An article by MattMcGrath, BBC.

Neonicotinoid pesticides are causing significant damage to a wide range of beneficial species and are a key factor in the decline of bees, say scientists.

Researchers, who have carried out a four-year review of the literature, say the evidence of damage is now “conclusive”.

The scientists say the threat to nature is the same as that once posed by the notorious chemical DDT.

Manufacturers say the pesticides are not harming bees or other species.

Neonicotinoids were introduced in the early 1990s as a replacement for older, more damaging chemicals.

They are a systemic insecticide, meaning that they are absorbed into every cell in a plant, making all parts poisonous to pests.

But some scientists have been concerned about their impact, almost since the moment they were introduced.

Much of the worry has surrounded their effects on bees.

There’s been a well documented, global decline in these critical pollinators.

Many researchers believe that exposure to neonicotinoids has been an important destabilising factor for the species.

‘Worldwide impacts’

In 2011, environmental campaigners, the IUCN, established an international scientific taskforce on systemic pesticides to look into the impacts of these chemicals.

The members have reviewed over 800 peer reviewed papers that have been published in the past 20 years.

Their assessment of the global impact says the threat posed goes far beyond bees.

In their report, to be published next month, they argue that neonicotinoids and another chemical called fipronil are poisoning the earth, the air and the water.

The pesticides accumulate in the soil and leach into water, and pose a significant problem for earthworms, freshwater snails, butterflies and birds.

The researchers say that the classic measurements used to assess the toxicity of a pesticide are not effective for these systemic varieties and conceal their true impact.

They point to one of the studies in the review carried out in the Netherlands.

It found that higher levels of neonicotinoids in water reduced the levels of aquatic invertebrates, which are the main prey for a whole range of species including wading birds, trout and salmon.

“There is so much evidence, going far beyond bees,” Prof Dave Goulson from the University of Sussex told BBC News.

“They accumulate in soils, they are commonly turning up in waterways at levels that exceed the lethal dose for things that live in streams.

“It is impossible to deny that these things are having major environmental impacts.”

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