Impact of anthropogenic activities on oceanic biodiversity
- As per Global Biodiversity Outlook 5 (GBO-5) 2020
- More than 60 percent of the world’s coral reefs biodiversity are under threat
- 2016 Marine heatwaves across north Australia led to severe bleaching of the Great Barrier Reef, led to mangrove die-offs in the gulf of Carpentaria
- The proportion of fish stocks fished sustainably is down by 5 percent since 2010
- Impact of marine litter: Ingestion, suffocation and entanglement of hundreds of marine species e.g. seabirds, whales, fishes. It contributes to spread of invasive marine organisms and bacteria which disrupts ecosystems, leading to mass loss of biodiversity.
- 8 million tons of plastic waste end up in ocean every year which make up for 80% of all marine debris (India dumps 6 lakh tones of plastic waste annually)
- As per Global Assessment Report on Biodiversity and Ecosystem Services 2019
- Over one-third of marine mammals and nearly one-third of sharks, shark relatives, and reef-forming corals are threatened with extinction
- One million species are threatened with extinction globally, and extinction rates have accelerated sharply in the past century.
- Human activities are the primary cause of these huge declines, particularly in the ocean where fishing is driving the greatest biodiversity loss
- Coastal land and sea use change has had the second largest impact on marine biodiversity after over fishing.
- Development along coastlines as well as offshore aquaculture, bottom trawling, and oil and gas extraction have altered habitats, and toxic pollutants in agricultural and industrial runoff poison coastal fish harvests.
Impact of anthropogenic activities on Oceanic food
- The food chains of the world’s oceans are at risk of collapse due to the release of greenhouse gases, overfishing and localized pollution
- The acidification of the ocean, where the pH of water drops as it absorbs carbon dioxide, will make it hard for creatures such as coral, oysters and mussels to form the shells and structures that sustain them.
- Marine heatwaves impact on food system:
- It affects ecosystem structure by supporting certain species and suppressing others e.g. after marine heatwaves in western Australia (2016) fish communities had a much more “tropical” nature: changing the behavior and habitat range of fish.
- Induced species range shifts, changes to vertical and across-shelf movement patterns, and losses in spawning habitats.
- Marine heatwaves led to impacts on fisheries and aquaculture e.g. outbreaks of Pacific Oyster mortality syndrome, thus impacting oyster aquaculture
- Issue of bioaccumulation and biomagnification: Toxic contaminants accumulate on the surface of plastic materials which when ingested by marine organisms enter their digestive systems leading to bioaccumulation
- Fish and other marine life ingest microplastics and nano plastic which in turn can find their way into the human food chain
Impact on Oceanic ecosystem
- As per UN’s 2nd World Ocean Assessment report:
- The number of “dead zones” – ocean areas where insufficient oxygen allows nothing to survive – are increasing, thus impacting the local ecosystem.
- There are now around 500 of these dead zones around the world.
- Marine ecosystems are connected and thus impact is worldwide: g. nutrients from the Amazon River have formed a seaweed bloom off the coast of West Africa that now exceeds 20 million tons 8,850 kilometers.
- Impact on seagrass ecosystem (considered ‘marine ecosystem engineers’): Human disturbance like eutrophication, mechanical destruction of habitat, overfishing, siltation, trawling is disturbing seagrass ecosystem (e.g. sea cow grass, needle seagrass)
- Impact on mangrove ecosystem: India has lost 40% of its mangrove’s areas in the last century, mainly due to agriculture, aquaculture, tourism, urban development and over exploitation
- Impact on coral reefs ecosystem: According to a study, since 1982 three mass bleaching events occurred in 1998, 2010 and 2016 have occurred in India.
- Impact on Polar ecosystem:
- Antarctica’s species are already changing their habitats. Many species have a narrow thermal tolerance.
- Adélie penguins, seals and krill are all moving south to colder parts of the continent, and the two flowering plant species have become increasingly commonplace.
- Emperor penguins are predicted to be extinct by the end of the century
- The Arctic is warming at least twice as fast (Arctic amplification)as the rest of the planet: temperate species are moving farther and farther north.
- There is higher abundance of trout and other fish that will compete with Arctic char, leading to a loss of those fish that are so vital for Indigenous communities
- Thawing permafrost creates chocolate milk like pool. They’re thick with all the mud that’s coming through them.” This can quickly wipe out invertebrate and fish communities.
- Blooms in phytoplankton occurring earlier in the year and even happening in autumn – a phenomenon rarely observed in Arctic waters previously.
- Antarctica’s species are already changing their habitats. Many species have a narrow thermal tolerance.
