Glyphosate is the active substance of the most used pesticide (herbicide) products globally: glyphosate-based herbicides (GBHs). They are used widely to kill plants, leading to their widespread presence in our ecosystems, surroundings and bodies. Soils are extremely biologically diverse and complex ecosystems, providing a wide series of essential functions, and directly interacting with groundwater, surface water and air. There is a misbelief that glyphosate-based herbicides are beneficial for agricultural production without having any negative consequences to beneficial species and soil health. This is far from the truth. Apart from killing beneficial plants and endangering important pollinators like bees, glyphosate can seriously disrupt soil health by harming the soil microbiome and earthworms.
- Soils are estimated to harbour about 59% of Earth’s species, or even more, as soils are understudied. For example, 90% of fungi, 85% of plants and 50% of bacteria are living in soils.
- Healthy soils provide a wide variety of ecosystem services such as biodiversity, nutrient cycling, sustainable plant production, natural pest control, good water quality, water and carbon storage and erosion management. Soil micro- and macrofauna are essential contributors to these functions, and harm to these organisms can impact soil functioning.
- Glyphosate and its metabolite AMPA are widely present in our environment, and the most frequently found pesticide residues in soils across Europe.
- The persistence of glyphosate in soils can vary from low to very high, depending on environmental conditions and properties.
- Glyphosate inhibits the shikimate pathway. This pathway is responsible for essential aromatic amino acid biosynthesis, and is present in plants and algae, but also in fungi and bacteria in soils and in the gut microbiome of animals and humans.
- Inhibition of this pathway leads to the death of plants. Given the same pathway is present in fungi and bacteria, researchers have looked at the impacts of glyphosate and GBHs on microorganisms.
- GBHs can harm the soil microbiome:
- GBHs can alter the composition and abundance of soil microorganisms (bacteria and fungi), and for example increase pathogenic and decrease beneficial organisms.
- GBHs can reduce the forming of mutually beneficial relationships between fungi and plant roots, called root mycorrhization, which can impact plant health/growth
- GBHs can also lead to changes in nutrient composition in the roots, leaves, grape juice and xylem sap.
- Scientists warn that microbiomes play an essential role in maintaining ecosystems health, and that microbiome alterations can have unforeseen impacts on functioning of organisms and ecosystems.
- Research also points at the importance of the possible links between the impact exposure to GBHs and other pesticides on the gut microbiome of animals and humans, and impacts on animal and human health, including cancer and neurological disorders.
- GBSs can harm earthworms:
- Research shows glyphosate contamination is common in earthworms.
- GBHs can severely negatively impact survival, body mass, microbiome and behaviour of earthworms
- Negative impacts on earthworms reach far beyond soils, for example, use of pesticides and fertilisers have been found as one of the main drivers for drastic declines in farmland birds, especially for invertebrate feeders.
- While there is a need for more long-term, detailed studies to further untangle possible impacts on soil life and highly complex processes, GBHs can clearly harm organisms and disrupt ecosystem functions, the very foundation on which safe and sustainable agricultural production depends. Furthermore, the use of GBHs poses a threat to the health of farmers and the general public.
- Fortunately, there are viable alternatives to GBHs, that are aligned with climate and pest resilient and nature-inclusive cropping systems, offering extensive benefits for ecosystems and citizens’ health, farmers wellbeing and food security.
- The EU assessment has major shortcomings and data gaps, particularly in assessing the impact of glyphosate and glyphosate products on biodiversity and microbiome
The soil microbiome, encompassing bacteria, archaea, viruses and fungi, comprises the highest biodiversity within soils, and performs multiple vital functions. Many soil microbiota form symbiotic relationships with plants, supporting plant growth, regulating nutrient cycling and biogeochemical cycles, decomposing organic matter, defining soil structure and suppressing pathogens. GBHs have been shown to impact the composition and abundance of soil microbial communities, potentially increasing pathogenic fungi or decreasing beneficial soil microorganisms. These disturbances within microbial communities can lead to long-term effects on the nutrient status of the plant-root interface and impact plant health and growth. Moreover, a growing body of literature points at the possible impacts of pesticides, including glyphosate, on the microbiome of animals and humans. Due to the important role of the microbiome for many functions, researchers highlight the possible impacts on animal and human health, and the possible links with illnesses. Earthworms, rightfully called ‘ecosystem engineers’, are responsible for breaking down and redistributing organic material in soil, increasing soil penetrability for roots, aeration and consequently, improving overall soil fertility. Earthworms can also significantly increase water retention capacity of soils. Nevertheless, these critical roles played by earthworms are adversely impacted by GBHs, which have been shown to affect their reproduction, behaviour, growth and survival of earthworms.
The impact on soil organisms goes far beyond soils, and extends also to animals dependent on soil organisms. For example, research has shown that the drastic declines in (farmland) birds in Europe are linked to pesticide and fertilizer use. The effects are very outspoken for birds that are invertebrate feeders.
Although more long-term studies are needed to further untangle the highly complex soil processes, and fully understand all possible impacts of GBHs on these processes, the evidence currently available clearly indicates that glyphosate and GBHs can negatively impact soil organisms and soil health. This, in turn, poses broader risks and implications for ecosystem health and human well-being. While only a minority of plant species is damaging to crop yields and considered pests, GBHs indiscriminately kill all plants and harm various organisms, including bees and soil organisms. Overall, GBHs disrupt ecosystem functions, the very foundation on which safe and sustainable agricultural production depends. Furthermore, the use of GBHs poses a threat to the health of farmers and the general public. Fortunately, there are viable alternatives to GBHs, that are aligned with climate and pest resilient cropping systems, offering extensive benefits for ecosystems and citizens’ health, farmers wellbeing and food security.
The EU is currently in the process of renewing the approval of glyphosate, with its current licence set to expire at the end of 2023. Unfortunately the EU assessment has major shortcomings and data gaps, particularly in assessing the impact of glyphosate and glyphosate products on biodiversity and microbiome. It incorrectly concludes that glyphosate is safe. This contradicts the provisions of the pesticide EU law and the implementation of the precautionary principle, which both prioritise a high level of human and the environment, including biodiversity and ecosystems. At the same time, the Green Deal and Farm to Fork strategy envision a 50% reduction in the use and risk of chemical pesticides in the EU by 2030, and the promotion of safer, nature-based alternatives. Given the important identified risks of the use of GBHs for human and environmental health, glyphosate use should be completely banned for use in agriculture as well as for non-agricultural uses (gardens, urban areas, railway tracks, …). To safeguard all soils, this ban should also encompass the export of glyphosate and glyphosate-based herbicides to third countries.