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Wednesday 19 August 2015

Food for Thought; the Future of Global Food?

A global food shortage may not appear to be a threat or worry for a lot of people; around half a billion have been diagnosed as obese, that’s 1 in 14 people worldwide[1]. However, with an estimated 1 in 9 people being malnourished, in many countries the threat is already a reality. Though numbers predicted vary, the global population was agreed to have breached 7 billion people by 2012[2]. Most estimates point to another 2 billion people on the planet by the middle of the century. To put that increase into perspective, when we reached the first billion by 1804 it took around 156 years to add 2 billion. At our current rate of growth, an addition of the same number again will happen more than five times faster.

Worldwide malnourishment data from United Nations World Food Programme 2012, and the global prevalence of obesity.
The prevalence of malnourishment and obesity across the globe, and the disparity between the two. South-east African countries appear most malnourished, whilst levels of obesity rose in almost every country last year. Image credits: Undernourishment by country (top) via wikimedia [CC BY-SA 3.0], obesity by country (bottom) from Institute for Health Metrics and Evaluation [CC BY-NC-ND 4.0]

The FAO are at the forefront of assessing how much food we have, and how long it’s going to last us at this rate of population expansion. In order to feed the world in 2050, they have predicted the need for nearly a billion tons more cereal grains per year than the world is already producing. That’s not just so everyone gets a good breakfast; rice, wheat and maize all come from cereal grains that are now accountable for 61% of food eaten globally[1]. So how are we going to do it?

Could we use more land for farming? The FAO estimate that about 30% of the land on Earth could be used for farming to some extent, and currently we are only using half of that[4]. However, other studies have been made that indicate agricultural expansion is not necessarily the way to go[5]. Improving harvest yields, reducing waste and moving diets away from meat are all viable options that have the potential to nearly double food production. Unfortunately, despite these promising figures, the global production of cereals is projected to drop by 1.5% this year[6]. Such a small percentage may not seem like much, but it works out as 39.1 million tons. That loss of cereal grains weighs more than 200,000 blue whales, 3,900 Eiffel towers or 6 pyramids of Giza. That’s in one year. It is very difficult to say exactly why this is happening, but scientists generally agree climate change is a large factor to be considered[7].

Two of the major effects of climate change are global increases in temperature and carbon dioxide (CO2) levels. Plants take CO2 from the air and make food for themselves whilst releasing oxygen (O2) in a process known as photosynthesis. Increasing CO2 has been predicted to increase yields in crops in years to come, but only to a certain extent[8]. Past a point, growth is limited by other environmental conditions; the nutrient content of the soil for example. Additionally, plants and pollinators relationships could be negatively impacted. The influence on growth periods caused by an increase in CO2 could change the life cycle of plants and move them away from the cycle of bees (for example).

Furthermore, the additional heat could almost cancel out that CO2 fueled gain[7]. The O2 released comes from water the plant absorbs through its roots. This water will be less accessible as more of it evaporates off the Earth’s hotter surface and droughts become more common. For this reason, one target of recent research has been stomata. When they are open, stomata are a major source of water loss for a plant. When water is an abundant resource this isn’t a problem. Increasingly that is not the case and if a plant cannot maintain its water levels it stops growing, so that less is used and water is conserved. This is one of the reasons drought can be catastrophic for crops.

There is potential to prevent crop damage caused by a lack of water; one technique for instance involves an ‘on-off’ switch being added to a plant protein that closes the stomata[9]. When water levels in the plant are reduced, it produces more of a hormone called abscisic acid (ABA). The protein that closes the stomata detects changes in ABA so when concentrations rise, the stomata close.

Natural mutations occur within this protein, and a team have tested which chemicals used in agriculture could be used to mimic ABA action on these mutants. They found that the fungicide mandipropamid worked well, effectively ‘switching on’ the protein when it was added. Mandipropamid could be a future solution to drought stress on plants, but the researchers are not yet sure how well it works ‘in the field’ (pardon the pun). This is an example of a project that involves managing water use of the current crop yields, however others are being directed at boosting the yields.

One such approach has a direct impact on photosynthesis itself, by aiming to improve the efficiency of the process. Found in all plants, there is an enzyme called Rubisco. This protein is responsible for converting CO2 to sugar; creating the plant’s food. However, it does this very slowly and so scientists have tested replacing it with bacterial Rubisco, a faster alternative[10].

It was done in two variants of a tobacco plant, and both used the foreign Rubisco enzyme to convert CO2 at a faster rate than was previously possible. Despite this progress, there is a long way to go for the method before it is used commercially. Though it was quicker, the bacterial Rubisco also occasionally reacted with O2 instead of CO2, wasting energy and reducing O2 output. This isn’t a problem in bacteria that photosynthesize because they have carboxysomes, which tobacco plants lack. Without carboxysomes plants have to be grown in artificially CO2 rich chambers, which isn’t sustainable. The future of the research is directed at creating tobacco (and other) plants that do have carboxysomes, but for now the method remains unviable.

3-D model of carbon-fixing enzyme Rubisco with projected charge interactions for compaction.
Rubisco is abundant within plants, because of how inefficient it is as an enzyme. A huge amount is required to convert CO2 into sugar for food, and so each protein has to be very compact in order to fit enough of them into the cells. Rubisco is charged, with positive and negative areas (shown in blue and red respectively). The charges attract each other within one and between multiple enzymes. This keeps them as tight as possible within the cells. Image credit: "RuBisCO". Licensed under CC BY-SA 3.0 via Wikipedia

One of the most important cereals across Africa is maize. It is also possible to predict its drought resistance, based on timings of the male pollen shedding and female silk production of the crop. This makes it an ideal target for new approaches to dealing with drought stress. The less water there is, the greater chance the silk emerges from the maize late. It then cannot be fertilised by male pollen that has been released earlier. So, the sooner the silk emerges after pollen release, the more drought resistant the maize is as it has a greater chance of being fertilised.

The International Maize and Wheat Improvement Center have seed banks with a wide variety of different maize. Researchers searched these banks, found maize that were drought resistant and then cross-bred them[11]. This process uses the same concepts that apply when a labrador and poodle are crossed to produce a labradoodle. Of the offspring produced, those that were the most efficient without water were again selected and cross-bred. After several repetitions, the resulting improved maize seed was crossed with plants that are already thriving in the dry conditions of Africa.

Several ventures are in progress using this method. The Drought Tolerant Maize for Africa project for example has created 153 new varieties of maize. The extra yields made possible by the variants will be put to use in thirteen countries, reducing poverty in nearly 1 in 10 people, equating to a total of over four million Africans.

Another way nature is offering us a solution is through crop wild relatives, or CWRs, found in China. These are plants similar to fundamental crops like rice and wheat, but live in much more extreme environments across the country and are exposed to a wide variety of different diseases and pests. Each CWRs (a total of 871 have been identified) therefore has traits that would dramatically improve current crops and crucially, both types of crop share enough of their genetic code to be viable for cross-breeding. Nearly half of the CWRs found occur nowhere else on Earth, and at least 17% are at risk of extinction in China. A database of the CWRs has now been produced and efforts are being shared between conserving these species and prioritising characteristics that could increase food security globally[12].

There is increasing contention for arable land as biofuels are becoming more prominent and require similar conditions to food crops. However, we may be able to grow both. Two methods have been tested; relay-cropping and double-cropping[13]. In the former, two crops (one for biofuel and one for food) are grown at the same time. In double-cropping one crop is planted once the other has been harvested.

Relay-cropping was shown to use less water, but the extra water use necessary for double-cropping was also beneficial as it occurred in spring, where farmers often have excess moisture in the soil from the melted snow of the winter. Though it has been mentioned[13] that the double-cropping method would be less ideal elsewhere as soil water levels vary geographically, potentially reducing yields. Pollinators benefitted from the relay system as the flowering in spring provided a new food source. Greater yields were also seen as a result of earlier planting leading to longer growing seasons. This may be the future solution to the problem of land utility for competing purposes, but more crops have to be tested before the method can be introduced.

In America it has been found that more than a third of the food supply is being wasted, costing the US economy an estimated $161.6 billion dollars annually[14]. In the same country, nutrients in the soil are decreasing more than ten times quicker than they’re being naturally replenished[15]. Many statistics will paint a bleak picture of our food security; we do not know exactly how we’ll feed the world in the future. However, any one of the multitude of ongoing projects may hold the answer - a sustainable recipe for a well fed world.

This article was written by Joshua Fleming, a biological sciences student from the University of Leicester conducting a summer internship as a science writer at TWDK.

why don't all references have links?

[1] Food And Nutrition In Numbers. 2014. PDF. 1st ed. Food and Agriculture Organisation of the United Nations.
[2] World Population. 2012. PDF. 1st ed. United Nations Department of Economic and Social Affairs.
[3],. 2015. 'Consumption Patterns And Food Demand In Australia To 2050'.
[4] FAO,. 2015. 'World Agriculture: Towards 2015/2030 - An FAO Perspective'.
[5] Foley, Jonathan A., Navin Ramankutty, Kate A. Brauman, Emily S. Cassidy, James S. Gerber, Matt Johnston, and Nathaniel D. Mueller et al. 2011. 'Solutions For A Cultivated Planet'. Nature 478 (7369): 337-342. doi:10.1038/nature10452.
[6] Food Outlook. 2015. PDF. 1st ed. Food and Agriculture Organisation of the United Nations.
[7] Lobell, D. B., and S. M. Gourdji. 2012. 'The Influence Of Climate Change On Global Crop Productivity'. PLANT PHYSIOLOGY 160 (4): 1686-1697. doi:10.1104/pp.112.208298.
[8] Reyes-Fox, Melissa, Heidi Steltzer, M. J. Trlica, Gregory S. McMaster, Allan A. Andales, Dan R. LeCain, and Jack A. Morgan. 2014. 'Elevated CO2 Further Lengthens Growing Season Under Warming Conditions'. Nature 510 (7504): 259-262. doi:10.1038/nature13207.
[9] Park, Sang-Youl, Francis C. Peterson, Assaf Mosquna, Jin Yao, Brian F. Volkman, and Sean R. Cutler. 2015. 'Agrochemical Control Of Plant Water Use Using Engineered Abscisic Acid Receptors'. Nature 520 (7548): 545-548. doi:10.1038/nature14123.
[10] Lin, Myat T., Alessandro Occhialini, P. John Andralojc, Martin A. J. Parry, and Maureen R. Hanson. 2014. 'A Faster Rubisco With Potential To Increase Photosynthesis In Crops'. Nature 513 (7519): 547-550. doi:10.1038/nature13776.
[11] Gilbert, Natasha. 2014. 'Cross-Bred Crops Get Fit Faster'. Nature 513 (7518): 292-292. doi:10.1038/513292a.
[12] Kell, Shelagh, Haining Qin, Bin Chen, Brian Ford-Lloyd, Wei Wei, Dingming Kang, and Nigel Maxted. 2015. 'China’S Crop Wild Relatives: Diversity For Agriculture And Food Security'. Agriculture, Ecosystems & Environment 209: 138-154. doi:10.1016/j.agee.2015.02.012.
[13] Gesch, Russ W., and Jane M.-F. Johnson. 2015. 'Water Use In Camelina–Soybean Dual Cropping Systems'. Agronomy Journal 107 (3): 1098. doi:10.2134/agronj14.0626.
[14] Neff, Roni A., Marie L. Spiker, and Patricia L. Truant. 2015. 'Wasted Food: U.S. Consumers' Reported Awareness, Attitudes, And Behaviors'. Plos ONE 10 (6): e0127881. doi:10.1371/journal.pone.0127881.
[15] Amundson, R., A. A. Berhe, J. W. Hopmans, C. Olson, A. E. Sztein, and D. L. Sparks. 2015. 'Soil And Human Security In The 21St Century'. Science 348 (6235): 1261071-1261071. doi:10.1126/science.1261071.

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