Photo: The diversity of the Chihuahuan Desert, Big Bend National Park. © 2017 Delena Norris-Tull
Glyphosate Impacts on Biological Diversity
Summaries of the research and commentary: Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, October 2020.
Sullivan & Sullivan, 2003, conducted a review of the research and a modified meta-analysis on the impacts of glyphosate on biological diversity. They only found 60 relevant articles, and they provided a summary of each. Here is a very brief summary of their summaries.
Sullivan & Sullivan, 2003, results:
Vascular plants: 10 of 12 studies reported that species richness and diversity of vascular plants, particularly herbaceous plants, were either unaffected or increased, in response to glyphosate treatments. One study found that species richness of shrubs was reduced, in response to “targeted reduction in biomass of these woody plants in conifer plantations.”
Birds: Three of the seven avian studies “reported declines in densities of some songbird species in at least the first post-treatment year.” In two studies, “The effect was diminished three years [and four years] post treatment.”
Small mammals: None of the 12 studies on small mammals found reductions in species richness or diversity.
Large mammalian herbivores: Overall, the 16 studies did not note significant reductions in species richness or diversity. The studies were conducted primarily on rabbits and hares, with a few studies on roe deer and black-tailed and white-tailed deer and moose.
Terrestrial invertebrates: Of the four relevant studies, little effects on richness or diversity were noted.
Sullivan & Sullivan, 2003, point out limitations of some of the studies they located. They primarily used quantitative data, thus the qualitative data, such as which species thrived and which did not, is only minimally noted. Some studies had poor controls or no replicates, or lacked pretreatment data, and many studies were short term, 1-3 years. Some studies on invertebrates did not include a list of species or relative abundance data. The longer-term studies, some 10 years long, provided the most useful data, as these are very rare in the ecological literature. As very few studies were available for each type of community, the ability to generalize to other similar or diverse communities is quite limited.
Increased toxicity of pesticides in recent decades
Schulz, et al., 2021, reported that since 1962, the year Silent Spring was published, “there has been a perceived reduction in the amount of pesticides used and shift in the kinds of pesticides available.” They looked at data from the USA on the “type, amount, and toxicity of pesticides applied over the last 25 years. They found that despite decreasing total amounts applied and decreased impacts on vertebrates, toxicity – in particular to insects and aquatic invertebrates – has increased substantially.”
Schulz, et al., 2021, examined 381 pesticides and “considered 1591 substance-specific acute toxicity threshold values for eight non-target species groups.” They assessed that there are greatly reduced amounts of applied insecticides in the US (reductions of more than 40% between 1992 and 2016), and lowered pesticide toxicities among fish, mammals, and birds, due to the reduction in use of organophosphates. But pesticides have increased toxicity for aquatic invertebrates and pollinators, including honeybees. For these species, applied toxicity has more than doubled between 2005 and 2015. Schulz, et al., 2021, found that “the toxicity of applied insecticides to aquatic invertebrates and pollinators has increased considerably - in sharp contrast to the applied amount – and that this increase has been driven by highly toxic pyrethroids and neonicotinoids, respectively.” They specifically recorded “increasing applied toxicity to aquatic invertebrates and pollinators in genetically modified (GM) corn and to terrestrial plants in herbicide-tolerant soybeans.” While this study used data from the USA, which is more readily available than for many other countries, they expect similar results in many other regions of the world where modern agriculture is dominant.
References:
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Glyphosate Impacts on Biological Diversity
Summaries of the research and commentary: Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, October 2020.
Sullivan & Sullivan, 2003, conducted a review of the research and a modified meta-analysis on the impacts of glyphosate on biological diversity. They only found 60 relevant articles, and they provided a summary of each. Here is a very brief summary of their summaries.
Sullivan & Sullivan, 2003, results:
Vascular plants: 10 of 12 studies reported that species richness and diversity of vascular plants, particularly herbaceous plants, were either unaffected or increased, in response to glyphosate treatments. One study found that species richness of shrubs was reduced, in response to “targeted reduction in biomass of these woody plants in conifer plantations.”
Birds: Three of the seven avian studies “reported declines in densities of some songbird species in at least the first post-treatment year.” In two studies, “The effect was diminished three years [and four years] post treatment.”
Small mammals: None of the 12 studies on small mammals found reductions in species richness or diversity.
Large mammalian herbivores: Overall, the 16 studies did not note significant reductions in species richness or diversity. The studies were conducted primarily on rabbits and hares, with a few studies on roe deer and black-tailed and white-tailed deer and moose.
Terrestrial invertebrates: Of the four relevant studies, little effects on richness or diversity were noted.
Sullivan & Sullivan, 2003, point out limitations of some of the studies they located. They primarily used quantitative data, thus the qualitative data, such as which species thrived and which did not, is only minimally noted. Some studies had poor controls or no replicates, or lacked pretreatment data, and many studies were short term, 1-3 years. Some studies on invertebrates did not include a list of species or relative abundance data. The longer-term studies, some 10 years long, provided the most useful data, as these are very rare in the ecological literature. As very few studies were available for each type of community, the ability to generalize to other similar or diverse communities is quite limited.
Increased toxicity of pesticides in recent decades
Schulz, et al., 2021, reported that since 1962, the year Silent Spring was published, “there has been a perceived reduction in the amount of pesticides used and shift in the kinds of pesticides available.” They looked at data from the USA on the “type, amount, and toxicity of pesticides applied over the last 25 years. They found that despite decreasing total amounts applied and decreased impacts on vertebrates, toxicity – in particular to insects and aquatic invertebrates – has increased substantially.”
Schulz, et al., 2021, examined 381 pesticides and “considered 1591 substance-specific acute toxicity threshold values for eight non-target species groups.” They assessed that there are greatly reduced amounts of applied insecticides in the US (reductions of more than 40% between 1992 and 2016), and lowered pesticide toxicities among fish, mammals, and birds, due to the reduction in use of organophosphates. But pesticides have increased toxicity for aquatic invertebrates and pollinators, including honeybees. For these species, applied toxicity has more than doubled between 2005 and 2015. Schulz, et al., 2021, found that “the toxicity of applied insecticides to aquatic invertebrates and pollinators has increased considerably - in sharp contrast to the applied amount – and that this increase has been driven by highly toxic pyrethroids and neonicotinoids, respectively.” They specifically recorded “increasing applied toxicity to aquatic invertebrates and pollinators in genetically modified (GM) corn and to terrestrial plants in herbicide-tolerant soybeans.” While this study used data from the USA, which is more readily available than for many other countries, they expect similar results in many other regions of the world where modern agriculture is dominant.
References:
- Schulz, R., Bub, S., Petschick, L.L., Stehle, S., & Wolfram, J. (April 2, 2021). Applied pesticide toxicity shifts toward plants and invertebrates, even in GM crops. Science, 372, (6537), 81-84. DOI: 10.1126/science.abe1148
- Sullivan, T.P., & Sullivan, D.S. (March 1, 2003). Vegetation management and ecosystem disturbance: Impact of glyphosate herbicide on plant and animal diversity in terrestrial systems. Environmental Reviews, 11: 37-59. NRC Canada.
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