Plastic use in industrial-scale farming is likely contributing to climate change, according to recent research from Wuhan University, China. Polyethylene (PE) is commonly used to irrigate and mulch croplands in large arid areas. However, the combination of temperature and humidity changes incurred by these methods was shown to impact rainfall cycles and increase heat and moisture at dramatic levels. 

Shujing Qin and other university researchers decided to investigate plastic’s influence on the climate since “drip irrigation under mulch” (DM) in croplands has become a typical technology, largely due to it providing suitable soil moisture and thermal conditions that can promote crop growth. 

Qin and her colleagues hypothesized that the wide distribution of DM in croplands would inevitably influence regional climate through land-atmosphere interaction processes. 

However, the dual effects of both plastic mulch cover and drip irrigation are complicated, they said, and the impacts unpredictable. 

To investigate the issue, the researchers used weather forecasting models to study five growth cycles, simulating both the use of plastic and non-plastic irrigation and mulching methods. 

Polyethylene use in agriculture is reportedly raising heat and humidity rapidly.The results show that the combination of plastic mulch and irrigation increased local temperatures by around 0.7°C and humidity by nearly 25%.

Climate change 
The findings were presented at the Frontiers in Hydrology meeting last month in San Juan, Puerto Rico. Data was taken from crop seasons (April to September) between 2014-2018 and used a model known as the Noah-MPM land surface scheme and incorporated the Weather Research and Forecasting model. 

After comparing the model simulations with and without consideration of plastic mulch or drip irrigation, the warming and wetting effects were demonstrated to “significantly” increase the atmosphere temperature by 0.7 ℃ and average humidity by 1.3 g kg. 

An increase in localized precipitation was also detected both over and outside croplands. According to the study authors, such dramatic changes can boost local rainfall and even impact the monsoon cycles. 

Plastic concerns
These discoveries add to concerns that plastics use throughout the food supply chain, including in agricultural production, contributes to climate change. 

Last year, the Food and Agriculture Organization of the United Nations called on food sectors to take action and manage practices that incorporate plastic, following the release of a report on plastic contamination in agricultural land. 

The report underscores how land used to grow food is contaminated with far larger quantities of plastic pollution, posing a significant threat to food security, human health and the environment. 

It found that in the absence of viable alternatives, demand for plastic in agricultural greenhouse, mulching and silage films will increase by 50%, from 6.1 million metric tons tallied in 2018 to 9.5 million metric tons in 2030.