Atmospheric drought, an under-researched crop stress, is reducing yields globally, meaning urgent action is needed to protect food security, according to new research from institutes including the University of Minnesota.
Senior author Walid Sadok explained that climate change was undoubtedly behind the trend.
The paper, called Systemic effects of rising atmospheric vapor pressure deficit on plant physiology and productivity, has been published in Global Change Biology. It involved a large-scale analysis covering 50 years of research and 112 plant species.
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The team found that various plant species, including wheat, corn, and even birch trees, take cues from atmospheric drying and anticipate future drought events.
They re-programme themselves to become more conservative, to grow smaller, shorter and more resistant to drought, even if the drought itself does not happen.
Plants become less able to perform photosynthesis and produce seeds, leading to a decrease in productivity.
“This is a new stress nobody was thinking about. Productivity will decrease more than we thought”
“As we race to increase production to feed a bigger population, this is a new hurdle that will need to be cleared,” says Walid Sadok. “Atmospheric drying could limit yields, even in regions where irrigation or soil moisture is not limiting, such as Minnesota.
“This is a new stress that nobody was thinking about. Productivity is going to decrease more than we thought because of this stress.
“You can be spoon feeding your plants with water nutrients, so there’s no shortage of water, but if they are exposed to a drier atmosphere they start growing more slowly.
“They delay their reproductive windows. Trees become shorter. They change the internal piping, so to speak, which is the vascular system that allows water to move from the roots or soil into the atmosphere.
“This is something only plants can do, it is why they have more genes than us.
“Regarding the conditions, overall the trend we found shows less precipitation. Even in those areas where you have plenty of water in the soil, atmospheric dryness will probably negatively affect productivity. So, this is a problem for everyone, not already environmentally challenged countries.
“We look at outliers within a species, champions, and we can breed varieties that are more tolerant”
“This trend started from the late 90s, early 2000s. Of course in terms of climate change, the release of carbon dioxide into the atmosphere started earlier. Things didn’t react immediately because the earth is a huge mass to warm up. The system is complex enough that you see temperatures rising, then you see water levels rising and then you see atmospheric dryness going up. So, it’s one of those delayed effects of climate change.
“One of the immediate solutions is that we can breed for this. Within a single species of corn, wheat, legumes, you can have huge varieties that respond to atmospheric drying. Like us, you can have athletes and super athletes whose abilities don’t seem human, but those outliers are part of our collective DNA.
“So we look at those outliers within a species, champions, and we can breed varieties that are more tolerant.
“It’s about being a little bit smarter, finding ways to make crops more resilient but also less demanding in terms of inputs, like water, nitrogen, pesticides, etc.
“If you look at it one way it sounds scary but it has been scary since humans settled and decided to do agriculture.
“Every solution has to be contextualised. What works well in certain environments is not at all as predictable in other environments.
“In some places, we need to be more aggressive because it’s about food security”
“In places like the US where we have a lot of infrastructure, a lot of money frankly, we can be reasonably optimistic about having some better adapted varieties within the next decade or so.
“In other places, we need to be more aggressive because there it’s about food security in the strictest sense. When we talk about the nexus between politics, business and science in those places, I think there are a lot of opportunities to really move the needle forward.
“One simple thing to be done is to leverage natural genetic resources. There are wheat varieties that have been developed by Middle Eastern farmers, for example, for hundreds if not thousands of years.
“These are not super productive, but they’re really resilient.
“The seed market sometimes results in un-adapted varieties being almost imposed on farmers in environments where there’s a lot of risk.
“If you adopt those varieties on favourable years you will have really nice yields, sometimes you can even export. On bad years which happen maybe once every two years, which is a very high frequency, you lose like 50 per cent, 70 per cent of your yield, you so you have this very oscillated system. Any reasonable economist will tell you that’s not good.
“Regardless of where you are, assume this is happening to you”
“Science, technology, genetics can help to absorb this oscillation. More robust local production is very important. Encouraging local breeding programmes, developing locally adapted varieties. Most of these local varieties have very unique qualities, probably they are richer in protein and they are more nutritious.
“The bottom line is that we should be doing something about the trend we have identified. Regardless of where you are assume this is happening to you. People need to start reacting right now.
“But an optimistic outlook is also important. Working with social scientists in the humanitarian area is relevant because it’s not going to be a top down approach. A co-construction effort needs to happen, otherwise there’s a huge bottle neck in adoption.
“You need social science to understand how to progressively change farmer habits or behaviour, work with farmers. There’s a human factor.
“The other message is there are a lot of economically sound opportunities to generate wealth, to create meaningful jobs.
“Developing locally adapted varieties is one of those. Local breeding companies managed by local farmers with university educated young folks. Also, developing models on a local level. Look at historical data in the location of interest and use available climate models to predict what type of temperatures and atmospheric dryness will happen locally. So really you can empower local breeding programmes.
“It’s a win-win in terms of mitigating but also in terms of doing work that develops local economies.”
