New research claims climate and land-use change will greatly lower rice yields by the end of the century.
Rice yields in the Philippines and Vietnam could decline 30% by the year 2100.
“Because of a temperature increase in the Philippines and Vietnam of up to 4°C, rice yields can be kept steady only at the expense of natural vegetation, which would likely reduce native habitat and biodiversity,” say the authors of the new study published in the journal Environmental Research Letters.
The researchers created simulation models (from 2000-2099) comprising seven study areas to arrive at these conclusions. For climate change, two future scenarios were considered: a 1.5°C-2°C trajectory and a 3°C-4°C trajectory. For land use change, three future scenarios were chosen: low rice conversion, high rice conversion, and one based on global economic trends. The scientists then determined how these models affected ecosystem services—benefits humans gain from the environment—provided by rice ecosystems.
Along with rice yields, the study predicted a climate-induced decline in two other ecosystem services: carbon storage and carbon sequestration.
Carbon storage, a plant’s ability to store carbon long-term, is estimated to decrease 15% by the end of the century. This loss of storage capacity is caused by less photosynthesis (absorbing carbon) and more respiration (releasing carbon). Just like the proteins in our bodies, proteins driving photosynthesis slow down at high temperatures.
Land-use change also worsened carbon storage. As land is converted to rice fields, forests are decimated and the stored carbon is released
The outcome of climate and land-use change on carbon sequestration is more nuanced, though. Sequestration can be thought of as a carbon scale: photosynthesis as a weight on one side and respiration as a weight on the other side. Overall, by the end of the century, respiration outweighed photosynthesis—carbon sequestration declined by 12%.
However, when land-use change was added in high amounts, carbon sequestration shot up. To rapidly grow, crop plants—like rice—imbibe large amounts of carbon, while releasing little. This is in contrast to older forests, which absorb less carbon as their growth slows.
Another ecosystem service, irrigation water, was projected to increase by 10%-20%. Despite this, rice yields still markedly decreased. Although more land-use somewhat offsets the effects of climate change on yields in the early 21st century, those offsets are later negated in the latter half of the century by rising temperatures.
As rice is a staple food for 3.5 billion people—nearly half of the world’s population—declining yields could have prodigious consequences. Rice cultivation is the main source of income for over 100 million households across the world.
Cultural identity is at stake, too. These ecosystems shape farmers’ values, spiritual experiences, and connection to the natural environment.
“Locally specific land use policies and development plans have to consider more than the availability of rice,” the researchers say. “Cultural services to maintain future human wellbeing must be included.”