ReGenesis | Science & Society
Episode 8: Brood 14
ReGenesis strays into Hitchcock territory with this episode. NorBAC is called in to investigate when seemingly unprovoked crow attacks threaten a US military base and surrounding area. David and Carlos find a town under siege, and the problem is spreading. They discover that pesticide use over many decades has resulted in a buildup of copper sulphate and other toxic compounds in the local soil and trees. The local cicada population further concentrates these toxic chemicals, and when the cicadas are eaten by the crows, brain damage results.
The Legacy of Silent Spring
Up until the late 1950s, pesticide use was generally considered entirely beneficial. The most effective pesticide was DDT, which is particularly potent against mosquitoes. The promise of DDT and related compounds was that they might suppress or eliminate malaria, which has been one of the leading causes of human death throughout history. Because it was thought to have no effect on people, DDT was sprayed indiscriminately and widely in densely populated areas of the US and Latin America. DDT spray trucks would douse crowded beaches, and it was sprayed throughout homes, particularly on walls and other surfaces where mosquitoes land. It proved so effective that massive spraying programs for central Africa were planned.
Rachel Carson's book Silent Spring was published in 1962. If any book could be said to have launched the environmental movement in the West, it is Silent Spring. Carson claimed that irresponsible overuse of pesticides was wreaking havoc with the ecosystem and threatening human lives as well. In particular she questioned the safety of DDT, citing some evidence that it caused cancer. The backlash from the chemical industry was immediate and fierce, but within a year of Silent Spring's publication the industry was backing down. Carson never advocated the complete elimination of pesticide use, nor the banning of DDT use to control malaria. Despite her relatively moderate stance, however, Carson became a lightning rod for attacks on environmentalism, and was accused of advocating a "return to the dark ages."
Whether Carson intended it or not, the questions she raised about DDT ultimately resulted in its being banned for use in the US. The perceptions that Silent Spring created in the public mind proved more powerful than the nuanced arguments in the book itself. The result has been a great deal of bitterness and division. On one side are those who feel that the chemical industry betrayed public trust by hiding the toxicity of their products. On the other side are those who believe that banning DDT use has resulted in millions of unnecessary deaths.
DDT use has continued worldwide, and it remains a key weapon in the ongoing battle against malaria. Malaria continues to claim a million lives every year.
Biomagnification
Since the environmental awakening of the 1960s, pesticides such as DDT have been tightly controlled--or, at least, they are no longer used indiscriminately. In fact, indiscriminate or criminal use of pesticides is not the cause of the crow attacks in Brood 14. Instead, David and Carlos find themselves in an area where pesticide use has been careful and moderate for decades. There are no bad guys dumping toxic wastes. There is, in fact, nobody to blame.
So what's happened here? The problem, as NorBAC discovers, is that even where the pesticides themselves are used responsibly, their byproducts and residues can accumulate in the environment. The residues are filtered out and concentrated by living organisms through a process called biomagnification.
When we're told to consume tuna sparingly because it contains mercury, we're experiencing the effect of biomagnification. Organisms at the bottom of the food chain will accumulate substances like mercury, but only at levels equal to the local background concentration. The animals that eat these bottom feeders acquire a dose of the toxins with every meal, and don't excrete it. They concentrate it, and when they in turn are eaten by animals further up the food chain, the concentration increases. Tuna are near the top of the food chain, hence they contain the collected mercury of the whole chain beneath them. In Brood 14, it's the crows who are at the top of the food chain, and it's copper sulphate they are receiving in massive doses.
The Law of Unintended Consequences
The ultimate effect our many chemical products will have on Earth's ecosystem is unknown. DDT does biomagnify, as do PCBs, mercury and arsenic. Is it prudent to ban such products entirely? DDT in particular has saved millions of lives and continues to do so around the world. Its toxicity has proven to be much less than Rachel Carson feared, although it may be carcinogenic. In cases such as this, one may validly ask which is greater: the risk of dying from malaria, or the risk of dying from cancer caused by the pesticides used to prevent the malaria. There are no easy answers, as Carson herself knew when she wrote Silent Spring.
Boimagnification is a further, unintended consequence of industrial chemical use. It is not the only consequence: organisms such as mosquitoes evolve rapidly to become resistant to toxins such as DDT. The same effect can be seen in bacteria which evolve resistance to antibiotics. There may yet be new consequences discovered, but as a matter of policy we can only balance the benefits against the risks that we know about. Unforeseen problems may develop, but is there any alternative to saving lives using the technologies we have at hand?
--Karl Schroeder
About the Author
Karl Schroeder is an award-winning science fiction writer and the author of eight books. He also consults on technology foresight for clients such as the Canadian government and military. His articles and commentary can sometimes be found on the popular weblog WorldChanging.com, and he maintains his own website and blog at www.karlschroeder.com.
Want to read and learn more?
http://www.idrc.ca/en/ev-5593-201-1-DO_TOPIC.html
IDRC is a Canadian Crown corporation that works with researchers from the developing world to improve public health and safety. This link is to their policy statement on DDT.
http://toxics.usgs.gov/definitions/biomagnification.html
The US Geological Survey tracks information on many issues including biomagnification.
