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Methane, water, birds, pollution — how can rice farmers tackle trade-offs?

Rice fields

Flooding rice fields creates methane emissions but also provides habitat for birds. How do we reduce one without impacting the other? Image courtesy of Kellogg.

This article originally appeared as part of our Food Weekly newsletter. Subscribe to get sustainability food news in your inbox every Thursday.

Rice is the world’s most important crop. Over half of the global population relies on rice as their daily staple food; over a fifth depends on rice cultivation for their livelihood, according to the International Rice Research Institute and the U.S. Department for Agriculture. With such a massive footprint, it’s no surprise that rice is leaving its mark on the environment. 

Rice production is responsible for large amounts of methane emissions. According to the World Resources Institute, they equate to about 10 percent of global agricultural GHG emissions. It consumes 40 percent of global irrigation water. But nature also co-evolved with rice production. In particular, waterbirds such as waterfowls, wading birds and shorebirds take advantage of flooded rice fields to forage on a variety of prey, nest and stage during migration. 

This relationship is becoming ever more crucial for birds as humans continue to destroy natural wetlands. But as rice-producing countries and companies increasingly set their eyes on reducing methane emissions and water use to meet climate goals and respond to water shortages, there’s a risk that this crucial habitat within rice fields will also diminish. Is there a way to preserve the habitat while also reducing emissions? 

I won't attempt to solve the whole world’s rice puzzle in one article, but I’ll give you an example where reasonable outcomes for climate, water, biodiversity, local communities and farmers seem possible. 

A win-win-neutral for methane, water and birds 

Promising work on sustainable rice farming is happening in Arkansas and other states in the Lower Mississippi River Basin, home to two-thirds of U.S. rice fields, according to the Agricultural Research Service. 

Most rice grows in flooded fields, requiring large amounts of irrigation water. When the water covers the soil, it prevents oxygen from passing through, creating perfect conditions for bacteria that break down organic matter and emit methane — a process called anaerobic digestion. Any method that reduces water coverage, allowing soils to breathe, cuts emissions. 

[Interested in learning how we can transform food systems to equitably and efficiently feed a more populous planet while conserving and regenerating the natural world? Check out the VERGE 22 Food Program, taking place in San Jose, CA, Oct. 25-28.]

Benjamin Runkle, associate professor at the University of Arkansas, has been researching techniques to do just that. The method he’s most optimistic about is called alternate wetting and drying (AWD). Instead of continuously flooding fields, farmers let irrigated areas dry up for one or two days before pumping the next round of water. 

"Our measurements show that you can reduce methane emissions by 64 percent without impacting yield when it’s done right," Runkle said. At the same time, water use falls by 20 to 40 percent. Runkle isn’t worried about bird habitat since neighboring fields will be dried and flooded at different times, offering a mosaic of temporary wetlands for birds to use. 

Other practices that are gaining popularity may pose more considerable risks to birds. Row rice farming, also called furrow-irrigated rice, is a practice that doesn’t require flooding of fields, enabling rice farming in areas that aren’t perfectly flat and saving cost and labor. Instead, farmers plant the rice in narrow soil beds and run irrigation water through furrows between the beds. This drier type of rice farming doesn’t offer wetland-like conditions that birds typically co-existing with rice farms need to thrive. 

Farmer training and incentives have arrived 

The benefits of this technique have been known for a while, but the World Resources Institute (WRI) identified too many practical obstacles preventing the take-up of AWD in a 2014 study. 

Rice flood

A rice farmer in the background is burning the leftover stubble in their field. Image courtesy of AgriCapture.

Farmers don’t always have enough control over water to ensure good wetting and drying processes — for example, in tropical regions with heavy storms or when dealing with time-restricted water access. Done poorly, the practice can reduce yields. And finally, "farmers receive no reward for reducing emissions and suffer no penalty for increasing them," WRI concluded at the time. 

Eight years later, the good news is that at least the incentives have changed. Kellogg recently finished a three-year collaboration with The Nature Conservancy in Arkansas, Michigan, Illinois and Nebraska that provided technical and financial support to adopt conservation practices on rice fields. One aspect of the program was installing 180 irrigation pump timers on farms in Arkansas, saving over 8 billion gallons of water.

Next, Kellogg will partner with the greenhouse gas measurement startup ReGrow and Syngenta on a $2 million, five-year program in Northeast Louisiana to measure the climate impact of better irrigation, nutrient and soil health management and achieve Scope 3 emissions reductions on rice fields. In addition to providing training opportunities, the pilot financially rewards farmers for emissions reductions to make adopting new practices less monetarily risky. 

Other large food companies such as Mars have also adopted AWD, among other sustainable rice farming practices. 

What’s behind 'carbon neutral' rice?

AgriCapture, a Nashville, Tennessee-based carbon measurement startup, is embarking on a similar journey. This month, it launched a "carbon neutral" rice certification to allow distributors and restaurant groups to charge consumers a premium for rice grown according to the company’s climate-friendly rice standard. It includes practices such as AWD, more efficient nutrient management and no field burning.

Why don’t we just embrace the 50% to 80% emissions reductions as that’s an impressive and more easily verifiable achievement?

AgriCapture claims that its certified product has between 50 to 80 percent lower greenhouse gas emissions than conventional rice production in the region. This would be a substantial achievement, but it doesn’t make the rice inherently carbon neutral. Almost no food products actually are because of all the land and energy resources used to farm and manufacture them. The startup plans to offset the other half. 

I’m not a fan of such offset-based carbon neutrality claims since offsets are a tricky business. This framing can create false impressions for consumers unaware of the complexity. Why don’t we just embrace the 50 to 80 percent emissions reductions as that’s an impressive and more easily verifiable achievement?

Eventually, AgriCapture plans to create a carbon offset market based on methane and carbon reductions achieved on rice farms as a second business line in addition to certified rice. But currently, it’s still working on fine-tuning the underlying measurement, reporting and verification protocols. 

Weighing tricky trade-offs  

AgriCapture doesn’t perceive a biodiversity trade-off through its practices because there’s less overlap between the rice farming season and bird migrations in the Southwestern United States. "Thus far, we’re not aware of significant trade-offs like on the West Coast, but we’re studying the issue closely," said Sami Osman, president and chief policy officer at AgriCapture.

This might be true for fields using AWD. But as explained above, there’s potentially more biodiversity risk associated with row rice farming which the startup also encourages as part of its certification program. This issue still requires a better understanding. 

For now, what to do with leftover rice stubble in the fields after harvest is causing bigger headaches. Stubble is the straw-like lower part of the rice plant that remains on fields after harvesting the top portion containing the rice grains. When left on fields, stubble can improve soil health and provide feed for birds. But more organic matter leads to increased methane emissions in the next growing season, among other problems. That’s why farmers commonly burn leftover stubble, which, in turn, creates carbon emissions and dangerous air pollution for nearby communities. 

Runkle has studied the pros and cons of different approaches for rice stubble without coming to a straightforward best practice recommendation. "For this issue, it really depends on how you weigh the different trade-offs," Runkle said. AgriCapture is committed to reducing burning due to its social implications and is exploring alternative uses for the biomass. 

This brings us back to the often too familiar notion of sustainable agriculture: it’s complicated. There are always trade-offs involved, but they’re not an excuse for inaction. Rather,  we must think carefully about how to understand and weigh them.

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