Ocean environments in danger

Debapriya Mukherjee
For centuries, we thought that our vast ocean was limitless and immune to human impacts.  Upon death of 100,000 marine mammals ( whales, dolphins, porpoises, seals and sea lions )  and 1 million seabirds per year globally  as a result of plastic pollution,  we have realized - the ocean  environments in danger. Further,  climate change  is heating the oceans and altering their chemistry so dramatically that it is threatening  seafood supplies, fuelling cyclones and floods and posing profound risks to the hundreds of millions of people living along the coasts.  As per the record, the 10 years to the end of 2019  have been confirmed as the warmest decade and the amount of heat have been put in the world’s oceans in the past 25 years equals to 3.6 billion Hiroshima atom-bomb. Last year ocean temperature was 0.075 C above the 1981-2010 average. This measured ocean warming is irrefutable and is further proof of global warming.  As the planet warms, ice sheets and glaciers melt and warming sea water expands leading to  increasing the volume of the world’s oceans and sea level rise that  is another climate change’s  danger. As sea levels continue to rise throughout the century, chronic flooding will spread and more land will be permanently lost to the ocean. Human activities are the major cause of endangering our most valuable ocean ecosystems. For supplementing this view, some examples are stated. The discarded plastics and other residential waste, discharge from industries and agricultural areas without adopting any effective cleaning practices eventually find their way into the sea with devastating consequences for marine life and the habitats. The amount of discarded plastics will outweigh the amount of fish in our oceans by 2050 as reported.  Shipping accidents and oil spills add additional toxins to the mix. About 25 major accidents and  many smaller ones cause spillage of more than 700 tons of crude oil into the sea. In addition to this, deliberate dumping from vessels (mainly during the illegal cleaning of tankers) on the high seas further aggravates this problem. Some 140,000 tons of ballast water carried by merchant vessels, which  is often taken up in one port and released in another faraway from the point of origin, is ultimately dumped into the sea. Some of the species (including pathogens) in ballast water may be introduced in a new ecosystem leading to serious damage to the local flora and fauna. In addition to these, carbon emissions from human activities are causing ocean warming, acidification and oxygen loss with some evidence of changes in nutrient cycling and primary production. Oxygen in the oceans is being lost at an unprecedented rate leading to proliferation of  “dead zones”  on account of the climate emergency and intensive farming. Overfishing endangers ocean ecosystems and the billions of people who rely on seafood as a key source of protein. If fossil-fuel emissions continue to rise rapidly, for instance, the maximum amount of fish in the ocean that can be sustainably caught could decrease by as much as a quarter by century’s end. In addition, rapid urbanization along the world’s coastlines has seen the growth of coastal ‘megacities’ like Mumbai. Many of these populations put pressure on infrastructure where urban waste and sewage management is poor. Thereby ecosystems are changing, food webs are changing, fish stocks are changing, and this turmoil is affecting humans.
(To be contd)