Since the 1950s, there have been major changes in food supplies, diets, agricultural economies, and farmlands across different parts of the world. Moreover, aggressive expansion of a relatively small number of commercially valuable crops, including cereal crops such as wheat and maize, means there are now fewer crop lineages dominating agricultural lands.
Based on data from the Food and Agricultural Organization (FAO) of the United Nations, a team of Canadian researchers, led by Dr Adam Martin from the University of Toronto, assessed changes in the crop species and lineages being grown on large-scale industrial farmlands between 1961 and 2014. They observed three distinct periods:
- Little change in crop diversity from 1961 to the late 1970s
- A 10-year period of sharp diversification from the early 1980s
- Finally, a “levelling-off” of crop diversification starting from the early 1990s
The biggest increase in global crop diversity occurred in the 1980s when many different types of crops were introduced into new regions on an industrial scale. But even more interesting, they discovered that although the 1970s and 1980s marked regional increases in crop diversity, the period was also defined by increasing dominance of a small number of crop species.
So, what does all this mean? Whereas crop diversity has in fact increased, the same kinds of crops being grown but on a much larger scale. This means the same commercially valuable crops, such as soybeans, wheat, rice and corn, are now being grown on industrial farms across Asia, Europe, North, and South America ― these four crops now cover almost 50 per cent of agricultural lands. Furthermore, there is a lack of genetic diversity within individual crop species. For example, only six individual genotypes constitute around 50 per cent of all maize (corn) crops in North America.
In fact, many industrial farms are growing one crop species of a single genotype ― monocultures of cash crops ― across vast expanses of land. This increasing dominance by a few genetic lineages of crops poses huge risks in terms of susceptibility to pests or diseases. A deadly fungus could potentially knock out an entire global agricultural system. The trend is a distinct feature of the “Anthropocene epoch,” the period of Earth’s history dominated by humans. Human-induced environmental changes, as well as socio-economic factors, have played a key role in plant diversity on agricultural lands.
The authors hope this new analyses will guide new global priorities for agricultural sustainability and diversity. They suggest future initiatives should focus on the diversity of crops, and more specifically, within major crop lineages. More diversified agroecosystems with multiple crop species will be crucial to meeting sustainability targets. Moreover, policymakers will need to be more aware of the trend towards, and consequences of, increasing homogenization in global agricultural systems.