05 Dec 2018 Story Ecosystems and Biodiversity

What’s the big deal about dirt?

Photo by Neil Palmer/CIAT

World Soil Day on 5 December reminds us why healthy soil is vital, how pollution affects it and what can be done.

Did you know that a handful of soil can contain millions of bacteria and fungi as well as tiny insects and strange, microscopic animals like tardigrades? Healthy soil depends on a vibrant range of life forms living below the ground, but across the globe it’s being severely damaged by pollution.

Soil pollution can disrupt the delicate balance of interactions between chemicals and life forms below ground. To most people soil is “invisible” and seems far away, but everyone, everywhere is affected by it because soil is vital for life on Earth.

Most pollutants originate from human activities, such as unsustainable farming practices, industrial activities, mining, untreated urban waste and other non-environmentally friendly practices.

For instance, many discarded medicines end up in landfills where they can leach out into rivers or pollute the soil. The discharge of antibiotics and other antimicrobial compounds, such as disinfectants, along with heavy metals, into natural environments “has the potential to drive the evolution of resistant bacteria”, says the 2017 Frontiers report. “These compounds are present in waters and soils at a wide range of concentrations,” it notes. 

Infographic by UN Environment

Heavy metals are another threat. The uptake of metals by plants from soils may result in a significant risk to health. Lead and cadmium in food are particularly toxic to humans. For instance, cadmium absorbed via food intake can penetrate through the placenta during pregnancy, damaging membranes and DNA and disrupting the endocrine systems, and can induce kidney, liver and bone damage. Too much mercury in the soil is also dangerous to humans, according to a May 2018 report by the Food and Agriculture Organization of the United Nations, Soil Pollution: A Hidden Reality.

An emerging concern is plastic particle pollution which can occur when sewage sludge is spread on farmland. While there are no obvious solutions, it was reported recently that some fungi successfully degrade polyurethane in a matter of weeks. Plastic particles and microfibres can be found in wastewater effluent, sewage sludge, and plastic mulch from agricultural activities and are now being recognized as a potentially serious soil pollution issue.

Photo by Neil Palmer/CIAT

Soil, biodiversity and food

Soil is the foundation of the food system: 95 per cent of our food comes from soil. Our soils are the basis for agriculture and the medium in which nearly all food-producing plants grow. Healthy soils produce healthy crops that in turn nourish people and animals.

However, one third of the world’s soil is degraded. Only 8 per cent of soil in Africa is suitable for agriculture. In sub-Saharan Africa more than 180 million people are relying on depleted soil to grow food. This threatens their food security. The economic loss associated with land degradation in the region is estimated at US$68 billion per year, according to the Montpelier Panel Report of December 2014.

Below-ground biodiversity is vital for the healthy soils we depend on for food. The biodiversity of soil is immense compared to above-ground biodiversity. For example, an estimated 360,000 animal species live in soil. Soil biodiversity could make up a quarter of all described living species on the planet, although most of them remain unknown, according to a European Commission report The factory of life: why soil biodiversity is so important.

What can be done?

Pesticides and fertilizers should be used more sparingly and be better targeted to reduce the amount of pollution entering rivers. Wastewater treatment plants should be upgraded to more effectively remove pollution from the effluent. We should move towards a circular economy were nearly everything is recycled and reused.

The Food and Agriculture Organization of the United Nations is urging governments to facilitate remediation of contaminated soils that exceed contamination levels established to protect the health of humans and the environment.

Current possible solutions to counter antibiotic pollution include improved wastewater treatment and better wastewater management and tackling critical hotspots such as hospitals, drug manufacturing premises and disposal sites. Other precautions include ending the use of antibiotics as growth promoters in animal husbandry.

Photo by Neil Palmer/CIAT

Depending on the region, it can take from 100 to 1,000 years to form just one square centimetre (cm²) of soil. To nurture the soil we can:

  • Increase organic matter in soils through increasing groundcover, vegetation, mulch and compost
  • Use vegetation within managed landscapes to protect soils from the effects of wind and salinity
  • Practice minimal tillage (which reduces CO2 emissions) and retain crop residues
  • Implement time-controlled, planned rotational grazing
  • Encourage the use of bio-based fertilizers and other organic materials where possible to reduce reliance on chemical fertilizers; where needed, apply chemical pesticides and fertilizers with due care and ensure efficient and safe application
  • Aim to have 100 per cent groundcover throughout the year
  • Encourage biodiversity to thrive—above and below the soil
  • Support and protect soil microbial ecologies, including fungi
  • Reduce dependence on fossil fuels and non-organic fertilizers and pesticides
  • Half of our household waste could be composted to help create new soil

“Healthy soils have untapped potential for science and human well-being and we need to better understand how pollution and climate change affect it,” says UN Environment soil expert Abdelkader Bensada.

“The four main categories of life on Earth—bacteria, fungi, plants and animals—depend on soil for their existence. Healthy soil is a prerequisite for healthy ecosystems.”

The most recent United Nations Environmental Assembly (UNEA-3) adopted a resolution calling for accelerated actions and collaboration to address and manage soil pollution.

The theme for World Soil Day Be the solution to soil pollution aims to raise awareness and call people to #StopSoilPollution.

For further information, please contact Abdelkader Bensada: