The breadbasket regions of India and Pakistan are rapidly depleting their underground aquifers. In a Yale e360 interview, climatologist Sonali McDermid explains why this overexploitation, combined with global warming, is creating an urgent need to change local farming practices.
India and Pakistan are among the most heavily irrigated nations on earth, producing enough wheat, corn, and other crops to feed their combined populations of 1.5 billion. But in South Asia’s breadbasket, which includes the Punjab region, farmers have pumped water out of the ground so heedlessly for so long that scientists now estimate aquifers there could run dry by mid-century. Add to that the disruptive effects of climate change and it’s clear that South Asian agriculture is facing a perilous future.
Sonali McDermid, a climatologist at New York University, has been working to better understand this gathering threat and help find potential solutions. In an interview with Yale Environment 360, McDermid explains why India and Pakistan have the world’s most overburdened aquifers, describes how the scale of South Asian irrigation is so vast that it’s actually moderating temperature increases and altering the monsoon, and discusses why crop diversification is vital to mitigating the impacts of climate change.
“You are going to have to plant multiple crops in case you lose one,” says McDermid. “Farmers will need to experiment with crops that are heat-tolerant and drought-resistant. Diversification will need to be the leading component of adaptation.”
Yale Environment 360: Groundwater supply is critical to farming. You have said that it may soon run out in parts of India. Could you elaborate?
Sonali McDermid: South Asia is currently one of the most heavily irrigated areas on earth. Worldwide, about 70 percent of the water that we take out of the ground goes to agriculture. In the U.S., that proportion is slightly less because of efficiencies and precision irrigation techniques. In India, however, it is over 90 percent. As a result, India has by far the most stressed aquifers in the world. Eastern China is also stressed, as are parts of the southern Oglala aquifer in the U.S., which are overdrawn but not to the same degree. The U.S. is wealthy enough to have irrigation practices that are more conservation-oriented and reliable. Virtually all global groundwater aquifers are being depleted. But there is no question that India is going to be experiencing this problem first.
e360: What regions are you most concerned about?
McDermid: This is an aquifer in the western portion of the Indo-Gangetic basin, where India meets Pakistan. The major growing area there is the Punjab. It is a semi-arid region, a desert in places. Yet it is intensively irrigated. They grow rice in the summer and wheat in the winter.
A group in California looks at groundwater stores using a satellite that measures the tiniest variation in earth’s gravity fields, which allows you to detect how aquifers are changing underground. So you can get an estimate of how much water is left, and when you couple that with the rate of withdrawal and recharge, you’ve got a ballpark idea of how much longer the aquifer will last. Some estimate [in the Punjab] that aquifers will reach critical condition between 2025 and 2035. Others say by 2040. Some aquifers already have. So the situation is looking pretty dire there. That whole agricultural region, which is the most productive in South Asia, stands to fail.
e360: What can be done to save these critical groundwater stores?
McDermid: We have to understand that they are a finite resource. We need a game plan to wean ourselves off of that and into a system that’s more responsible, but I don’t think that this has been thought through. It’s not that the Indian government, and Pakistan as well, don’t know that there is a problem and the severity of it. But there is little incentive to change the system to do much about it.
Part of this issue is that there is a very cheap baseline price for electricity for farmers. It is essentially subsidized. You can pump up as much water as you want and not feel any pain from overdrawing the resource, with the result that there is very little precision irrigation. There are really no incentives to save water. The minute you try to impose a tax or raise the price for overdrawing the resource, you get a massive backlash. Once you have subsidized it for so long, the addiction is there, so what are you going to do?
e360: Other than cutting down on water consumption, are there other ways to restore depleted aquifers?
McDermid: The Indian government is experimenting with artificial recharge — digging channels to redirect rainwater into the wells so that it can be funnelled back into the aquifer. In other words, they are researching the possibility of using the same infrastructure that brings the water up from the water table to recharge it.
In central and south India, the government is also pushing community-based watershed management. For example, encouraging farmers to build farm ponds — low-tech community reservoirs that harvest rainwater for immediate use that season and also for natural recharge. Those systems work if they are married to [smallholder farming] and a more traditional view of what agriculture is meant to accomplish.
e360: Farming in eastern India depends more on seasonal rains and river water. Are there threats there too?
McDermid: Yes, more of the water in the east comes from Himalayan snowmelt and rainwater. Those glaciers have been melting quite rapidly, particularly over the last 10 or 15 years due to climate change. That can lead to flooding, made worse by really strong monsoon rains. With glacial melt, you get more water in the short term, but it’s a finite resource that is not getting replaced. So maybe you’ll have lots of water in the next 30 or 40 years, but by 2100 you’ll get deficits.
e360: Don’t many small farmers still depend on the rains? How will climate change impact these farmers?
McDermid: The consensus that is emerging right now— and this is true globally — is that, with climate change, we expect wet areas to get wetter and dry areas to get drier. And for those regions that are a combination of the two, like India’s monsoon areas, most of the models say that we will have more rainfall, but that a lot of it will come in more extreme events. So that if you tally it up over the four-month monsoon season, it looks like you’ve got more rainfall, and that might be a positive, but if it is all coming down in four or five massive events, then it is going to lead to flooding and soil erosion.
Even under normal monsoon conditions, you can go for two weeks without rainfall and then suddenly get a deluge, so that is very unpredictable. We think climate change will make this unpredictability worse. It may also tip the scales toward stronger droughts, perhaps, and longer droughts. When you talk about drought you are really talking about loss of water at depth in the soils. With water tables already in retreat in most of India, this becomes an especially severe problem.
e360: Climate clearly is going to have a big impact on farming. But one of the intriguing findings of your own research is that farming also has an impact on climate. Could you talk about this?
McDermid: In all areas with a lot of irrigation, we found that irrigation tends to cool things off. Temperatures still rise due to climate change, but less steeply. We do not see the extent of warming in the northern Indian region that we would expect given the degree of climate change that is happening. We think that is because of how much irrigation water is being added to the surface. You might think that this cooling is good, but ultimately it isn’t, because when that water runs out, you are going to suddenly feel that temperature effect and you won’t be adapted to it at all.
We also found out that adding all that surface water changes how the monsoon circulates. It actually changes the amount of water that is being taken from the tropical Indian Ocean and dumped onto the continent. It is slowing down that circulation.
e360: You are weakening the monsoon, so less rain if falling on the fields that depend on rain for growing crops?
McDermid: Yes, exactly, you’re weakening the circulation and less moisture is transported over the region. So not only are you masking the global warming response and using up all this water, but this smaller number of farmers who are massively irrigating are effectively changing the monsoon system for the other 60 percent of farmers who rely on that rainfall and are not irrigating.
Another study, which came out at about the same time as ours, showed an actual delay in onset of the monsoon, which is a big deal if you are trying to decide when to plant. The monsoon system is very complicated, so we don’t have the same degree of confidence in our climate models as we have for other regions. But it is incredibly important to include the impact of agriculture on these models.
e360: How will climate change alter agricultural productivity?
McDermid: In the Indo-Gangetic basin, climate change is going to decrease productivity of rice and wheat throughout northern India. This is primarily a temperature response. Wheat is a temperate crop. We are getting toward the limit of how hot it can get and still be grown. With the current varieties that we have now, we don’t expect them to fare very well under climate change conditions.
e360: One possible response to this might be to change the kind of crops that are being grown to ones that are better adapted to future conditions. Would that work?
McDermid: Diversification will need to be the leading component of adaptation. You have to hedge your bets. So instead of just planting rice or maize or wheat, you are going to have to plant multiple crops in case you lose one. Farmers will also need to experiment with crops that are heat-tolerant and drought-resistant, like chickpeas, pulses [lentils or beans], and coarse grains, like millet and sorghum. We can call these “orphan crops” because they haven’t gotten the kind of research and investment that the big four — maize, wheat, rice, and soybeans — have received. So there is a lot of room to traditionally breed and improve these varieties to the point where the yields become more competitive with the big four.
The great thing about these crops is that they are protein-rich and nutrition-dense, and they tend to do well in the Indian climate. The limitation is that they do not command as high a price or generally equal the yields of rice and wheat. That is changing, however, now that interest in [healthier] whole grains and pulses is becoming more in style. So the prices are improving.
e360: I understand that you are about to leave for south India, where you will be working on one such project to adapt farming to future climate conditions.
McDermid: I’ll be working with one of the heads of Tamil Nadu Agricultural University on crop models for a new management technique called the System of Rice Intensification (SRI) to see how this method will fare under anticipated climate change conditions. SRI is highly controversial within the academic literature. Some people question the reports of huge productivity gains. But the farmers in the field are seeing insane results. It employs [among other innovations] an alternate wetting/drying technique intended to keep the soil moist — rather than simply keeping the fields always flooded — which uses at least 30 percent less water than the usual way of growing rice. The state government has pushed forward with this because they know that the water table decline is a huge problem that they need to do something about.
e360: Agriculture in India is sometimes criticized for being inefficient, but you have argued that India does a remarkably good job in actually producing food for human consumption.
McDermid: Here in the U.S., about 60 percent of our maize and much of our soy is being converted into other uses that are not directly feeding people, like animal feed and biofuels. But in India, the vast majority of what is being produced is actually feeding people. Indian agriculture has very high conversion rates to food compared to other countries. The real agricultural challenge going ahead is not just upping the tonnage of production, but growing nutritious foods and creating food security for people. This is an approach that India is already well suited for.
Richard Schiffman reports on the environment and health for a variety of publications that include The New York Times, Scientific American, the Atlantic and Yale Environment 360.
This interview first appeared in Yale Environment 360 on 29 June 2017.