and organic would have made perfect bedfellows.

In a 2010 paper in the journal PNAS, Jennifer Burney and colleagues calculated the greenhouse gas savings achieved by modern farming by comparing emissions with a counterfactual low-yield scenario that held technology constant at 1961 levels. They concluded that "the net effect of higher yields has avoided emissions of up to 161 gigatons of carbon since 1961". This is an enormous saving, equivalent to a third of the entire stock of human carbon emissions put into the atmosphere since the industrial revolution. And the land savings were equally stunning, equivalent to 1.7 billion hectares of cropland, an area twice the size of the contiguous United States.

Genetic modification in its 'GMO' sense has only contributed a small latter portion to this improving picture—most of the gains were achieved through the earlier Green Revolution and the steady yield additions achieved thereafter. The challenge now is to build on this to both shrink the yield gaps that still bedevil developing countries, keeping them trapped in rural poverty, and to make conventional farming more sustainable in terms of soil conservation, reducing inputs and direct emissions and so on.

This means dropping the romantic fantasies so beloved of urban foodies. Instead, in the words of Mark Watney in the movie The Martian, we need to "science the shit out of this".