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From peregrines to european starlings


From peregrine falcons to european starlings

Just as peregrine falcons help alert us to the harmful effects of organochlorine pesticides,  european starlings alert us to the harmful effects of organophosphates.   The studies of these birds demonstrate the harmful effects on wildlife.


During the 1940s and 1950s, Derrick Ratcliff of the British Nature Conservancy noted a sharp decline in peregrine falcons across Europe. Soon after this observation correlations between eggshell thickness and reproductive failure in these falcons, other raptors, and fish-eating birds were discovered. The sharp fall in population of falcons was due to the effects of a pesticide, DDT on egg-shell thickness.  The egg-shells were breaking, causing the dramatic fall in reproductive success and thus the numbers of birds.

Organochlorine pesticides

The discovery that organochlorine pesticides could reduce eggshell thickness in raptorial species is perhaps the most well-known and extensively documented event in wildlife toxicology.  These findings, and evidence of human exposure to DDT led to a ban on their use in the United States in 1973, the year I started my studies in zoology, and in Europe in the 1980s.  Sadly, DDT is still used in pesticides in many parts of the developing world.

As a student, this story excited me because it showed the practical importance of pure nature research and conservation.  It continues to inspire me to this day.  We humans owe a great deal to the peregrine falcon! 

In this case action was taken to ban these harmful organochlorine pesticides.  Now, studies reveal  the harmful effects of other pesticides,  including organophosphates. 

Our understanding of organophosphates, and the way they work as neurotoxins, should at least have raised  alarm bells for their effects on wildlife and on humans.  Any substance designed to be neurotoxic is likely to be just that.   It begs a question, why these alarm bells have been ignored. 

Assurances were given that these pesticides are used in very low doses in crop pesticides and the residues do not have a prolonged life.  Yet, evidence has accumulated for its harmful effects on wildlife beyond the 'pest' species.  

These pesticides are not specifically targeted at 'pests'.  They make little or no distinction between 'pest' bugs and non-pest bugs, or between bugs and other animal species. 

They work by disrupting brain function, and as such are particularly harmful to  the developing brains of young animals, including human children.  They disrupt behaviour and cognition.   This is now recognised in the court judgement in the United States. 

In the northern bobwhite (Colinus virginianus), for example, low doses of organophosphate is found to affect the ability to avoid predation.

European Starlings

In the 1980s, studies with European starlings (Sturnus vulgaris) demonstrated reduced reproduction in birds nesting where organophosphate pesticides are used.   During the breeding season starlings feed primarily on terrestrial invertebrates that live in direct contact with pesticides present in the soil. This was evidence of these pesticides affecting the food chain.

Onus should be on the agrochemical industry to show they are not harmful

Why then does it take so long for these effects demonstrated in the 1980s to impact policies?  Why have these pesticides not been banned sooner?   We have known they are neurotoxic.  They were designed to be so.  Their effects on wildlife were in large part predictable and predicated on their impact on the brains of animals. 

The problem lies in the balance between the ever growing demand for food, the agrochemical business, and the effects on wildlife.  In that balance the cost to wildlife has been ignored.  The agrochemical business is a powerful lobby.

The process of approval of pesticides needs to change.  The agrochemical industry must demonstrate that they are safe before approval is given, and not the other way around.  They should demonstrate the effects on wildlife and on the environment with systematic studies.  Else it takes many decades of poorly funded research to accumulate data showing such harms.  We should not rely on this suck it and see approach.

About the author: Ray Noble is a certified biologist and Fellow of the Royal Society of Biology


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