Improved Rice Cultivation
20% of all calories[i] consumed worldwide comes from the humble rice grain, feeding approximately 3 billion people each year. Up to 20%[ii] of all methane (CH4) emissions each year also comes from rice—representing 10%[iii] of the agricultural sector’s yearly greenhouse gas (GHG) emissions (1.5%[iv] of the global total).
While methane does not stay in the atmosphere as long as carbon dioxide, it absorbs as much as 86 times more heat[v] in the 10-20 years before it decays into CO2. Since rice is the staple food crop for nearly half the world’s population, simply growing less of it isn’t a feasible solution—especially since climate change will itself cause production declines in some of the world’s most vulnerable and rice-dependent areas. According to a 2009 report[vi] by the International Food Policy Research Institute (IFPRI)[vii], rising sea levels flooding and over-salting rice fields, water scarcity, increased pest infestations, and other consequences of global warming[viii] will reduce rice production by 10% in East Asia and the Pacific, 14% in Southeast Asia, and 15% in Sub-Saharan African by 2050.
The ultimate solution lies in finding greener methods to grow rice: both adaptation strategies to reduce production declines and mitigation strategies to reduce production emissions. Drawdown[ix] estimates that, together, these adaptive and mitigating techniques could result in reducing emissions by 11.3 gigatons while realizing $519 billion in profits for farmers. That’s why Improved Rice Cultivation[x] is #24 on its top 100 solutions to reverse climate change.
Improved Rice Cultivation: Adaptation
Contrary to popular belief, rice does not need[xi] large amounts of water to grow. Yet it has been grown in floodplains for millennia. Why? Because rice is not only the only cereal that can tolerate such submersion[xii] but also one of the few plants that can—so growing in water is a simple method of weed eradication[xiii].
However, this ancient method of rice cultivation is no longer sustainable for our climate. For one thing, the waterlogged soil in which rice is traditionally grown creates the perfect conditions for methanogenesis[xiv], or the creation of methane by bacteria consuming decomposing organic matter. The methane releases into the atmosphere, thereby causing the rise in atmospheric emissions.
Moreover, increasing water scarcity and surplus flooding will both reduce the number of viable rice-growing floodplains. Improving water use efficiency, therefore, is at the heart of any good adaptation strategy—especially since rice production comprises approximately 34-43%[xv] of the world’s yearly irrigation water totals. Land leveling[xvi] is one such method: it spreads water more evenly across a field while improving yields by reducing weeds and ensuring all of the seeds come to maturity in a timely manner.
Centers like the International Rice Research Institute (IRRI)[xvii] are looking beyond changing the way we grow rice, however; they’re looking to change the rice itself. Using the International Rice Genebank[xviii]—the largest collection of rice diversity in the world, with over 130,000 varieties—they are working to isolate and breed rice that can better handle drought, heat, flooding, and even salinity[xix].
An even more promising breeding project is the global collaboration known as the C4 Rice Project[xx], led by 12 institutions (including the IRRI) in 8 countries. C4 rice aims to take advantage of C4 carbon fixation[xxi], a more efficient version of photosynthesis. Though still in development, the hope is that C4 rice could eventually yield[xxii] up to 50% more grain than current varieties while doubling water use efficiency.
Improved Rice Cultivation: Mitigation
According to the findings of an October 2018 workshop[xxiii] run by UN FAO, the most promising mitigation strategy for reducing GHG emissions is alternate wetting and drying (AWD). The Sustainable Rice Platform[xxiv], an organization dedicated to increasing sustainability through all aspects of the rice sector, defines AWD[xxv] as “a water management practice where irrigation is applied at intermittent intervals resulting in alternating wet and dry soil conditions.” Using tools as simple as a PVC tube with holes punched in it and a measuring tape, farmers can measure[xxvi] the subsurface water in a non-flooded field and top it up when the level has dropped to 15cm below the surface. As the UN workshop noted, AWD can reduce water and fuel use by 30% and methane emissions by 40%.
However, both AWD and crop rotation[xxvii]—another mitigation strategy—can create another problem if not managed carefully: the production of nitrous oxide[xxviii] (N2O). While it comprises only a small percentage of all GHG emissions, nitrous oxide not only warms the Earth but also destroys the ozone[xxix]. The good news is that N2O primarily comes from chemical fertilizers, so improving soil quality easily provide a sustainable solution. Burning biochar such as rice straw[xxx] to use as fertilizer instead can reinvigorate the soil with nutrients while also reducing methane emissions.
As Paul Nicholson, VP of Rice Research and Sustainability at Olam International argues[xxxi], rice production creates as much methane each year as landfills (11%) and even coal mining (6%). If adaptation and mitigation strategies like those promoted by the Sustainable Rice Platform (SRP) are put into place on a large scale, however, it’s possible to reduce emissions while increasing profits for smaller farmers. “Done right,” he writes, such methods “can reduce methane emissions by up to 70 per cent and improve farmer livelihoods at the same time.” That’s the type of change we want to see.
[i] Drawdown, 48.
[xiv] Drawdown, 48.