Researchers call for caution on agricultural pesticides

Researchers call for caution on agricultural pesticides

Risa Sargent

Risa Sargent

Feb. 2, 2023 – Common pesticides used in agriculture could be impacting organisms in unexpected ways through their ecological interactions.

A recent publication by UBC researchers says regulators need to carefully review the impact of common pesticides and take steps to reduce them until their impact on the ecosystem—including pollinators, animals, waterways, etc.,—is more fully understood.

The review, titled Common pesticides disrupt critical ecological interactions, is online and will be in the March 2023 print issue of Trends in Ecology and Evolution. Bringing together some current research on pesticides, the review was a collaboration by Risa Sargent, associate professor and Juli Carrillo, assistant professor in the Faculty of Land and Food Systems, and Claire Kremen, a professor in the Faculty of Science.

We asked Dr. Sargent to provide some insights.

What were the key findings?

This is a review paper where we describe concerning evidence that pesticides can indirectly impact critical ecosystem functions such as pollination, biological control and mutualistic fungal associations, causing unexpected downstream effects for agriculture and aquaculture, among other things.

What did the research team find surprising in the results?

Most people are aware that pesticides can directly affect non-target organisms, such as bees and birds. However, their ability to cause serious, negative downstream effects, such as a collapse of a fishery in Japan, are surprising.

In one case, a lake in Japan’s Shimane Prefecture has seen its commercial harvest of smelt fish collapse by more than 90 per cent since 1993, when insecticides known as neonicotinoids were first introduced to the area. It just so happens that zooplankton—the tiny creatures in the water that fish feed on—declined by 83 per cent during the same period.

Similarly, most people think of herbicides as mainly impacting weeds, which is their main intention. However, new research supports the idea that they can interrupt critical gut microbial communities, making animals sick or changing their behaviour or reproduction.

In regards to microbiomes, how do pesticides impact animals?

Several recent papers have come forward showing that gut microbial communities are changed following pesticide exposure. It’s not entirely clear why, but it’s likely that gut biota are reduced by some pesticides, altering the community.

Do pesticides impact humans?

We know that some compounds impact human gut microbiota communities, sometimes severely – antibiotics are a good example. This type of research is difficult to do in humans because exposing them to pesticides to explore changes to their gut microbiota would be unethical. At the same time, humans live in complex environments and pinpointing pesticides as a driver of living gut microbial communities would be nearly impossible. In insect systems we can do experiments that are not possible in humans.

What is the biggest concern you have, given what you learned from the review?

The area of agricultural land treated with pesticides in Canada has increased dramatically in recent decades. At the same time, the legislation that governs pesticide application in Canada is not keeping up with current research. For example, at this point we do not consider broader ecological implications of pesticide use in the Pest Control Act. The Act does not currently align with our Species at Risk Act, making it difficult, for example, to regulate pesticides in order to conserve species at risk, such as Monarch Butterflies or threatened bumblebees, such as the Rusty-Patched Bumblebee. This is in spite of the fact that pesticides are major contributors to the decline of these endangered species.

Do you have any recommendations on what you’d like to see happen?

I would like to see a few steps taken in Canada that I can summarize as follows.

1/ Data on potential downstream ecological impacts, such as those on microbiomes, pollinators, birds and invertebrate communities, should be considered before a pesticide is allowed to be released. Cumulative assessments should be performed on all existing and potential pesticides, as most pesticides are applied together with a number of different formulas and compounds (e.g., fungicides, insecticidal seed coats are increasingly being used on our most common crops).

2/ Canada should follow the recommendations of the EU’s Biodiversity Strategy and reduce pesticide use and risk by 50% by 2030.

3/ Canada should require risk assessments of species at risk and their habitats and ban the use of pesticides in protected areas.

4/ Canada should collect and make available data on pesticide use across agricultural lands, including neonicotinoid seed coats applications, for which we currently have very little data on application rates and areas. There is almost no usable Canadian data available for research, making pesticide impacts very difficult to study in Canada (this is in contrast to the U.S., which keeps very good detailed records of application rates by county). Most of our recommendations for Canada can only be extrapolated from U.S data.

Read the review here: