Not good: Research shows irrigation has limited ability to save crop yields from drought

I’ve written before about my view that we need to get away from food production that relies on seasonal weather patterns, and some new research has been published that reinforces that opinion. In particular, the capacity for irrigation to mitigate the effects of drought:

“Plants have to balance water supply and demand. Both are extremely critical, but people overlook the demand side of the equation, especially in the U.S. Corn Belt,” says Kaiyu Guan, principal investigator on two new studies, Blue Waters professor in the Department of Natural Resources and Environmental Sciences and the National Center for Supercomputing Applications at Illinois.

The demand Guan refers to is atmospheric dryness, often expressed as vapor pressure deficit (VPD). The drier the air, the more moisture is sucked out of pores, or stomata, in plant leaves. Plants have to open stomata to take in carbon dioxide as their food, but if they sense the atmosphere is too dry, they’ll close pores to avoid drying out. Keeping stomata closed too long leads to reductions in photosynthesis, plant growth, and grain yield.

The kicker? Plants shut down stomata due to atmospheric dryness even when there’s an adequate supply of moisture in the soil.

“If you only consider rainfall and soil moisture, which is how most people think about drought, that’s mostly describing the supply side. Of course if you have low soil moisture, plants will be stressed by how much water they get. But the supply is often pretty sufficient, especially here in the U.S. Corn Belt,” Guan says. “However, the demand side from the atmosphere can also severely stress plants. We need to pay more attention to that drought signal.”

Guan’s two recent studies used multiple technological approaches, including field measurements, various sources of satellite data, hydrological model simulations, and government crop yield statistics. The first study, published in Agricultural and Forest Meteorology, used data from seven sites across the Corn Belt to conclude VPD accounts for nearly 90% of the changes in crop stomatal conductance, a proxy for drought stress, and approximately 85% of changes in gross primary productivity, a measure of productivity.

“By comparison, soil moisture typically accounts for 6-13% of these measures for corn and soybean, and up to 35% when considering time lag effects,” says Hyungsuk Kimm, doctoral student in Guan’s group and the study’s lead author.

In the other study, published in the Journal of Hydrology, Guan’s team focused on grain yield. Yield depends on many factors related to water cycles, but the researchers found that VPD explains the biggest proportion of variability in crop yield and also provides the earliest warning for yield loss when comparing with other water cycle metrics and traditional drought indices.

“This led us to build a new drought index integrating VPD, soil moisture, and measures of evapotranspiration, which can account for more than 70% of yield variation. Our index outperforms all the existing drought indices,” says Wang Zhou, postdoctoral researcher in Guan’s group and the study’s lead author.

Guan adds, “In these two studies, we tried to understand the demand side of drought from two major angles, one using eddy covariance data which measures landscape water and carbon use very accurately — the gold standard — and the other leveraging satellite data and model-simulated hydrological variables correlated with regional yield,” Guan says. “In both, we demonstrate VPD is more important than soil moisture to explain the crop drought response in the U.S. Midwest.”

The researchers are continuing to look into things like how to breed more drought-resistant crops, but I honestly feel that that is too little, too late. There are limits to how drought-resistant you can make any given plant, and from what I can tell there are not predictable limits on how severe droughts and heat waves may be getting in the coming decades. If we want to avoid food shortages, we should be working on indoor food production. That could be the various techniques mentioned in my recent post on climate change and agriculture, or it could be something like seawater greenhouses, but in any case, there is zero question that the world’s food production is vulnerable to droughts, and there is zero question that droughts and heat waves are going to continue getting worse.

In my opinion, there is no greater threat to the United States in the coming decades than the degree to which our food production relies on the stability of a climate that is now so unstable that it’s warming at a rate that may be unprecedented in the history of life on this planet.

I continue to believe that if we take urgent action, we can survive what’s coming, and even build a better human society in the process, but we do need to act, and the longer we continue to delay, the higher the death toll will become.

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“…rather luxurious caves with highly-efficient facilities…”

A lot of discussion about solving “the energy problem” of climate change focuses on changing sources of energy, and finding ways to store energy. This makes a lot of sense. Fossil fuels are an incredibly efficient way to store and transport chemical energy that can be easily converted into heat and motion. If we’re going to stop using fossil fuels, that means finding an alternate means to store and transport energy, and while battery technology is improving, it’s got a ways to go. I think we’re well past the point at which we should be working much harder to roll out the technology we currently have, but it’s good that research continues.

That said, the question of efficiency in the use of that energy is one that can sometimes fall by the wayside. Most of it seems to revolve around the red herring of individual action, with things like LED lightbulbs, more efficient appliances, and better energy habits like turning off lights, and using less heat or cooling. It turns out that changing how we use power can dramatically reduce how much we need to maintain a “modern” standard of living.

The study led by the University of Leeds has estimated the energy resource needed for everyone to be provided decent living standards in 2050 — meaning all their basic human needs such as shelter, mobility, food and hygiene are met, while also having access to modern, high quality healthcare, education and information technology.

The findings, published in in the journal Global Environmental Change, reveal that decent living standards could be provided to the entire global population of 10 billion that is expected to be reached by 2050, for less than 40% of today’s global energy. This is roughly 25% of that forecast by the International Energy Agency if current trends continue.

This level of global energy consumption is roughly the same as that during the 1960s, when the population was only three billion.

The authors emphasise that achieving this would require sweeping changes in current consumption, widespread deployment of advanced technologies, and the elimination of mass global inequalities.

However, not only do the findings show that the energy required to provide a decent living could likely be met entirely by clean sources, but it also offers a firm rebuttal to reactive claims that reducing global consumption to sustainable levels requires an end to modern comforts and a ‘return to the dark ages’.

The authors’ tongue in cheek response to the critique that sweeping energy reform would require us all to become ‘cave dwellers’ was: “Yes, perhaps, but these are rather luxurious caves with highly-efficient facilities for cooking, storing food and washing clothes; comfortable temperatures maintained throughout the year, computer networks — among other things — not to mention the larger caves providing universal healthcare and education to all 5-19 year olds.”

The study calculated minimum final energy requirements, both direct and indirect, to provide decent living standards. Final energy is that delivered to the consumer’s door, for example, heating, electricity or the petrol that goes into a car, rather than the energy embedded in fuels themselves — much of which is lost at power stations in the case of fossil fuels.

The team built a final energy-model, which builds upon a list of basic material needs that underpin human well-being previously developed by Narasimha Rao and Jihoon Min.

The study compared current final energy consumption across 119 countries to the estimates of final energy needed for decent living and found the vast majority of countries are living in significant surplus. In countries that are today’s highest per-capita consumers, energy cuts of nearly 95% are possible while still providing decent living standards to all.

Study lead author Dr Joel Millward-Hopkins from the School of Earth and Environment at Leeds said: “Currently, only 17% of global final energy consumption is from non-fossil fuel sources. But that is nearly 50% of what we estimate is needed to provide a decent standard of living for all in 2050.”

“Overall, our study is consistent with the long-standing arguments that the technological solutions already exist to support reducing energy consumption to a sustainable level. What we add is that the material sacrifices needed to for these reductions are far smaller than many popular narratives imply.”

I’ve long maintained that the path to a sustainable human society that responsibly manages its effects on the rest of the biosphere continues in the direction of scientific and technological advancement. There are a few reasons for that. The first is that I don’t believe it’s possible to convince most people to give up the comforts and safety of modern technology. Primitivist visions of the future might appeal to some people, but for most, it’s a non-starter. Second, I think it’s too late for that.

In the years I’ve been active on the issue of climate change, I’ve repeatedly encountered the attitudes discussed in the quote above – If I care so much about the problems of modern technology, why don’t I just go live in a cabin in the woods somewhere. Obviously this is a bad-faith argument, and it misses a lot of points, but I’ve always been personally annoyed by it because I’d love to do that. I’d love to live in a small hut by the sea, keep a goat and some chickens, and grow most or all of my own food, while writing science fiction and fantasy. That future is no longer possible. Even leaving aside the money required to set up and maintain such a lifestyle in a capitalist society with mandatory participation, I can’t do it because the climate is changing. My crops will fail from heat waves or droughts.. My seaside home will flood. That kind of agrarian lifestyle may have been possible in the world in which my parents were born, but that’s not this world.

For us to survive in this world, we need to be able to artificially cool our homes and workplaces. We need to be able to withstand increasingly unpredictable and powerful weather. We need to shift to food sources that don’t rely on the seasonal weather patterns and stable ecosystems of the past. We desperately need to transcend the boundaries of nation-states to work together in solidarity to face the existential threat of climate change.

The press briefing for this research that I quoted above ends with a vital statement.

Study co-author Professor Narasimha Rao from Yale University said: “This study also confirms our earlier findings at a global scale that eradicating poverty is not an impediment to climate stabilization, rather it’s the pursuit of unmitigated affluence across the world.”

Not only do we live in a post-scarcity world, where poverty is created and maintained as a matter of policy for the benefit of the ruling class, but in order to survive what’s coming in our lifetimes, we need to end that way of doing things. We must work together for the material betterment of all, if we’re to have any shot of survival.