Where Has All the Crop Diversity Gone?
In the News
April 30, 2014
Our diets around the world are becoming more and more alike which could have detrimental consequences for both consumer health and crop sustainability, according to research from the International Center for Tropical Agriculture, Global Crop Diversity Trust, and a number of research universities and published in Proceedings of the National Academy of Sciences.
The study looked at different crop plants in national food supplies worldwide over the past 50 years, using national per capita food supply data published by the Food and Agriculture Organization (FAO) of the United Nations. Researchers analyzed trends in the richness, abundance, and composition of measured crop commodities in the food supplies of 152 countries (98% of the world’s population) from 1961 to 2009.
Researchers found that as more countries around the world adopt a globalized diet, their preferences for energy-dense foods like animal products, plant oils and sugars, and for some major crop plants over traditional crops, has led to the dominance of major crop species around the globe to the detriment of alternative crops. Crops predominant in diets around the world now include wheat, rice, maize, and potato as well as soybean, sunflower oil and palm oil. Meanwhile, many regionally important crops like sorghum, millets, rye, sweet potato, cassava and yam, are declining. Today, wheat is a major staple in most countries (97.4%), as is rice (90.8%) and soybean (74.3%). The greatest changes in crop composition took place in East and Southeast Asia as well as sub-Saharan African countries.
One of the major concerns here is that homogeneity can make agriculture more vulnerable to drought, pests and diseases, therefore threatening food security. Colin Khoury, study co-author and a visiting researcher at the International Center for Tropical Agriculture (CIAT), says that plant breeders are always looking for new varieties (i.e. new genetic compositions) in order to stay one step ahead of pests and diseases. It is a similar issue with drought. If you have only one variety planted, it has its limits in what it can tolerate, and if the year happens to be a bad one, meaning beyond the limits of tolerance, then the whole crop is lost. On the other hand, if many varieties (or many crop species) are planted, it is likely that in any given year some do well, and some do not, but very unlikely that all will fail. It is hedging one's bets by not putting all of one's eggs in the same basket, he says.
“Crop diversity is our insurance – our reservoir of potential – to be able to handle the unknown issues of the future. That is why, even if we develop super productive varieties that everyone wants to plant (actually especially in this case), we need to conserve and maintain crop diversity (typically in seedbanks and also in farmer's fields) so that when that variety has its inevitable demise, we are able to find/create a new variety to replace it,” says Khoury.
Genetic diversity really means different genetic compositions, each of which has distinct characteristics that display themselves visibly (like color or the size of a fruit, for instance) or invisibly (like different degrees of immunity to particular diseases or drought). Homogeneity means less diversity in agricultural areas – more of the same crop species, and very often more of the same varieties of those crops. In both senses, it equates to more of the same genetic compositions being planted, increasingly vulnerability. And as a growing global population becomes increasingly dependent on a narrowing food source, the interdependence among countries in their food supplies, plant genetic resources, and nutritional priorities is heightened.
“Increasingly eating the same worldwide means greater reliance worldwide on a certain limited set of crops. The once regionally/locally important crops are becoming more marginalized. People are moving into the cities and so they are eating less wild foods and garden foods, and often more of the globalized foods. The question is this: are these globalized crops prepared to meet their increasing responsibilities?” says Khoury.
In addition to potential threats on food security, these homogenous diets are likely contributing to worldwide obesity, heart disease and diabetes. The study found that 50 of the measured crop commodities currently contribute to the top 90% of calories, protein, fat and weight around the world. Not only that, but changes in diet have resulted in a decrease in certain gut microbiota, which has also negatively affected health outcomes.
“We have a 'nutrition transition' occurring worldwide, where people have the issue of having plenty of access to cheap, energy dense (high calorie, fat, sugar) foods. Eating these foods is associated with obesity, heart disease, Type 2 diabetes, and so on. This is now occurring worldwide. We are therefore more similar, or interdependent worldwide in dealing with this huge health burden,” says Khoury. “We have done a lot to provide more food around the world, to solve the issue of hunger. But in the meantime we have brought up other sides of malnutrition – insufficient micronutrient diversity, and diet related non-communicable diseases of overabundance.”
Crop diversity is the biological basis for all agriculture. Only about 150 crops are cultivated on any significant scale worldwide, yet they come in a vast range of different forms. To ensure productive harvests, farmers and scientists have been combining genes for different traits in desired combinations for generations.
Unfortunately, much of the world’s crop diversity is not currently being preserved. Khoury not only recommends promoting the adoption of a wider range of varieties of the major crops worldwide (three crops – wheat, rice and maize – provide two-thirds of the world’s food energy intake, yet each of these crops comes in a variety of forms) to boost genetic diversity and reduce vulnerability, but also enhancing the nutritional quality of the major crops on which people depend. Additionally important is the promotion of alternative crops – like sorghum, millet and sweet potatoes – that may be able to boost the resilience of farming.
“We need to make sure we are conserving, researching, and using genetic diversity within our globalized crops to ensure they have a lot of varieties that are genetically distinct. We also need to deal with the myriad of environmental issues associated with production of these crops in order to make their negative impacts on the environment as minimal as possible. Next, we need to make sure that the political system for sharing genetic resources between countries is working well so that people can get the diversity they need. Lastly, we need to boost education regarding nutrition, and policy directed at making more diverse and healthier food available and accessible,” says Khoury.