Glyphosate Herbicide Roundup Triggers Loss of Biodiversity Among Freshwater Algae

The glyphosate-based herbicide Roundup has been found to trigger the loss of biodiversity among phytoplankton communities in freshwater ponds. In their experiments, scientists found that while some populations developed resistance to the herbicide and were able to survive exposure at high levels, this came at a cost, with a 40 percent loss in biodiversity.

The team say their findings are concerning, as it could mean these food web staples are more vulnerable as environmental conditions become more extreme under a changing climate.

Roundup is the world's most popular weedkiller. Since the mid 1970s, around 8.6 billion kilograms has been used. Crops were developed that were "Roundup Ready," meaning farmers could spray their land to kill weeds, while boosting production. However, research now shows glyphosate has a number of unintended ecological impacts. It has been linked to the global decline in bees and appears to have adverse impacts on earthworms.

"The ubiquitous presence of glyphosate in the environment has sparked concerns over its potential health and ecotoxicological effects," Andrew Gonzalez, from Canada's McGill University, told Newsweek.

"Like fertilizers, pesticides may have unintended ecological consequences when leaked into the environment. Evidence is accruing that glyphosate may be having broad ecotoxicological effects on many species beyond the weeds it was designed to kill."

Gonzalez is one of the authors of a study published in Nature Ecology and Evolution that looks at what happens when phytoplankton—microscopic marine algae that form the base of a number of aquatic food webs—are exposed to the chemical.

When farmers spray their fields, some ends up reaching the surrounding environment, including freshwater sources. In their experiment, the team created ponds with phytoplankton communities. Some of the ponds were exposed to low levels of glyphosate.

They then exposed all the ponds to extremely high levels of the herbicide to see what would happen. Findings showed those that had previously been exposed developed resistance to glyphosate and were able to survive lethal doses—a trait known as "community rescue." This helps prevent the extinction of an entire population, allowing the species to survive

"We wanted to know if glyphosate can induce rapid evolution, causing a long-term effect on the diversity and functioning of our freshwater ecosystems," Gonzalez said. "Selection by glyphosate is expected to produce winners and losers among the species in our freshwater ecosystems."

I’d like to share a thread about our paper just out in @NatureEcoEvo showing that freshwater communities can evolve resistance to glyphosate (aka RoundUp), but lose diversity in doing so.

Link to access the paper lead by @V_Fugere here:

— Andy Gonzalez (@bio_diverse) March 2, 2020

He said they were expecting the ponds to stop functioning when glyphosate was applied at high concentrations. "The loss of ecosystem functioning did not occur if the ponds had been pre-exposed to sublethal levels of glyphosate; the emergence of glyphosate resistance in the ponds is akin antibiotic resistance we hear about often," he said.

While some communities were able to survive the high dose of glyphosate, it led to around a 40 percent loss in biodiversity. "The potential for this loss of diversity to go 'unseen' in nature is great," Gonzalez said. "Moreover, the loss of phytoplankton diversity might be expected to affect the productivity and stability of the food chains that support other species in our freshwater ponds and lakes."

The loss of biodiversity could be problematic in the future, the team say. With less diversity, future shocks and disturbances to the environment, "such as those arising from climate change or other forms of contamination and pollution," could mean these ecosystems are less resilient.

"The growing global trend in glyphosate use because of our reliance on Roundup ready crops suggests that the ecological and evolutionary effects that we have uncovered should be added to the important health and ecotoxicological concerns that have already been raised for glyphosate," Gonzalez said.

Image showing Roundup on the shelves of a retail store in Glendale, California, in 2018. Researchers have found the herbicide can cause a loss of biodiversity in phytoplankton. ROBYN BECK/AFP via Getty Images