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A dietary shift from rice to potatoes could “notably reduce” the climate and environmental impacts of staple crop agriculture in China, according to a new study.
The research was published in Nature FoodIt examines the land and water use as well as greenhouse gas emissions related to growing four staple crops, including potatoes, maize, wheat and maize. It finds that a large-scale dietary shift towards potatoes, combined with better growing methods, could reduce the greenhouse gas emissions of these staples by up to 25%.
In addition to the emissions reductions, the researchers find that integrating more potatoes into the diet would cut the total land used for staple-crop agriculture by about 17% by 2030 – even when accounting for the country’s growing calorific need.
The authors caution that it is still uncertain whether such a significant dietary shift can occur on a large scale. And, they warn, if the higher potato production isn’t matched by domestic demand, the climate benefits will be offset by the need for rice imports from neighbouring countries.
‘Potato’s comparative advantage’
In 2015, the Chinese government implemented a national strategy known as the “Potato as Staple Food” policy. Its stated goal is to improve food security – the country’s ability to feed its own population without reliance on imports – by increasing both production and consumption of potatoes across China.
The strategy included a target to have 30% of potatoes as staples by 2020. The tuber is a staple food in some parts of China, but in most of China it is used as an ingredient in meaty or vegetarian dishes.
Many advantages over other staple crops are attributed to potatoes. They are more drought-resistant than other staple crops and more adaptable to changing climates. Potatoes also have higher levels of micronutrients like potassium and vitamin C than rice, wheat, and maize.
Although China is a major supplier of staple crops – producing around one-quarter of the world’s rice, maize and potatoes and nearly one-fifth of its wheat – potatoes only take up 6% of the nearly 1m square kilometres of cropland devoted to staple crops in the country.
The production, processing and transport of food is responsible for approximately 80% of all global food consumption. about one-thirdof human-driven greenhouse gas emission. But discussion of lowering agriculture’s impact generally only focuses on reducing consumption of beef, dairy and other red meats.
According to the report, focusing on meat can leave out other areas where climate change could reduce emissions. Prof Laura SchererAn industrial ecologist, and an environmental scientist at Leiden UniversityThe study did not include any participants. (Scherer wrote a commentary pieceThat was included with the paper. Scherer tells Carbon Brief:
“[Staples] are not really the foods with the highest impact intensities, but because we consume such vast amounts of staples, that change can still make a significant contribution.”
Since China’s policy is focused on food security and nutrition it has not been interested in the environmental consequences of large-scale dietary changes. Prof Yi Yang, an industrial ecologist at Chongqing UniversitySays. Carbon Brief speaks with Yang, one of the authors of this new study.
“Very little research has been done on ‘what’s the environmental implications of this policy?’ And why it might matter is that different crops have different environmental footprints. That’s very clear to those of us who have studied agricultural systems, but not necessarily clear to the policymakers.”
Yang and his colleagues analyzed the environmental impacts of the four staples and found that potatoes had a lower impact in many ways. Potatoes emit significantly lower levels of greenhouse gases per calorie than wheat, rice, and maize. Potatoes also required less land and used less water than any of the other staples.
The chart below shows the total land use, greenhouse gas emissions and water use for each of the four staple crops studied – from rice in the left-hand maps through to potatoes on the right – as well as the intensity of land use, emissions and water use (defined as the use or emissions on a per-calorie basis). The darker shading indicates higher totals and intensities across China’s provinces.
The paper examines three major contributors to greenhouse gases in staple crop agriculture: crop plant, fertiliser application, production and transportation.
Virtually all of the greenhouse gas emissions from staple-crop planting in China come in the form of methane emitted as a result of rice farming – more than 150m tonnes of CO2e (MtCO2e) in 2015.
Glossary
Fertiliser applicationAnother major source of agricultural emission is nitrous oxide, which has seen a 300% increase in China over the past three decades. Nearly half of 128MtCO2e which can be attributed to fertilisers can be attributed to maize farming.
Last but not least, potatoes only account 4.5% for 267MtCO2e that is emitted by the transportation and agricultural sectors. This, the researchers note, is “relatively smaller than its share of cultivated land” because potato farming does not require as much diesel and electricity as farming other staples.
Taken together, the authors write, these figures demonstrate “potato’s comparative advantage” among staple crops in lowering greenhouse gas emissions.
‘Room for improvement’
To assess the potential effects of the policy, researchers looked at three scenarios using models of crop growth, yield growth, and land use. Each scenario was built upon the previous and included the projected rise in calorific demand of staple crops (expectedly to rise by more than one-third by 2030).
The first scenario (“S0”) assumes no dietary or production changes. Researchers determined that to meet the calorific need, the amount of land needed for farming would have had to increase by approximately 17%. The researchers also found that staple crop agriculture would see an increase in greenhouse gas emissions as well as water consumption by 20% by 2030.
Under the second scenario (S1) Potato-as-Staple-Food strategies to improve potato production were accounted for. These strategies include the adoption and increase of high-yielding potato varieties and the sourcing of more potatoes for calories. They envision increasing potato yields to 125% and using potatoes as a way to bridge the gap between demand and yield for other staples. The authors estimate that this would result in a 14% decrease in greenhouse gas emissions, 10% less total land cultivation, and a 10% increase of the staples’ mean calorific yield by 2030.
For the final scenario (S2) a “strategic siting” plan was enacted on top of the other policies. This linear-regression model reallocates the crops to minimise greenhouse gas emissions while making “only slight adjustment[s]” to the planting areas of the other staples. When combined with the other changes S2 results in a 25% decrease in emissions, 17% lower land use and 19% more calorific output.
The chart below shows the projected land usage (left), emissions and water use for each scenario. Each figure shows the relative contributions of rice, wheat, maize, maize and potatoes.
One key to successfully implementing the policy will be closing the “yield gap” with other countries, Yang tells Carbon Brief. The average yield of potatoes in China was 15% below the world average in 2015 and 65% below that of “high-yield” countries such as the US, New Zealand and Belgium.
China’s potato yields lag behind high-yielding countries for many reasons. Dr Philip Kear, a plant breeder, geneticist, and a country link scientist at the International Potato CenterCarbon Brief was told by a person who was not part of the study, namely.
Potatoes are often grown on “marginal land” in China, where soils are poorer or water is more scarce, Kear explains. He also explains that China’s farming is dominated by small-scale farmers, which means that the level of mechanisation in farms is lower than elsewhere in the globe.
There is also, Kear says, “a lot of room for improvement” in selecting or breeding higher-yield varieties than those that are currently planted.
‘Dietary shift is hard’
Despite its potential environmental benefits, there are risks that the policy could lead to some of its negative effects.
Scherer states that potatoes spoil faster than other staples, such as rice. In order to be successful, she tells Carbon Brief, changes need to be made “at different stages in the value chain” – not just on the production side, but in terms of consumer behaviour, food storage and how processed food products are made.
(Another recent example) Nature Food studyIt was found that nearly one-quarter of China’s food is lost annually. This is due to poor storage and handling after harvest.
The authors warn that an increase of potato production without accompanying increases in potato consumption is dangerous. change in consumption patternsSwitching to potatoes for other staples could be detrimental. China will need to import rice from other countries if rice production in China falls.
Yang tells Carbon Brief:
“We can compare rice production in China versus rice production in those other countries. It turns out that rice production is more efficient in China than in other countries. However, the yields in these other countries are lower. So in this case, we’re kind of leaking our problem to other countries.”
Yang admits that convincing an entire nation to change their diet is not an easy task. Because of this, he says, the policy is “probably lagging behind” the targets it initially set out. Beijing News reported last yearThe country’s potato yields had only slightly increased and the consumption patterns hadn’t changed much since the policy was announced.
You can make potatoes more appealing by substituting them for other staples, such as noodles and buns, in processed foods. Yang explains:
“I do see that dietary shift is hard…But technologically speaking, you can add a little bit of potatoes into wheat [products]. And that doesn’t really alter the flavour of the noodles you eat. And that can, to some extent, help this policy or help in promoting potatoes.”
Kear tells Carbon Brief that the study is “quite useful and quite beneficial” in considering both the nutritional benefits and the environmental impacts of the Potato-as-Staple-Food policy. He also added:
“Creating that bridge between these two different stories, I think that’s really important. And it’s not the sort of thing that I’ve seen before.”
Liu, B. et al. (2021). Promoting potato as a staple food can reduce the carbon land-water impact of crops in China. Nature Food, doi:10.1038/s43016-021-00337-2.
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