On the horizon: Options for cultivating rice as climate changes and salinity increases

For the latest post in our series looking at developing issues in the world of conservation, Erica Fleishman explores food security and the production of rice in a changing climate.

Rising sea levels, drought, and agricultural irrigation have increased the salinity of soils in both coastal and inland areas. Mineral deficiencies and toxicity may accompany local increases in salinity. As a result, scientists aim to develop salt-tolerant strains of staple crops, including rice (Oryza sativa). The Consultative Group on International Agricultural Research (CGIAR) estimated that in 2009, nearly 20% of global human per capita energy came from rice and noted that global demand for milled rice may increase by more than 25% from 2010 through 2035. It may be possible to genetically modify rice to reduce salt stress while maintaining yield. Recent selection experiments in eastern China and Dubai also generated excitement. In these experiments, strains of rice that were irrigated with dilute seawater yielded at least 6000 t / ha, which is generally comparable to commercial yields in many of the world’s major rice-growing regions. If the outcomes of the experiments are transferable to extensive areas, rice production may become feasible on saline and alkaline soils that currently do not support cultivation of rice. Breeding of salt-tolerant rice also may facilitate continued cultivation in areas where salt intrusion is projected, such as the Mekong Delta, where salt levels are affected by variation in precipitation and the El Niño climate oscillation.

Riche terraces - Japan
Rice terraces, Japan

However, it is unclear whether selection or development and cultivation of salt-tolerant rice will increase global food security. For example, increases in air temperature lead to heat stress in rice, both above ground and in floodwaters and soils, and are likely to reduce yields. At least some physiological responses to salinity and to high temperature are different, so adaptations to one stressor may not mitigate fully for reductions in yield. Furthermore, the salinity of sea water is about ten times that of water used in the experiments, so appropriation of freshwater will still be necessary. Ecological effects of changes in land use that might be associated with commercial cultivation of salt-tolerant rice, especially in coastal areas, have not been explored fully. For example, salinization may accompany commercial cultivation of salt-tolerant rice in areas that have not previously been used for agriculture. Moreover, research on salt-tolerant rice in salinized areas of Myanmar suggested that gender is associated with preference for different varieties, which can have different yields in addition to different heights, grain lengths, number of tillers, and other morphological features.

Potential investments in development of salt-tolerant rice by Huawei Technologies, a major Chinese information and communications technology company, have been reported and disputed. Nevertheless, other commercial investments may support expanded experiments in Dubai and elsewhere. CGIAR reported that both population growth and increases in per capita consumption of rice in the Middle East are contributing to the rise in regional demand, whereas per capita rice consumption in many Asian countries is projected to decrease as income increases.

A Horizon Scan of Emerging Issues for Global Conservation in 2019 is available to read in Trends in Ecology and Evolution.

Read more from our ‘On the horizon’ series here:

Introduction  by Bill Sutherland and Nancy Ockendon

Climate change and the capacity of Antarctic benthos to store carbon by Nathalie Pettorelli

Deforestation expansion of plantations and infrastructure threaten Indo-Malay island species by Nafeesa Esmail and Alice Hughes

Plastic alternatives – the ecological impact is not always clear by Becky LeAnstey

Mercury rising by Colleen Seymour

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