Crop diversity is the foundation of agriculture, enabling it to evolve and adapt to meet the never-ending challenge of sustainably producing sufficient and nutritious food for an increasing population.
For millennia, food plants have been domesticated, selected, exchanged, and improved by farmers in traditional ways, within traditional production systems (Plucknett et al., 2014). This process has been hugely accelerated and focused by scientific crop improvement, leading to such historic achievements as the Green Revolution and the steady rise in yields since then. Half of the increase in food production globally can be attributed to genetic improvement. The UN Food and Agriculture Organization (FAO, 2003) details a long list of other benefits from the development and release of improved varieties, which include a reduced need for environmentally harmful inputs such as pesticides; smaller fluctuations in yield; higher nutritional value of food crops; and increased resource-use efficiency on farms (of land, labor, etc.) that reduces the need to clear forests and cultivate on marginal areas.
Despite these undoubted achievements, much remains to be done. There are two billion people who are still malnourished, and of these about 749 million do not get enough calories (IFPRI, 2015). Meanwhile, yield gains are slowing down for some major food crops. Climate change has introduced additional, urgent challenges to farmers (Box 1). Today, modern tools and methods allow researchers to be ever more accurate and efficient in managing and manipulating genetic diversity. However, for breeders to continue delivering benefits, they require continued access to the raw materials of old.
Recognition of the significance of crop diversity to our future is perhaps most clearly epitomized by the agreement of a global treaty addressing the issue, the International Treaty on Plant Genetic Resources for Food and Agriculture (ITPGRFA), which came into force in 2004. This provides a legal structure for how crop diversity is conserved and made available for food and nutritional security. More recently, the UN Sustainable Development Goals have challenged the global community to eradicate hunger, and highlight the protection and use of crop diversity as an important means to that end in Targets 2.5 and 2.a:
- 2.5 By 2020, maintain the genetic diversity of seeds, cultivated plants and farmed and domesticated animals and their related wild species, including through soundly managed and diversified seed and plant banks at the national, regional and international levels, and promote access to and fair and equitable sharing of benefits arising from the utilization of genetic resources and associated traditional knowledge, as internationally agreed
- 2.a Increase investment, including through enhanced international cooperation, in rural infrastructure, agricultural research and extension services, technology development and plant and livestock gene banks in order to enhance agricultural productive capacity in developing countries, in particular least developed countries and landlocked developing countries, in accordance with their respective programmes of action.
Climate change and the future of crop diversity
Evidence of rising temperatures, changing seasonal patterns and increasing frequency of extreme weather events is growing. The consensus is that climate change will affect agricultural productivity worldwide. The adaptation of the agricultural sector will be crucial to ensure food security for a global population of nine billion people in 2050. Although climate change is one of the drivers of loss of biodiversity in general, crop diversity in particular is expected to play a significant role both in mitigating the adverse effects of, and adapting to, climate change. A report by FAO (2015) places crop diversity at the forefront of adaptation solutions. A key to achieving adaptation, according to Asfaw and Lipper (2012), is broadening the genetic base of crops. Simulation studies have demonstrated simple and feasible changes in farm practices that can have significant impacts on crop productivity, such as changing varieties and planting times to avoid drought and heat stress during dry periods.
The continued availability and accessibility of both traditional and improved varieties is key to future improvements in crop productivity. For example, the “scuba” rice varieties released in India, Bangladesh, the Philippines, Indonesia, Myanmar, Lao PDR and Nepal, which are able to grow in flood-prone areas and withstand submergence under water for up to two weeks, were produced by the International Rice Research Institute (IRRI) through the introduction of a gene from an Indian landrace (Almendral, 2014; CGIAR Consortium, 2012; IRRI, 2015). Such conditions are expected to become much more common under even conservative climate change scenarios.