Crops are engineered in a number of ways. Often, they are made resistant to an herbicide, so a farmer can spray one on their fields and keep their plots free from weeds without killing the crop itself. Or they can be innately poisonous to its predators, like milkweed is, which reduces the amount of pesticides needed to keep a crop safe.
But do these things harm the environment? According to the data: not really. GM crops appear to be just as sustainable and productive as non-GM crops, if not more so.
"Sustainability," in addition to being a buzzword, is a measure of a local environment's ability to remain diverse and productive. Studies show that choosing to farm either non-GM or GM crops doesn't make much difference when it comes to sustainability. And in both aspects, biodiversity and productivity, GM agriculture has been performing better than non-GM crops for the last 20 years.
Any kind of farming inevitably results in biodiversity loss: the immense diversity of forests and woods is cleared for the monotony and monoculture of the crops we need for our food, feed, fibers, and fuel. And this deforestation and agriculture account for 20-30 percent of all greenhouse gases emissions.
But cultivating GM crops has proven better for biodiversity than the conventional alternative, because one way to maintain biodiversity in a local ecosystem is to reduce pesticide use. A GM crop can do this by carrying its own defenses, making pesticides less necessary. For instance, "Bt" corn is engineered to be toxic to predators that would otherwise prey on it. They don't need as much outside assistance in the form of pesticides sprayed over an entire field.
Another upside to GM crops is that the toxin they carry is specific to their predators, making them less harmful than a spray with collateral effects. That means that primary predators like the European corn borer (nicknamed "the billion dollar bug" because of its heavy effects on the corn market) can be precisely targeted, while leaving other harmless, passerby insects unaffected. Such genetic engineering is remarkably efficient – according to a 2014 meta-analysis, GM-based farming has required 37 percent fewer pesticides than conventional agriculture.
The biodiversity of a field can also be monitored through the levels of insects living on it. A recent meta-study based on 839 publications released over 20 years reaches the conclusion that, worldwide, GM corn does not effect the majority of insect families. Basically, no ladybugs or butterflies were harmed - at least, not more than they would’ve been through conventional agriculture. The only insects that were affected by the Bt-corn were the European corn borer (the intended target), the Western corn rootworm, and other corn pests.
And, finally, an important aspect of biodiversity is the soil in a given area: one teaspoon of soil contains more living organisms than people in the world and soil microorganisms have a crucial impact on the fertility and the sustainability of agricultural systems. For example, the majority of plant roots establish symbiotic relationships with fungi or bacteria living in the soil that both siphons them nutrients and provides protection against root diseases. Soil microbial communities are not affected by GM crops, which interact with soil microorganisms (worms, insect, fungi, and bacteria) in the same way as non-GM crops.
The productivity of GM plants is typically 20 percent higher than that of non-GM ones, making it an appealing way to approach the pressures of the rising global food demand due to population growth. GM crops are also an appealing approach in the face of climate change and pollution. As climate change progresses, land becomes more arid, usable topsoil is depleted, and water becomes more scarce. Conventional crops are typically not drought tolerant, and so as human-caused climate change continues, agricultural yields could drop. One study found that each degree of warming will result in anywhere from a 3-7 percent drop in global yield in wheat, rice, corn, and soybean. Tactics to adapt to this include engineering crops to retain more water, or adding genes that essentially stabilize cells, make them hardier, and hopefully able to withstand the stresses of a drought.
We have gathered enough data in research performed over 20 years in different parts of the world to show that GE crops are generally beneficial to the environment, given their reduced land usage, need for pesticides, and lack of off-target effects. If we continue to engineer plants for other characteristics (like, say, improved photosynthesis and enhanced plant growth, which would increase yield and reduce land usage further), genetic engineering can be an important ally in protecting the environment and achieving a more sustainable agriculture.
Herbicides are chemicals used by farmers to prevent the growth of weeds which compete with crop plants for sunlight, water, and soil nutrients. They're an important part of modern agriculture, and by allowing non-mechanical methods of weed-control, like tilling (ploughing) or hand-weeding (as is still practiced in much of the developing world), they allow farmers to limit soil erosion as well as save on labor and energy. There are many different herbicides available to farmers today, and their use is dependent on things like which crop is planted, what weeds are prevalent, and the type of cropping system.
Most cultivated GM plants are designed to be used with an herbicide called glyphosate. These glyphosate-tolerant plants can withstand the application of glyphosate as it kills the surrounding weeds. Glyphosate was originally introduced in 1974, and has since become the predominant herbicide used in agriculture. A major reason for this widespread adoption is that glyphosate is a very broad-spectrum herbicide (i.e. it affects a lot of different weed species), and is also very safe for humans. And since its original patent expired in 2000, its cost has fallen, allowing for even wider adoption by farmers. Glyphosate-tolerant GMOs offer a safe weed management technique to farmers, while also reducing the use of environmentally damaging practices, like tilling. One 2007 study found that the adoption of glyphosate-tolerant GM plants in the US over 10 years had prevented the release of as much carbon dioxide as that produced by 4 million family-sized cars.
Glyphosate is considered one of the safest available herbicides. Its acute and chronic toxicity is less than that of 90 percent of the herbicides used in the US. Acute toxicity is measured in terms of something called an LD50, this is the amount of a chemical per milligram of bodyweight that is required to kill 50 percent of animals in a study. The LD50 values for glyphosate in different animals range from 1,500 to 10,000mg/kg. This is incredibly high; caffeine, for instance, has a LD50 of about 200mg/kg, meaning that it is about ten times more toxic than glyphosate. (Caffeine however, is very safe too. An average adult would need to consume about 130 cups of coffee in a single sitting for it to become poisonous.)
Tests of glyphosate's chronic toxicity in multiple animal species have also found that it's safe. In 2010 and in 2017, the federally funded Agricultural Health Study reported on the effects of herbicides on the health of 89,000 Americans. The reports found no statistically significant evidence that use of glyphosate herbicide is carcinogenic to humans. In fact, a recent study by Andrew Kniss, a weed science professor at the University of Wyoming, concluded, "if glyphosate use were discontinued (as was recently proposed in the EU) the resulting displacement of glyphosate by other herbicides is likely to have a negative impact on chronic health risks faced by pesticide applicators."
Another reason why one USDA scientist calls glyphosate a "once in a century herbicide" is that, unlike most other herbicides, it binds tightly to soil and thus doesn't leach into groundwater reservoirs. It is also rapidly degraded by soil microbes (so it has a low persistence in the soil) and it can't escape into the atmosphere.
However, the very efficacy of glyphosate has meant that its rampant use, particularly in the United States, has led to the development of weed species resistant to it. As a result, farmers are forced to turn to more toxic herbicides or less environmentally sound crop practices. The good news, though, is that herbicide resistance (much like antibiotic resistance) is closely tied to farming practices, which can be changed. For example, just across the border in Canada, farmers tend to rotate the use of different herbicide-resistant systems in a single field much more than in the US. As a result, by 2014 only seven cases of glyphosate-resistant weeds were reported there. Another recent study published in the journal Weed Science, analyzing data collected by the USDA and the International Survey of Herbicide Resistant Weeds, found that the use of glyphosate-tolerant GMO cotton and soybean led to an increase in the use of glyphosate, but that this also led to the decline in the use of other herbicides that are more prone to causing the development of herbicide-tolerant weeds.
There is much to be gained by retaining the use of glyphosate-tolerant GMOs, but this needs to be balanced with appropriate limits, to prevent its overuse.
Over the next decades agriculture will face tremendous challenges, such as global warming, desertification and biodiversity loss. Therefore, we will need all our knowledge in order to devise new ways to keep feeding the ever-growing world population.
Today we are able to easily "stack" the characteristics of different GM plants ( y creating plants resistant to more than one disease). And we can specifically target plant genes that we know regulate traits like fruit size (see the work from Zachary Lippman, below). With the advent of genome editing techniques like CRISPR, our ability to modify plants has finally caught up to our ability to understand how they're built.
Nevertheless, food in the near future will look pretty much like food already looks today, but with tweaks that make them last a bit longer, grow a bit larger, or taste a bit sweeter. And, perhaps more importantly, crops will continue to require fewer pesticides than were needed before, further reducing the need for environmentally harmful broad-use pesticides.
Here are a few GM foods or technologies you can expect to see on shelves in the near future.
The newest GM crop teetering on the edge of approval is frost-resistant eucalyptus. Eucalyptus is a fast-growinghardwood tree often used as a paper and biofuel source. However, it's sensitive to cold and so is usually grown in warm climates across Asia, Africa, and South America. Genes from Arabidopsis – or thale cress, a small flowering weed –that confer resistance to frost were inserted into the eucalyptus genome. This would allow eucalyptus to be grown in more temperate regions of the US. The USDA last year suggested lifting restrictions on frost-resistant eucalyptus, but it hasn't happened yet. Eucalyptus uses large amounts of water, and concerns about its effects on other plants around it and surrounding ecosystems, particularly aquatic ecosystems, have not been addressed.
There are interesting developments on the horizon for tomatoes. There's the tomelo, which is not a sinister hybrid between tomatoes and pomelos. Rather, it's a tomato plant created to be resistant to attacks by a fungus, jointly created by the The Sainsbury Lab in Norwich and the Max Planck Institute in Tuebingen. Researchers there showed that CRISPR can be used in a fast and efficient way to create a tomato plant resistant to a pathogen without leaving any trace of the process.
Their approach deleted a tiny chunk of one gene. That one gene, MILDEW RESISTANT LOCUS O (plant biology naming convention requires all caps like everyone's screaming at each other), allows mildew to grow on tomatoes. The little deletion inactivated the gene and conferred resistance to the mildew. Although the Tomelo will not be available on the market (the experiment was done on a variety that we don't usually eat), it's special because the process that made the Tomelo left behind no foreign DNA of any kind (like the insertion of a gene from another species). Instead, it resembled a naturally occurring mutation. It is a bit like a high-tech surgery that saves a life in which you do not leave any single scar on the patient. The same tomato plant would have also been possible with a traditional approach but it would have taken years of work instead of 10 months.
Also working on tomatoes, Zachary Lippman, a researcher at Cold Spring Harbor Laboratory in Long Island, New York, solved two long-lasting problems for breeders: flowering time and yield. Genome editing tools allowed him to select plants with different flowering time, meaning he was able to program a fruit harvest according to need and to climate, with the potential of harvesting twice as much as before. In parallel, they also show the feasibility of modifying genome parts that are known regulators of plant height or fruit size. By modulating those parts of the genome, we can induce variation and then select the favorite characteristics, more adapted to our needs and flavors. The same old principle of agriculture but with some more precise tools we have now in our hands.
Engineering Nitrogen Symbiosis for Africa (ENSA), a visionary research project led by Giles Oldroyd and funded by the Bill and Melinda Gates Foundation, aims to create GM crops able to sustain their own nitrogen demand. Plants need more nitrogen than they typically get from the soil, so farmers often apply costly and environmentally hazardous nitrogen-based fertilizers. However, some plants, like soybeans, are able to get nitrogen from bacteria in their roots that can capture nitrogen from the air and pass it to the plant. ENSA hopes to use genetic engineering to give other plants this ability, dramatically reducing the need for additional nitrogen fertilizers.
Altogether, recent advances in genome editing technologies represent a great resource for the future of agriculture. Over the next few years, crop genetic modification will become even easier, more affordable and precise and, most importantly, the final product will be often impossible to distinguish from traditional breeding. Tailor-made GM plants are an immense resource for agriculture that can be easily tuned for the needs of a changing world.