Rice cultivation and ecosystem services

Rice (Oryza sativa) is a major food crop and is world’s most widely consumed staple food.

According to FAO, rice is grown in 112 countries of the world, in different climatic conditions from temperate to tropical, spanning over 160 million hectares¹⁴⁸. Rice, wheat, and maize are the main cereal crops consumed worldwide. Rice is however arguably the most popular food crop worldwide, with a unique word translation in 80 languages¹⁴⁹. However, the importance of rice in global food security as well as poverty alleviation is evident from fact that in many low and medium-income countries, rice is the major staple food as well as a source of livelihood. It is the staple food to more than half the world population and provides about 25%

of the global energy consumption. The global calorie consumption from rice has seen a marked increase in the last few decades, going from 391 to 541 kcal per person per day from 1961 to 2013. In the last decade, much of this increase has been observed in Africa but Asia still remains the region with the highest rice calorie consumption, at 780 kcal per person per day¹⁴⁸. One reason for the popularity of rice is that it is consumed as whole grains and has considerably higher carbohydrate and protein content than, for example, maize, millet, and cassava¹⁵⁰. The global rice production was 740 million tonnes in 2016, almost 90% of which was produced and consumed in Asia ^148,151. In addition to being important as a food, rice production systems provide livelihood for more than 144 million farming families¹⁵¹. With growing population, the demand for rice is increasing, especially in sub-Saharan Africa¹⁴⁹, while as the contribution of Africa to global rice production is still very low, at 3.3.%. However, the problems associated with rice are not restricted to its yield; problems of malnutrition, micronutrient deficiency, and overweight have been found common with rice consumers. On the other hand, monocropping systems enjoy a monopoly when it comes to growing rice, resulting in reduced on farm biodiversity¹⁴⁹. In this context, a diversification of rice farming systems presents itself as a timely intervention, increasing on farm biodiversity on one hand and the nutrient content of rice on the other, in addition to aiding in the nutrition of the plants^6,133,144.

35

REVIEW OF RESEARCH ISSUES

Figure 12. Major rice growing areas in the world; irrigated in light blue; rainfed-lowland in yellow; rainfed-upland in red (GRiSP, 2013)

Rice farming has traditionally been done in regions with abundant water supply, owing to its large water footprint of around 2-3 times that of upland crops. Of the total 160 million hectares under rice cultivation worldwide, 58% of the land area is irrigated while as 33% is under rainfed lowland, and the rest 9% is upland rice ecosystem (Figure 12). The produce contribution of these three different rice ecosystems are rather skewed in favour of irrigated rice, being, 75%, 19%, and 6% respectively¹⁵¹. Alone in this context, with better management strategies in rainfed lowland and upland rice systems, the total global rice production can be increased by 30%, taking the irrigated rice efficiency as the target. Irrigated rice systems employ continuous flooding of the field and are intensive monocropping systems heavily dependent on fertilizers, pesticides, and herbicides, which does not make it an ideal candidate when it comes to environmental concerns and biodiversity. For example, the nitrogen fertilizer losses have been found to be the higher in paddy rice systems, compared to wheat and maize. Nitrogen losses due to ammonia volatilization up to 60% of applied nitrogen have been reported in paddy rice systems ¹⁵².

Rice is native to Asia and Africa, the two continents that together house more than 75% of the world population. More than being a source of food and livelihood, rice has become an integral part of the cultural inheritance in different regions of the world. In Japanese, the word rice is used to mean a complete meal: ‘gohan’, while as in Kashmiri the word for cooked rice ‘batteh’

is used refer to the lunch and dinner meals. Rice is considered divine in many Asian cultures, with Indonesians referring to it as ‘Me Posop’ (Mother Rice), while as in the Philippines, rice

36

REVIEW OF RESEARCH ISSUES

is known as ‘gatas ng langit’ by the Aetas people, which translates to breast-milk from the heavens. In the South Asian region, a single variety of rice based dish, the biryani, has more than 20 regional variants, including those with beef, mutton, chicken, prawn, fish, eggs, or even vegetables. It is seen as a long lasting cultural communion of central Asian and south Asian cuisines, cutting across the different religious, ethnic, and linguistic barriers¹⁵³. In some regions, the sharing of this rice based dish called biryani on Muslim festivals of Eid Fitr and Eid al-Azha forms an important part if the celebrations. Rice cultivation can also have subsidiary purposes, as is the case in the Kashmir valley, where the rice straw is used either as livestock feed or as a packaging material for horticultural products like apples. It is almost a closed loop.

As soon as rice is harvested, the horticultural growers take away the straw as soon as the rice is shredded. This also takes mitigates some effects which rice cropping has on air quality in countries like India and China, where the burning of rice straw causes smoke that affects millions of people in big cities like New Delhi and Beijing¹⁴⁹. The issue of methane emissions is another challenge for rice farming. Methane is a greenhouse gas with a global warming potential 25 times greater than carbon dioxide. It is produced in anaerobic conditions during the flooding of rice fields. The extent of this challenge can be gauged from the fact that India and China contribute about 22% and 19% of the global methane emissions¹³¹, with rice farming contributing 11% of the global methane emissions¹⁴⁹. In this regard, better water management strategies like the alternate wetting and drying (AWD) in rice farming system have led to a decrease in the methane emissions¹⁵⁴.

Flooded rice systems also have an associated health risk, particularly in tropical and sub-tropical regions, in terms of potentially aiding the proliferation of water-borne diseases like malaria and Japanese encephalitis¹⁵⁵. In this regard, more than 137 species of mosquitoes, many of them potentially transmitting the above mentioned diseases, that breed in flooded rice paddies have been recorded worldwide^155,156. The flooding of paddies during rice farming has another potential risk, which is associated with food safety in terms of toxic residues of pesticides and metalloids/metals like arsenic, cadmium, and mercury. These can be a health risk particularly when rice forms a large percentage of the diet, which is the case with South Asia. Hence arsenic pollution is a widespread concern in the Bengal and Punjab regions of South Asia, which straddle the Bangladesh, Pakistan, and India^157–160. In this regard, it has been reported that aerobic water management in rice systems is expected to reduce the risk of arsenic uptake in the crop but could exacerbate cadmium uptake¹⁶¹. Pesticide residue in rice has been reported to result from the application of pesticides in the late cropping season¹⁴⁹.

37

REVIEW OF RESEARCH ISSUES

The productivity of rice farming systems has increased in the last 5 decades, in the Green Revolution, which was accompanied by a massive increase in the application of fertilizers and agrochemicals in intensive rice monoculture. While as this increase in productivity contributed to increased food availability, it was associated with environmental degradation and greenhouse gas emissions. The potential of rice farming systems in different ecosystem services including nutrient cycling, carbon sequestration, climate mitigation and adaptation, and biodiversity conservation is huge, which remain untapped in the absence of the necessary adjustments and changes in the way rice is grown, in the was soil, water, and plants are managed in rice farming systems¹⁴⁹.