California rice grower Tom Butler is on a fact-finding mission. For four years, he has been applying two new practices to his Sacramento Valley fields. He is dry seeding crops to reduce irrigation and draining the fields earlier when preparing for harvest. In doing so, Butler conserves water, but he may be helping the environment another way: by reducing greenhouse gas (GHG) emissions, such as methane and nitrous oxide.

Butler is participating in a pilot program funded by the Environmental Defense Fund. Though it’s too early to measure, he has seen promising signs from the project.

“We’ve had good results with yield and water conservation, which really was our goal,” says Butler. “We’re happy that greenhouse gases go down as a result of that, but they weren’t the initial reason why we do that.”

Greenhouse gases are only a minor concern because California rice production emits relatively little of the potentially harmful gases. According to a study by a group of researchers that includes Chris van Kessel from the University of California, Davis, increasing methane emissions by rice agriculture – a natural result of climate change – are a growing concern on the global scale. The study found that a rise in carbon dioxide (CO2) in the atmosphere has increased the intensity of GHG produced from rice cultivation by more than 31 percent. 

“Together, higher carbon dioxide concentrations and warmer temperatures predicted for 2100 will lead to a doubling of the amount of GHG emitted per kilo of rice produced,” says van Kessel. “However, it is also very likely that in 90 years from now, significant progress will have been made in reducing GHG from rice fields.”

Of the global GHG accumulation for all sectors, 0.001 percent comes from California rice fields, according to data compiled by Louis Espino, UC Cooperative Extension rice farm advisor for Colusa County. An inventory by the California Air Resources Board (ARB), meanwhile, puts agriculture at 7 percent of the total statewide GHG emissions. Of this amount from agriculture, rice cultivation accounts for just 1.8 percent. In other words, rice contributes about a tenth of 1 percent of the GHG emissions from California’s agriculture sector – nearly the same as the global contribution.

“It’s such a new issue I don’t think much has been done in that area,” says Espino. “Right now UC Davis is doing the research, doing the modeling, trying to understand what goes on in the soil.”

Espino points to high yields – with greater efficiency and higher production – per acre as the main reason why California rice GHG intensity is low. Little land is devoted to rice cultivation (540,000 acres) when compared to the large rice exporting countries across Asia. With less land in production, less opportunity is available for production of methane gas.

Cap and trade

Recognizing the severity of the state’s total GHG emissions, the California legislature enacted a cap and trade law under the 2006 Global Warming Solutions Act. Though the trade market is not yet structured for the rice industry, researchers and growers, like Tom Butler, have taken proactive steps that may lead to carbon offsets available on the market for capped sectors.

“In fact, rice is now the first agricultural protocol to be adopted under what’s called the American Carbon Registry,” says Paul Buttner, environmental affairs manager for the California Rice Commission. A rice protocol has also been approved by the market registry Climate Action Reserve and soon, he hopes, by the California Air Resources Board.

California rice emits an estimated three to four tons of GHGs per acre per year, with a potential reduction of half a ton through costly control measures. This translates to just $5 an acre on the current carbon trading market.

If less land were put into rice production, less habitat would be available for migratory birds. Since 1990 rice growers have reduced post-season burning by 80 percent, allowing rice straw to instead decompose. By flooding the fields in winter, growers accelerate the breakdown of this resilient straw. This, notes the Western Hemisphere Shorebird Reserve Network, has encouraged more than 400,000 shorebirds annually to return to the Sacramento Valley – with millions of other migratory birds visiting the Central Valley via the Pacific Flyway – in search of nesting sites and to feast on the grain left behind after harvest. Rebuilding wetland reserves for the amount of rice acreage flooded each winter would run an estimated $1.5 billion, with yearly maintenance costs around $30 to $40 million.

Environmental leader

For other environmental concerns, the California rice industry has often led the response. Since the 1980s, changes in irrigation management and other practices have led to a 98 percent reduction in pesticide residues entering public waterways from rice fields, according to Cass Mutters, also a UC Cooperative Extension advisor for Butte County.

“Right now the ongoing water monitoring program is paid for by the rice industry itself. So they’re policing themselves,” says Mutters. The reduction is attributable to an ongoing grower education program and to stringent water holding regulations that provide time for chemicals to break down before the water leaves the field.

Along with water quality, the rice industry supports an air quality monitoring network that enables the ARB to model how many acres can be burned without exceeding federal air quality standards. 

“So rice growers realize that being environmentally sensitive is part of their responsibility and they’re actually putting the dollar on the table to cover a lot of these costs,” says Mutters.

Ultimately, the industry has taken these efforts to reduce greenhouse gas emissions while the percentage of emissions from California rice cultivation on the global scale is too low to be alarming. While California rice is a valuable crop within the U.S. and a major commodity in California, it represents 0.2 percent of the world’s rice acreage. Nonetheless, management practices tested in California could lead to massive GHG reductions, if applied globally.

“UC researchers will continue to collaborate with the rice industry to address important issues such as air and water quality and its impact of yield,” says van Kessel, “which is significant for California’s economy and contributes to global food security.”