This grain is one of the most widely eaten and highly threatened foods on the planet. Rice. It's a vital crop that feeds 3.5 billion people. It provides 20% of the world's calories. And it's a beloved staple of kitchens in countries from India to Italy. "Mamma mia!" But rice had a problem
that almost everybody ignores. Climate change is bad for rice. But rice is also bad for the climate. So do we have to kiss sushi, stir fries and curries goodbye or can we grow rice better? The first thing to understand is that rice is not like other crops. It was domesticated on three separate continents and has fed hungry civilizations across Asia, Africa and South America for thousands of years. Across the world, rice farmers
learned a common technique. They found the grain grew better
in wet soils than dry ones – and when they flooded fields,
they found weeds died but rice survived! That's why, even today, farmers keep fields flooded for months at a time. And here's what makes rice one of the dirtiest crops we grow. When bacteria in the soil break down dead plants, they usually release carbon dioxide. But in a flooded field where air can't get in there's less oxygen to react
with the carbon in the organic waste. That encourages the growth of bacteria that make a gas called methane instead. Methane doesn't last as long in the air as CO2, but it heats the planet 80 times more over a 20-year-period. What's more, the nitrogen in the fertilizer means paddies spew out nitrous oxide, which is 270 times more powerful than CO2. So how bad is rice for the planet? If you look at emissions per kilogram, rice is not as bad as the same amount of eggs, cheese or meat, though it is worse than other carbs. But if you look at total emissions it's a completely different story. We eat so much rice that it heats the planet more than basically everything else but the beef industry. So a bowl of rice itself isn't worse than a pork sausage or a block of cheese. But the sheer amount we eat means fixing rice could save a ton of pollution. The most obvious solution is to drain fields so bacteria don't make more methane. Across East Asia, farmers
have drained their paddies in the middle of the growing season to save water. And as water has grown even scarcer, they're trying a method of alternatively wetting and drying the paddies. "So, the rice still has enough water at its roots, but you're just reducing the amount of water that's sitting around, and that reduces the amount of methane that's being produced in the fields." This is Marci Baranski, a scientist cleaning up rice in Thailand. "So in principle, it's a simple technology and doesn't require any special machinery. You literally put a perforated tube or even a soda can into the ground, which shows you the level of the water below the surface. And so you let the field drain naturally until it reaches that level, which is the bottom of the roots of the rice. And then that's when you flood the field again." This simple trick has halved methane emissions on some farms and it saves water that's growing increasingly scarce. But if intermittent flooding is so great, why aren't farmers growing all rice in this way? The first reason is changing habits and policies. In Bangladesh, a recent study found that alternate wetting and drying has failed to take off because farmers don't have an economic incentive to save water. They pay for the area of land they irrigate, not the amount of water they use, so they see little benefit from using less. The second problem is nitrogen. Fields where the water content
varies over the season produce more nitrous oxide than fields that are either wet or dry. That's because wetting and drying creates cracks in the soil that let in oxygen, which reacts with nitrogen to form nitrous oxide. Using less fertilizer can help avoid this, but scientists are still trying to work out how to stop it entirely. The third problem is that you get less rice if the soil gets too dry. One review found yields fell 5% in fields that were repeatedly drained and flooded. It doesn't sound like a lot but it can be life-changing for farmers. A simple way to fix this is by wetting and drying fields only sparingly, instead of flipping from bone dry to soaked. This means you get the same amount of rice but can still save one quarter of the water. Another solution is to boost
yields with other techniques. One approach is a System of Rice Intensification that has spread around the world. It creates a better environment for growing rice by doing four things. Farmers take only the healthiest seedlings to plant in the paddies. They space them further apart so they don't fight over nutrients. They wet and dry fields. And they churn soil to kill weeds. Smallholder farmers have started using the technique, which has gained support from governments in countries from India to Indonesia. The extra yield from healthier plants more than compensates for the losses from drainage. But it takes time and money to teach farmers. It also can't just be parachuted in: farmers need to adapt the practice so it works on their farm. But growing rice cleanly
is just one piece of the puzzle. The hundreds of millions of
tons of farm waste is another. And the way farmers usually deal with it is toxic for both people and the planet. There are only a couple of useful things you can do with rice straw, like turning it into animal feed or using it in packaging. "But, these are very small scale applications for rice straw. What you need to do is somehow use it to make either energy or some viable product that can be used on the farm itself." This is Anubhuti Bhatnagar, a scientist trying to work out what to do with the straw. "In India there is only two weeks between the harvest of rice straw and the next crop cycle. So within two weeks, you have to both collect it, transport it and use it somehow. Otherwise it will degrade." That tight window means the cheapest option for the farmers is to just burn it. Stubble burning is a practice that blasts pollutants into the air and chokes entire cities. The biggest problem here isn't even climate change – it's the deadly gases that everybody breathes. One way to fix this is to spray the fields with bacteria that break down the straw into mulch. Farmers can mix this into the fields to improve the fertility of the soil – which is great for crops. But breaking down the straw takes three full weeks. Until scientists can speed up the process, it'll eat into the planting time. Another option is to take the straw out of the field and heat it at high temperatures to turn it into a dry mass called biochar. Biochar is a porous, carbon-rich substance that can be mixed into topsoil. It has tiny holes that trap water and fertilizer in the soil for longer, reducing the amount farmers need to add. And it can even be chucked into power plants to replace dirtier fuels like coal. It's a promising idea. But setting up a biochar industry is tricky because the quality of rice straw varies so much. That makes it hard for the owner of a reactor to actually sell biochar with consistent properties. "When we're talking about any industrial process or any commercial process, we need to ensure uniform quality. Like every day that I run the reactor, I need to get the same quality of product out." But if researchers iron out these technical kinks, they could create a powerful alternative to burning rice straw. For now though, breaking it down on the farm may be the more promising solution. The final piece of the puzzle is to just grow less rice. And the most powerful solution we're not using is dirt cheap: Reducing the amount of rice we waste. Only 76% of the emissions from food come from food that's actually eaten. 15% is from what's lost on the way to our tables and 9% of the waste from restaurants and kitchens. It's not even limited to rich countries, either. In Indonesia and Vietnam, for instance, about 10% of rice grown is lost or wasted after the harvest. So as well as tightening up supply chains, the UN wants to halve the amount of food people and restaurants dump by the end of the decade. But changing people's behavior is tough and few governments even seem to be trying. A more radical idea to grow less rice is to swap it for cleaner and
sturdier crops – like potatoes. Now this might sound absurd: the richest countries, who did the most to heat the planet, telling poorer ones to ditch a staple crop at the heart of their culture while they dine on steaks and cheeseburgers... But there are other reasons governments in Asia might want to encourage other crops. "Rice, wheat and corn – staple foods for Chinese people for thousands of years. But now a new entrant: the humble potato." In 2015 China launched a national strategy to make potato a staple crop – in a bid to improve the country's food security. Potatoes are more resistant
than rice to floods and droughts. Eating lots more of them could
cut greenhouse gas emissions from China's staple crops by a quarter. But so far, it hasn't really worked. Potato yields are only up a little and diets haven't shifted. Subsidies might help – but they do more for the planet if they were pumped into less radical changes like meat alternatives. Fixing rice is a no-brainer: it keeps the planet from heating. It saves dwindling water supplies. It cuts air pollution. And it makes the global food system more secure in the face of increasingly extreme weather. What makes the task easier is that – unlike meat or dairy – there's no big rice industry lobbying against change and holding back progress. The challenge instead is to change the habits and traditions of farmers around the world – who can afford neither lower yields nor more extreme weather. "Climate change affects everything, including the food we eat. So if you liked what you saw and want more videos evaluating solutions to get us out of this mess, then click subscribe, we've got new videos coming out every Friday for you."
