Climate change will impact the way we grow our food. How can we tackle future threats to our crops?
Can we really feed 9 billion people?
“How can crops thrive in a warmer world?”
That’s the estimated global population in the year 2050.
It should be possible, but things are looking tricky – especially when we also factor in the climatic instability caused by global warming.
Food security in peril
These are some of the current threats to food security and what we could do about them.
Demands for water for human use and to grow crops are increasing, but changing weather patterns because of global warming means we can’t rely on enough rain falling where we need it.
So how can crops still thrive in a warmer world?
Back in the 1990s, a simple experiment was devised to test how grapes were affected by signals from their roots in dry soil.
Vines were grown with their roots split. They were given plentiful water through one half of their roots, but the others were not watered.
The effect was astounding: The fruit yield was the same, but only 70 percent of the water was used.
If plants reduce their water loss, they can’t take up as much carbon dioxide for photosynthesis and thus growth.
However plants direct their resources to their fruit and seeds to protect the next generation.
This works well for us humans: As fruits and seeds are frequently the edible parts of the plant, so-called partial root drying often sustains crop yields.
Pathogens – anything that causes disease, such as a virus, bacterium or fungi – have always been a feature of agriculture, and there are a number of current causes for concern.
For example, current varieties of a wheat rust fungus have no resistance and are spreading from Africa to the Middle East.
Bananas are also an important staple crop for hundreds of millions of people in Africa, but a new variety of the fungus that causes Panama disease has devastated plantations of previously-resistant varieties and is spreading from Southeast Asia.
Crops often already have resistance mechanisms that could stop a new pathogen in its tracks.
What they lack is a defense-trigger mechanism.
Plants use “R proteins” to detect invading pathogens and trigger their defense responses in a way analogous to our antibodies.
An R protein from another variety of the same species, or sometimes even from another plant species resistant to the pathogen, can be copied into a vulnerable crop by genetic engineering, where it will identify the pathogen and activate defenses against it.
In the long run, it may be possible to defeat evolving pathogens by equipping crops with a barrage of different R proteins so that evading one way of detecting them is not enough.
Water used for irrigation isn’t pure H2O, and often it contains minerals including sodium and calcium salts.
When a crop takes up the water, these substances are left behind in the soil, just as mineral impurities in tap water cause your kettle to fur up.
Salts accumulated in soil now affect crop yields in many parts of the world.
Most plants exist in symbiotic relationships with fungi.
For example, rice inoculated with fungi from plants from a salty coastal area became salt tolerant, and tomato plants receiving fungi from plants growing in the warm, geothermic soils in Yellowstone National Park could then withstand root temperatures of 50℃.
Crops depend on fertilizers to get the bumper yields required to feed the current 7 billion people and their livestock.
Nitrogen, one of the three main “macronutrients” plants need, is generally taken from the atmosphere and converted into usable ammonia fertilizer by reacting it with hydrogen at high temperatures.
This is known as the Haber-Bosch process.
The industrial process was a vital part of the Green Revolution in the mid 20th century, which boosted agricultural production across the world.
The chemists responsible, Fritz Haber and Carl Bosch, have been said to have saved more human lives than any other individuals, although their process was developed for explosive manufacturing in Germany during World War I.
Scientists sometimes accidentally cause harm while attempting to do good, but this is a spectacular case of the opposite.
“The Green Revolution wasn’t actually green.”
The process requires temperatures of up to 500°C and pressures equivalent to those 3km below the surface of the ocean.
This means large factories, carbon emissions and more global warming.
Additionally, excess fertilizer can cause ecologically destructive algal blooms and chemical fertilizers adversely affect soil microorganisms. The Green Revolution wasn’t actually green.
No more fertilizer?
So how to wean ourselves off fertilizer? The most important of our staple crops are cereals such as wheat, rice and maize, which originated as domesticated grasses.
Together they contribute more than 60 percent of global calorie intake. These crops are annual species, growing from seed to produce the next generation in a single season before dying.
Because of this, fields have to be plowed and reseeded each year, and cereal root systems never penetrate deeply into the soil. This is why they need fertilizer.
However, not all grasses are annuals. Many prairie grasses are so-called perennials that don’t die after producing seed and are productive even without additional fertilizer.
Their roots grow deeper and deeper each year and can tap nutrients and water far beneath the soil surface.
What if we could make perennial versions of these key crops?
It would be a much more environmentally-friendly way to grow food.
This article originally appeared on the World Economic Forum and was republished with permission.
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