Water pollution by unsustainable agricultural practices poses a serious threat to human health and the planet's ecosystems, a problem that is often underestimated by both policy makers and farmers, warns a new report.
In many countries, the biggest source of water pollution is agriculture - not cities or industry - while, globally, the most common chemical pollutant in underground aquifers is nitrates from agricultural activity, warns the report “More people, more food, worse water? A Global Review of Water Pollution from Agriculture ”, presented by FAO and the International Institute for Water Management (IVMI) at a conference in Tajikistan (June 19-22).
Modern agriculture is responsible for the discharge of large amounts of agrochemicals, organic matter, sediment and salts into water bodies, the report says.
This pollution affects billions of people and generates annual costs that exceed billions of dollars.
“Agriculture is the largest producer of wastewater, by volume, and livestock generate much more excreta than humans. As the use of land has intensified, countries have greatly increased the use of synthetic pesticides, fertilizers and other inputs ", said Eduardo Mansur, director of the Division of Lands and Water of FAO (United Nations Organization for Food and Agriculture), and Claudia Sadoff, IWMI Director General, in their introduction to the report.
"While these inputs have helped boost food production, they have also led to environmental threats, as well as potential human health problems," they add.
The agricultural pollutants of greatest concern to human health are livestock pathogens, pesticides, nitrates in groundwater, trace metals, and emerging pollutants, including antibiotics and antibiotic-resistant genes excreted by livestock.
The new report represents the most comprehensive review of the scattered scientific literature on the subject to date, and aims to fill information gaps and design solutions at the policy and farm level in a single consolidated reference.
How agriculture affects water quality
The boom in global agricultural productivity that followed World War II was achieved largely through the intensive use of inputs, such as pesticides and chemical fertilizers.
Since 1960, the use of mineral fertilizers has increased tenfold, while since 1970 world sales of pesticides have risen from about $ 1 billion a year to $ 35 billion a year.
Meanwhile, intensification of livestock production - the world's number of cattle has more than tripled since 1970 - has seen the emergence of a new class of pollutants: antibiotics, vaccines, and hormonal growth promoters that travel through water from farms to ecosystems and the water we drink.
At the same time, water pollution by organic matter from livestock is much more widespread today than organic pollution from urban areas.
And another booming sector, aquaculture (which has increased twentyfold since 1980) is now releasing increasing amounts of fish excrement, uneaten feed, antibiotics, fungicides, and antifouling agents into surface waters.
What can be done?
Water pollution from agriculture is a complex challenge and its effective management requires diverse responses, according to the study “More people, more food, worse water? A global review of water pollution from agriculture ”.
The most effective way to mitigate pressure on aquatic and rural ecosystems is to limit the emission of pollutants at the source, or to intercept them before they reach vulnerable ecosystems. Once off-farm, repair costs increase progressively.
One way to do this is to develop policies and incentives that encourage people to adopt more sustainable diets and limit increases in demand for food with a large environmental footprint, for example, through taxes and subsidies.
At the consumer level, reducing food waste can be helpful. A study included in the report estimates that nitrogen pollution from food waste adds up to 6.3 teragrams per year.
“Traditional” regulatory instruments will also continue to be a key tool for reducing polluting agricultural products.
These include water quality standards; pollutant discharge permits; mandatory best practices; environmental impact assessments for certain agricultural activities; buffer zones around farms; restrictions on agricultural practices or the location of farms; and limits on the marketing and sale of dangerous products.
However, the report acknowledges that well-known principles for reducing pollution, such as "polluter pays," are difficult to apply to non-point agricultural pollution, as identifying the real culprits is neither easy nor cheap.
This means that measures that promote “buy-in” by farmers are essential to address contamination at the source, such as tax breaks for the adoption of practices that minimize the release of nutrients and pesticides or payments for “landscape maintenance. ”.
At the farm level, there are various best practices that can reduce the emission of pollutants to surrounding ecosystems, for example: minimizing the use of fertilizers and pesticides, establishing buffer zones along waterways and farm boundaries. , or improve drainage control facilities.
Another useful tool is integrated pest management, which combines the strategic use of pest resistant agricultural varieties with crop rotation and the introduction of natural predators of the most common pests.
In livestock activities, traditional techniques such as restoring degraded pastures and better management of animal feeding, feed additives and medicines are needed, while more should also be done with new techniques and technologies for farming. recycling of nutrients, as biodigesters of agricultural residues.
Agricultural Water Pollution: Highlights
- Irrigation is the world's largest producer of wastewater by volume (in the form of agricultural drainage).
- Globally, agricultural lands receive about 115 million tons of mineral nitrogen fertilizers annually. About 20 percent of these nitrogen inputs end up accumulating in soils and biomass, while 35 percent end up in the oceans.
- The environment is sprayed each year globally with 4.6 million tons of chemical pesticides.
- Developing countries account for 25 percent of the world's use of pesticides in agriculture, but account for 99 percent of the deaths from their use in the world.
- Recent estimates indicate that the economic impact of pesticides on non-target species (including humans) is approximately US $ 8 billion annually in developing countries.
- Oxygen depletion (hypoxia) resulting from man-made nutrient overload affects an area of 240,000 km2 globally, including 70,000 km2 of inland waters and 170,000 km2 of coastal areas.
- It is estimated that 24 percent of the irrigated area in the world is affected by salinization.
- Currently, more than 700 emerging pollutants, their metabolites and transformation products are listed as present in the European aquatic environment.
This article was originally published by the FAO Regional Office for Latin America and the Caribbean. IPS distributes it through a special dissemination agreement with this FAO regional office