Climate change threatens wild relatives of key crops

Wild relatives of plants such as the potato and the peanut are at risk of extinction, threatening a valuable source of genes that are necessary to boost the ability of cultivated crops to resist pests and tolerate drought, according to a new study released today by scientists of the Consultative Group on International Agricultural Research (CGIAR). The culprit is climate change, the researchers said.

Like many agricultural research organisations, CGIAR is worried about the effects of global warming on agriculture's capacity to provide food and fuel to growing populations. Because so many of the rural poor in developing countries depend on agriculture, the organisation has made the issue central to its research efforts, which include the development of new crops that can cope with climate change induced stresses (earlier post). But the irony is that in order to design and domesticate such climate resilient crops, plant breeders will be relying on wild relatives more than ever - that is, on the very species that are now found to face extinction.

According to the new CGIAR study, in the next 50 years as many as 61 percent of the 51 wild peanut species analyzed and 12 percent of the 108 wild potato species analyzed could become extinct as the result of climate change. Most of those that remained would be confined to much smaller areas, further eroding their capacity to survive. The study also examined wild relatives of cowpea, a nutritious legume farmed widely in Africa. It found that only two of 48 species might disappear. However, the authors predict that most wild cowpeas will decline in numbers because climatic changes will push them out of many areas they currently inhabit. The results of the study were announced on International Biodiversity Day, organized by the Convention on Biological Diversity (CBD).

"Our results would indicate that the survival of many species of crop wild relatives, not just wild potato, peanuts and cowpea, are likely to be seriously threatened even with the most conservative estimates regarding the magnitude of climate change. There is an urgent need to collect and store the seeds of wild relatives in crop diversity collections before they disappear. At the moment, existing collections are conserving only a fraction of the diversity of wild species that are out there." - Andy Jarvis, agricultural geographer at the CGIAR-supported Colombia-based International Center for Tropical Agriculture and at Bioversity International.

Jarvis, the study's lead author, says the extinction of crop wild relatives threatens food production because they contain genes for traits such as pest resistance and drought tolerance, which plant breeders use to improve the performance of cultivated varieties. The reliance on wild relatives to improve their cultivated cousins on the farm is expected to intensify as climate change makes it too hot, too cold, too wet or too dry for many existing crop varieties to continue producing at their current levels:
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Jarvis and his colleagues looked specifically at the effects of climate change on the three crops in Africa and South America. The scientists focused on the two continents because this allowed them to consider how known populations of wild plants would fare in a wide variety of growing conditions. They found the impact of climate change is likely to be more pronounced in some species than in others but that, in general, all three groups of species would suffer.

Though not apparent to the average consumer, the wild relatives of crops play an important role in food production. All food crops originated from wild plants. But when they were domesticated, their genetic variation was narrowed significantly as farmers carefully selected plants with traits such as those related to taste and appearance as well as to yield. When trouble arises on the farm - attacks by pests or disease or, more recently, stressful growing conditions caused by climate change - breeders tend to dip back into the gene pool of the robust wild relatives in search of traits that will allow the domesticated variety to overcome the threat.

In recent years, genes available in wild relatives have helped breeders develop new types of domesticated potatoes that can fight devastating potato blight and new types of wheat more likely to survive drought conditions. Wild relatives of the peanut have helped breeders provide farmers with varieties that can survive a plant pest known as the root knot nematode, and resist a disease called early leaf spot. In fact, according to the report, more than half of new domesticated peanut varieties developed in the last five years have incorporated traits from wild relatives. Cowpea wild relatives are known to be a reservoir of genes that could confer resistance to major insect pests. In the US alone, the value of the improved yield and quality derived from wild species is estimated to be in the hundreds of millions of dollars a year.

Jarvis said the vulnerability of a wild plant to climate change can depend on its ability to adapt by, for example, extending its range as warming in its native regions becomes too hot to handle. One reason wild peanut plants appear to be so vulnerable to climate change is they are largely found in flat lands and would have to migrate a long way to reach cooler climates, a predicament exacerbated by the fact that peanuts bury their seeds underground, a meter or less from the parent plant. That limits the speed at which seeds can move into more favorable climates. By contrast, plants in mountainous locations could theoretically survive by extending their range slightly up a slope, even by only a few meters, to find cooler weather. What scientists must do, Jarvis said, is identify which wild relatives are most likely to suffer from climate change and give them priority for conservation.

"The irony here is that plant breeders will be relying on wild relatives more than ever as they work to develop domesticated crops that can adapt to changing climate conditions," said Annie Lane, the coordinator of a global project on crop wild relatives led by Bioversity International. "Yet because of climate change, we could end up losing a significant amount of these critical genetic resources at precisely the time they are most needed to maintain agricultural production.

Research that identifies crop wild relatives threatened by climate change is part of a broader CGIAR effort to anticipate and blunt the effects of global warming on agriculture. In the local, national, and international policy arenas, CGIAR researchers are generating innovative options to foster adaptation to climate change. In addition, new research at CGIAR-supported centers focuses on understanding the impacts of shifting climate patterns on natural resources, such as water, fisheries, and forests, and on planning for improved management of these resources to meet the needs of growing populations as the climate changes.