By the early 70s, when Bald Eagle populations had doubled from their low point, DDT was already on a serious decline in use in the US (it peaked in 1959 at 80 million pounds) and was almost exclusively used in its later years on Cotton in the US (~80% of use) so when you consider how big the US is and how little was used outside the South (~2.5 Million pounds), it's impact on Bald Eagles would have been at best minor since nearly sterile Cotton fields in the South would not be considered a main hunting ground for this predator.
Indeed we have annual bird counts courtesy of the Audubon Society which clearly show that the increasing use of DDT was never correlated to the numbers of Bald Eagles.
http://birds.audubon.org/historical-results
Table is: Year Birds Counted, Birds per person counting (For elusive birds like Bald Eagles this last number helps to get a better idea of density of birds, so looking at the chart you can see that in 1970 they counted over 10 times as many birds, but only twice as many per person, the real census then likely likes between those two numbers, i.e., in 1945 there were certainly more than 132 Eagles, they just weren’t seen because the number of counters was low, of course in 1970 there weren’t likely to be 10 times as many Eagles either, just fewer were not seen, a more reasonable interpretation is the population was probably three times as large in 1970 as it was in 1945)
1945 132 0.07 <== DDT starts being used
1950 393 0.11
1955 424 0.06
1960 609 0.08
1965 759 0.07
1970 1648 0.13 <== peak sightings per person, nearly twice as many as in 1945
So over the timeframe DDT was used in the US, the density of sightings went up quite a bit and the number of actual birds was maybe two to three times what it was when DDT was first used
In contrast, it’s affect on Brown Pelicans is even less likely as the Brown Pelican only lives next to salt water and only feeds on fish living in the ocean, so the amount of DDT that they would consume from eating fish living in the Gulf waters and along the Eastern Seaboard would not be likely be that much. And of course plenty of Brown Pelicans also lived where DDT was not used at all, so it alone would never have caused their extinction, (Teddy Roosevelt created the first Federal Bird Sanctuary, Pelican Island, in Florida in 1903 (now called the Merritt Island National Wildlife Refuge]) the reason is they were being extensively hunted for their feathers and later by fisherman. Indeed the hunting of birds in the US at this time was so extensive that Congress passed the Migratory Bird Treaty Act of 1918, which included protection for the Brown Pelican.
The fact is Brown Pelican numbers began to decline sharply in the 1920’s and 1930’s, when adult birds were killed and nesting colonies destroyed by fishermen, in the mistaken belief that pelicans competed with man for food. It is estimated that pelican numbers declined by more than 80% in just 16 years, between 1918 and 1934.
This was decades before the use of DDT.
From the Audubon Bird Count database we can see that the number of Brown Pelicans also increased significantly and were at much higher counts in 1972 than they were in 1945.
1945 2689
1950 3898
1955 4674
1960 4898
1965 14912
1970 11591
1972 16683 <== year of ban
1975 14019
1980 15296
I know nearly everything one reads blames DDT for the decline of these birds, but the facts really support the conclusion that well before DDT was used men deliberately killed these animals to near extinction; That laws passed before DDT was used were starting to work, such that over the timeframe that DDT was used both of these bird species actually increased in numbers and density.
Now I am NOT saying that DDT had no impact on the birds. You can’t make that conclusion from just these numbers. But what you can conclude is that in both cases these two bird populations increased while the amount of DDT was going up and the logical explanation is that while there are certainly biological reasons why DDT might have had a negative impact on some populations of these birds, DDT wasn’t sprayed evenly throughout the country, so clearly there would be places where the impact would be high and others where it would be low. A more plausible explanation then is that during this period we did a much better job of stopping the hunting and destruction of their nesting sites and providing sanctuaries for the birds which allowed them to slowly recover. For some populations, stopping the use of DDT may have also helped.
As to Malaria, a ban on its use doesn't matter if no one makes it or is willing to supply it to the poorer countries that needed it, and so if you look at it's use in the world against Malaria it was indeed effectively banned.
The U.S. decision had a rapid effect in the developing sector, where the State Department made U.S. aid contingent on countries not using any pesticide that was banned in the United States. The U.S. Agency for International Development discontinued its support for DDT spraying programs, and instead increased funding for birth control programs.
Other Western nations—Sweden and Norway, for example—also pressured recipient nations to stop the use of DDT. Belize abandoned DDT in 1999, because Mexico, under pressure from the United States and NAFTA, had stopped the manufacture of DDT, which was Belize’s source. Purchases of replacement insecticides would take up nearly 90 percent of Belize’s malaria control budget. Mozambique stopped the use of DDT, “because 80 percent of the country’s health budget came from donor funds, and donors refused to allow the use of DDT,” reported the British Medical Journal (March 11, 2000).
The World Bank and the World Health Organization, meanwhile, responded to the rise in malaria incidence with a well-publicized “Roll Back Malaria” program, begun in 1989, which involves no insect control measures, only bed nets, personnel training, and drug therapies—a prescription for failure.
http://www.21stcenturysciencetech.com/articles/summ02/DDT.html
Last post on this matter.
Arthur