India’s heatwave again highlights just how seriously extreme weather conditions threaten our ability to put sufficient nutritious food on all our plates. Headlines have focused on the human deaths – at least 2,500 at last count – but a heatwave can hit farming too. There are reports of scorched crops and livestock struggling to survive in temperatures of 40C or more. More than 17 million chickens have died so far, leading to rapid price increases.
What is not yet so clear is the effect of the current extreme conditions on crop yields and food supply later in the year. Crop scientists the world over are grappling with these questions – but can their work can really protect food security in the face of extreme climate challenges?
Extreme weather like that India is experiencing at the moment presents crops not just with extreme high temperatures, but also with drought. Of those linked challenges, drought is the easier of the two to deal with, at least at first sight. Farmers have been watering crops for millennia, but the scale of modern food production means agriculture is already a major user of freshwater resources in many parts of the world, competing with the demands of other industries and, of course, the need for adequate safe drinking water.
Irrigation water has to come from somewhere. That might be from lakes and rivers, perhaps diverted into reservoirs, or from groundwater. However all these sources are already under intense pressure, both in India and elsewhere – California is another very topical example.
Taking too much water from those sources has knock-on effects on rivers and wetlands. Over-extraction of groundwater can also allow sea water to seep in to groundwater, reducing its quality for both people and crops. So, while irrigation has a part to play, we have to recognise that water is a limited resource in much of the world, and that we need to use it as efficiently as we possibly can.
Poorly managed irrigation, especially using poor quality water, also contributes to the build-up of salts in agricultural soils. Ironically, trying to deal with the heat and drought can introduce a third threat to food production, saline soils. So, beyond irrigation, what options are there?
GM vs heatwaves
Producing crops that can grow and yield in the face of high temperature, drought and salty soils is a top priority for crop scientists around the world.
Some employ modern genetic modification techniques to produce new crop varieties that can cope with these harsh growing conditions. There are teams around the world manipulating specific crop traits to do this, but the problem lies in those three words: “specific crop traits”.
GM has given us the means to modify single genes. Whatever your views on GM crops, there is no doubt that changing a single gene can produce crops that are resistant to a herbicide or attack by a particular pest. But heat, drought and salinity damage crops through a range of mechanisms. You may be able to change a gene to reduce one type of damage but that’s just one piece in a complex puzzle.
You could look to combine different traits. Improving root growth for instance can allow a crop to access water deeper in the soil. Leaves might be modified to reduce water loss or to reflect more light to reduce the heat load. Or plant chemistry might be changed, for example to help the plant deal with cellular damage caused by extreme heat, drought or salinity.
Combining these and other possible modifications might ultimately produce much more robust crops. For example the International Rice Research Institute (IRRI) is using these approaches to develop drought resistant rice, but that remains a huge technical challenge and is certainly no “quick fix”.
This “bottom up” combination of specific characteristics actually has many parallels with traditional breeding – crossing existing crop varieties to combine good characteristics and then screening thousands of offspring under challenging growing conditions to identify those that have improved performance. Again, that’s possible, and is being done now to produce new heat resistant maize varieties for Asian farmers, but it certainly isn’t a quick or easy process, even with modern methods that can accelerate traditional breeding.
Crop scientists are also looking to alternatives to these genetic methods. For example, we now understand how roots perceive drying soil, and then communicate that to the shoot to induce water-saving changes in the leaves. That understanding has led to new water-efficient irrigation that delivers “more crop per drop”, an approach that can be deployed at very low cost even by small farmers.
Understanding how plants regulate their response to heat stress and salinity also provides routes by which we might intervene to boost these responses – a little like boosting our immune system to help prevent disease rather than cure it. There is a great deal of promising research here, and hints that a new generation of anti-stress agrochemicals may not be too far away, many based on plant’s own natural defence systems.
Increasing crop losses are one symptom of the weather extremes which are becoming ever more commonplace. Advances in crops and agricultural methods help reduce the severity of that symptom, but we have to be realistic about the limits. Even the best application of crop science can’t make the world’s staple crops able to cope with every extreme of weather. Simply dealing with the symptom is useful, but it can’t be a substitute for a cure to the underlying cause. While we can’t simply link the current heatwave in India with climate change, the message surely isn’t all that hard to read. Let’s hope that’s a message which is heard in Paris this Autumn.
Nigel Paul receives funding from the UK Biotechnology and Biological Sciences Research Council.
Authors: The Conversation