More misunderstanding of the case against DDT

December 21, 2011

Well-meaning but misinformed dog breeder Terrierman (a guy who goes by the handle PBurns, too)  is just the latest to fall victim to false and nearly false claims about DDT and its effects on birds.

One of the claims made by pro-DDT and anti-environmental protection, anti-science groups is that DDT is not the bad guy in bird deaths.  The late DDT-nut Gordon Edwards said DDT had nothing to do with eagle deaths, and pointed to the 300-year decline in eagle populations from the time European settlers began shooting at them.  This idea has been touted by the chief junk science purveyor, Steven Milloy, and by many others over the years.

So, in one of his several posts slamming eagle conservation efforts that include stopping the use of DDT, Terrierman said:

What’s the story? Simple: that Bald Eagles and Osprey were pushed to the edge of extinction by DDT.

Not True.

Actually, that is true.  Terrierman got it wrong.  DDT was, indeed, threatening the very existence of the bald eagle.  While it is true that there were other pressures, some long-standing, it is also true that once those problems were cleared, DDT still barred the recovery of the eagle, plus other species like osprey, peregrine falcons, and brown pelicans.

What is the story?  The story is that eagles have been under assault since Europeans found America.  By 1900, eagle populations across North America were dramatically and drastically reduced.  A federal law in 1918 made it illegal to shoot eagles, but it had little effect.  A tougher law passed in 1940 finally got some traction.

But eagle recovery didn’t take off.  In the late 1940s and early 1950s bird watchers, and bird counters like those volunteers who contribute to the annual Audubon Christmas Bird Count, noticed that young eagles disappeared.  Simply, adult, breeding eagles were not able to produce young who survived to migrate, mature, and breed later.

The culprit was DDT.  DDT kills young eagles in three ways, known in the 1960s.  It poisons them so they cannot grow in the egg.  It poisons them so they die after a period of growth.  It poisons them so they are unable to eat and digest properly, so they die shortly after they hatch.

DDT can also screw up the sexual organs of young birds, so they are unable to breed — perhaps a fourth way DDT kills young, by simply preventing their creation.

Then, in the 1970s, we found another way DDT kills species:  DDT makes the eagle hens unable to form competent eggshells.  The young die because the eggs cannot survive incubation.

DDT also kills adult eagles, especially migrating birds.  DDT accumulates in fat tissues, those fats that migrating birds burn.  When the birds migrate, the DDT comes out, and it can literally stop the heart or brain of the bird in flight.  (It kills bats the same way.)  Birds lost in migration rarely get found for necropsy.   The bird count simply falls, the population sinks one individual closer to extinction.

Does the dog breeder know all of this?  I can’t tell — I tried to correct his errors at his blog site, but after I provided a link to an article that showed DDT appears to be harming California condors as well — in a post he has censored in moderation and which will never see the light of day at Terrierman, I predict — it’s clear he’s not up to gentle correction.

One more blog from which I am banned from telling the facts.

PBurns, if you’re bold enough to comment here, your comments won’t be censored (so long as not profane).  We need robust discussion, and I encourage it.

Below the fold — my final post to Terrierman, which he won’t allow through moderation.

Read the rest of this entry »


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