杏吧原创

SPRING brings the hum of bees, and this year it heralds further rumours of their demise 鈥� and the spread of the pesticide that seems to be to blame.

Neonicotinoids, already subject to temporary bans in the EU, UK and parts of Canada, are under intense scrutiny. Regulators in Europe are poring over hundreds of studies to guide whether these temporary restrictions will become an outright ban.

But what effect will a ban actually have? These compounds aren鈥檛 just in pesticides 鈥� you might find them in products for your pet. And from many sources, they have leached into the environment, and seem to show up wherever we look, including last week in .

Although a ban seems like a rational response, it may lead to worse problems. So what are the right lessons to take from the neonicotinoid saga?

Systemic attack

When these neurotoxins were introduced in the 1990s, they were heralded as the future of pesticides. If coated onto a seed, they spread through the growing plant. When sucking pests like aphids eat any part of the plant, the neonicotinoid gums up the same receptors that nicotine targets in the brain, killing the insects. It was thought the toxins could target pests without doing much harm to beneficial insects like bees, and neonicotinoids quickly became the most widely used pesticide in the world.

Then lab studies began to suggest they weren鈥檛 as harmless for pollinators as advertised. Bees fed a neonicotinoid diet had fewer queens, reproductive systems, and were . Their foraging trips were longer but they . Were these effects to blame for reports of colony collapses?

Years of toing and froing ensued, with many claiming the lab studies were overblown and gave the bees a higher dose than that found in fields. The trouble was, no one really knew at what levels neonicotinoids were hanging around in the plants or the general environment.

鈥淯sing neonicotinoids is like taking antibiotics all the time to fight against a potential infection 鈥� crazy鈥�

鈥淓veryone knows insecticides can kill bees,鈥� says honeybee biologist Francis Ratnieks at the University of Sussex in Brighton, UK. 鈥淭he question is do the levels of contamination cause harm.鈥�

The conversation continued to go in circles as industry-funded studies came up with contrasting findings, even as the EU instituted a temporary ban on the use of the pesticides for some plants (see 鈥�Sowing confusion鈥�). The European Food Safety Authority was tasked with deciding whether to keep the ban after a two-year review.

Then, amid the buzz, it became clear that we should be looking at more than just honeybees. When ecologists cast a wider net, they found clear evidence of harm to other pollinators. One study examined crops of oil seed rape. On Swedish farms, the use of neonicotinoids showed no impact on honeybees 鈥� but alarming declines in survival and reproduction in wild bumblebees.

鈥淲ild bees tend to show more negative effects,鈥� says Richard Pywell at the UK Centre for Ecology & Hydrology. His of wild bees that forage on oil seed rape in the UK.

For other pollinators, the evidence started to come thick and fast. A 2015 study found that neonicotinoid levels in milkweed could .

Troubled waters

Next came the birds. A Dutch study found that birds needing plentiful insects in the spring to raise their chicks declined more in areas with higher surface-water concentrations of the neonicotinoid imidacloprid.

And the more , the lower the numbers of aquatic species like caddisflies, aquatic worms and mayfly larvae. Christy Morrissey at the University of Saskatchewan, Canada, says neonicotinoids are regularly at 鈥渃oncentrations exceeding levels that would cause harm to aquatic invertebrates鈥�.

Yet another report found that neonicotinoids were also harming microbes, lizards, earthworms, birds and even coastal shellfish.

How had the chemicals spread to all these environments? It seems the compounds break down more slowly than early tests suggested, and spread further. Perhaps 5 per cent makes its way from seed to plant, with the rest leaching into the soil and waterways.

The problem is made worse by their prophylactic use. 鈥淔armers are fighting pest problems before they exist,鈥� says Menzel. 鈥淭his is crazy. It鈥檚 like taking antibiotics all the time to fight against a possible infection.鈥�

Neonicotinoids aren鈥檛 just found in industrial pesticides. In the UK, they also show up in products like ant killer and flea treatments for cats and dogs: a 鈥渇air amount鈥� of neurotoxin for your pet, says Dave Goulson, a bee ecologist at the University of Sussex, UK. But much of it will wash off in the rain.

In the US, they are likely to be in your garden. 鈥淵ou can buy flowers at the garden centre with 鈥榖ee-friendly鈥� logos,鈥� he says. 鈥淭hese actually have neonicotinoids.鈥�

In urban areas in the southern UK, most bees have .

Then, earlier this month, chemists in the US detected three neonicotinoids in treated tap water in Iowa. They concluded that Iowa is far from alone.

Many ecologists believe that a continued or strengthened ban is on the way in Europe. point to a total ban except in greenhouses 鈥� even though the European Food Safety Authority has delayed its recommendation, citing an overwhelming number of studies. The date is now set for November.

鈥淚鈥檝e seen what the earlier insecticides did to bees. There were heaps of dead bees outside my hives鈥�

The big question is what would replace neonicotinoids. Growing oil seed rape without agrichemicals isn鈥檛 viable, says the UK National Farmers Union, and it is the only crop that can be profitably rotated with wheat. Production of it has already dropped in the UK since the ban.

The most likely way to control aphids 鈥� and the diseases they carry 鈥� will be to spray pyrethroids. 鈥淭hese broad spectrum insecticides are like using a hammer to crack an egg,鈥� says Julian Little, spokesperson for Bayer Crop Science. Worse, resistance to them is increasing.

Upping the use of such chemicals would hardly help bees, says Ratniek. 鈥淚鈥檝e seen what the earlier insecticides did to bees. I saw heaps of dead bees outside my hives in the 1980s.鈥�

If the ban is extended beyond flowering crops, Little says people will need to accept reduced yields of food crops and higher food prices. This would probably lead Europe to import more crops from places that still use neonicotinoids.

And for all that, a ban won鈥檛 even reverse the decline in pollinators in Europe. For one thing, it will only apply to agrichemicals, not to any of the pet and home uses. But that could be missing the point. 鈥淭he major threat is conventional agriculture becoming more intensive and the effects of climate change,鈥� says Adam Vanbergen at the Centre for Ecology & Hydrology. But intensification of agriculture and declining biodiversity don鈥檛 grab headlines in quite the same way.

鈥淚f neonicotinoids were banned tomorrow, it wouldn鈥檛 help much,鈥� says Goulson, who thinks we will never break the cycle of pesticides coming to market and science playing catch-up to uncover the harm they could do.

Many think any new ban should involve an assessment of the effect on pollinators. Had this already been in place, much infighting might have been avoided.

Others hope the neonicotinoid saga will help drive fundamental changes in farming. 鈥淔arming assumes the answer always comes in a bottle,鈥� says Goulson. 鈥淲e need to be clever in how we manage pests.鈥� Many ecologists argue for integrated pest management, which looks to nature to help control pests, reserving chemicals for emergencies.

Unless we change the way we farm, new pesticides will come along and it will all start again. And eventually spring won鈥檛 bring any buzz at all.

This article appeared in print under the headline 鈥淲ill a ban bee enough?鈥�