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The blue marble

50th Anniversary of Silent Spring: Synthetic chemicals cause the decline of bees

This Sunday we are celebrating Earth’s day, and Earth corresponded to our recognition by slowly spinning once again around its own axis, thereby allowing us to enjoy yet one more beautiful sunrise and, later on, a beautiful sunset.

As our planet completes one more spin, my thoughts on the 2012 Earth Day are with Rachel Carson and her landmark book “Silent Spring” published in September 1962, 50 years ago.

Silent Spring alerted society, with very compelling, scientifically-sound arguments and beautiful prose, of the risks of the massive use of synthetic pesticides, in particular DDT. Over a decade before this publication, Paul Müller received the Noble Award in Physiology for the demonstration of the efficiency of DDT to control insect populations.

Whereas massive application of DDT proved to be effective in reducing the prevalence of malaria, arguably saving many human lives; it came at a huge cost to all life, as DDT was not only effective in controlling mosquitoes carrying human pathogens, but all insects alike. DDT accumulated in living tissues and increasing in concentration upward in the food web. Decades after the ban on the use of DDT, all of us can still detect significant, but decreasing, concentrations of DDT in our own blood. Hence, massive application of DDT affected insects, both beneficial and noxious, wildlife and humans alike.

Rachel Carson’s work reacted to emerging evidence at the high environmental impacts of DDT, but was met with vigorous opposition from industry, which tried to prevent the publication of her book and made every possible attempt at discrediting her.

Much too often we have seen this same pattern: with the role of CFCs in destroying the ozone layer; the dirty campaign of industry to suppress the evidence for the health impacts of smoking; and the concerted campaign of some industrial sectors to discredit climate science and scientists.

Rachel Carson was, however, a brave woman, if with fragile health, and held her ground against these pressures, driving President J.F. Kennedy to consider seriously the risks of synthetic pesticides. Almost a decade later, following Rachel’s death from cancer, her efforts came to fruition in the form of US legislation regulating the application of synthetic pesticides.

Whereas Rachel Carson’s fight was hugely successful, it is not yet over. Our biosphere continues to receive emissions of synthetic chemicals, many of which have important negative consequences on biota, humans and the Earth System (e.g. acting as powerful greenhouses, impacting upon the ozone layer or interfering with the immune and reproductive systems of organisms, including our own).

The inventory of synthetic chemicals ever synthesized by humans is in the order or a million compounds, of which tens of thousands have been produced industrially and thus released in the environment. Many of these chemicals are biologically active, persistent in the environment and enter global transport. The resulting “anthropogenic chemosphere” (Dachs and 2010) is an important, if not sufficiently acknowledged, vector of global change.

Indeed, Rachel Carson’s fight is not yet over, and we need to continue to be alert at the pervasive effects of synthetic chemicals. A recent paper in Science (Whitehorn et al. 2012) provided compelling experimental evidence, linking the widespread and hereto mysterious decline of bumble bees with Neonicotinoid insecticides. Bees, tiny as they are, play a fundamental role in maintaining biodiversity, and even the production of fruits for human consumption, through their role as pollinators. The widespread decline of bees can have, thus, major impacts on biodiversity and food webs.

The Stockholm Convention on Persistent Organic Pollutants, effective from May 2004, aims at eliminating or restricting the production and use of persistent organic pollutants (POPs). The original list of twelve compounds was expanded to add ten more compounds in 2010, and an additional 3 have been proposed for regulation. Yet, the rate of adding synthetic compounds to the Stockholm Convention is far slower than the rate of release of new POPs.

One of the POPs included in 2010 is PolyBrominated Diphenyl Ethers or PBDEs. PBDEs are used as flame retardants in a diversity of materials, including building materials, electronics, furnishings, vehicles, airplanes, plastics, polyurethane foams and textiles. They have been shown to reduce human fertility at levels found in households; and we can be certain that these households include our own.

A mature industry should produce sufficient robust scientific evidence for the absence of significant impacts of new synthetic chemicals in the environment, assess their likely persistent and transport pathways in the environment, and provide the scientific community and governmental labs with analytical techniques to resolve the ambient levels of these chemicals. A mature society should demand that industry does just that.

This is, however, not the case, and much too often we discover dangerous impacts of synthetic chemicals long after they were introduced in markets and, therefore, in the environment.

As the Earth Day comes to a quiet end, I see the reflections of the purple tones of the clouds in the quiet waters of the Mediterranean, and remember that Rachel Carson should also be celebrated for other contributions, including her beautiful books about the marine environment. Try, for one, Rachel Carson’s “The Sea Around Us”.


Dachs, J., and L. Méjanelle. 2010. Organic Pollutants in Coastal Waters, Sediments, and Biota: A Relevant Driver for Ecosystems During the Anthropocene?. Estuaries and Coasts 33:1–14

Whitehorn, P.R., S. O’Connor, F.L. Wackers, and D. Goulson. 2012. Neonicotinoid Pesticide Reduces Bumble Bee Colony Growth and Queen Production Science DOI: 10.1126/science.1215025.

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