DDT and Declining Raptors
Even 50 years after being banned in the U.S., raptor species are still suffering from effects.
What is DDT?
Dichloro-diphenyl-trichloroethane is an organochloride chemical that started being used around the world in the 1940’s to eliminate the presence of mosquitoes that carried deadly diseases. DDT was seen as a miracle pesticide essentially eliminating Malaria. DDT also has a long history of being a topic of controversy to legislators, public health officials and environmentalists.
DDT has been identified as a carcinogenic. It can cause fatal illnesses in humans such as cancers and organ failure. The chemical can even produce harmful effects in small levels to the nervous system and hormone production. DDT is most commonly ingested through food in modern times, and is hard to detect in trace amounts since in raw form it is it a powder with no taste or smell.
Am I at risk for ingesting DDT?
In the United States, the EPA banned the use of DDT in 1972 to protect wildlife and for public health concerns. The “Stockholm Convention on Persistent Organic Pollutants” was a global treaty signed by many countries around the world to protect the environment and the public.
An article published in the Malaria Journal stated that DDT is only to be used to fight Malaria and other deadly vector borne diseases. Even though the chemical has been banned in the United States for almost 50 years, there are still recorded amounts found in ecosystems, wild game, and seafood due to how long it naturally takes to break down. Because of the affordability and effectiveness of DDT, some countries see the benefits of disease prevention outweighing the risks.
What About Environmental Effects of DDT?
A book called Silent Spring was published in 1962 by Rachel Carson that outlined the dangers of DDT before the EPA was even established in 1970. Specifically, this book included startling evidence about how DDT was effecting raptor species.
The Cooper’s hawk in particular (Accipiter cooperii), is an Accipiter hawk found across the United States now, but populations of this raptor were drastically reduced due to DDT.
The Cooper’s Hawk can presently be found in every state across America year-long with some populations migrating to Mexico in the colder months. In northern states and parts of Canada, some populations chose this as their breeding location but resident populations are limited.
This is an observation map from 2105-2020 of the Cooper's Hawk form The Cornell Lab
Populations of the Cooper's hawk are abundant now, and they have adapted well to living in urban ecosystems, but this was not always the case.
This graph from Hawk Mountain displays the population index of the Cooper’s Hawk seen in their fall migration from 1936-2019. The trend of the graph shows a decline of the Cooper’s hawk during the peak of DDT use and growing slowly after it was banned by the EPA in 1972.
How Are Raptors Being Effected by DDT Now?
In most developed countries, DDT is rarely seen in the news and is not a topic of concern when it comes to health risks anymore, but is still effecting people and important apex predators around the world where it is still needed to combat vector borne diseases.
Raptors are important bioindicators to the environment because they provide useful information about chemicals that accumulate and where there are concentrations. This information is used to track down sources of the chemical in an attempt to reduce their use.
Below is a map that displays countries that still use DDT and have over 30 declining raptor species listed. Some of the surrounding countries that have high levels of declining raptor species could be attributed to neighboring DDT usage.
DDT and declining raptors
Controversy Persists Over DDT
Other chemicals are used in countries to cut down the amount of DDT used or to replace it entirely as a pesticide, but other alternatives are usually costly or do not keep the mosquitoes away for as long. Perhaps the most viable alternative to spraying DDT and other harmful insecticides is the prevention of malaria through routes such as vaccines and pharmaceutical treatments. Until better alternatives are readily available, vector-borne illness is a top priority of health leaders.
It has been proven by The Cooper's Hawk and other raptor species of North America that a population resurgence after a DDT event is probable. Unfortunately, as long as DDT remains prevalent in the environment, the raptor's food source remains poisoned and populations cannot recover themselves without healthy nutrition.
