Ocean sustainability: essential for blue planet

Abstract

Oceans cover over 70% of earth's area which is more than two thirds of the planet, providing huge services to mankind and other life forms. But since recent past, these natural treasures are facing increasing constraints due to unprecedented anthropogenic activities which have negatively hampered their sustainability. Oceans are now being over-exploited for food supply, as transport of goods and humans, and a convenient dumping zone for various types of wastes. With technological advancements humans have accessed even the remotest parts of marine ecosystems. This has caused severe degradation of oceans, resulting in lack of replenishment and a catastrophe in making. Rising sea levels due to rapid pace of global warming, acidification due to increasing carbon emissions, unsustainable overfishing, and ocean pollution due to industrialization, agricultural wastes and oils spills are some of the major threats faced by marine life (Arora and Mishra 2019). Reports claim that global mean sea level have risen by 8–9 inches since 1880, mainly due to melting of ice sheets and glaciers and thermal expansions in sea water. It has also been reported that the year 2018 witnessed sea level rise of 3.2 inches which is the highest recorded (for a single year till that year) (https ://www.clima te.gov/news-featu res/under stand ing-clima te/clima te-chang e-globa l-sea-level ). The Intergovernment Panel on Climate Change (IPCC) has predicted that even if the current greenhouse gas (GHG) emissions are reduced, the global mean sea level could still rise by 30 to 60 cm by 2100 (https ://www.ipcc.ch/2019/09/25/ srocc -press -relea se/). Similarly, Kwok (2018) reported that thickness of Arctic ice sheet has been lost by 50% during 1977–2017. In the same context, loss of Antarctic ice sheet has tripled between 2007 and 2016 (IPCC 2019). The rise in sea level will threaten the human population and infrastructure, particularly in coastal regions, and especially during deadly cyclones/storms or tsunamis, which can cause havoc in the mainland and especially in Small Island Development States (SIDS) which have low resilience to such extreme weather events. On the other hand, high levels of carbon emissions are causing acidification of oceans. Unchecked pace of deforestation, burning of fossil fuels, shrinkage in available land due to population explosion, industrialization, are some of the key factors responsible for increasing CO2 levels. Oceans are regarded as sinks of CO2, and as it dissolves in water, formation of carbonic acid takes places decreasing the pH. Ocean acidity is projected to increase by up to 0.042 pH units by 2100 (Gaines et al. 2019). These alterations in chemistry of ocean systems adversely affect sea creatures such as corals, oysters, sea urchins, sea shells and other calcareous phytoplanktons. Acidification also affects the behaviour, growth and reproduction process in marine life. This can have profound effects on markets based on marine products. Moreover, global warming is also interrupting the circulation pattern of the ocean known as ‘global conveyor belt' which is responsible for maintaining equilibrium in heat distribution on the globe. The injudicious amount of pollution faced by marine environment has adverse effects on the biology of oceans which has entered at several levels of food chain. The human activities on land are the major drivers of pollution in water bodies. Waste runoff from agricultural farms (e.g. fertilizers) trigger the formation of algal blooms, resulting in eutrophication of oceans, suffocating the marine life. Moreover, release of contaminants such as heavy metals, petroleum hydrocarbons, pesticides, sewage and radioactive disposal get absorbed by tiny planktons, which when consumed by other small fishes enter the food chain and get biomagnified at different trophic levels. Consumption of these infected sea foods by humans cause genetic disorders, cancer, and infertility, to name a few. Plastic pollution is another menace playing havoc in oceans which has resulted in great loss of ecosystem services on the whole. A report by Our World in Data estimates that about 80% of plastic pollution in oceans * Naveen Kumar Arora nkarora.bbau@gmail.com