Glyphosate-based herbicides do not contribute to sustainable agriculture

Fonte: GMO Watch

Scientific paper concludes that glyphosate-based herbicides such as Roundup harm human and animal health, soils, and biodiversity. Report: Claire Robinson

Glyphosate-based herbicides do not contribute to sustainable agriculture, a recently published peer-reviewed paper concludes. These herbicides have become the leading agricultural weedkillers used globally since the development of GM herbicide-tolerant crops.

The paper contradicts claims by GMO proponents, such as the agbiotech industry consultant Graham Brookes, that glyphosate-based herbicides are an environmental boon on the grounds that they enable farmers to avoid ploughing, thus conserving soil and reducing the use of fossil fuels.

The paper investigates whether glyphosate-based herbicides (GBHs) support agricultural sustainability, which is defined as promoting agroecology; protecting the resource base of natural systems for future generations, including and especially the soil; protecting biodiversity; and enhancing the quality of life and health of farmers, farm workers, and society as a whole.

The paper is authored by Sheldon Krimsky, Professor of Urban and Environmental Policy and Planning at Tufts University and adjunct professor in the Department of Family Medicine and Community Health at Tufts University School of Medicine, and is published in the journal Sustainability.

Through an in-depth examination of the scientific literature, the paper explores whether GBHs are consistent with sustainable agriculture in the areas of human health, no-till agriculture, soil quality, aquatic ecosystems, and beneficial, non-target species. The findings on each of these areas of study are summarised below.

Human health

The paper cites the classification of glyphosate as a probable human carcinogen by the International Agency for Research on Cancer (IARC), as well as studies showing that the glyphosate-based herbicide Roundup damages DNA (is genotoxic) and is an endocrine disruptor in animal studies. A table is included that shows many different toxic effects in various animal species, ranging from neurological effects to damage to sperm. The conclusion is that there is circumstantial evidence of toxicity to humans and enough direct evidence of toxicity to animals to indicate that humans and the environment are at risk.

No-till agriculture

No-till agriculture has several environmental advantages – it reduces soil loss, fossil fuels usage, and atmospheric carbon release. It can be practised in organic and conventional non-GM, as well as GM, farming systems. GM herbicide-tolerant crops were long promoted as environmentally beneficial because they enabled farmers to control weeds by spraying herbicide rather than ploughing, enabling the adoption of no-till agriculture. But the paper points out that the rapid spread of glyphosate-resistant weeds has meant that glyphosate-based herbicides cannot by themselves deliver a no-till agriculture system.

Soil quality

An EU-based study shows that glyphosate and its main metabolite AMPA have often been detected in agricultural soils. Separate studies show that glyphosate herbicide applications alter soil microbe populations, which may have contributed to the proliferation of plant and animal pathogens, and negatively impact plant growth and productivity.

Aquatic creatures

Studies on fish and aquatic species like crayfish and frogs show that exposure to glyphosate-based herbicides has toxic effects, including deformities and causing oxidative stress in the brain, which impairs fish behaviour.

Beneficial, non-target species

Populations of monarch butterflies have been decimated by the massive spraying of herbicides – predominantly glyphosate-based ones sprayed on GM glyphosate-tolerant crops. Studies show that glyphosate damages the gut microbiome of honeybees and impairs their cognitive abilities, including navigation.

Widespread harm identified

Based on the above findings, Prof Krimsky concludes that glyphosate-based herbicides are "harmful to soil health, human and mammalian health, and biodiversity".

GMWatch asked Prof Krimsky what prompted him to research and write the paper. He replied that he had written a few articles on glyphosate, focusing on why IARC and the US EPA came out with such different findings about the chemical's links to non-Hodgkin’s lymphoma – with IARC concluding that glyphosate is a probable human carcinogen and the EPA concluding that it is not carcinogenic.

He also co-authored an article on the Monsanto discovery documents, obtained from litigation against Monsanto over its glyphosate-based herbicide, which plaintiffs believed had caused their cancers, as well as from Freedom of Information requests.

Prof Krimsky said, "It occurred to me that most of the emphasis was being placed on whether glyphosate caused human cancer and not on its impacts on the environment.

"That’s when I thought that if glyphosate was ever to be compatible with sustainable agriculture, it would have to have benign effects on the quality of the soil, non-target species, and mammalian cells. Pro-glyphosate supporters emphasised its value for protecting topsoil in no-till agriculture. That is what got me to investigate the science of glyphosate-based herbicides in their system-wide effects."

GMO proponent proven wrong

Prof Krimsky said what surprised him most about his findings was that they directly contradicted a statement by Nina Fedoroff, a preeminent plant geneticist and proponent of GM crops and their associated pesticides. Fedoroff had written, "Roundup does not harm insects, fish, birds, or mammals (including humans) because none of these creatures have the enzyme EPSP synthase. Unlike plants, animals do not make these three amino acids (phenylalanine, tyrosine, or tryptophan)."[1] But, Prof Krimsky found, "The science shows quite the opposite for the animals and fish."

Fedoroff's reasoning hinges on the fact that the enzyme EPSP synthase is the biochemical target for glyphosate. Plants have this enzyme, but animals, including humans, do not. When glyphosate herbicide is applied to plants, it inhibits this enzyme, making the plants unable to synthesise the amino acids they need to grow and thus killing them. Fedoroff believes (along with Monsanto) that because animals don't have this enzyme, glyphosate should be non-toxic to them.

Except for one rather obvious factor, which Fedoroff and Monsanto failed to consider: It was always possible that glyphosate herbicides would be toxic through other pathways than via the enzyme EPSP synthase. And so it turned out, with IARC confirming the ability of glyphosate to cause oxidative stress and damage DNA, two mechanisms that can contribute to a variety of diseases, from cancer, to birth defects, to autism, ADHD, heart failure, and more general toxic effects.

Another scientific paper finds GM "highly unlikely" to improve sustainability

Prof Krimsky's review follows hot on the heels of a separate scientific paper by Dr Allison Wilson, which asked whether genetically modified crops, foods and animals, both those produced using older transgenic GM techniques and those produced using newer gene-editing techniques, could improve the sustainability of food and farming.

Dr Wilson found that the widespread use of older-style Bt insecticidal and herbicide-tolerant crops had led to the problematic development of pest resistance, superweeds, and secondary pests. In response to these problems, "farmers increased both insecticide and herbicide use. Some also increased tillage and other mechanical methods of weed control."

Regarding newer gene-editing techniques, Dr Wilson found that the evidence thus far shows that gene editing is "imprecise and unpredictable" and prone to introducing unintended effects.

She concluded, "While in theory it might someday be possible to create a GM crop that meets the broad requirements of sustainable agriculture, in practice this seems highly unlikely to ever happen."

GMO proponents are trying to create demand for their products by hitching their wagon to current concerns about the sustainability of our food and farming systems. Prof Krimsky's and Dr Wilson's findings confirm the futility of looking to GMO and agrochemical developers for solutions to problems that were caused in many cases by the activities of these same companies.

Notes

1. Nina Fedoroff, Mendel in the Kitchen, p. 274.

The recent paper:

Sheldon Krimsky (2021). Can Glyphosate-Based Herbicides Contribute to Sustainable Agriculture? Sustainability 2021, 13, 2337. https://doi.org/10.3390/su13042337

Photo credit: London Permaculture. Reproduced under Attribution-NonCommercial-ShareAlike 2.0 Generic (CC BY-NC-SA 2.0) licence