Ed Darrell just can’t get enough, I guess. Not satisfied with my most recent response to him, he returns to this “frustrating”, “not the place to carry on a discussion” blog to ask for more information.
Ed claims that there are a thousand studies that confirm Carson’s claims. Personally, I don’t see them — certainly Ed doesn’t link to all of them (in fact, between the two incredibly lengthy articles of his that I have now linked to, he links to very few studies indeed).
But then, you can’t find a single link to any study which contradicts anything Carson wrote. You criticize me for pointing to the studies that do exist, while Milloy functions on misrepresentation, outright falsehood, and non-existent studies.
I challenge you again: Find a study that says eagles were not harmed by DDT. Don’t cite a third-hand, hearsay piece from Milloy: Cite the study.
Go to Discovery Magazine and looke at the number of studies they cite. Milloy doesn’t offer numbers of studies, only misquotes from a few — Discover counted those that corroborated Carson’s work. 1,000 to how many? Count ‘em, if you can find ‘em.
When your side is down 1,000 to one, it’s an expected tactic for you to call me a liar. Shame on you.
I’m not actually threatened by the prospect of being “down” a thousand to one, so long as the one that I do have is correct. It’s like John da Fiesole always asks: but is it true? So long as I have one that’s true, the other side is welcome to their thousand.
For example, the reason I’m calling Ed a liar is because I caught him in a lie by demonstrating that a statement which he made is false. Predictably, in keeping with the general modus operandi of a biased activist, Ed has not yet retracted his erroneous statement — a crime he accuses Steven Milloy of being guilty of, mind — but has instead persisted in saying that nothing out there exists which challenges Rachel Carson’s writings.
Ed insists I cite the study. Okay, fine, I can cite the study. But Milloy cites studies as well, and Ed doesn’t accept those — some he dismisses as non-existent, others he dismisses as invalid for a host of nebulous reasons. Perhaps, dishonestly, Ed only accepts as valid those studies which agree with his biases? That would certainly be typical of a biased activist, wouldn’t it, O Reader?
But to humour his demands one more time, here’s a few things I was able to cobble together in the 20 or so minutes I had left in the day when this latest bit of correspondence from Ed arrived in my mailbox. Just to be clear: every article or study I link to here, I found online within twenty minutes. Given a day, or a week, and both the internet and a comprehensive database of old articles on microfiche, how many other gems might I find?
Remember also Ed’s claim that nothing has been published which refutes Carson’s claims. All I need is one.
First, in an analysis of DDT and its derivatives, the International Programme on Chemical Safety found that “DDT and its derivatives DDE and TDE have moderate to low toxicity to birds when given as an acute oral dose or in the diet.” Moreover, it was found that there “is no obvious pattern of relative toxicity between the three compounds. In some species it is DDT that is the most toxic, while in other species it is TDE.” (and remember: what toxicity exists is rated as “moderate to low”) The study does not specifically address eagles, however, noting that in the wild, “the most severely affected species of birds are raptors at the top of food chains. There is little direct laboratory data on toxicity to these birds.”
That should begin to paint us an interesting picture, O Reader, one which I will come back to later. There is “little laboratory data” on the toxicity of DDT and its byproducts to high-level predatory birds like eagles. And yet some people assert with terrifying certainty (when is science ever certain?) that DDT is the causitive factor in the bald eagle’s near brush with extinction.
The study goes on to note that whether or not DDT exposure affected hatchability of eggs (particularly due to eggshell thinning) varied greatly between bird species — some were succeptible to it, some were not. Care must be taken in looking at the results, however, because some of the test birds were also fed a low-calcium diet, which would also negatively impact eggshell thickness. This was specifically being tested for, as earlier studies (most notably by Joel Bitman of the United States Department of Agriculture, in 1969) had exposed the test birds not only to DDT or one of its derivatives, but had also fed them a low-calcium diet.
The reduction of calcium in the diet of test birds was found to be a significant factor in the outcome of the studies (which shouldn’t come as a surprise): “In contrast to the earlier studies, there was no effect of either DDT or DDE on shell thickness or egg weight when dietary calcium was higher. There was an increased incidence of egg breakage in birds fed DDT and DDE, but this was less pronounced than with the low calcium diets.”
Moreover, “Robson et al. (1976) studied the effects of DDE and DDT fed to Japanese quail in two different diets containing adequate or low calcium. DDT was fed at 100 mg/kg diet, whereas DDE was given at 0, 199, or 300 mg/kg diet, and the two calcium levels were 0.5% and 3%.
DDE at 300 mg/kg was detrimental to adult body weight, fertility, and survivability. There was no effect of either DDT or of DDE at up to 100 mg/kg diet on adult body weight, food consumption, egg production, egg weight, fertility, hatchability, cracking of eggs, or eggshell thickness. Low dietary calcium had the effect of reducing the thickness of eggshells, increasing the incidence of cracked shells and decreasing egg production and hatchability.” In other words, DDT and its derivatives (DDE is the most common — it is formed when DDT sheds a hydrogen cholride molecule) did not have at all the same effect on eggshell thickness in test birds as it was found to have in previous studies, because those studies had also involved feeding the birds a calcim-deficient diet, something they probably wouldn’t have been exposed to as frequently in the wild.
It’s not just the Bitman study that is thrown into doubt, either — researchers from the University of Alberta, writing to Nature Magazine, also question the findings of Wiemeyer and Porter’s work with American kestrels, pointing out that in the Wiemeyeer/Porter study, it was the control group of birds who had the thinnest eggshells. This was written in response to an article in Nature Magazine by Blus, Gish, Belisle and Prouty in 1972. The U of A researchers, in their letter, note that to “support their conclusions, the authors [Blus, Gish, Belisle and Prouty] state that concentrations of residues in the female determine shell thickness, a claim which is unreferenced, largely hypothetical, and without consideration of contradictory experimental evidence.”
Now, when one does even as little as a Google search for DDT and eagles, one finds a lot of different articles alleging that there is a connection between DDT usage and the decline in the eagle population. Keeping in mind that there isn’t that much laboratory data available on high-end predatory raptors, most of these studies and articles tend to cite earlier studies, such as those by Bitman or Wiemeyer and Porter, in support of their conclusions. Certainly, that was the case in the Nature Magazine article mentioned above (Nature, 235, 376 (1972)). In that specific case, it was shown, quickly and rather easily, that the authors of the article not only incorrectly interpreted the evidence that they considered, but also that they ignored evidence which contradicted their conclusions.
Ed asserts that there are a thousand studies done. I see a number of studies, to be sure, but I also see a number of articles drawing upon the same pool of studies. Perhaps I’m in error to suspect this, but if we assume that Ed’s hyperbolic claim of a thousand studies is actually an accurate number, how many of those studies are unique inquiries, and how many are follow-up articles in scientific publications which draw upon the same pool of earlier research data? And how many of those ignored contrary evidence? Was it just the writers at Nature, or were some of the writers at, say, Discovery also guilty of sweeping under the rug later studies which contradicted some of their conclusions?
As recently as 2003, IBIS - the International Journal of Avian Science, published by the British Ornithologists Union, found that their revisiting of the DDE/eggshell thickness issue in American condors “revealed major problems in using the thickness or DDE content of shell fragments from eggs of unknown size to study contamination problems.” They urged that “future studies of the effects of DDE on shell thinning in any species be limited to whole-egg samples when possible. DDE analyses of shell fragments should be regarded as inherently suspect, unless they are run immediately after eggs are fragmented, and direct shell thickness measurements should always be interpreted in the light of egg-size effects on thickness. Studies in which egg size is neglected can miss potentially important effects of egg size on shell thickness and DDE on egg size.
The failure of many previous avian DDE studies to investigate potential DDE effects on egg size or egg-size effects on thinning does not necessarily invalidate any of these studies, especially if the species involved suffered no changes in egg size during periods of contamination. However, results with the California Condor suggest that re-analyses taking egg-size information into account might modify conclusions in some cases.”
Now, admittedly, none of these articles addresses bald eagles directly — but that is because there is very little lab data available on eagles to begin with. What the studies I have linked to do is point to a trend that calls into question earlier studies on the relationship between DDT or one of its derivatives and eggshell thickness in different bird species, especially in light of the suspect nature (see the IBIS article, above) of studies of eggshell thickness done on eggshell fragments that were not collected and analyzed at or very near the moment of fragmentation.
In Photography, there is a technique that shooters sometimes use which is called bracketing. Bracketing can mean many things, but in essence distills down to this: one aspect of the camera’s operation or image capture parameters is varied over a series of shots, while the subject of the picture is held constant. For example, let us say that one is taking a picture of someone who is backlit by a strong light source. One could use bracketing to take a series of pictures, varying the exposure each time, in order to try and capture an image that strikes a balance between overexposing the background and underexposing the subject in the foreground. Bracketing is used, in essence, to extract an optimal, if not a maximum, level of detail from a scene, especially a scene in which harsh conditions concerning dynamic range are present.
What does this have to do with eagles?
Science News, in 1998, noted that “[l]ong before DDT was a glimmer in a farmer’s eye, some other menace, as yet unknown, was sapping the strength of eggshells.” This could possibly have been a result of acidification as a result of early industrialization, but at any rate it was found that a thinning trend in the eggshell thickness of various bird species could be traced back as far as 1850, predating DDT by many decades (the same study noted that some bird species have “withstood eggshell declines of up to 15 percent”). The Reader will have to pardon the rather “dated” look of the Science News article archives — evidently, the changeover in format that has been done to their main site has not yet been bubbled down to all the old content.
Moreover, the American Council on Science and Health, in their Facts Versus Fears publication (Edition 3, June 1998 — an extract of the ACSH article can be found here) noted that “[i]n 1968 two researchers, Drs. Joseph J. Hickey and Daniel W. Anderson, reported that high concentrations of DDT were found in the eggs of wild raptor populations. The two concluded that increased eggshell fragility in peregrine falcons, bald eagles, and ospreys was due to DDT exposure. Dr. Joel Bitman and associates at the U.S. Department of Agriculture likewise determined that Japanese quail fed DDT produced eggs with thinner shells and lower calcium content.
In actuality, however, declines in bird populations either had occurred before DDT was present or had occured years after DDT’s use. A comparison of the annual Audubon Christmas Bird Counts between 1941 (pre-DDT) and 1960 (after DDT’s use had waned) reveals that at least 26 different kinds of birds became more numerous during those decades, the period of greatest DDT usage. The Audubon counts document an overall increase in birds seen per observer from 1941 to 1960, and statistical analyses of the Audubon data confirm the perceived increases. For example, only 197 bald eagles were documented in 1941; the number had increased to 891 in 1960.
At Hawk Mountain, Pennsylvania, teams of ornithologists made daily counts of migrating raptors for over 40 years. The counts — published annually by the Hawk Mountain Sanctuary Association — reveal great increases in most kinds of hawks during the DDT years. The osprey counts increased as follows: in 1946, 191; in 1956, 288; in 1967, 457; and in 1972, 630.13 In 1942 Dr. Joseph Hickey — who in 1968 would blame DDT for bird population decline — reported that 70 per-cent of the eastern osprey population had been killed by pole traps around fish hatcheries. That same year, before DDT came into use, Hickey noted a decline in the population of peregrine falcons.
Other observers also documented that the great peregrine decline in the eastern United States occurred long before any DDT was present in the environment. In Canada peregrines were observed to be “reproducing normally” in the 1960s even though their tissues contained 30 times more DDT than did the tissues of the midwestern peregrines allegedly being extirpated by the chemical.18 And in Great Britain, in 1969, a three-year government study noted that the decline of peregrine falcons in Britain had ended in 1966 even though DDT levels were as abundant as ever. The British study concluded that “There is no close correlation between the decline in population of predatory birds, particularly the peregrine falcon and the sparrow hawk, and the use of DDT.
In addition, later research refuted the original studies that had pointed to DDT as a cause for eggshell thinning. After reassessing their findings using more modern methodology, Drs. Hickey and Anderson admitted that the egg extracts they had studied contained little or no DDT and said they were now pursuing PCBs, chemicals used as capacitor insulators, as the culprit.”
This is what I’m getting at, O Reader, when I talk about bracketing — looking at the data outside a single frame of reference. The fact is, eggshell thicknesses were already in decline by the time DDT usage became widespread, and that decline continued in some species well past the time when DDT began to fall out of use (the early 1960s), and well past the time when it was banned. To a truly critical mind, that detail, plus the fact that there is now grounds for doubt about the conclusions of many of the studies done demonstrating a direct correlation between DDT concentration and the welfare of various bird species, should be cause enough for a re-evaluation of whether or not the doom prophecies of Silent Spring were really all that correct in the first place.
Yes, nothing I have cited pertains directly to eagles…but given the studies that I have dug up, we must now diverge our thinking. Either eagles were uniquely succeptible to DDT and its derivatives, and were particularly vulnerable to it, or else they — like many other bird species — were already under pressure from a variety of other environmental factors at the same time. One cannot help but note that around the same time that DDT was falling out of use and heading toward its eventual banning, both automobiles and various industries were being subjected to steadily more strict environmental regulations, and were installing better emission control systems. How can the effects of those changes be measured separately from any perceived changes brought on by a reduction or cessation of DDT usage if, as may well be possible, acidification due to industrial pollution also had a detrimental effect on eggshell thickness?
And finally, there is one other consideration. “In Ceylon (now Sri Lanka) DDT spraying had reduced malaria cases from 2.8 million in 1948 to 17 in 1963. After spraying was stopped in 1964, malaria cases began to rise again and reached 2.5 million in 1969. The same pattern was repeated in many other tropical — and usually impoverished — regions of the world. In Zanzibar the prevalence of malaria among the populace dropped from 70 percent in 1958 to 5 percent in 1964. By 1984 it was back up to between 50 and 60 percent. The chief malaria expert for the U.S. Agency for International Development said that malaria would have been 98 percent eradicated had DDT continued to be used.
In addition, from 1960 to 1974 WHO screened about 2,000 compounds for use as antimalarial insecticides. Only 30 were judged promising enough to warrant field trials. WHO found that none of those compounds had the persistence of DDT or was as safe as DDT. (Insecticides such as malathion and carbaryl, which are much more toxic than DDT, were used instead.) And—a very important factor for malaria control in less developed countries—all of the substitutes were considerably more expensive than DDT.”
Nearly three million people die every year (another of Ed’s lies was to claim that only 1 million people die each year from this disease — he has yet to retract that statement as well) from malaria. Perhaps it is callous of me to say so, but for some reason, I cannot bring myself — in the face of statistics that basically mean one malarial death every thirty seconds — to care more about eight hundred observed eagles as opposed to merely three hundred.
Ed mentions shame. Yes, it would be a shame if the bald eagle went extinct — but it’s a bigger shame that 2.7 million people die every year from a disease that was on the road to eradication at one point.
Ed will just have to forgive me if I don’t get all misty over the plight of a bird that isn’t even a food source for humans.
