Pesticides are made to kill something somewhere — it says it in the name and there is always a trade-off, says Pierre Mineau, Ph.D., co-author of a new study that found that pesticides are the leading cause of grassland bird deaths.
Contrary to a widely held belief that loss of habitat has been driving down bird numbers, the 23-year-long study reveals pesticides are responsible for four times the amount of bird deaths than the other five potential causes: changes in cropped pasture, farming intensity and permanent pasture and rangeland, as well as overall insecticide use and herbicide use.
The study was published by PLOS One, an online, peer-reviewed journal, using data collected by Mineau, recently retired from Environment Canada, and Mélanie Whiteside of Health Canada.
The study was conducted from 1980 to 2003 and focused on the effects of acute pesticides organophosphate and carbamate on grassland birds.
Organophosphate and carbamate pesticides are chemical insecticides that affect the nervous system of an insect by disrupting the enzyme that regulates acetylcholine, a neurotransmitter. Developed in the 19th century, these chemicals were used during World War II as chemical warfare against humans, according to the Environmental Protection Agency’s website.
Grassland birds are most likely exposed to chemicals through food supply — contaminated seeds or insects — combined with skin exposure, mostly through the feet or feathers. Chemical absorption into the bird’s body poisons the bird.
“The period we just went through with the organophosphates and carbamates was particularly bad for birds,” Mineau says. “Although I’m concerned about new compounds coming out, there is no doubt that those two were killing a lot of birds.”
Other causes of recession of bird populations are still of concern, but the findings suggest a need to rein in the use of lethal pesticides, according to Cynthia Palmer, manager of the Pesticides Program at the American Bird Conservancy.
“We need to be especially careful about any new pesticides we introduce into these ecosystems, such as the neonicotinoid insecticides,” Palmer says.
The Food Quality Protection Act of 1996 addressed the dangers of older pesticides after it was revealed children were being neurologically affected by exposure to extremely toxic chemicals through residue on food. The act mandates that the EPA encourage the use of pesticides that meet low-risk criteria over older, conventional pesticides like organophosphates and carbamates.
“The most dangerous pesticides have been taken out of circulation mostly because they weren’t working anymore and for a concern on human health, but the class of compounds replacing them are still very toxic to birds and pollinators,” Mineau says.
Since organophosphate and carbamate use has been reduced, grassland birds are making a small recovery, moving away from potential extinction, but some will probably still die due to pesticides through more indirect ways.
“We have fewer acute problems than before — we’re not killing quite as many birds outright,” Mineau says. “But the loss of insect biomass is so extreme, we’re probably going to start killing birds through the food supply.”
The problem comes down to economics, Mineau says. Manufacturers of pesticides need to make a profit and are doing so by developing chemical compounds that can be used on multiple crops to combat many pests.
The most eco-friendly solution would be herbicides that only work on a few pests or a few crops, but the approach remains blockbuster: Develop one that can kill every pest because it’s cost-effective, Mineau says, but it’s this approach that is fueling the pesticide problem.
“We have a sledgehammer approach when we need the scalpel,” Mineau says.
The use of dangerous pesticides cannot be entirely blamed on agriculture. About 90 percent of homeowners in the United States use 136 million pounds of pesticides per year, according to pesticide information on the Boulder County website.
The city of Boulder has been working towards reducing their use of pesticides for more than 12 years, according to Rella Abernathy, integrative pest management coordinator for the city.
Boulder focuses on maintaining healthy grass for parks and turfs without relying on pesticides, she says.
“The most important thing to consider when you are trying not to use pesticides on grass is to maintain healthy grass so you can crowd out your weeds,” Abernathy says. “People tend to rely on products instead of overall health maintenance.”