Insecticides are a bigger threat to the natural food chain than thought, warns study

Neonicotinoid type pesitcides have been linked to bee population collapse, but may be having other - mush wider - effects on the food chain, say researchers.

Legislation needs to take into account the harmful effects some insecticides have on insect-eating birds as the risk is greater than previously thought, according to a new study.

The study looked at the impact of the neonicotinoid insecticide, imidacloprid, on bird populations such as starlings and barn swallows. Imidacloprid is the most widely used insecticide in global agricultural systems, applied to treat seeds and bulbs, as a crop spray in greenhouses and in the open.

It affects insects’ central nervous systems, so that they become disorientated and paralysed, then die. It has also been linked to a decline in bee numbers, and other invertebrates, which birds eat.

The Netherlands-based study, published this month in the journal, Nature, is said to be the first to correlate imidacloprid to possible indirect harmful effects, via the food chain, for vertebrates – in this case, birds.

One of the authors, Caspar Hallmann, said that the natural food chain seems susceptible to this class of insecticides.

He told FoodNavigator: “Whereas we always were told that neonics are relatively harmless to vertebrates, owing to their high selectivity towards invertebrates, we now see that once these compounds leach into the environment, we may encounter unforeseen adverse effects on the ecosystem.

“High levels of this insecticide in the natural water ways may knock out insect populations, on which many vertebrates (including our birds) heavily rely on.”

Hallmann added that the risk to humans (if any) was likely to be indirect, such as losing pollinators like bees, which play a fundamental role in pollinating many plants and crops relied on for food.

The study concluded: “Our results suggest that the impact of neonicotinoids on the natural environment is even more substantial than has recently been reported and is reminiscent of the effects of persistent insecticides in the past.

“Future legislation should take into account the potential cascading effects of neonicotinoids on ecosystems.”

Risk to birds

Farmland birds have experienced declines in Europe in the past three decades and pesticides are said to be a major threat.

So far the suggested potential risks of neonicotinoids for birds have focused on the acute toxic effects from direct consumption.

The study hypothesis was that imidacloprid, which recently replaced older intensively used insecticides, has a negative impact on insectivorous bird populations such as starlings and barn swallows.

Data analysis

The research combined water quality data with systematic bird counts taken before and after imidacloprid was introduced in 1995.

It showed that the higher the concentrations of imidacloprid in the surface water, the greater the decline in bird numbers. For the fifteen bird species included, numbers decreased on average by 3.5% per year in areas with more than 20 nanograms of imidacloprid per litre.

Other factors relating to the decline in birds were considered but this was said to be the best explanation.

The researchers don’t precisely know what causes the decline, although possible explanations include a lack insects and eating contaminated insects.

Source: Nature
Published online 9 July 2014, doi:10.1038/nature13531
“Declines in insectivorous birds are associated with high neonicotinoid concentrations”
Authors: Caspar A. Hallmann, Ruud P. B. Foppen, Chris A. M. van Turnhout, Hans de Kroon & Eelke Jongejans.   

Related News

The organisation wants any pesticides with evidence of harm to bees taken off the shelves

Campaigners win case against Bayer over pesticide bee claims

Study delivers fresh bee population warnings over pesticide use

Study delivers fresh bee population warnings over pesticide use

Neonicotinoids and bee deaths: What does the science say?

What does the evidence say? Scientists issue statement on the science for neonicotinoids and pollinator deaths

Research has again linked the low level sue of neonicotinoids to bee colony collapse disorder.

Harvard study backs link between neonicotinoids and bee population collapse

Can going organic help to save pollinator bees?

Can going organic help to save pollinator bees?

Have no fear, the bees are still here, says EU Commission

EU Commission: The bees are OK, but the pesticide ban stays

The EU ban on pesticides will have a significant impact on profit for oilseed crushing in Finland, says Raisio.

EU pesticide ban will block 'profitable' vegetable oil crushing, says Raisio

Bee population size is 'just one factor' that will affect food security - with other land management issues either helping or hindering bee polination

Bee population size is just one production factor, researchers warn

Related Products

See more related products

Comments (1)

Sumant Chavan - 19 Jul 2014 | 04:53

Third World awareness of Environment

When the countries like India will start using natural practises of agriculture thoroughly? India is having history of natural farming for more than 5000 years. By blindly following western countries, we have ruined our heritage. Moreover new generations to come, have missed the link of farming.

19-Jul-2014 at 04:53 GMT

Submit a comment

Your comment has been saved

Post a comment

Please note that any information that you supply is protected by our Privacy and Cookie Policy. Access to all documents and request for further information are available to all users at no costs, In order to provide you with this free service, William Reed Business Media SAS does share your information with companies that have content on this site. When you access a document or request further information from this site, your information maybe shared with the owners of that document or information.