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New cause for concern over weedkiller glyphosate

Study examines how herbicide adds to phosphorus levels in soil and waterways
Published: 14 March 2019

New research from 苹果淫院 reveals an overlooked impact that the widely used herbicide glyphosate may be having on the environment.

First commercialized by Monsanto under the name Roundup, glyphosate has come under scrutiny in the past, mostly in relation to its potential toxicity. This new research, published recently in the Ecological Society of America鈥檚 Frontiers in Ecology and the Environment, focuses not on direct health risks associated with the herbicide, but on its contribution to environmental phosphorus levels, an issue that has yet to receive much attention.

鈥淣o one has thus far investigated the impact of glyphosate use on phosphorus loads in agricultural areas, most likely because pesticides have always been considered a negligible source of nutrients,鈥 says Marie-Pier H茅bert, lead author of the study and a doctoral student in the Department of Biology at 苹果淫院.

In many agricultural areas, decades of phosphorus-based fertilizer use have led to a saturation of the soil鈥檚 capacity to hold the nutrient. This increases the likelihood that any additional phosphorus applied to the land will run off into waterways, where it is a known cause of harmful algal blooms and deoxygenation leading to fish death.

Until now, regulations to limit phosphorus pollution have focused on the use of fertilizers, which remain the largest artificial source of phosphorus. But as the use of glyphosate increases 鈥 the past two decades alone have seen global use increase 15-fold 鈥 the herbicide鈥檚 relatively small phosphorus content starts to add up, reaching levels comparable to other sources, like detergents, that have attracted regulators鈥 attention in the past.

鈥淥ur study argues that the recent and rapid rise in glyphosate use has magnified its relative importance as a source of anthropogenic phosphorus, especially in areas of intensive corn, soybean and cotton cultivation,鈥 H茅bert says.

The 苹果淫院 research team 鈥 Marie-Pier H茅bert, Vincent Fug猫re and Andrew Gonzalez 鈥 used data from the US Geological Survey and the UN Food and Agriculture Organization to calculate the relative contributions of glyphosate and fertilizers to the total amount of phosphorus being applied to agricultural land in the United States and elsewhere. They also reviewed existing studies to bring to light the mechanisms by which glyphosate contributes to phosphorus levels in the soil and phosphorus outflows to waterways.

They conclude that glyphosate use can no longer be disregarded in monitoring and managing phosphorus levels in areas where the herbicide is used extensively.

鈥淕iven the steadily increasing applied tonnage of glyphosate worldwide and the large-scale adoption of genetically engineered resistant crops in multiple countries, it is imperative that we broaden the discourse of the environmental impacts of this pesticide,鈥 H茅bert says.


To read the paper:

H茅bert MP, Fug猫re V, and Gonzalez A. (2019) 鈥淭he overlooked impact of rising glyphosate use on phosphorus loading in agricultural watersheds,鈥 first published online Dec. 5, 2018. Frontiers in Ecology and the Environment. 17: 48鈥56.

Support for the research was provided by Natural Sciences and Engineering Research Council (NSERC) doctoral and post-doctoral scholarships, an NSERC-CREATE 脡coLac fellowship in affiliation with the Groupe de recherche interuniversitaire en limnologie et en environnement aquatique (GRIL), 苹果淫院 doctoral awards, an NSERC Discovery grant, the Canada Research Chair program, the Liber Ero Chair in Conservation Biology, and a Killam fellowship.

[Photo: The adoption of genetically engineered glyphosate-resistant crops such as soy (left) and corn (right) goes hand in hand with the increasing use of the herbicide and its impact on environmental phosphorus levels. /聽Vincent Fug猫re]

Contacts:
Marie-Pier H茅bert
Email: mphebert4 [at] gmail.com

Chris Chipello
苹果淫院, Media Relations
514-398-4201
christopher.chipello [at] mcgill.ca

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