• Crop burning is the deliberate burning of a farm's field, to make way for a new crop.
  • Some farmers believe burning is the most effective and cost-efficient way to clear land and fertilize the soil.
  • Crop burning is a source of black carbon, contributing to air pollution which kills around 7 million people a year.

People around the world are bracing for what has become known as the season of smog.

With autumn around the corner, many countries are entering agricultural crop burning season, where farmers burn their fields to make way for a new crop, sending up plumes of toxic smoke.

These large areas of agricultural lands set ablaze every year are contributing to the air pollution that, according to the World Health Organization (WHO), kills 7 million people a year including 650,000 children.

“Improving the quality of the air we breathe is absolutely necessary to our health and well-being,” says Helena Molin Valdés, Head of the United Nations Environment Programme (UNEP)-hosted Climate and Clean Air Coalition Secretariat. “It is also critical to food security, climate action, responsible production and consumption – and fundamental to equality. In fact, we can’t talk about the 2030 Agenda for Sustainable Development unless we are serious about air quality."

Black carbon

Many farmers consider agricultural burning the most effective and cost-efficient way to clear land, fertilize soil and prepare it for new plantation. However, these blazes and the wildfires that spread from them are the world’s largest source of black carbon, a threat both to human and environmental health.

Improving the quality of air we breathe is absolutely necessary to our health and well-being.

—Helena Molin Valdés, Climate and Clean Air Coalition Secretariat

Black carbon is a component of PM2.5, a microscopic pollutant that penetrates deep into the lungs and bloodstream. PM2.5 increases the risk of dying from heart and lung disease, stroke and some cancers, causing millions of people to perish prematurely every year. In children, PM2.5 can also cause psychological and behavioural problems. In older people, it is associated with Alzheimer’s, Parkinson’s disease and dementia. And because air pollution compromises respiratory health, it may also increase vulnerability to COVID-19.

Black carbon is also a short-lived climate pollutant, meaning that, although it exists only for a few days or weeks, its impact on global warming is 460–1,500 times stronger than carbon dioxide.

A better way

Slash and burn agriculture takes a heavy toll on Madagascar’s natural wealth.
No-burn alternatives almost always save the farmer money.
Image: Global Environment Facility

Ironically, far from stimulating growth, agricultural burning actually reduces water retention and soil fertility by 25 to 30 per cent, and thus requires farmers to invest in expensive fertilizers and irrigation systems to compensate. Black carbon can also modify rainfall patterns, especially the Asian monsoon, disrupting the weather events necessary to support agriculture.

“Burned lands actually have lower fertility and higher erosion rates, requiring farmers to overcompensate with fertilizer,” says Pam Pearson, Director of the International Cryosphere Climate Initiative, which has worked with farmers globally to introduce fire-free cultivation.

“The no-burn alternatives, such as incorporating stubble back into fields or even planting right through the stubble, almost always save the farmer money.”

Pearson notes that changing the long-established habit of burning agricultural waste will require education, awareness-raising and capacity-building for farmers. It is a lofty undertaking, but the impacts would be considerable and far-reaching. Reducing air pollution from farms in Northern India, for example, could prevent increased flooding and drought caused by black carbon accelerating the melting of Himalayan ice and glaciers – a life-changing outcome to the billions who depend on rivers fed by those mountains.

Worldwide effort

The Climate and Clean Air Coalition works in countries and with regional networks to promote alternatives to field burning. In India, for example, it provides farmers with information and assistance to access alternatives to crop fires, using satellites to monitor fires and track their impact, supporting policy interventions, subsidizing farmers and ultimately turning agricultural waste into a resource.

In Punjab, the coalition and the UN Food and Agriculture Organization (FAO) are looking at ways to turn the crop residue that would otherwise be burnt into a renewable fuel source. Creating a circular economy for such waste provides farmers with more income and reduces air pollution.

Countries around the world are working to reduce air pollution. That drive will be front and centre on 7 September, the International Day of Clean Air for blue skies, which is designed to spur global action against dangerous particulates.

With an eye on global warming and food security, a project called the Koronivia Joint Work on Agriculture is mainstreaming farming into the United Nations Framework Convention on Climate Change. The next round is to take place at the UN Climate Change Conference (COP26), this year.