As the climate becomes increasingly temperamental, wild relatives of today's crops are increasingly threatened. Although they may bear little resemblance to today's cultivated crops, the wild cousins play an integral part in breeding programs and maintaining yields.
When pests or diseases attack a crop, breeders can often find an answer in the genetics of wild relatives. If such genetics are lost to climate-fueled extinction, solutions to crops' future problems could vanish as well.
A recent study by the Consultative Group on International Agricultural Research (CGIAR) warns that if climate trends continue — whether too hot, cold, wet or dry — 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.
And those that survive will likely be hemmed into much smaller areas, making them more vulnerable.
“Results indicate the survival of many species of crop wild relatives — not just wild potatoes, peanuts and cowpeas — are likely to be seriously threatened even with the most conservative estimates regarding the magnitude of climate change,” says the study's lead author, Andy Jarvis, an agricultural geographer at the CGIAR-supported, International Center for Tropical Agriculture.
“There's 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.”
Jarvis and colleagues studied the effects of climate change on three crops in Africa and South America: wild potatoes, wild peanuts and cowpeas. This approach allowed them to consider how wild plants would fare in a wide variety of growing conditions.
Jarvis, who has been in his current job for seven years, recently spoke with Delta Farm Press from his California office. Among his comments:
On Jarvis' work…
“I work from the offices of the International Center for Tropical Agriculture, one of the big gene banks. A large seed collection for beans, cassava and forages is here.
“I work in the unit that deals with agricultural biodiversity and analyses. I do a lot of the modeling about how species are distributed and what threats to biodiversity there are.”
On findings from the latest study…
“We've been working on this for about five years, although not necessarily in the context of climate change. We were interested in how the wild species of crop relatives were doing, how they're distributed in the wild, how threatened they are and prioritizing their conservation. That involves a bit of promoting of their conservation so they're taken into account and mainstreamed into conservation strategies.
“The recent study was the icing on the cake — to see what the threat of climate change is presenting to these species. The truth is these species are already threatened from land-use changes and exploitation. Now, we're showing climate change is a lasting impact that could cause considerable extinctions.
“We worked on wild peanuts, wild potatoes and wild Vigna (a genus containing many beans), which includes cowpeas. We looked at these in both Latin America and Africa. What we found is a high percentage of these wild species are predicted to go extinct.”
On the need to preserve wild relatives…
“Over the history of evolution, these wild relatives have shown how important they are. They've developed resistances to many pests and diseases. They can have novel adaptations to drought stresses, for example. Or, in wild potatoes, they may have adapted to prevent frost damage. So there are very many interesting traits that could prove useful for improving today's crops.
“There's a classic example of this in peanuts. There are a number of new varieties out that use traits from wild relatives to increase resistance to root knot nematode, a serious problem for cultivated peanuts around the world.
“The wild relatives are becoming more and more useful. Biotechnology allows us to select for needed traits much more easily.
“Historically, the wild relatives have been undervalued. Partly that's due to their use in breeding.”
On ensuring a viable population of the wild relatives…
“Among the next steps would be to look carefully at threats to each species and identify the most appropriate conservation strategy. Normally, that means a complementary approach.
“On one hand, there's the need for a safety net, a collection, so the seeds can be held and grown out as needed. So we'd identify the sites we expect to find the species under the greatest threat, collect the seed and place it in a gene bank. We do collecting through partners.
“The second strategy is to look at conserving the plants in situ, in the wild. That's a much more valuable, preferable approach. That way the species can continue to evolve.
“If we can put in place management strategies in existing protected areas, or argue for the creation of new protected areas, then we're doing well.”
Why Africa and South America?
“We focused on the two continents to look at three specific, very different environments. And we wanted to use three very different species with different biologies. We wanted to cover a variety of gene pools and geographic regions, although the message is valid for other crops and regions. We could do a similar analysis for wild barley, wild wheat, wild chickpeas or others.
Regional differences? What you find in the savannah versus a mountainous region?
“That's precisely why we chose these species. Wild potatoes are typically found in the mountains from the southern tip of the Andes into the United States. Wild peanuts are in the savannah. And we looked at wild Vigna, which is widely distributed across Africa.
“What's very interesting is we found much of this boils down to how well these threatened species might migrate. As the climate changes, the range these species is adapted to moves, as well. The question becomes how far do these species have to move to stay within their preferred range?
“What we've found in mountains is that distance is much shorter. When temperatures rise, the plants might just need to move up the mountain 100 meters to a suitable habitat.
“The wild peanuts were most heavily affected by climate change. That's partly because they're already in lowland regions — already harsh environments with very strong drought and high temperatures. Climate change typically knocks them out of their adaptation range. They'd have to move thousands of kilometers to find a climatic niche in the future.”
Did the study cover what could come after the climate change? More disease and pests?
“That's something for the next iteration. It's very difficult to get to grips with that. But, yes, many scenarios for climate change show there will be greater pest and disease pressures.”
On the reception of the report by breeders…
“Breeders are well aware these wild species are under threat in the wild and under-conserved in gene banks. They know these things.
“Really, the most important audiences for this study are the national institutions that have the capacity to follow up and go collect these species. This study will help them target and prioritize their collecting strategies.
“Second, this is a message with implications that should contribute to a change in policy. This thing needs looking at because, on the whole, climate change is creating more and more problems. Our crops will suffer and this will have very serious economic implications unless something is done now. This is just more evidence that there needs to be a policy shift.”
On findings and surprises…
“There have been a number of studies done in other wild species that predict similar levels of extinction. This was in that expected range.
“What was surprising to me were the differences in the extinction rates between the crop-wild relatives.
“The peanuts, for example, were hit very, very hard. Whereas, the Vigna species in Africa — where climate change will mean the most suffering — weren't as badly bothered because of a broad adaptation. For me, the unexpected outcome was in the great variability between these wild species we looked at.”