Farming for the future

27th October 2017

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Rebecca Nesbit explains why GM foods and agricultural methods should each be judged on their own merits if we are to prepare for an ever-increasing demand for food production while protecting the environment

It’s hard to see the facts about genetically modified foods. Activists cry ‘frankenfood’ and ‘poison’, while proponents speak of environmental success, so it is perhaps no surprise that they are surrounded in controversy. As a society, however, we need to make decisions about if, and how, we use this technology.

Stakes are high; we can’t feed the world’s growing population without increasing the amount of food we produce. Without agricultural improvements, more people will go hungry. Meanwhile, we are facing a global extinction crisis, and agriculture is a major culprit.

The current debate serves neither food production nor the environment, so how do we end this bitter stalemate? To make any progress we need to start by distinguishing the product from the techniques.

How do we modify a plant’s DNA?

The techniques that we class as genetic modification are by no means our only way of altering a plant’s DNA. Decades before genetic engineering tools were developed, breeders began using chemicals and radiation to introduce random mutations. Although many of these mutations are damaging, some are beneficial. This increases the variation available for breeders, allowing them to develop a huge variety of crops. The crops we grow today look very different to their wild ancestors, and this was made possible through mutagenesis breeding.

Next came genetic modification, which introduces whole genes into plants. These genes can be from other organisms, such as bacteria or algae, or can be synthetic genes created in the lab.

More recently, genome-editing tools have been developed, the most famous of which is CRISPR-Cas9. These techniques can introduce new genes, just as older GM methods do. Alternatively, they can also be used to make more subtle changes to individual DNA base pairs.

The diversity of technologies now used to alter crop DNA highlights the folly of defining a plant by the technology used to create it. Very similar products can be produced in different ways, yet have the same risks and benefits.

What are the benefits and the challenges?

A wide range of characteristics can be introduced into crops to make them healthier, hardier or higher yielding, and these are what determines the crop’s impact.

During the research for my book Is that Fish in your Tomato? it became clear that putting all GM crops into one category masks the issues, both positive and negative. I needed to judge each crop on a case-by-case basis.

The risks and benefits of vitamin-fortified rice are completely different to those of insect-resistant cotton, for example, and they can’t be assessed with generic arguments about the technology that created them. The issues are much better discussed in the context of specific crops.

The GM crops currently grown around the world are almost all resistant to herbicides or insects. Last year, over 99% of the 185m hectares of land planted with biotech crops contained crops resistant to herbicides, insects or both. Herbicide-tolerant crops have brought environmental advantages of ‘no-till’ farming systems.

Farmers have reduced their reliance on mechanical techniques such as ploughs for weed control. This protects the soil and reduces greenhouse gas emissions.

However, it has also given rise to a common criticism of GMOs: the creation of ‘superweeds’, which are hard to control. The crop can survive being sprayed with a specific herbicide, making weed control easier, but some weeds have evolved to survive this spraying.

Both these issues are important for users of herbicide-resistant crops, but they aren’t relevant for other types of GM crop. Also, they are by no means restricted to GM varieties. Herbicide-resistant crops can also be created using conventional breeding techniques, and resistant weeds evolve whenever herbicides are used.

Where do we go from here?

If we’re going to reap the environmental and humanitarian potential of GM crops, we must look beyond this kind of commercial crop to those with characteristics that meet the needs of poorer farmers. One example is virus-resistant papaya, developed by academic scientists and now grown by Hawaiian farmers.

Other crops being developed with humanitarian goals in mind include drought-tolerant corn. If approved, this will be available royalty-free to smallholders in Sub-Saharan Africa.

Among the most exciting crops under development are those created using newer techniques of genome editing. In the laboratory, genome editing has been used to create disease-resistant rice and wheat, and enhance drought tolerance in corn. The lower cost has increased the opportunities to work with crops grown on a smaller scale, and scientists are working to develop disease-resistant citrus trees and wine grapes.

Field studies currently under way include early-yielding tomatoes, with the hope this could be used to create varieties that are suitable for a changing climate.

These examples show the future possibilities of GM crops, and we must judge the positive and negative impacts of each one individually.

If we are looking to build an equitable food system that benefits society while minimising damage to the natural world, we can’t afford to waste resources by making GM a scapegoat. Banning the use of tools that modify a plant’s genome wouldn’t solve problems such as superweeds, and it may prevent us from developing crop varieties that support our true objective of sustainable agriculture.

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