{"id":31846,"date":"2022-11-11T00:01:47","date_gmt":"2022-11-11T05:01:47","guid":{"rendered":"https:\/\/beyondpesticides.org\/dailynewsblog\/?p=31846"},"modified":"2022-11-10T21:17:36","modified_gmt":"2022-11-11T02:17:36","slug":"explosion-of-weed-killer-use-destroys-soil-life-and-ecosystems-paper-finds","status":"publish","type":"post","link":"https:\/\/beyondpesticides.org\/dailynewsblog\/2022\/11\/explosion-of-weed-killer-use-destroys-soil-life-and-ecosystems-paper-finds\/","title":{"rendered":"Weed Killer Use Destroys Soil Life and Ecosystems, Paper Finds"},"content":{"rendered":"\r\n

(Beyond Pesticides<\/em>, November 11, 2022)\u00a0A paper published in Trends in Ecology & Evolution<\/em><\/a> in late October sounds an unnerving alarm about the globally ubiquitous use of herbicides and the ecological destruction being caused. It asserts that widespread environmental contamination with these herbicide compounds is influencing soil, plant, and animal microbiomes in ways that are not only not well understood, but also, can have significant impacts on the functioning of organisms and their ecosystems \u2014 with evolutionary implications. Impacts of herbicides on microbiota in soils include, for example, those on nutrient cycling, and altered organism and plant performance, which can affect pollination and animal consumption of plants. This research reinforces what Beyond Pesticides wrote<\/a> in covering a 2021 study<\/a>: \u201cThe popular herbicide glyphosate negatively affects microbial communities, indirectly influencing plant, animal, and human health. Exposure to sublethal concentrations of glyphosate shifts microbial community composition, destroying beneficial microorganisms while preserving pathogenic organisms.\u201d<\/p>\r\n

Herbicides are a category of pesticide used to control weeds in agriculture and commercial forests, on managed landscapes, byways, gardens, and lawns, and directly on surface waters to control aquatic weeds. They are designed to kill \u201ctarget\u201d plant species considered undesirable in any of those circumstances. Herbicide use has exploded in the past two decades, in large part due to the advent of the agro-biotech industry\u2019s deployment of genetically modified, herbicide tolerant crop seeds<\/a> that pair with herbicide use.<\/p>\r\n

This increased use has ramped up the development of weeds\u2019 resistance<\/a> to multiple herbicides. Glyphosate<\/a> formulations (including the infamous Roundup) are the most commonly used, in agriculture, horticulture, silviculture, and urban environments. In the aggregate, glyphosate contributes mightily to global environmental contamination; other widely used herbicides include [triazines (e.g., atrazine<\/a>), acetochlor<\/a> and metolachlor<\/a>, paraquat<\/a>, and dicamba<\/a>. Residues of herbicides are found in soil, water, non-target plants, animals, and humans, and are associated with pollinator and insect declines<\/a> and biodiversity losses<\/a>, compromise of other organisms<\/a> (including keystone species<\/a>), ecosystem dysfunction<\/a>, and human health anomalies<\/a>.<\/p>\r\n

The study authors also note<\/a> that adjuvant, \u201cinert\u201d ingredients in herbicide formulations can sometimes be even more toxic to non-target organisms than the active ingredients themselves, and that in the U.S., such co-formulants are not required to be tested for toxicity to non-target organisms. To make matters worse, information about such adjuvants is usually considered \u201cproprietary\u201d and therefore, is not shared with regulators or the public. Beyond Pesticides has covered this \u201cinert\u201d ingredient phenomenon<\/a>.<\/p>\r\n

If present patterns persist, the use of herbicides is predicted, by BusinessWire<\/em><\/a>, to increase annually by 2\u20133% through 2025. Most of that increase is expected in the agricultural sector because of (1) increasing resistance to herbicides by weed species, (2) an increase in agricultural intensity in Central and South America and the Asian\/Pacific region, and (3) the ongoing development of new herbicide formulations (in part because of #1) and \u201cherbicide use education\u201d in developing markets.<\/p>\r\n

Though herbicides are designed for target species, they also expose nontarget plants, animals, humans, and ecosystem function to risks. This study focuses on the compounds\u2019 effects on microbiota in flora, fauna, and soils. The authors assert that<\/a>, \u201cWhile many herbicides were initially considered safe for\u00a0non-target taxa,\u00a0as their mechanism of action was thought to be absent in these organisms, it has been understood only recently that herbicides may have profound effects on non-target taxa via alterations of microbial communities and microbial function in soil, plants, and animals. Given the imperative role of microbes in driving eco-evolutionary adaptations since the origin of life, and that microbes and their hosts comprise coevolving, multipartite entities [known as holobionts], a comprehensive understanding of the risks associated with altered\u00a0microbiomes\u00a0is needed.\u201d (A holobiont<\/a> is an assemblage of a host and the many other species living in or around it, which together form a discrete ecological unit through symbiosis.)<\/p>\r\n

The assumption that herbicides would be safe for nontarget taxa was based on the idea that their modes or mechanisms of action \u2014 how the compounds actually work to kill or disable weeds \u2014 were lacking in nontarget organisms. More-recent research has shown, however, that these compounds\u2019 mechanisms of action can have profound effects on the microbial communities harbored by non-target organisms. These communities, or microbiota, are present in all living things and are critical to healthy organism function \u2014 and to optimal immune response in particular, a primary task being the control of pathogens. When herbicides damage or kill a plant or animal\u2019s resident microbes, they alter the organism\u2019s ability to execute this protective function.<\/p>\r\n

The study identifies classes or modes of action for a host of herbicide active ingredients, including whether they act directly or indirectly on microbiota, and their respective effects on soil, plant, or animal microbiomes. Among the modes (and sample compounds) that have direct impacts on microbes are:
\r\n\u2022 ACC (acetyl-CoA carboxylase) inhibitors (e.g., diclofop-methyl<\/a>, haloxyfop<\/a>)<\/p>\r\n