DDT and evolution

Naomi Oreskes’ book about climate change deniers makes some interesting points about the pesticide DDT. Apparently, there has been a kind of campaign recently to challenge the history of the substance and its ban, with some anti-regulation groups claiming the regulation of DDT was unneccessary and caused many human deaths. They argue that if DDT use had not been regulated, malaria could have been eradicated.

Oreskes seems to rebut this argument convincingly. Critically, she points out how DDT had been stripped of its effectiveness through over-use, particularly in agriculture. She makes the point that the consequences of different sorts of DDT use for the genetics of the mosquito population can be very different. Spraying indoors exposes only a small minority of mosquitoes to the chemical, leaving most of the population isolated from it. As a consequence, there is only a small advantage for those mosquitoes that are more resistant to the poison. By contrast, widescale agricultural spraying exposes whole populations of mosquitoes to the toxin. Those who are a bit resistant to it have a huge advantage, and soon come to dominate the population. Over time, the indiscriminate use of DDT breeds mosquitoes who are troubled less and less by the toxin.

Oreskes documents how the banning of DDT took place only after its effectiveness was lost, as well as how the environmental and human health effects of the substance were sufficiently worrisome to justify the ban. She argues that the recent attempt to change the historical narrative is not about DDT itself – which nobody is seeking to reintroduce. Rather, it is intended to foster and enlarge a general sense that taking precautions to protect human health and the environment is unjustified, and that science that supports the regulation of industry and individual behaviour is ‘junk’.

A related situation that I have written about before is the abuse of antibiotics in the livestock industry. Just as the agricultural use of DDT provided ideal circumstances for insects to evolve resistance, today’s factory farms may as well have been custom designed to render our antibiotics ineffective. Crowding huge numbers of unhealthy animals close together, flooding them with chemicals to make them grow as quickly as possible, feeding them unnatural diets, and then using antibiotics to try and keep them from dying too early, is a string of compounding errors. Not only does it demonstrate considerable disregard for the welfare of the animals in question, but it demonstrates a lack of foresight when it comes to maintaining the effectiveness of our drugs and the relative manageability of the bacteria out there.

Of course, the political system tends to favour the small group of farmers that benefits from the status quo and which would suffer significantly from a change in policy, rather than the great majority of people who are incrementally harmed by the emergence of ever-more-dangerous superbugs, and the dilution of the effectiveness of the relatively small class of chemicals capable of safely killing bacteria inside human beings, without causing undue harm to the person.

Author: Milan

In the spring of 2005, I graduated from the University of British Columbia with a degree in International Relations and a general focus in the area of environmental politics. In the fall of 2005, I began reading for an M.Phil in IR at Wadham College, Oxford. Outside school, I am very interested in photography, writing, and the outdoors. I am writing this blog to keep in touch with friends and family around the world, provide a more personal view of graduate student life in Oxford, and pass on some lessons I've learned here.

9 thoughts on “DDT and evolution”

  1. I’ve also seen graphs that show that once widespread agricultural use of DDT was banned (while indoor anti-malarial use continued) deaths from malaria dropped dramatically.

  2. There is a similar self-serving revisionist line among pro-nuclear people who argue that Chernobyl wasn’t such a big deal, after all.

  3. “The most efficient way to use pesticides against disease is through application to the insides of buildings – the Indoor Residual Spraying on which the World Health Organization largely relied. DDT is particularly potent in this use, as an application can last up to a year. Most important, it doesn’t produce resistance very quickly, because most insects don’t wind up in buildings and therefore aren’t subjected to the poison. Indoor Residual Spraying just affects the small percentage of the population that makes it indoors, where they are likely to bite people and transmit disease, so the selection pressure on the insect population isn’t very high. It’s a very sensible strategy.

    However, when pesticides are sprayed over large agricultural areas, they kill a large fraction of the total insect population, ensuring that the hardy survivors breed with only other hardy survivors; the very next generation may display resistance.”

    Oreskes, Naomi and Erik Conway. Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues from Tobacco Smoke to Global Warming. p.225 (hardcover)

  4. “Admittedly, some public health experts think that DDT could play a useful role in malaria control in some places in the world today, but it never was the miracle cure that Lomborg, Sowell, Cohen, and Tierney have made it out to be. There is no scientific evidence to support the claim that millions of lives have been needlessly lost, and there is substantial scientific evidence that a good deal of harm – both to humans and the other species we share the planet with – has been avoided.”

    Oreskes, Naomi and Erik Conway. Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues from Tobacco Smoke to Global Warming. p.229 (hardcover)

  5. “The network of right-wing foundations, the corporations that fund them, and the journalists who echo their claims has created a tremendous problem for American science. A recent academic study found that of the fifty-six “environmentally skeptical” books published in the 1990s, 92 percent were linked to these right-wing foundations (only thirteen were published in the 1980s, and 100 percent were linked to the foundations). Scientists have faced an ongoing misrepresentation of scientific evidence and historical facts that brands them as public enemies – even mass murderers – on the basis of phony facts.

    There is a deep irony here. One of the great heroes of the anti-Communist political right wing – indeed one of the clearest, most reasoned voices against the risks of oppressive government, in general – was George Orwell, whose famous 1984 portrayed a government that manufactured fake histories to support its political program. Orwell coined the term “memory hole” to denote a system that destroyed inconvenient facts, and “Newspeak” for a language designed to constrain thought within politically acceptable bounds.

    All of use who were children in the Cold War learned in school how the Soviet Union routinely engaged in historical cleansing, erasing real events and real people from their official histories and even official photographs. The right-wing defenders of American liberty have now done the same. The painstaking work of scientists, the reasoned deliberations of the President’s Science Advisory Committee, and the bipartisan American agreement to ban DDT have been flushed down the memory hole, along with the well-documented and easily found (but extremely inconvenient) fact that the most important reason that DDT failed to eliminate malaria was because insects evolved. That is the truth – a truth that those with blind faith in free markets and blind trust in technology simply refuse to see.”

    Oreskes, Naomi and Erik Conway. Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues from Tobacco Smoke to Global Warming. p.236 (hardcover)

  6. Nice quotes and I’m glad someone has taken on the DDT myth in print. Those stats on the origin of environmentally sceptic books in the 80s and 90s are eye-opening. I wonder what the other 8% are like.

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