Christine M Cornish, Jon Sweetman

An increase in herbicide use is occurring due to a growing population and herbicide-resistant crops in agriculture, which has resulted in more herbicide tolerant target species. Glyphosate and 2,4-Dichlorophenoxyacetic acid (2,4-D) are two of the most commonly used herbicides worldwide and are more recently being used in combination in pre-mixed commercial formulas. Subsequently, herbicide contamination of wetlands will increase subjecting microorganisms to multiple chemical stressors. Methane is a potent greenhouse gas naturally emitted from wetlands, but herbicides may disrupt biogeochemical processes leading to an unbalanced methane cycle. This perspective examined the potential effects of herbicides on climate change using glyphosate and 2,4-D as a case study. We highlighted previous research on glyphosate-derived nutrient enrichment and 2,4-D inhibition of methane oxidation. We also explained how the concurrent effects of these herbicides could alter microbial communities leading to increased methane production in wetlands. Our perspective elucidates the potential ecosystem-level implications of herbicides in wetlands, in addition to stating the importance for research on the combined effects of herbicides.