More than half of the world's population consumes paddy as a staple food. Paddy fields cover approximately 170 million hectares and account for nearly a quarter of cereal crop cultivation globally. The world's population is expected to exceed 10 billion by 2050. If current post-harvest losses and food waste patterns continue, this would necessitate a one-third increase in global food production.
Climate colonialism is evident in the assertions made by numerous international organisations that 'rice is harming the environment' and 'rice is twice as harmful as previously thought'. There is no 'Big Rice' lobby to oppose the promotion of potatoes and other crops as an alternative staple to rice in Asia because paddy cultivation is primarily carried out by smallholder farmers. It is impossible to achieve sustainability by focusing only on net-zero emissions. Sustainable agriculture prioritises long-term productivity while minimising both environmental and social impacts that are unfavourable.
Extending beyond a carbon tunnel vision
The largest constructed wetlands on Earth are lowland paddy fields that seasonally flood. During the growing season, the anaerobic conditions in flooded fields are ideal for methane production, making them a contributor to global agricultural emissions. However, they have a higher capacity for soil organic carbon (SOC) sequestration than uplands.
In warmer climates, double- or triple-cropping systems are possible due to favourable climatic conditions in terms of temperature, precipitation, and other factors, as opposed to single- or double-cropping systems in cooler climates. As a result, SOC differences between paddy fields and uplands are greater in warmer climates than in colder climates.
Since the microbial transformation of plant residues in paddies is inhibited by anaerobic conditions, paddy soils accumulate more carbon in the form of plant-derived carbon than upland soils. Furthermore, flooding in paddy fields reduces SOC's sensitivity to a variety of climatic conditions. However, the carbon that has been stored may be lost due to changes in land use. In tropical climates, removing the flooding stage will result in significant carbon dioxide emissions from paddy soils as plant-derived carbon becomes available for microbial decomposition.
When paddy land is converted for other uses or flood frequency or intensity is altered, anaerobic respiration in paddy soil changes to aerobic respiration, and the rate of organic carbon mineralization increases tenfold. In cooler climates, the transition from paddy to upland has little effect on surface SOC stocks, but in warmer climates, it is likely to result in a significant loss of SOC. Protecting tropical and subtropical paddy systems is thus crucial.
Monsoons irrigate 80% of Asia's paddy fields. The alternating aerobic and anaerobic conditions brought on by floods and drainage during paddy cultivation enable effective microbial activity for the breakdown of organic debris and chemical residues. Rainwater is collected by paddy fields, which slowly drain to boost groundwater recharge. The standing water also prevents weed growth. By building paddy field dams and providing farmers with financial incentives, existing rice fields can be upgraded to function as flood mitigation infrastructure.
Paddy fields help to reduce soil erosion while also providing other ecosystem services including recreation and tourism. Fish and prawns can also be bred in them. Flooded paddy fields reduce the air temperature in areas where the wind blows directly from the field. Recognizing agriculture's multifunctionality is vital to its sustainability.
The biodiversity of the paddy agroecosystem is also influenced by the neighbouring water sources, fallow fields, farmlands, wetlands, and forests. A paddy field is a home to both migratory species conditioned to use rice as an annual crop and resident species accustomed to continuous rice farming in the same field. Due to the scarcity of natural wetlands in the world today, paddy fields are critical to the life cycles of many different wetland organisms. To manage paddy field agroecosystems sustainably, agroecologists and conservation biologists must work together to develop strategies that use biodiversity as an organising principle.
A systems approach in ecosystem conservation
Sustainable use and equitable conservation require integrated management of physical and biological resources. The natural capital of the paddy agroecosystem must be recognised holistically.
Switching from a bowl of rice to a bowl of mashed potatoes can never be the solution to reducing the ecological degradation of farmlands in Asia. On the contrary, an absence of systems thinking will be a downward spiral to environmental chaos and social unrest.
(Ann Rochyne Thomas is a bio-climatic spatial planner and founder of the Centre for Climate Resilience - a sustainability and climate change advisory.)
