Relocating global croplands would slash CO2 emissions, eliminate irrigation and save species from extinction, say Cambridge researchers
The world map of agriculture has been reimagined by Cambridge scientists to show where the major food crops should be grown to maximise yield and minimise environmental impact.
The redesign would cut the carbon impact of global croplands by 71 per cent by allowing land to revert to its natural forested state.
If enacted, it would capture 20 years’ worth of our current net CO2 emissions, they say, and reduce agricultural use of freshwater to virtually zero.
While devising this agricultural utopia might seem like a mere modelling exercise, the researchers believe it should influence policy as it highlights very unproductive croplands that have the potential to be hotspots for biodiversity and carbon storage.
“It’s currently not realistic to implement this whole redesign. But even if we only relocated a fraction of the world’s cropland, focusing on the places that are least efficient for growing crops, the environmental benefits would be tremendous,” said first author Dr Robert Beyer, formerly a researcher in the University of Cambridge’s Department of Zoology.
The optimal reworked map assumes high input, mechanised farming and does not rely on dietary changes, as the researchers point out that switches to more plant-based diets are not happening quickly.
It includes large new farming areas for many major crops around the cornbelt in the US mid-west and below the Sahara desert, while huge areas of farmland in Europe and India would be restored to natural habitat. Trees would capture carbon as they grow, but also enable the soil to capture more carbon than when it is used to grow crops. It proposes a 98 per cent reduction in the tropical forest area used for growing crops today.
The researchers examined where 25 major crops - such as wheat, barley and soybean - that account for more than three-quarters of croplands worldwide are currently grown, then developed a mathematical model to look at how to distribute it globally without altering overall production levels.
“In many places, cropland has replaced natural habitat that contained a lot of carbon and biodiversity – and crops don’t even grow very well there. If we let these places regenerate, and moved production to better suited areas, we would see environmental benefits very quickly,” suggested Dr Beyer, who is now based at the Potsdam Institute for Climate Impact Research (PIK) in Germany.
Under the optimal scenario, the negative impact of crop production on global biodiversity would be reduced by 87 per cent, dramatically reducing the extinction risk for many species.
Within a few decades, croplands would revert to natural states.
The researchers did not consider the emissions associated with transport of food, but argued these have been shown to be small compared to other food chain emissions
Conscious of the economic and social implications of such changes, they did devise a pared-back approach that would redistribute croplands within national borders, rather than globally.
This would still cut its global carbon impact by 59 per cent and reduce the existing biodiversity impact by 77 per cent.
And a less drastic option still of relocating only the worst offending 25 per cent of croplands nationally would still lead to half of the benefits of the optimal model, they found.
The findings are expected to be relevant to the end of the century.
“Optimal cropping locations are no moving target. Areas where environmental footprints would be low, and crop yields high, for the current climate will largely remain optimal in the future,” said Professor Andrea Manica at the University of Cambridge, senior author of the paper published in the journal Nature Communications Earth & Environment.
The researchers point to set-aside schemes that give farmers financial incentives to retire part of their land for environmental benefit as a way of bringing about such change, in tandem with financial incentives to encourage people to farm in better suited locations
Different global distribution maps were created based on farming methods, ranging from advanced, fully mechanised production with high-yielding crop varieties and optimum fertiliser and pesticide application, through to traditional subsistence-based organic farming.
But they found even redistribution of less intensive farming practices could substantially reduce their carbon and biodiversity impacts.
Many croplands are in areas where they have a huge environmental footprint, and have replaced carbon-rich, highly biodiverse ecosystems, while being a huge drain on local water resources.
Agriculture is responsible for about 70 per cent of global freshwater use, causing water shortages in many drier parts of the world, but relocation could virtually eliminate the need for irrigation.
The study says: “The vast majority of production, corresponding to 99.4 per cent of global croplands, could be nationally relocated so that rainfall provides sufficient water supply.”
Historical factors - typically the proximity to human settlements - were behind the siting of our croplands, but the researchers argue it is time to rethink.
“The conversion of nearly half of the world’s ice-free land area to agricultural areas has contributed to three of humanity’s most pressing environmental challenges: (i) agriculture is a major source of anthropogenic greenhouse gas emissions, largely from the release of carbon stored in natural vegetation and soils; (ii) agriculture is the main driver of habitat loss, the greatest threat to terrestrial biodiversity; and (iii) agriculture is responsible for about 70 per cent of global freshwater consumption, leading to shortages of potable water in many arid parts of the world,” they write.
The work was funded by the European Research Council.
Read more
