05 Dec 2017 Story Ecosystems

Tackling the growing challenge of soil pollution

By Thomas Hammond, Senior Officer for Land at the UN Food and Agriculture Organization

Soils are the foundation of our food system, and the basis for many of the ecological processes on which we depend. The conservation and sustainable management of soils is essential to our goals of eliminating food insecurity and tackling climate change, while at the same time maintaining the resilience of ecological processes that support life on land.

But soils are under pressure from population growth, pollution and higher demands for land uses other than food production. About a third of our global soils are degraded. Against this backdrop, over the coming decades the Food and Agriculture Organization (FAO) predicts a roughly 50 per cent increase in food production by mid-century to meet growing global demands.

Notwithstanding the advances made in organic agriculture, this growth in production will likely entail similar increases in the use of plant protection products such as pesticides. This has led to growing concerns about the effects of these inputs on the environment and soil health. In particular, the World Health Organization estimates that over 3 million people are hospitalized due to pesticide poisoning every year, resulting in a quarter of a million premature deaths.  

The Food and Agriculture Organization predicts a roughly 50 per cent increase in food production by mid-century to meet growing global demands.

It is relatively easy to undertake a cost/benefit analysis of the use of pesticides, fungicides, and other plant protection products as they relate directly to food production outcomes. It is much more difficult, however, to estimate the externalities associated with their use, particularly for major ecosystem processes such as soil biodiversity or water quality, and for human health.

For instance, filtering and buffering of substances in water, and the transformation of contaminants, is one of the essential regulating services provided by soils. Soils are also alive with micro-organisms, bacteria, and micro-fauna which are responsible for much of the nutrient cycling processes essential for food production and terrestrial carbon stocks – and we know relatively little about long-term exposure (or mixture) effects of agro-chemicals on soil biodiversity or people.

More research is coming to light, however, on the effects of various classes of plant protection products – and earthworms and bees in particular have been increasingly heavily studied. Glyphosates represent a widely used group of pesticides, and their use effects on earthworms and other soil invertebrates under different conditions are increasingly well understood: On average the decreasing use of pesticides is beneficial for earthworm communities.

Neonicotinoids represent another popular group of agrochemicals. Recently published research found at least one of five tested compounds in the neonicotinoids family in 75 per cent of sampled honeys from around the world. While this research confirms the exposure of bees (and other pollinators) to these products, what remains unclear is precisely how much these chemicals may be harming pollinators.

The presence of pesticides in regions far removed from the point of application is well known, as illustrated by recent studies on pesticide detection in polar regions.

Many other questions remain as well. For instance, what are the limits for change in soil functions or biodiversity at which we would judge the effects of plant protection products to be unsustainable? What are the mixture effects of different classes of plant protection products on soil function, biodiversity, and human health, and how far do these chemicals travel in the environment?

The presence of pesticides in regions far removed from the point of application is well known, as illustrated by recent studies on pesticide detection in polar regions. The mobility and degradation of a pesticide in the environment is strongly dependent on properties such as biotic and abiotic processes, solubility, and adsorption – properties which are often only poorly understood.

So what can be done? We know, for instance, that in many farm settings significant reductions could be made in the use of agro-chemical inputs while preserving yields (and profitability) – with benefits to soil health and water quality. Integrated Pest Management policies have been mandated in the European Union, and similar practices are now promoted in many parts of the world. The Voluntary Guidelines for Sustainable Soil Management, developed by the Intergovernmental Technical Panel on Soils through the Food and Agriculture Organization’s Global Soil Partnership, also include integrated or organic pest management as an important best practice. The International Code of Conduct on Pesticide Management provides internationally recognized management and mitigation strategies for the safe use of pesticides. Integrated land management practices at scale, such as the landscape approach, also have benefits for limiting the use of pesticides or the transfer of residues to waterbodies.      

These questions and management strategies will be addressed at the upcoming Global Symposium on Soil Pollution (2-4 May 2018) at FAO Headquarters in Rome – organized by the Global Soil Partnership and the Intergovernmental Technical Panel on Soils. The Symposium will bring together global soil experts along with UN Environment, FAO, The World Health Organization, and the Basel, Rotterdam, and Stockholm Conventions to address the environmental, health, and agricultural implications of soil pollution – and develop concrete strategies to address this challenge.

5 December is World Soil Day. The theme this year is "Caring for the planet starts from the ground".

Pollution is the theme of the 2017 UN Environment Assembly, which is gathering in Nairobi from 4-6 December. Sign the pledge and join the #BeatPollution movement.