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Current Affairs for UPSC IAS Exam – 12 April 2021 | Legacy IAS Academy


  1. Dolphin boom in Odisha’s Chilika lake
  2. Indus and Ganges river dolphins- 2 different species
  3. Impact of oceans becoming quiet during the pandemic
  4. Meghalaya villages oppose dam on India’s clearest river



The population of dolphins in Chilika, India’s largest brackish water lake, and along the Odisha coast has doubled in 2021 compared to 2020.

The population estimation exercise for dolphins and other cetacean species covered almost the entire coast of Odisha.


Prelims, GS-III: Environment and Ecology (Species in news, Conservation of Ecology and Environment, Protected Areas in News)

Dimensions of the Article:

  1. About Chilika Lake
  2. Threats to Chilika Lake ecosystem
  3. About Irrawaddy dolphins
  4. Steps taken to protect Dolphins
  5. Highlights of the population estimation exercise of Dolphins

About Chilika Lake

  • Chilika Lake is a brackish water lagoon, spread over the Puri, Khurda and Ganjam districts of Odisha state on the east coast of India.
  • It is situated at the mouth of the Daya River, flowing into the Bay of Bengal.
  • It is the largest coastal lagoon in India and the second largest brackish water lagoon in the world after The New Caledonian barrier reef.
  • In 1981, Chilika Lake was designated the first Indian wetland of international importance under the Ramsar Convention.
  • It has been listed as a TENTATIVE UNESCO World Heritage site.
  • It is the largest wintering ground for migratory birds on the Indian sub-continent, hosting over 160 species of birds in the peak migratory season.
  • Birds from as far as the Caspian Sea, Lake Baikal, Aral Sea and other remote parts of Russia, Kirghiz steppes of Kazakhstan, Central and southeast Asia, Ladakh and Himalayas come here.
  • Geological evidence indicates that Chilika Lake was part of the Bay of Bengal during the later stages of the Pleistocene period (1.8 million to 10,000 years BP).
INDIA ORISSA Chilika Lake Bengal

Threats to Chilika Lake ecosystem

Over the years, the Chilika lake ecosystem of the lake encountered several problems and threats such as:

  1. Siltation due to littoral drift and sediments from the inland river systems
  2. Shrinkage of water surface area
  3. Choking of the inlet channel as well as shifting of the mouth connecting to the sea
  4. Decrease in salinity and fishery resources
  5. Proliferation of freshwater invasive species and
  6. An overall loss of biodiversity with decline in productivity adversely affecting the livelihood of the community that depended on it
  7. Fights between fishermen and non-fishermen communities about fishing rights in the lake and consequent court cases

About Irrawaddy dolphins

  • Irrawaddy dolphins (Orcaella brevirostris) are found in coastal areas in South and Southeast Asia, and in three rivers: the Irrawaddy (Myanmar), the Mahakam (Indonesian Borneo) and the Mekong (China).
  • The IUCN Red List classifies the Irrawaddy dolphins as ‘Endangered’.
  • The total population of these aquatic mammals in the world is estimated to be less than 7,500 and more than 6,000 Irrawaddy dolphins have been reported from Bangladesh.
  • Dolphin distribution in Chilika is considered to be the highest single lagoon population.

Steps taken to protect Dolphins

  • Setting up of the Conservation Action Plan for the Gangetic Dolphin (2010-2020), which has identified threats to Gangetic dolphins and impact of river traffic, irrigation canals and depletion of prey-base on dolphin populations.
  • Gangetic dolphins have been included in Schedule -I of the Wildlife Protection Act, 1972, which means they have the highest degree of protection against hunting.
  • They are also one among the 21 species identified under the centrally sponsored scheme, “Development of Wildlife Habitat”.

Highlights of the population estimation exercise of Dolphins

  • Three species were recorded during the census, with more than 500 Irrawaddy, bottle-nose and humpback dolphins sighted in 2021, compared with less than 250in 2020.
  • Wildlife activists are elated over the sizeable growth in the population of endangered Irrawaddy dolphins, which are mostly found in Chilika lake.
  • Apart from Chilika, Irrawaddy dolphins were sighted in the Rajnagar mangrove division.
  • The highest growth has been noticed in the case of humpback dolphins.

Reasons for the increase in numbers:

  • The rise in the Irrawaddy dolphin population in Chilika can be attributed to the eviction of illegal fish enclosures.
  • After thousands of hectares of Chilika water were made encroachment-free, Irrawaddy dolphins found unobstructed area for movement.
  • Moreover, due to the COVID-19 lockdown last year, there were comparatively fewer tourist boats on Chilika lake, which made it conducive for dolphins to move from one part of the lake to another.

-Source: Down to Earth Magazine, The Hindu



The researchers studied ancient DNA that they got out of skulls and skeletons which were 20 to 30 to even 150 years old of South Asian river dolphins and the detailed analysis has revealed that the Indus and Ganges River dolphins are not one, but two separate species.


Prelims, GS-III: Environment and Ecology (Species in news, Conservation of Ecology and Environment)

Dimensions of the Article:

  1. Divergent species
  2. About the Ganges river dolphin and Indus river Dolphin
  3. Threats to the dolphins
  4. Steps Taken to conserve and protect dolphins

Divergent species

  • Currently, Indus and Ganges river dolphins are classified as two subspecies under a single species – Platanista gangetica – and this needs a revision.
  • The study estimates that Indus and Ganges river dolphins may have diverged around 550,000 years ago.

About the Ganges river dolphin and Indus river Dolphin

Ganges River Dolphins

  • The Ganges river dolphin (Platanista gangetica gangetica) was officially discovered in the 1800s and these Ganges river dolphins once lived in the Ganges-Brahmaputra-Meghna and Karnaphuli-Sangu river systems of Nepal, India, and Bangladesh. (But the species is extinct from most of its early distribution ranges.)
  • The Ganges river dolphin was recognised as the National Aquatic Animal in 2009, by the Government of India.
  • The Ganges river dolphin can only survive in freshwater and is essentially blind.
  • They are frequently found alone or in small groups, and generally a mother and calf travel together.

Indus river Dolphins

  • Indus river dolphins (Platanista minor) are believed to have originated in the ancient Tethys Sea. When the sea dried up approximately 50 million years ago.
  • They can now only be found in the lower parts of the Indus River in Pakistan and in River Beas, a tributary of the Indus River in Punjab, India.
  • In Pakistan, their numbers declined dramatically after the construction of an irrigation system, and most dolphins are confined to a 750 mile stretch of the river and divided into isolated populations by six barrages.
  • They have adapted to life in the muddy river and are functionally blind.
  • They rely on echolocation to navigate, communicate and hunt prey including prawns, catfish, and carp.

Conservation status

  • The Indus and Ganges River dolphins are both classified as ‘Endangered’ species by the International Union for Conservation of Nature (IUCN).
  • The Ganges dolphin is a Schedule I animal under the Indian Wildlife (Protection) Act 1972, and has been included in Annexure – I (most endangered) of Convention on International Trade in Endangered Species (CITES).
  • The Ganges dolphin is also listed under Appendix II of the Convention on Migratory Species (CMS) (migratory species that need conservation and management or would significantly benefit from international co-operation).

Threats to the dolphins

  • Physical barriers such as dams and barrages created across the river reduced the gene flow to a great extent making the species vulnerable.
  • River flow is also declining very fast as river water is being diverted through the barrages and this has affected the dolphin habitats.
  • Previously fishermen used to hunt dolphins and use their oil as bait, but though that practice of directed killing has stopped and they are not being hunted intentionally they end up as accidental catches.
  • Both point and non-point sources of pollution are also affecting the dolphin habitat.

Threats to Gangetic river dolphin

  1. Pollution: It faces a number of threats such as dumping of single-use plastics in water bodies, industrial pollution, and fishing.
  2. Restrictive Flow of Water: The increase in the number of barrages and dams is also affecting their growth as such structures impede the flow of water.
  3. Poaching: Dolphins are also poached for their flesh, fat, and oil, which is used as a prey to catch fish, as an ointment and as a supposed aphrodisiac.
  4. Shipping & Dredging: It is also called a blind dolphin because it doesn’t have an eye lens and uses echolocation to navigate and hunt.

Recently, the Chinese river dolphin went extinct and we need to learn from this and have more ground action and close work with local communities to help them survive, besides the legal protection given to the dolphin by the Indian Government.

Steps Taken to conserve and protect dolphins

  1. Project Dolphin: The Prime Minister announced the government’s plan to launch a Project Dolphin in his Independence Day Speech 2020. It will be on the lines of Project Tiger, which has helped increase the tiger population.
  2. Dolphin Sanctuary: Vikramshila Ganges Dolphin Sanctuary has been established in Bihar.
  3. Conservation Plan: The Conservation Action Plan for the Ganges River Dolphin 2010-2020, which “identified threats to Gangetic Dolphins and impact of river traffic, irrigation canals and depletion of prey-base on Dolphins populations”.
  4. National Ganga River Dolphin Day: The National Mission for Clean Ganga celebrates 5th October as National Ganga River Dolphin Day.

-Source: The Hindu



The reduced noise pollution during the novel coronavirus disease (COVID-19) pandemic made the birds and the bees and other terrestrial creatures flourished; and in the underwater world, too, anthrophony (human-made sounds) reduced substantially for long months in 2020. Scientists are now trying to understand the impact of these quiet months on the marine ecosystem.


GS-III: Environment and Ecology (Environmental Pollution & Degradation, Conservation of Ecology and Environment)

Dimensions of the Article:

  1. Understanding Ocean Noise / Acoustics
  2. The International Quiet Ocean Experiment (IQOE)
  3. What is Hydrophone?

Understanding Ocean Noise / Acoustics

The International Quiet Ocean Experiment (IQOE) has identified a network of over 200 non-military hydrophones (underwater microphones) in oceans across the world.

The three broad components of oceanic acoustics that are being studied are are:

  1. Geophony: Sounds created by non-biological natural events like earthquakes, waves and bubbling.
  2. Biophony: Sounds created by the ocean’s living creatures.
  3. Anthrophony: Sounds created by human beings (a large portion of which is shipping noise).
  • According to ‘the Soundscape of the Anthropocene Ocean report’ published in Science Journal in 2021, geophony and biophony dominated the soundscape of oceans before the industrial era.
  • In the short-term anthrophony masks the auditory signal processing by marine animals, weakening their ability to forage for food, escape a predator or attract a mate. In the long run, it can thin out the population of some underwater species.
  • The oceans of the current geological era (Anthropocene era – when human-made disruptions largely influence the environment) are noisier than the pre-industrial times.
  • During the first few days of the pandemic, ocean sound monitors at several places recorded a decibel (dB) drop.
  • The hydrophones at the Endeavour node of Canada’s Neptune Ocean Observatory showed an average decrease of 1.5 dB in year-over-year mean weekly noise power spectral density at 100 hertz.

The International Quiet Ocean Experiment (IQOE)

  • The International Quiet Ocean Experiment (IQOE) is an international scientific program to promote research, observations, and modelling to improve understanding of ocean soundscapes and effects of sound on marine organisms.
  • IQOE is developing methods to make ocean acoustic data more comparable. These data will be compiled into a global dataset to establish trends in ocean sound and look for effects of the Covid-19 pandemic on ocean sound.
  • The IQOE has identified a network of over 200 non-military hydrophones (underwater microphones) in oceans across the world.

What is Hydrophone?

  • Just as a microphone collects sound in the air, a hydrophone detects acoustic signals under the water.
  • Most hydrophones are based on a special property of certain ceramics that produces a small electrical current when subjected to changes in underwater pressure.
  • When submerged in the ocean, a ceramic hydrophone produces small-voltage signals over a wide range of frequencies as it is exposed to underwater sounds emanating from any direction.
  • By amplifying and recording these electrical signals, hydrophones measure ocean sounds with great precision.

-Source: Down to Earth Magazine



People of at least a dozen villages fear the death of Umngot River and their tourism-based livelihood if the 210 MW hydroelectric project on Umngot (considered India’s clearest river) comes up.


Prelims, GS-I: Geography (Important rivers and drainage system of India), GS-III: Industry and Infrastructure (Dams, Hydroelectricity projects)

Dimensions of the Article:

  1. About the recent news regarding opposition to dam
  2. About Umngot (Dawki) River
  3. About Shillong Plateau

About the recent news regarding opposition to dam

  • The villages are near the border with Bangladesh in East Khasi Hills district but the dam is proposed upstream in the adjoining West Jaintia Hills district.
  • Hundreds of people from more than a dozen villagers obstructed officers from conducting the public hearing at Moosakhia in West Jaintia Hills district.
  • The locals fear that the project, if executed, would cause irreparable losses by wiping out their areas from the tourism map, besides affecting many villages in the downstream areas dependent on the Umngot.
  • The project documents say that people of 13 villages along the Umngot are likely to lose 296 hectares of land due to submergence if the dam comes up.

About Umngot (Dawki) River

  • The Umngot river attracts many tourists to Dawki bordering Bangladesh.
  • Dawki lies between India and Bangladesh and is the trade hub between the two countries.
  • The water of the river is so clear that boats seem to rest on a crystal glass surface besides casting their shadows on the river bed.

About Shillong Plateau

  • Shillong Plateau, highland region in eastern Meghalaya state, northeastern India.
  • It is a rolling tableland and the highest portion of the hill mass that comprises most of Meghalaya.
  • The plateau’s western, northern, and southern escarpments are called the Garo, Khasi, and Jaintia hills, respectively.
  • The Shillong Plateau is an outlier of the plateau of peninsular India and is composed primarily of ancient rocks.
  • It contains reserves of coal and iron ore, and limestone is quarried.
Khasi Hills Autonomous District Council - Wikipedia

-Source: The Hindu

February 2024