Seven species of Hawaiian yellow-faced bee, decimated by invasive species and habitat loss, are now federally protected.
New research has provided some of the strongest evidence yet that pesticides can do serious, long-term damage to bee populations. And the findings may help fuel the ongoing debate about whether certain insecticides should be permitted for agricultural use at all.
The new study, published Tuesday in the journal Nature Communications, examines the question of whether the use of a common (and highly controversial) class of pesticides called neonicotinoids can be linked to wild bee declines in England. The results suggest that this could be the case.
Using 18 years of data collected on more than 60 bee species in England, the researchers found that species foraging on pesticide-treated crops have experienced much more severe losses than species foraging on other plants. The study provides some of the first evidence that the effects of neonicotinoid exposure can scale up to cause major damage to bees.
“It’s nice to see the use of long-term data to look at trends in pesticide impacts over longer time scales,” said Dara Stanley, a plant ecology lecturer at the National University of Ireland Galway, by email. (Stanley has previously conducted research on the effects of neonicotinoids in bees, but was not involved with the new study.) “That is something that has been missing in the debate on bees and pesticides so far, and there have been many calls to look at effects over time.”
The use of neonicotinoid pesticides has become hotly contested in recent years, due largely to concerns about their effects on bees and other pollinators. Numerous studies have indicated that exposure to these pesticides can have adverse effects in insects they were not intended for, hindering their ability to pollinate or reproduce or leading to increases in mortality.
In fact, in 2013, the European Union placed a ban on the use of multiple neonicotinoid pesticides, citing their potential danger to bees, although a few exemptions have since been allowed in the United Kingdom. Neonicotinoids are still widely used in many other places around the world, including in the United States. They’re produced by a number of different manufacturers and include household names such as Bayer’s Admire Pro insecticide, which includes a neonicotinoid called imidacloprid, or Syngenta’s Actara insecticide, which contains thiamethoxam.
Until now, most of the research on their effects has been limited to short-term, small-scale studies, many of them performed in laboratory settings, said Ben Woodcock, an ecological entomologist at the Centre for Ecology and Hydrology in the U.K. and the paper’s lead author. They’ve also tended to focus on just a few species. The new study, on the other hand, relies on field data collected on many species over nearly two decades.
The researchers focused on the different responses between bee species that forage on pesticide-treated oilseed rape crops — the same plants commonly used to make canola oil — and bees that forage on other plants. Oilseed rape crops are widely treated with neonicotinoids around the world, and the practice began on a wide scale in the U.K. starting in 2002. It’s the biggest mass flowering crop in the U.K. where neonicotinoids have been widely applied, according to Woodcock, making it an ideal subject for the study.
The researchers were interested in finding out whether bee species that forage on oilseed rape plants have experienced greater declines than bee species that don’t. So they gathered nearly 20 years’ worth of data, mostly collected in surveys by citizen scientists between 1994 and 2011, on where bee species have been spotted and what plants they foraged on. Different species often prefer to snack on different plants, and some of the included species visited oilseed rape plants while others didn’t do so at all. The researchers incorporated all the data, along with information on oilseed rape cover and pesticide use in the U.K., into a model that helped them analyze all the information.
Using the model, the researchers zeroed in on individual plots of land. Using all the survey data they’d compiled, they were able to note which species had been observed in each plot and which ones disappeared from those plots over the course of the study period. To be clear, the researchers weren’t able to say whether the number of individual bees in any given plot decreased or increased in abundance. Rather, they simply took note of which species vanished, or went locally extinct, in any given area over time.
“The way we look at it is whether or not a species was present in a location and not present in the next year,” Woodcock said.
Overall, the researchers found that these little extinctions were three times more severe in bees that foraged on oilseed rape plants than in bees that didn’t. It’s impossible to say for sure that the neonicotinoids were responsible for this difference, but the results suggest a link. The findings support the previous research which indicates that neonicotinoids can have damaging effects on bees — and they also suggest that these effects could result in serious population declines on a large scale in the long term.
Looking at these mini extinctions rather than overall population abundance has its advantages, said Christian Krupke, an entomologist at Purdue University, who was not involved with the new study.
“When you take an extinction-type event, you have more confidence that what you’re seeing is a true effect,” he said. “We know populations go through ebbs and flows, but when there are no insects there, it’s a lot more difficult to make the case that this is an ebb.”
In the future, though, “it would also be interesting to see whether abundances (or populations) of particular species were affected,” said Stanley, the National University of Ireland scientist, in her email. And Woodcock agreed that long-term population monitoring programs, which sample the same species in the same locations with the same intensity year after year, would be ideal in the future — they just haven’t been implemented yet.
In the meantime, scientists from Bayer Crop Science, a major manufacturer of neonicotinoid pesticides, took issue with the study’s correlational findings, which they’ve pointed out cannot be used to argue with certainty that pesticides cause declines in bees. A statement from the company, sent to The Washington Post by Bayer spokeperson Jeffrey Donald, summarized their complaint.
“The authors chose to investigate only one potential factor, namely neonicotinoid insecticides,” the statement said. “This was chosen out of many different factors which may have an influence on the development of wild bees, for example landscape structures, climatic conditions, availability of specific foraging plants and nesting habitats. It is a well-known fact that the structure of agricultural landscapes in large parts of Europe has changed substantially in the last decades. The area of landscape structures available for nesting or foraging, especially for specialized species, has significantly declined, resulting in fewer habitats for pollinators.”
A statement from Ray McAllister, senior director of regulatory policy at CropLife America, a trade association representing the manufacturers of pesticides and other agricultural chemicals, expressed similar concerns.
The authors of the new study acknowledged that pesticides are by no means the only factor contributing to bee declines — and were likely not the only factor at play even in this individual study.
“Bees have been undergoing declines for a long time and it’s been linked to a number of things — habitat fragmentation, climate change,” Woodcock said. “This is a contributing factor to bee declines, it’s not the sole cause. If you stop using neonicotinoids tomorrow, you wouldn’t solve the problem.”
But many experts feel that limiting their use would certainly help.
“I think it’s still the case that when people talk about population declines, there’s broad agreement that there are many effects — it’s multifactorial — and it depends on the species you’re talking about,” said Krupke, the Purdue entomologist. “But I think in areas where pesticides are used extensively…that pesticides are high on the list of concern.”
Tribal leaders in Oklahoma have vowed to plant nectar-producing plants for the butterflies whose numbers have dwindled.
Seven Native American tribes in Oklahoma will provide habitat and food on their lands for monarch butterflies, whose numbers have plummeted in recent years due to troubles along their lengthy migration route.
Tribal leaders said at a news conference on Tuesday in Shawnee, southeast of Oklahoma City, they will plant crucial vegetation for the butterflies, including milkweed and native nectar-producing plants, on their lands.
“For the last several years, we have been raising bees and pollinators, so when his opportunity came along, it fit with what we were doing,” Thalia Miller, director of the Chickasaw Nation Horticulture Department, told reporters.
The tribes will work with the University of Kansas’ Monarch Watch program and the Euchee Butterfly Farm in Bixby, Oklahoma. The project is supported by a grant of about $250,000 from the National Fish and Wildlife Foundation.
Monarch butterfly numbers have plummeted over the years from the expansion of farmland, sprawling housing developments and the clear-cutting of natural landscapes along their migration path, experts say.
Monarchs lay eggs only on milkweed plants, which grow wild throughout the United States. But milkweed, on which butterfly larvae feed, can cause stomach problems for cattle that eat it, so ranchers and farmers destroy the plant, researchers say.
While an estimated 1 billion monarchs migrated in 1996, only about 35 million made the trip in 2013, according to Marcus Kronforst, a professor of ecology and evolution at the University of Chicago who has studied monarchs.
Their numbers have rebounded in recent years but are still well below what they were two decades ago.
“The tribes are natural leaders on this issue,” said Jane Breckinridge, project co-director and owner of the Euchee Butterfly Farm, which breeds butterflies.
By DEAN FOSDICK, Associated Press
Even a little effort — a potted plant, say, on an apartment balcony — can mean a lot when trying to help restore declining pollinator populations like bees, bats, and butterflies.
“Every contribution is worthwhile,” said Victoria Wojcik, research director for the Pollinator Partnership in Toronto, Ontario. “You’re making a better environment for pollinators, no matter how small.”
Butterflies and other pollinators don’t need large areas for foraging but they do need a flower, she said.
“A planter on a balcony, even on the 30th floor — they will find it and visit it,” she said. “If people do this all over the city, it will definitely help.”
Pollination is needed by at least 80 percent of the world’s crop species. Wind does the job for numerous plants, notably grasses, while many others are served by a variety of animal pollinators.
Both sides benefit. Wildlife feed on the pollen and flower syrup while helping their plant partners reproduce.
But changing land use, viruses and pesticides are being blamed for massive pollinator losses, especially among the 4,000 native bee species in the United States and the thousands of managed stocks of non-native honeybees.
Enter pollinator planting.
“Native plants attract native pollinator species,” said Kari Houle, an extension educator with the University of Illinois. “Know which are suitable for your growing zone. Find a beneficial fit.”
She suggests a number of pollinator-friendly annuals for container use: alyssum, cleome, flax, lantana, snapdragon and zinnia, among them.
Select different flower sizes and shapes to match pollinator-feeding habits.
“Butterflies like places to sit,” Wojcik said. “Hummingbirds like bugle-shaped plants. Fragrant, sweet-smelling flowers attract night-flying creatures like bats and moths.”
Certain flower colors are pollinator magnets. Bees seem to like bright whites and yellows, while butterflies appear drawn to reds and purples.
More tips for attracting pollinators to pots
Use succession planting to provide pollen and nectar from early spring to late fall. Spring is an important season, especially for overwintering honeybees, because their food stocks of honey are low, and spring-blooming flowers are harder to find. That could mean tolerating dandelions, a favorite pollen source.
Place containers in full sun and shelter them from high winds. Include water in the menu by adding a birdbath or dripping faucet.
Provide host plants like milkweed that are popular with Monarch butterfly larvae.
Stop using pesticides. “You may see a little damage to some of your plants, but eliminating chemicals will greatly benefit pollinators,” Wojcik said.
Choose double-duty plants, like colorful edibles. “Herbs are a big one, especially rosemary and chives,” Wojcik said.
Fruit trees can be grown in patio planters but their production is limited. Get them into the ground before they become root-bound.
Blueberries and raspberries deliver sizable crops in containers but need protection from killing frosts in winter.
“Vegetables do extremely well in pots, particularly cucumbers and tomatoes,” Wojcik said. “Bumblebees love (gathering pollen from) tomatoes. They’re uniquely adapted to that.”
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