Study shows that getting pesticide reduction policies right is critical to food security

by KeAi Communications Co.

Mimic effects of Shanghai’s policy to reduce pesticide use on the environment and food security. Credit: Yuquan Zhang

The term peri-urban agriculture is generally used to describe the cultivation of plants and livestock on the fringes of large population centres. However, factors such as urbanization, rising labor costs and a limited supply of labor put peri-urban agriculture under increasing pressure. As a result, agricultural companies are looking for ways to reduce workloads and increase returns; For example, many rely more on pesticides; A move likely to adversely affect urban environments and their residents.

In a study published in basic researchIn this study, researchers from China and the United States explored the agro-food and environmental impacts of a policy to reduce the use of agrochemicals (pesticides) introduced in Shanghai, eastern China. The policy aimed to reduce the use of agrochemicals by 20% by 2020, compared to 2015. Official statistics show that Shanghai achieved this goal with a decrease of just over 40% in pesticide use (from 4,415 to 2,644 tons). However, the area under cultivation shrank by about 25% over the same period (from 340,200 to 255,200 ha), with staple crop production declining by 18% and vegetable production by 31%. This was despite the municipality’s stated goal to keep peri-urban agriculture as intact as possible, and to ensure food security.

According to one of the paper’s authors, Yuquan Zhang of China’s Shanghai Jiao Tong University, while other factors, such as urbanization, have contributed to the shrinking of peri-urban hectares in the city, questions remain about the extent to which pesticide reduction policy plays a role. . To measure the policy’s impact, he and his colleagues worked with Bruce McCarl, a professor and specialist in GAMS (General Algebraic Modeling System) at Texas A&M University in the US. Together, they developed a new optimization model that simulates a semi-urban agricultural sector in Shanghai, rich with data on the use of crop- and region-specific inputs, including pesticides. They then explored the effects of a series of pesticide use reduction scenarios, including the Shanghai municipality’s 20% target.

The team found that imposing the current reduction policy at the county and regional levels led to significantly different results. When each county followed the 20% reduction mandate, both rice and vegetables (leafy greens and cabbage) saw a significant reduction in acreage, resulting in lower production levels. However, for regions such as Chongming (North Island) and Qingpu (West), this reduction in acreage – and use of pesticides – also had a positive result, mitigating pollution in the Yangtze Estuary and Dianshan Lake. The latter is an important source of drinking water.

Regionally, the 20% reduction mandate has led to larger reductions in peri-urban agricultural acreage in areas with high pesticide use, such as Chongming and Qingpu, and marked changes in crop mix, with rice being severely affected. The team also found that adopting machines to more precisely apply the pesticides had a positive effect on the model’s results.

Zhang concludes, “While it is currently impossible for Shanghai to feed itself, given its massive population (24.87 million people) and limited land availability, the population’s strong appetite for leafy vegetables means that the city needs to be able to produce sufficient supplies in order to meet About 85% of this is in demand. But the downside is that vegetables usually contain much higher amounts of agrochemicals than field crops. The crop mix is ​​dominated by non-cereals in Shanghai, which often use pesticides heavily.”

“Runoff from this peri-urban agriculture has been a major contributor to water pollution. Our study indicates that when a policy of quantity-use control is implemented at the regional level, rather than ‘one-size-fits-all’ at the district level, both can obtain improved agricultural nutritional effects. and improved environmental outcomes, rather than the sharp trade-off we see so often.”

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more information:
Yuquan W. Zhang et al, Operating Reducing Pesticide Use Within Peri-Urban Food Security Boundaries, basic research (2022). DOI: 10.1016 / j.fmre.2022.04.003

Provided by KeAi Communications Co.

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