New Study Finds Pesticides Leading Cause Of Grassland Bird Declines

Monday, February 25, 2013
Horned Lark and chicks
Horned Lark and chicks
- photo by Middleton Evans

A new study led by a preeminent Canadian toxicologist identifies acutely toxic pesticides as the most likely leading cause of the widespread decline in grassland bird numbers in the United States, a finding that challenges the widely-held assumption that loss of habitat is the primary cause of those population declines.

The scientific assessment, which looked at data over a 23-year period – from 1980 to 2003 – was published on Feb. 20, in PLOS One, an online peer-reviewed scientific journal. The study was conducted by Dr. Pierre Mineau, recently retired from Environment Canada, and Mélanie Whiteside of Health Canada.

The study looked at five potential causes of grassland bird declines besides lethal pesticide risk: change in cropped pasture such as hay or alfalfa production, farming intensity or the proportion of agricultural land that is actively cropped, herbicide use, overall insecticide use, and change in permanent pasture and rangeland.

“What this study suggests is that we need to start paying a lot more attention to the use of pesticides if we want to reverse, halt or simply slow the very significant downward trend in grassland bird populations. Our study put the spotlight on acutely toxic insecticides used in our cropland starting after the Second World War and persisting to this day – albeit at a lower level. The data suggest that loss of birds in agricultural fields is more than an unfortunate consequence of pest control; it may drive bird populations to local extinction,” Dr. Mineau said.

Many grassland bird species have undergone range contractions or population declines in recent decades. In fact, analyses of North American birds indicate that these birds are declining faster than birds from other biomes.

Habitat protection has long been considered a central pillar in efforts to stem the decline of grassland bird species, such as the Vesper Sparrow, the Ring-necked Pheasant, and the Horned Lark.

“We are still concerned about loss of habitat in agriculture, range management, and urban development,” said Cynthia Palmer, manager of the Pesticides Program at American Bird Conservancy, a leading U.S. bird conservation organization. “This study by no means diminishes the importance of habitat fragmentation and degradation. But it suggests that we also need to rein in the use of lethal pesticides in agriculture, and that we need to be especially careful about any new pesticides we introduce into these ecosystems such as the neonicotinoid insecticides. It reminds us that the poisonings of birds and other wildlife chronicled a half century ago by famed biologist and author Rachel Carson are by no means a thing of the past.”

The researchers focused on the extent to which lethal pesticides, such as organophosphate and carbamate insecticides, are responsible for the decline in grassland bird populations. The study found that lethal pesticides were nearly four times more likely to be associated with population declines than the next most likely contributor, changes in cropped pasture – an important component of habitat loss associated with agricultural lands.

The publication says that “…..large quantities of products of very high toxicity to birds have been used for decades despite evidence that poisonings were frequent even when products were applied according to label directions.”

The authors argue that only a small proportion of total cropland needs to be treated with a dangerous pesticide to affect overall bird population trends. The production of alfalfa stands out for its strikingly high chemical load, constituting the third highest lethal risk of any crop based on toxic insecticide use. Pesticide drift from croplands is also affecting birds that favor the adjoining grasslands.

Using data from the U.S. Geological Service Breeding Bird Survey for the years 1980 to 2003, the study found that declines of grassland birds were much more likely in states with high use of toxic insecticides lethal to birds. The species with the greatest number of declines included the Eastern Meadowlark (declining in 33 States), the Grasshopper Sparrow (25 States), the Horned Lark (25 States), the Ring-necked Pheasant (19 States) and the Vesper Sparrow (18 States). The states with the greatest number of declining grassland species were Minnesota (12 species), Wisconsin (11 species), and Illinois, Michigan, Montana, Nebraska and New York, all with nine species.

The current study relies on pesticide data from the 1980s and early 1990s, a time when organophosphates such as diazinon and chlorpyrifos, and carbamates such as carbofuran and methomyl, were still largely in vogue. Since that time, a new class of insecticides, the neonicotinoids, have soared to the top of global pesticide markets. Unfortunately, a major toxicological assessment soon to be released by American Bird Conservancy puts to rest any notion that birds and other organisms will fare much better under the new pesticide regime.


New York Peace Monument Receives Preservation Facelift

Chickamauga and Chattanooga National Military Park announced that the New York Peace Monument is currently receiving a long overdue preservation facelift.   This iconic Civil War memorial located within Point Park, atop Lookout Mountain, last received a thorough cleaning in 1988.  The monument was originally erected in 1907. Gordon Ponsford, a conservator from Acworth, ... (click for more)

Guided Walking Tour Of Snodgrass Hill/Horseshoe Ridge On May 2

Chickamauga and Chattanooga National Military Park invites the public to participate in a 2-hour, 2-mile guided walking tour of Snodgrass Hill/Horseshoe Ridge on Saturday, May 2, at 9:30 a.m. The tour will begin at the Chickamauga Battlefield Visitor Center and caravan to Snodgrass Hill/Horseshoe Ridge. Officials said, "As the right flank of the Union army collapsed under the ... (click for more)

Prominent Business, Civic Leader, And Philanthropist Scotty Probasco Dies At 86

Prominent Chattanooga business, civic leader and philanthropist Scotty Probasco has died at the age of 86. Scotty, as he was affectionately greeted by most of Chattanooga, was known for his modesty, generosity, dependability, and unswerving loyalty. “Great work” was always on the tip of his tongue – a manifestation of his joyous humility. He was a man of high ideals, of kind ... (click for more)

Chemical Odor In Lookout Valley Traced To Chattanooga Tank Wash

Chattanooga firefighters in Lookout Valley were sent out Friday night to investigate reports of a strange odor in the area. The firefighters searched the area, but never found the source of the odor.  John Schultz, an investigator with the Air Pollution Control Bureau, was also out Friday night and eventually tracked the source of the odor to a business, the Chattanooga ... (click for more)

Proud Of Hometown Boy Turned Global Leader, Bob Corker

Time Magazine has it right.  Not only is Chattanooga’s own U.S. Senator Bob Corker one of the “100 Most Influential People in the World,” but he is probably now the most prominent leader in the history of our city.   At a time of extreme frustration with Washington and Congress in general, Bob continues to rise above the division and rancor to build consensus and solve ... (click for more)

Roy Exum: Great Work, Ol’ Pro!

Years ago I was lucky enough to be the seatmate of Scotty Probasco on an airplane bound for somewhere and he taught me a word that has helped me be a much better person than I ever thought I could. We were already swell friends, since he’d watched me grow up at First Presbyterian Church every Sunday with his kids, and he liked some of the stuff I tried to write back then. So ... (click for more)