chris title

by Christopher Gerry
figures by Kristen Seim

Summary: The human population has grown at a breakneck pace and threatens to further exacerbate a problem that has worsened in recent years: chronic hunger. Genetically modified crops could help to relieve this problem by providing increased yields and being more resistant to environmental stressors. In particular, the increasing prevalence of drought has prompted the development of crops that are more tolerant of high temperatures. These efforts, however, have afforded mixed results due to the genetic complexity of drought resistance and similar traits. Regardless, continuing to research this type of genetic engineering remains a promising strategy for feeding the world’s growing population.

An Unsustainable Trend

If you’ve recently been feeling more claustrophobic than usual, you might want to blame your growing cohort of fellow humans. The world population has doubled over the past 50 years and continues to grow by roughly 100 million people each year (Figure 1). Even though the growth rate appears to be slowing, the population will likely continue to grow throughout the 21st century and could reach 11 billion by 2100 [1]. This dramatic boom has evoked fears that our rapidly-growing population will surpass Earth’s inherent “carrying capacity” for humankind, echoing Thomas Malthus’ warnings from the late 18th century. Thankfully, with regard to physical living space, these fears appear to be overblown; to reiterate a popular factoid, every human on the planet could live in a Texas-sized area that has the same population density as New York City [2].

Figure 1: 2015 UN Population Projections for the 21st Century
The chart above illustrates previous world population trends and future probabilistic projections using data derived from the 2015 Revision of the World Population Prospects.  The current model projects an 80% likelihood that the population will reside within the dark band for any given year and a 95% likelihood that it will reside within either the light or dark band.  It’s typically more difficult to predict events that will take place further into the future, as illustrated by the widening of the bands over time.

Feeding that many people, on the other hand, is a much more difficult challenge. Roughly 800 million people remain undernourished despite the fact that the current output of the world’s farms could supply over 11 billion people with 2,000 calories per day [3]. As a result, more people die annually from chronic hunger than from HIV/AIDS, malaria, and tuberculosis combined [4]. Many of the world’s hungry live in developing countries, so increasing the food supply in impoverished regions would be an efficient way to ease suffering and save lives. A warming global climate, however, threatens to exacerbate local food shortages by increasing the frequency and duration of crop-crippling droughts. Even the most optimistic projections of population growth and climate change could represent potential catastrophe if we don’t improve our means of growing, harvesting, and distributing crops.

Farming 2.0

Modifying the genomes — the biological instruction manuals that dictate how organisms are assembled and maintained — of staple crops like rice, corn, and soybeans could relieve many of the pressures on the worldwide food supply. Recent advances in genome editing technology have allowed scientists to precisely add, delete, and rearrange pieces of genetic code to imbue crops with desirable characteristics (see this article). While it may sound like science fiction, large chemical companies like DuPont and Monsanto have been using this technology for over two decades on a wide variety of plants, many of which may alleviate world hunger. In 1994, Calgene introduced the first GM crop to be sold in the United States, the Flavr Savr tomato, which ripened slowly and had an extended shelf-life [5]. Flavr Savr tomatoes eventually disappeared from grocery stores because high production costs prevented them from becoming profitable, but lengthening the amount of time that produce stays fresh may be used to increase the food supply in underdeveloped areas.

Figure 2: A Common Misconception Regarding the Production of GM Crops
Despite what you may see on the Internet, GM crops are not prepared by injecting them with mysterious fluorescent solutions.  In reality, genetic engineering is a much less dramatic process that often involves pipetting clear, colorless liquids into other clear, colorless liquids.

A more direct solution to chronic hunger involves GM crops that have been engineered to increase yield, which is a measure of the amount of food that may be harvested from a given area of land. A popular strategy that scientists use to increase this metric is to insert a gene that confers resistance to commonly used weedkillers. Farmers that adopt these herbicide-resistant crops are able to clear their fields of unwanted plants without tilling the soil, which allows them to plant higher densities of crops. Geneticists have also developed pest-resistant crops that are poisonous to hungry insects, greatly reducing farmers’ reliance on chemical pesticides. Lastly, genetic engineering can generate crops that are resistant to microbial infections, such as the potato blight that triggered the Irish Potato Famine in the mid-19th century [6].

How these scientific ideas actually translate to the fields is often the subject of intense debate, but a recent review of almost 150 studies has concluded that GM technology has significantly increased crop yields and farmer profits over the past 20 years. GM soybeans, maize, and cotton were associated with a 22% overall increase in yield, 37% decrease in pesticide use, and 68% increase in farmer profits, despite the higher cost of GM seeds (Figure 3) [7]. Furthermore, farmers in developing countries experienced yield and profit gains that were 14% and 60% higher, respectively, than those observed by their counterparts in industrialized countries. This is particularly encouraging because food shortages often take their most severe toll in underdeveloped regions. Even with these new crops, however, some areas of the world have seen their agricultural output begin to plateau [8]. Therefore, increases in yield alone will likely not be able to sustain our ever-growing populace.

Figure 3: Overall Effects of Farming with GM Crops
The graph above shows the average percentage differences in several important metrics that result from farmers adopting GM crops.  Overall, GM crops were associated with substantially higher yields and lower pesticide use.  The slight increase in total production costs is likely attributable to the increased price of GM seeds, but it is dwarfed by the dramatic increase in farmer profits.  Data obtained from Klumper and Qaim [8].

Trial by Fire

Another strategy that genetic engineers are currently pursuing is the development of drought-resistant crops. As the climate steadily warms, droughts are projected to occur more frequently and to last longer, threatening harvests worldwide. In fact, the drought that’s been wringing California dry for almost four years is the worst that the Golden State has seen in over a century [9]. Additionally, a drought-mediated contraction in the food supply would likely result in higher prices and, thus, further lower the amount of food that’s accessible to the world’s poor. Farmers could hedge against these potential losses by planting GM crops that can flourish in both wet and arid conditions. African farmers, in particular, may be able to use these crops to exploit previously untapped agricultural opportunities. By doing so, these crops could also increase the food supply in one of the world’s most malnourished areas.

Unfortunately, current GM drought-resistant crops typically fare no better in dry conditions than do drought-resistant crops that have been developed via “conventional” genetic engineering — selective breeding. Just as human height and intelligence are influenced by a poorly understood interplay of many different genes and environmental factors, complex traits like drought resistance are typically determined by more than one or two pieces of genetic code. Present-day research has not precisely identified the intricate combination of genes that allows crops to thrive in arid conditions, so these crops have likely not yet reached their full potential.

Plummeting research costs, however, will likely allow genetic engineers to modify more complex traits in the years to come. The current cost of determining the sequence of your genetic code is roughly five thousand dollars, which is only 0.05% of the ten million dollars you would have had to pay 8 years ago (Figure 4) [10]. Lower research costs likely will lead to an expansion of our molecular toolkit for combating hunger as we draw connections between traits and specific genes, such as those that successfully confer drought resistance to selectively bred crops.

Figure 4: The Cost to Sequence a Human Genome has Fallen Precipitously
The cost of sequencing an entire human genome has fallen so dramatically over the past few years that it has outpaced Moore’s law of computing – note the logarithmic scale on the Y-axis.  Moore’s law states that technology advances at such a rate that the maximum number of transistors in a microchip (and, thus, computing power) doubles every two years.  Genome sequencing costs aligned well with Moore’s law’s projection from 2001-2007, but advances in genome sequencing technology that were introduced in 2008 have left Moore’s law in the dust.  Data obtained from the National Human Genome Research Institute.

One such innovation that has already come to fruition is a new rice plant that was described just last month in the journal Nature. This new strain contains an additional gene that transfers growth away from the roots and towards the parts of the plant that humans can actually eat. The resulting GM rice produces 43% more grain and emits up to 97% less methane than conventional rice does. Methane is a powerful greenhouse gas (roughly 84 times more potent than carbon dioxide), so this rice should not aggravate the environmental problems that other GM crops are trying to solve. In fact, rice paddies are responsible for up to 17% of global methane emissions, so widespread adoption of this strain would be a boon for both our stomachs and our environment [11]. Unfortunately, it won’t be available to farmers until 10 to 20 years from now, but field trials have largely been encouraging.

Other promising GM crops of the not-so-distant future include flood-resistant rice, maize that can grow in nitrogen-poor soil, and potatoes that can immunize consumers against hepatitis B infection [12]. Some of these ideas remain science fiction for the moment, but overwhelming evidence has already shown that changing food on the molecular level can help to solve some of the world’s biggest problems.

Christopher Gerry is a first-year graduate student in the Department of Chemistry and Chemical Biology at Harvard University. He is currently studying the science of therapeutics in Stuart Schreiber’s lab.

This article is part of the August 2015 Special Edition, Genetically Modified Organisms and Our Food.

References

1. Carrington D. “World population to hit 11bn in 2100 – with 70% chance of continuous rise”. The Guardian. 18 September 2014. http://www.theguardian.com/environment/2014/sep/18/world-population-new-study-11bn-2100
2. Falk T. “Could 7 billion people live in a Texas-sized city?”. ZDNet. 1 November 2011. http://www.zdnet.com/article/could-7-billion-people-live-in-a-texas-sized-city/
3. Biello D. “Human Population Reaches 7 Billion – How Did This Happen and Can It Go On?”. Scientific American. 28 October 2011. http://www.scientificamerican.com/article/human-population-reaches-seven-billion/
4. Hunger Statistics. World Food Programme. Accessed 29 June 2015. http://www.wfp.org/hunger/stats
5. Bruening G and Lyons JM. “The case of the FLAVR SAVR tomato”. University of California: California Agriculture (2000), 54, 6-7. http://californiaagriculture.ucanr.org/landingpage.cfm?article=ca.v054n04p6&fulltext=yes
6. McGrath M. “Genetically modified potatoes ‘resist late blight’”. BBC News. 17 February 2014. http://www.bbc.com/news/science-environment-26189722
7. Klumper W and Qaim M. “A Meta-Analysis of the Impacts of Genetically Modified Crops”. PLoS ONE (2014), 9.
8. Grassini P, Eskridge KM, and Cassman KG. “Distinguishing between yield advances and yield plateaus in historical crop production trends”. Nature Communications (2013), 4, Article number: 2918.
9. Guzman, Z. “California’s Drought is Worst In Over a Century, Analysis Shows”. NBC News. 16 July 2015. http://www.nbcnews.com/business/business-news/californias-drought-worst-over-century-analysis-shows-n393376
10. Raj A. “Soon, It Will Cost Less To Sequence A Genome Than To Flush A Toilet – And That Will Chance Medicine Forever”. Business Insider. 2 October 2014. http://www.businessinsider.com/super-cheap-genome-sequencing-by-2020-2014-10
11. Su J, Hu C, Yan X, et al. “Expression of barley SUSIBA2 transcription factor yields high-starch low-methane rice”. Nature (2015), 523, 602-606.
12. Wilcox C. “GMOs of the Future: Two Recent Studies Reveal Potential of Genetic Technologies”. Discover Magazine. 31 March 2015. http://blogs.discovermagazine.com/science-sushi/2015/03/31/gmos-of-the-future-two-recent-studies-reveal-potential-of-genetic-technologies/#.VZlFtPm6fIU

5 thoughts on “Feeding the World One Genetically Modified Tomato at a Time: A Scientific Perspective

  1. Dear Christopher,
    You seem to be pro-GE at the expense of consistency in the ‘bigger picture’ of your supporting arguments. You write that herbicide-resistant GE crops allow farmers “to clear their fields of unwanted plants without tilling the soil, which allows them to plant higher densities of crops”; and therefore espouse an economic agenda that harms the environment through toxicity and greenhouse gas emissions. Later, you laud the recently developed rice that releases less methane, a “powerful greenhouse gas,” and so “should not aggravate the environmental problems that other GM crops are trying to solve.” Roundup Ready corn and soy etc., etc. are not trying to solve environmental problems. They are enabling those problems.

    Personally, I see high promise in biotechnology (because we are in a dire state that requires accelerated and super-charged responses). However, the only way for biotechnology, like genetic engineering, to benefit us is if it benefits all of us and all that we depend on. We cannot afford to pollute the Earth and ourselves anymore with petroleum extraction, processing, and releasing in the atmosphere, in the soil, and in the water. We can afford disease-resistant, vitamin-enriched, drought-tolerant, and season-extending crops — if and only if they are proven not to be harmful to other beings. Granted, as you point out, there are many genes associated with these traits, making them hard to successfully control. Mother Nature doesn’t work in a laboratory.

    Unfortunately, the institutions monopolizing these developments are for-profit corporations. Their conflicts of interest go without saying. They are interested in feeding the world not because people are hungry and farmers are heroes, but because their hegemony translate to cash money and power.

    And to anyone reading who opposes the amoral reign of multi-national seed corporations and agrochemical companies (which, 60% of the time, are the same thing): these corporations are made of people with physical addresses and hearts (however saturated with GE-canola oil). They can be reached. They and politicians do the same business. It’s time we start treating them like we do our representatives and voice our concerns.

    That’s all for now.

    Haleigh

    1. Hi Haleigh,

      Thanks for your comment! It is true that roundup ready crops have caused pesticide-resistant weeds, which can be an environmental problem, but they (and other GE crops) have also reduced the use of more harmful pesticides and in some cases, even increased the insect populations in the regions in which they’re grown. I’m curious what environmental problems you are referring to when you say “GE crops are enabling those problems.”

      You’re right that there are larger social, political, and economic factors at work here when we’re talking about the monetization of GE crops by corporations. And I think we need to think about that as we move forward–things like public funding for science so that public sector research can address these problems and test for safety of GE crops is important!

  2. Hi, I am curious as to why you quote studies claiming an increase in yields for GM crops, but don’t mention studies that report the comparison of GM crop yields with those of conventional crops. As far as I can tell, there is no overwhelming evidence that GM crops are significantly superior to conventional crops in terms of yield or nitrogen use efficiency. Here is one link, I would include more, but it’s hard to do on my phone.
    http://www.nature.com/news/cross-bred-crops-get-fit-faster-1.15940
    In light of these revelations, and all of the problems GMOs are creating, I am still left wondering “why?”

    1. Hi Maya,

      You’re right that studies regarding GM crop yield can show different results. That’s why the study I reference in my article (Ref #7 – Klumper and Qaim, PLoS One) is a meta-analysis of 147 different studies. Meta-analyses allow statisticians to consolidate the results from many different, and possibly contradictory, studies so the underlying truth is not drowned out by the “noise” of any one study (“good” or “bad”). Using this method, Klumper and Qaim show that adoption of GM crops leads to significant increases in both yield and farmer profits.

      I’m not sure what you mean when you reference “all of the problems GMOs are creating.” The safety of GM crops is supported by a massive amount of scientific evidence. They have yet to deliver on their full potential in several regards, as stated by the Nature News article you mention, but I’d argue that we shouldn’t abandon a technology simply because we haven’t perfected it yet. The benefits of GM technology are already being felt today, and it’s likely they’ll improve with time.

Leave a Reply

Your email address will not be published. Required fields are marked *