Europe should expand a ban on bee-harming pesticides, environmental lobby group Greenpeace said Thursday, as it released a report warning of widespread risks to agriculture and the environment.

The report by biologists at the University of Sussex, commissioned by Greenpeace, concluded that the threat posed to bees by neonicotinoid pesticides was greater than perceived in 2013 when the European Union adopted a partial ban.

"New research strengthens arguments for the imposition of a moratorium" on the use of three neonicotinoids -- clothianidin, imidacloprid and thiamethoxam, the analysis concluded.

"It has become evident that they pose significant risks to many... organisms, not just bees."

A global review last November said about 1.4 billion jobs and three-quarters of all crops depend on pollinators, mainly bees.

There are some 20,000 species of bees responsible for fertilising more than 90 percent of the world's 107 major crops.

Last year, the United Nations said 40 percent of invertebrate pollinators -- particularly bees and butterflies -- risk global extinction.

Bee populations have been hit in Europe, North America and elsewhere by a mysterious phenomenon called "colony collapse disorder".

The blight has been blamed on mites, a virus or fungus, pesticides, or a combination of factors.

"These essential insects are in serious trouble," Greenpeace wrote in a foreword to Thursday's report, which its authors said involved analysing hundreds of scientific studies published since 2013.

"The case that neonicotinoids are contributing to wild bee declines and exacerbating honeybee health issues is stronger than it was when the partial EU ban as adopted," said co-author Dave Goulson.

Neonicotinoids appeared also to be linked to declines of butterflies, birds and aquatic insects, he said in a statement.

"Given evidence for such widespread environmental harm it would seem prudent to extend the scope of the current European restriction."

- Taken seriously -

"The European Union takes the protection of bees very seriously," European Commission spokesman Enrico Brivio told AFP in response.

"It is exactly because their protection is a priority that (neonicotinoid) restrictions are, and will remain, in place until an evaluation is finalised."

Neonicotinoids are lab-synthesised pesticides based on the chemical structure of nicotine.

They were introduced in the mid-1990s as a less harmful substitute to older pesticide types. They are now widely used to treat flowering crops, and are designed to be absorbed by the growing plant and attack the nervous system of insect pests.

But studies have blamed neonicotinoids for harming bee reproduction and foraging by diminishing sperm quality and scrambling memory and navigation functions.

It has also been linked to lower disease resistance.

One study suggested that -- similar to nicotine for humans -- neonicotinoid may hold an addictive attraction for bees, which sought out pesticide-laced food in lab tests.

The European Food Safety Authority (EFSA) declared in 2013 that neonicotinoid pesticides posed an "unacceptable risk" to bees, followed by a temporary European moratorium.

The partial ban excluded neonicotinoid use on barley and wheat as well as gardens and public spaces.

An EFSA neonicotinoid review is due to be finalised in the second half of this year.

Officials this week placed the patched bumblebee on the endangered species list -- the first ever continental American bee in that category.

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