Can GMO crops help fight global warming?

Kenrick Vezina | June 12, 2014

Proponents of genetic engineering in agriculture often argue that the technique is a necessary tool for our food supply to cope with a warming planet and an ever-growing population. Only the power offered by genetic manipulation, the logic goes, will give agriculture enough adaptability to endure major changes to the climate without a correspondingly major drop in productivity.

But what if engineered plants could do more than help feed us in a warming world? What if they actively helped fight the warming process? As anyone who has flown across the U.S. can tell you, there is a lot of farmland across the middle of North America.

Indeed, across the world some 15 percent of the non-water, non-ice surface is devoted to agriculture. Surfaces matter when it comes to global warming. Specifically, reflective surfaces like ice. John Upton at the Pacific Standard explains:

The planet is losing its albedo […] Albedo refers to reflectiveness, and high albedos help keep the globe cool by reflecting light and heat back out to space. For every drip of sheer white ice that melts away from the Arctic, the planet’s albedo droops a little more, hurrying global warming along.

It’s a nasty feedback loop, and only promises to get nastier. Melting ice caps can release methane, a potent greenhouse gas that will only move warming along more quickly. Plants may seem an unlikely candidate to help us reflect light. After all, Upton writes, “Plants generally evolved to soak up as much of the sun’s light as possible.” They turn sunlight into food for themselves, it’s their singular trick. But a team of American scientists led by Praveen Kumar of the University of Illinois’s civil and environmental engineering department, noted that “crop progenitors evolved over the last 25 million years in an atmosphere with less than half the [CO₂] projected for 2050.” Photosynthesis uses water and carbon dioxide as well as sunlight; tweaking the available carbon dioxide might alter the amount of water or light needed. In a warmer world where evaporation is a bigger threat than lack of carbon dioxide, plants might benefit from reflecting more light (i.e. heat) than before. Kumar and his team used computer models of soybean crop canopies to test whether the plants could be bred to reflect more sunlight — and whether this change could help conserve water or even increase productivity. Their predictions were promising. Upton summarizes:

The scientists discovered that crop productivity could be boosted by seven percent through canopy changes without changing water use or albedo. Alternatively, water use could be reduced by 13 percent without affecting harvest sizes. And by focusing just on albedo, the scientists found that one-third more of the sun’s rays could be mirrored away from soy fields than is currently the case—just by re-engineering the plants’ leafs, through strategies like manipulating known gene mutations.

Kumar and his team aren’t the first to float the idea of manipulating crops’ albedo as a strategy for mitigating climate change. The idea has been around since at least 2008, when a team at the University of Bristol in the UK argued that replacing existing crops with higher-albedo strains could cause average summer temperatures in temperate zones to fall by as much as 1° C. This idea is arguably a less dramatic version of the geoengineering advocated by some. Matthew Worsdale, writing at Ecologist, is one such advocate. Some of his propositions to deal with the crisis of melting ice caps and the potential for “runaway methane”:

The fastest and simplest way to do this is to mimic a natural phenomenon we know cools the climate on a global scale. A volcanic eruption emits vast quantities of sulphur dioxide, SO₂, into the atmosphere and in the case of the eruption of Pinatubo in 1991, was sufficient to cool the climate by 0.5C for two years. The strategy in the Arctic would be to add small quantities of SO₂ to the upper atmosphere in the summer months. This would be a low cost option for a few years to buy time to switch to a more sustainable longer term option. Another technique is Marine Cloud Brightening (MCB) – you can create a whitening of existing cloud formations, by spraying up fine seawater droplets to increase the droplet density, thereby making clouds more reflective.

Such dramatic interventions understandably make many people nervous. Small-scale increases to albedo even in areas less vital than the ice caps can help, though. Reflective roofs can help cool cities and buildings and conserve energy and water.

Engineering the crops we’re already growing so that they help fight global warming and help conserve water seems to occupy a comfortable middle ground in terms of scale and potential environmental ramifications. Regardless, before any such agricultural “bio-geo-engineering” can get off the ground, high-albedo varieties would need to be developed for the world’s major crops and farmers would need to adopt them on a large scale.

In cases where reduced water consumption or improved yield are part of the high-albedo package, farmers will have a common sense reason to use them. But, Upton and Kumar note, if we want to get farmers around the world to adopt higher-albedo crops with no direct “performance boost” it’s likely to take some economic incentives.

For me the most striking argument made by Kumar and his colleagues is actually the bit (mostly ignored by Upton) about how the crops we’re growing now were developed in a pre-global-warming world with less carbon dioxide and cooler temperatures. It’s this fact, and the implication — supported by their models — that we might be able to both improve our crops and fight global warming at the same time that makes this idea one that I hope finds some real-world traction soon.

Kenrick Vezina is Gene-ius Editor for the Genetic Literacy Project and a freelance science writer, educator, and naturalist based in the Greater Boston area. Sources: