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Redesigning Crops for the 21st Century

The world needs to double its food supply, and scientists have proposed a major genetic engineering program to make it happen.
Rice "terraces" in China. (Photo: jackfrench/Flickr)

Rice "terraces" in China. (Photo: jackfrench/Flickr)

Though we don't always find what we want at the grocery store, in the United States, we don’t worry that the store will run out of food. The world, however, can run out—and there is a good chance that it will, unless we make major upgrades to crop production. By 2050, the global demand for food crops will likely double, as the world's population grows by more than 30 percent, and as the citizens of developing nations emerge from poverty and can afford to eat more and better foods. Unless we increase the world's capacity to grow food, the demand for food will outstrip supply in the next few decades.

This is a tall order, because can't meet our needs by simply clearing more land for agriculture—important ecosystems would be damaged and the emission of greenhouse gases would be accelerated. Compounding the problem, demand for non-food crops that make up raw materials for biofuels is growing; these crops are now competing with food crops for available land. If we're going to meet the growing global demand for crops in a sustainable way, we will need to increase yields from the cultivated land that we already have.

By 2050, the global demand for food crops will likely double, as the world's population grows by more than 30 percent, and as the citizens of developing nations emerge from poverty and can afford to eat more and better foods.

To meet this challenge, an international group of academic, government, and industry scientists has come up with an unusual solution: re-designing photosynthesis, the fundamental biological process by which plants use sunlight to convert water and carbon dioxide in the atmosphere into something that we can eat. The group of scientists—led by Donald Ort, a plant biologist at the University of Illinois and a research leader at the United States Department of Agriculture—has just published a proposal that lays out several ambitious ideas on how to improve photosynthesis in crop plants. Despite being one of nature's most fundamental and widespread biological processes, photosynthesis is not especially efficient in crop plants as they grow in the unnatural setting of a farm field. The inefficiency of photosynthesis presents an untapped opportunity to improve crop yields, Ort and his colleagues argue, because "photosynthesis is the only determinant [of yields] that is not close to its biological limits." Using biotechnology, they claim, scientists can re-design the process to produce crop plants with higher yields, and move closer to solving our "looming agricultural crisis."

The notion of re-designing the extremely complex process at the core of a plant's biology might sound like fantasy—biologists struggle to re-design even simple biological systems, and all existing genetically modified crops were created through alterations that are minor compared to those it would take to re-design photosynthesis. Yet, the researchers argue, the rapid pace of innovation in biotechnology over the past several decades has often made bold ideas that seem overly ambitious become feasible much sooner than expected. "Creative and radically new ideas for redesigning photosynthesis are therefore worth pursuing because even strategies that presently seem fanciful may inspire new thinking in unimagined directions," the team writes. And, in fact, some ideas for re-designing photosynthesis are already being developed in the lab. Ort and one of his co-authors, Stephen Long, direct a project at the University of Illinois called Realizing Increased Photosynthetic Efficiency, which is funded by a $25 million grant from the Bill & Melinda Gates foundation and focused on improving photosynthesis in several important food crops.

In their proposal, the researchers discuss several key aspects of photosynthesis that could be improved. For example, photosynthesis is not particularly efficient in full sunlight, because crop plants absorb more light than they can actually use, and therefore they waste energy dealing with harmful byproducts created by the extra photons. Another inefficiency is caused by the increased levels of carbon dioxide in our atmosphere: Too much carbon dioxide leads to a metabolic bottleneck at a key step in photosynthesis, which slows down the overall process. Interestingly, other organisms have evaded some of the inefficiencies of photosynthesis found in crop plants. The simplest way to re-design photosynthesis in crop plants is to swap in more efficient components from these other photosynthesizing organisms, like algae and certain bacteria. Ort and his colleagues point out that, technologically, swapping these components is not quite feasible yet, but likely will be soon.

Another intriguing idea is developing what the researchers term a "smart canopy," by planting different versions of the same crop together. Taller plants would photosynthesize better in full sunlight, while shorter plants, shaded by the taller ones, would do best in low light. As the researchers write, "An optimized canopy would have lighter green upright leaves at the top of the canopy and dark green horizontal leaves at the base." This is the opposite of how most crop plants grow. The dramatic crop re-design necessary for a smart canopy is also not yet feasible, since it would require extensive genetic modifications that are prohibitively difficult with current technology.

In fact, few of the ideas proposed by Ort and his colleagues are feasible with current technology, but that’s the point: The researchers are urging us to think about the long game, and to begin developing the technology we’ll need to upgrade crops in the future. The world's population will grow from seven billion now to up to 12 billion by the end of the century, and climate change will have an increasingly negative effect on our crops. “Overcoming these challenges,” the researchers argue, “will require major investments in long-term research programs, which are presently not being made, at least not in the public sector.” It’s not clear how many of these investments would yield results on the time scale we need, but some of them might if we begin making them now.

Genetically engineering crops to increase their yield isn't the only proposed approach to expanding the world's agricultural capacity, but, whether we like it or not, genetic engineering will certainly have to be part of the conversation. It's true that we can get more out of the crops we already have by closing what's called the yield gap, the difference between how much a crop could yield per acre with enough water and nutrients, and how much we're actually harvesting. (One recently published study estimated that by closing yield gaps, crop output could increase by as much as 80 percent in some cases.) However, this is not easy, and in many areas around the world, major staple crop yields are stagnating or even declining, rather than improving. 

To solve the world's looming food shortage in a way that's environmentally sustainable, we can't just rely on closing the yield gaps of existing crops—we also need crops that yield more. A public commitment to make such crops would require not only more investment in the necessary research, but also a critical mechanism that we currently lack: a modernized regulatory process for evaluating GMO crops that is both scientifically sound and publicly transparent. As the proposals by Ort and his colleagues demonstrate, genetic engineering is a potentially powerful tool for addressing the world’s food problem; as a society, we need to decide quickly whether to use it.

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