Air Pollution's Impact: Are Our Crops At Risk?

Air pollution is a pressing environmental issue that negatively impacts various aspects of human society. It has been established that air pollution poses risks to human health, but it also damages the yield of food crops and their nutritional quality and safety. A study from 2014 found that in India, air pollution cut yields of wheat and rice crops by half. This is mainly attributed to ground-level ozone, a short-lived pollutant formed when nitrogen oxides, produced in combustion processes, react with air pollutants. Ozone damages crops by entering leaves during normal gas exchange, causing symptoms such as yellowing, cell injury, and reddening, which directly affect crop growth and yield.

Ozone pollution

Ozone is a short-lived pollutant, and its levels have approximately doubled since the earliest measurements in the 1870s. Despite its relatively short atmospheric lifetime, it poses a significant threat to crop production and food security worldwide. The impact of ozone pollution on crops is expected to worsen, with models predicting that ground-level ozone will continue to rise in many areas.

The relationship between ozone pollution and crop damage is complex and influenced by various factors. One factor is the concentration of ozone in the atmosphere. Increasing ozone levels can lead to more severe symptoms and a greater impact on crop yields. Additionally, the presence of other pollutants can interact with ozone, potentially exacerbating or mitigating its effects on crops. For example, studies have shown that increasing CO2 concentrations can reduce the negative impact of ozone on maize and soybean yields by decreasing stomatal conductance and, consequently, reducing ozone uptake by the plants.

The vulnerability of crops to ozone pollution also depends on their unique phenology and physiological characteristics. Human-managed crops, such as maize, soybean, winter cereal, and temperate cereal, have distinct phenologies that govern how they allocate assimilated carbon. This can influence their sensitivity to ozone and other pollutants. Furthermore, factors such as irrigation methods and regional variations can also play a role in the extent of crop damage caused by ozone pollution.

To address the challenges posed by ozone pollution to agriculture, it is crucial to implement strategies to reduce air pollution and mitigate its impact on crops. This includes adopting sustainable agricultural practices, improving air quality, and developing strategies to enhance the resilience of crops to changing environmental conditions. By tackling ozone pollution and its effects on crops, we can help ensure food security and mitigate the negative consequences on human health and the environment.

Nitrogen dioxide and nitrogen oxide pollution

Nitrogen oxides (NOx) are among the most widely emitted pollutants in the world, and they have a detrimental impact on crop growth. Nitrogen dioxide (NO2) is the primary form of NOx and is a good indicator of total NOx levels. NO2 is released into the atmosphere primarily through the burning of fuel, including emissions from vehicles, power plants, and industrial processes.

NOx has direct and indirect negative effects on crops. As a phytotoxin, NOx can directly damage crop cells and reduce yields. It also has indirect effects, such as promoting the formation of ozone (O3) and aerosols, which are harmful to crops. Ozone, a strong oxidant, enters leaves during normal gas exchange, causing symptoms like yellowing, cell injury, spots, and reddening, which ultimately reduce crop yields.

The presence of ammonia, common in agricultural regions due to the use of nitrogenous fertilizers, can interact with NOx to increase the concentration of ammonium nitrate aerosols (NH4NO3). These particles scatter sunlight, altering the radiation environment for crops and reducing their access to photosynthetically active radiation, which can negatively impact their growth.

Recent studies have utilized satellite technology to measure crop greenness and NOx levels, providing valuable insights into the relationship between NOx and crop health. These studies found consistent negative associations between NO2 and crop greenness, indicating that higher NOx pollution leads to reduced crop yields. For example, reducing NOx levels in China could increase yields for winter crops by ~25% and summer crops by ~15%.

The findings highlight the importance of reducing NOx emissions to improve crop yields, mitigate climate change, and enhance local air quality. By taking actions such as vehicle electrification, we can not only address climate change but also significantly improve agricultural productivity and food security.

Ammonia emissions from agriculture

Air pollution is a well-known environmental crisis that negatively impacts society and the natural world in numerous ways. Ozone pollution, for example, has been shown to directly harm crops and reduce yields. Ozone enters leaves during normal gas exchange, causing leaf tissue to collapse, and leading to symptoms such as yellowing, cell injury, and tiny light-tan irregular spots. Wheat, for instance, is very sensitive to ozone exposure, and in India, air pollution has caused a third of the loss in wheat yield and one-fifth of the loss in rice yield.

Agriculture, meanwhile, is a significant contributor to air pollution, especially in terms of ammonia (NH3) emissions. Livestock manure and chemicals comprise 95% of ammonia emissions, which in turn account for 58% of the particulate matter air pollution in European cities. Globally, agriculture contributes to more than 81% of all NH3 emissions, which is concerning given that NH3 is a substantial contributor to fine particulate matter (PM2.5) pollution. PM2.5 can penetrate deep into the lungs and cause long-term illnesses such as Chronic Obstructive Pulmonary Disease (COPD) and lung cancer. In 2012, about 25% of global agricultural ammonia emissions were related to international exported goods, causing 61 thousand PM2.5-related premature deaths.

Ammonia emissions from agricultural sources can cause severe health impacts and lead to economic losses amounting to billions of dollars annually. Atmospheric ammonia released from agriculture also contributes significantly to acidification. While the direct impact of NH3 on the general public health is underrepresented in scientific literature, studies indicate that it has a detrimental effect on the respiratory health of those who handle livestock. These health impacts can include reduced lung function, irritation to the throat and eyes, and increased coughing and phlegm expulsion. More recent studies have indicated that agricultural NH3 may also influence the early onset of asthma in young children.

Regulating NH3 emissions is cost-efficient and will protect human health. Effective cooperation within trade-dependent communities will achieve considerable NH3 emission reductions, and technological advancements and trade structure adjustments can be leveraged to this end.

Climate change

A recent NASA study published in the journal Nature Food found that climate change may affect the production of maize (corn) and wheat as early as 2030 under a high greenhouse gas emissions scenario. Maize crop yields are projected to decline by up to 24%, while wheat yields could potentially increase by about 17%. These changes are due to projected increases in temperature, shifts in rainfall patterns, and elevated surface carbon dioxide concentrations from human-caused greenhouse gas emissions.

The impact of climate change on agriculture is complex and far-reaching. Rising temperatures and carbon dioxide concentrations may increase some crop yields in certain places, but the yields of major commodity crops such as corn, rice, and oats are expected to be lower than they would be without climate change. Warmer temperatures and changing precipitation patterns can affect the timing of plant blooming and the activity of pollinators, leading to potential decreases in pollination. Additionally, heavy precipitation can harm crops by causing soil erosion and depleting soil nutrients.

The effects of climate change on agriculture are already being felt, and the challenges are expected to intensify in the coming decades. Adaptation and mitigation strategies, such as crop rotation and integrated pest management, are crucial for building resilience and minimizing the negative impacts of climate change on the agricultural sector.

Food security

Ozone (O3) is a key pollutant that causes yield loss in crops. As a strong oxidant, it enters leaves during normal gas exchange, leading to symptoms such as yellowing, cell injury, and reduced growth. Wheat, for example, is highly sensitive to ozone exposure, and in India, ozone and soot pollution have caused up to a 50% loss in wheat yields. Other crops, such as soybean, peanut, and cotton, are also vulnerable to ozone pollution.

Nitrogen oxides (NOx) are another significant pollutant, emitted primarily from vehicle exhaust and industrial processes. These invisible gases can directly damage crop cells and contribute to the formation of ozone and particulate matter, which further reduce crop yields by scattering sunlight away from plants. High levels of nitrogen oxides pollution have been linked to significant declines in crop yields globally.

Addressing air pollution is crucial for ensuring food security. Studies suggest that reducing emissions of common air pollutants, such as nitrogen oxides, can lead to dramatic increases in crop yields. For example, decreasing emissions in China by half could result in a 25% increase in crop yields, while other parts of the world could see up to a 10% increase.

To improve food security, it is essential to recognize the threat that air pollution poses to crop yields and nutritional quality. This requires global action, with investments from industries and governments worldwide, as well as the implementation of international agreements to reduce ozone and nitrogen oxides pollution. By addressing these air pollution issues, we can help ensure that the world has enough food to meet the demands of a growing population.

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