Terres et eaux

Agriculture: cause and victim of water pollution, but change is possible

Agriculture, which accounts for 70 percent of water withdrawals worldwide, plays a major role in water pollution. Farms discharge large quantities of agrochemicals, organic matter, drug residues, sediments and saline drainage into water bodies. 

Diagnosis, prediction and monitoring are key requirements for the management of agricultural practices that mitigate these harmful impacts on water resources, according to a new publication released today. The executive summary of Water Pollution from Agriculture: A Global Review, A Global Review, a precursor to the launch of the full report next year, highlights that water pollution is an increasing global concern that damages economic growth and the health of billions of people.

According to the report – from the Food and Agriculture Organization of the United Nations (FAO) and the Water, Land and Ecosystems (WLE) program led by the International Water Management Institute  – exploding demand for food with high environmental footprints, such as meat from industrial farms, is contributing to unsustainable agricultural intensification and to water-quality degradation.

This growth in crop production has been achieved mainly through the intensive use of inputs such as pesticides and chemical fertilizers. Today, the global market in pesticides is worth more than USD 35 billion per year. Some countries – such as Argentina, Malaysia, South Africa and Pakistan – have experienced double-digit growth in the intensity of pesticide use.

“In most high-income countries and many emerging economies, agricultural pollution has overtaken contamination from settlements and industries as the main factor in the degradation of inland and coastal waters,” said Eduardo Mansur, Director of FAO’s Land and Water Division. “Acknowledging we have a problem is the first step to finding solutions.”

The area equipped for irrigation has more than doubled in recent decades, from 139 million hectares in 1961 to 320 million in 2012, transferring agricultural pollution to water bodies.

Meanwhile, the total number of livestock has risen from 7.3 billion units in 1970 to 24.2 billion units in 2011.  Livestock production now accounts for 70 percent of all agricultural land and 30 percent of the planet’s land surface. 

Additionally, aquaculture has grown more than 20-fold since the 1980s, particularly in Asia. Total global aquatic animal production reached 167 million tonnes in 2014. Fish excreta and uneaten feeds from fed aquaculture diminish water quality. Increased production has combined with greater use of antibiotics, fungicides and anti-fouling agents, which may contribute to polluting downstream ecosystems.

Nitrate from agriculture is now the most common chemical contaminant in the world’s groundwater aquifers. Aquatic ecosystems are affected by agricultural pollution; for example, eutrophication caused by the accumulation of nutrients in lakes and coastal waters impacts biodiversity and fisheries. Despite data gaps, 415 coastal areas have been identified experiencing eutrophication.

Meanwhile, about one-quarter of produced food is lost along the food-supply chain, accounting for 24 percent of the freshwater resources used in food-crop production, 23 percent of total global cropland area and 23 percent of total global fertilizer use.

As a result of all of the above, 38 percent of water bodies in the European Union are under pressure from agricultural pollution. In the US, agriculture is the main source of pollution in rivers and streams, the second main source in wetlands and the third main source in lakes. In China, agriculture is responsible for a large share of surface-water pollution and is responsible almost exclusively for groundwater pollution by nitrogen.

This pollution poses demonstrated risks to aquatic ecosystems, human health and productive activities. For example, high levels of nitrates in water can cause “blue baby syndrome”, a potentially fatal illness in infants. 

In Organization for Economic Co-operation and Development (OECD) countries alone, the environmental and social costs of water pollution caused by agriculture are estimated to exceed billions of dollars annually.

And, over the last 20 years, a new class of agricultural pollutants has emerged in the form of veterinary medicines (antibiotics, vaccines and growth promoters), which move from farms through water to ecosystems and drinking water sources. 

But there are ways to deal with these issues, the report finds.

Policies and incentives

The right policies and incentives can encourage diets that are more sustainable and healthy and so moderate increases in food demand. For example, financial incentives such as taxes and subsidies on food and coupons for consumers positively influence dietary behavior. Food losses and waste should be reduced to minimize the waste of resources and associated environmental impacts. 

A broader range of measures policy measures addressing other areas has also evolved. Recent analyses suggest that a combination of approaches (regulations, economic incentives and information) works better than regulations alone. 

On-farm responses

On-farm practices in crop production, livestock and aquaculture are crucial for preventing pollution. In crop production, management measures for reducing the risk of water pollution due to organic and inorganic fertilizers and pesticides include limiting and optimizing the type, amount and timing of applications to crops. 

Establishing protection zones along surface watercourses, within farms and in buffer zones around farms, have been shown to be effective in reducing pollution migration to water bodies. 

Also, efficient irrigation schemes will reduce water return flows and therefore can greatly reduce the migration of fertilizers and pesticides to water bodies 

Off-farm responses

The best way of mitigating pressures on aquatic ecosystems is to avoid or limit the export of pollutants. Simple off-farm techniques, such as riparian buffer strips or constructed wetlands, can cost-effectively reduce loads entering surface water bodies.

Buffer strips are a well-established technology. Vegetated filter strips at the margins of farms and along rivers are effective in decreasing concentrations of pollutants entering waterways. 

Integrated systems in which crops, vegetables, livestock, trees and fish are managed collectively can increase production stability, resource use efficiency and environmental sustainability. Integrated farming ensures that waste from one enterprise becomes inputs to another, thereby helping to optimize the use of resources and reduce pollution.

Before any action, to design cost-effective measures for preventing pollution and mitigating risks, managers, planners and lawmakers need to know the state of aquatic ecosystems, the nature and dynamics of the drivers and pressures that lead to water-quality degradation, and the impacts of such degradation on human health and the environment.

“This report lays out many ways to reduce pollution through tried-and-tested methods, as well as emerging options,” said Mansur. “We now have to step up the pace of our efforts to meet the goal of the 2030 Agenda to provide a more-sustainable and fairer world for all.”

Download the Executive Summary Here >>