How the American bald eagle ‘returned’ from the brink of extinction
Context- The American bald eagle was removed from the United States’ list of endangered species on June 28, 2007.
Since then, the population of the bird has steadily risen. A 2021 report by the US Fish and Wildlife Service said that the number of bald eagles in the wild has quadrupled since 2009.
However, just a few decades back, the bird was on the verge of extinction, facing multiple threats to its existence.
(Credits- Wikipedia)
Population decline since the 1800s
- Once upon a time, bald eagles were abundant across the United States. When they were adopted as the country’s national symbol in 1782, there were as many as 100,000 nesting birds in the continental United States (including Alaska), as per the American Eagle Foundation.
- However, their populations began to decline in the early 1800s. Bald eagles began to be seen as a threat to livestock, especially domestic chicken, and started to be hunted. Often, counties placed bounties on bald eagles – ostensibly to protect farmers’ interests.
- Hunting intensified in the latter half of the century, when feather hats became a fashion staple. While the Migratory Birds Treaty Act came into force in 1918, populations steadily declined till about the 1940s.
- This compelled the US Congress to pass the Bald and Golden Eagle Protection Act in 1940 expanding protections and prohibiting even the possession of eagle feathers.
- However, eagles would soon face a different, arguably more dangerous, threat than hunting and habitat destruction.
The appearance of DDT decimates the bald eagle population
- DDT or dichloro-diphenyl-trichloroethane was first synthesised in 1874. However, it was in 1939 that it was first promoted as an insecticide and began to be used to kill malaria-carrying mosquitos and agricultural pests. By the mid to late 1940s, DDT was being widely used for agriculture across the US.
- While extremely effective as an insecticide, DDT had a catastrophic impact on the bald eagle population.
- Water bodies were soon contaminated with DDT, which in turn contaminated the fish in them. The chemical would enter the bald eagles’ bloodstream when they would eat these fish. Notably, DDT resulted in female eagles laying extremely thin-shelled eggs, leading to nesting failures.
- Notably, like the bald eagle, birds such as ospreys and peregrine falcons also faced a similar dropoff in population.
Silent Spring, the ban on DDT and the Endangered Species Act
- In 1962, Rachel Carson’s book Silent Spring was published. This book, for the first time, documented the detrimental effects of chemical pesticides on the environment and meticulously described how DDT was the prime cause behind the decline in bald eagle populations.
- While railed by companies in the chemical industry, the book became the rallying point for the burgeoning environmental movement of the 1960s.
- Notably, a nationwide ban on the use of DDT for agricultural use was introduced in 1972 and in 1973, the Endangered Species Act was enacted. This act broadened protections already in place for endangered species, particularly focussing on the protection of animal habitats.
- The bald eagle was one of the original species listed for protection under this act.
Captive breeding programmes and strict habitat protections
- Captive breeding programmes were launched in the 1970s and proved to be crucial in helping the resurgence of bald eagles.
- The US Fish and Wildlife Service would head programmes where eagle colonies were bred in captivity at centres such as the Patuxent Wildlife Research Center in Maryland before being released into the wild. This allowed conservationists to closely monitor fragile eggs and nestlings, increasing their survival rates significantly.
- A practice known as hacking was commonly used by conservationists. Hacking is a controlled way to raise and release bald eagles into a wild viable environment from artificial nesting towers. This method simulates a wild eagle nesting site and aids in recovery in an area where re-population is desirable.
- Moreover, strict restrictions were brought in with regard to human activity around eagle nests or known nesting areas. For instance, any construction activity was barred within a radius of roughly 100 m of a bald eagle nesting site.
A success story
- In 2007, when the bald eagle was removed from the endangered species list, there were roughly 9,789 known breeding pairs in the US.
- The latest figures (from 2021) put the number of nesting pairs at about 71,4000 with the overall population standing at roughly 316,700.
Lessons for the future
- The success of bald eagle conservation teaches some important lessons about conservation.
- It shows that there is seldom a silver bullet when it comes to conservation – policies have to be comprehensive, taking into account the complexity of factors that generally lead to the decline of animal populations.
- While the banning of DDT was monumental, without habitat protections and captive breeding programmes, the success would be far from certain.
Conclusion- As climate change poses novel risks and challenges to flora and fauna around the world, the story of the American bald eagle serves as an important case study on the importance of persisting with conservation efforts – even if their impact is not immediately obvious.
Syllabus- GS-3; Biodiversity
Source- Indian Express
