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ONLINE NEWSLETTER
 
DDT DANGER REMAINS

The Nice Myth: Bald eagles are recovering on Catalina because DDT is gone from the environment.

The Filthy Truth: Actually, DDT (or more correctly it’s byproduct: DDE), will be with us for a very long time to come.

What’s actually happened is that DDT/DDE has broken down enough that the more severe effects that caused reproductive issues in years past are fading.  It’s likely that DDE is still causing harm in the environment, but the impacts are now low enough that natural reproduction for bald eagles is possible. The rate of persistence of chemicals like DDT in the environment is often measured in terms of half-lives. A half-life is the amount of time it takes for a chemical to break down by 50 percent.  Based on a reasonable estimate of a 15-year half-life -- beginning with 100 kilograms of DDT -- it would break down as follows:

Year

Amount Remaining

0

100 kg

15

50 kg

30

25 kg

45

12.5 kg

60

6.25 kg

75

3.13 kg

90

1.56 kg

105

0.78 kg

120

0.39 kg

Source: http://www.marietta.edu/~biol/102/2bioma95.html

As you can see, after 40 years, it’s not gone…it’s just present at a lower concentration.

When isn’t an “eagle” an eagle? Read Grand Ole Osprey

 

 

 


THE ISLAND NATURALIST
Issue #4 / All About Eagles


IN THIS ISSUE...


Bald Later in Life
DDT Danger Remains
Grand Ole Osprey
Fact or Fiction: Island-Mainland Tie?
Did You Know…Two Mice on Catalina




Photo by Steffani Jijon/Courtesy of the Institute for Wildlife Studies

Bald eagle hatchlings were at risk for decades from DDT-caused thin egg shells.




 

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