How is the ocean changing?
A series of reports and findings over the last ten years have identified the detrimental impact of human activity on the ocean. Climate change, over-fishing, pollution, resource exploitation and acidification are causing the ocean to suffer its most extreme disruption for at least 250 million years. The evidence of deoxygenation, warming and acidification in the ocean have led scientists to warn that humans are creating the conditions necessary to produce the planet’s third great mass extinction event .
8 ways the ocean is changing:
1. Marine species
60% of the world’s major marine ecosystems have been degraded or are being used unsustainably.. 28.8 percent of global fish stocks are unsustainably fished according to official statistics. However, re-estimates of fish catches accounting for small-scale, recreational and illegal fisheries as well as discards suggest that fish catches are declining at a greater rate than has been thought. On the current trajectory, many of the world’s marine species may stand on the brink of extinction by 2100.
2. SEALEVEL RISE
Sea levels have risen approximately 20 cm (eight inches) compared to pre-industrial times. The Intergovernmental Panel on Climate Change (IPCC) predicts that if CO2 emissions continue on their current trajectory, sea levels will rise by a further 99 cm by the end of the century. 13 of the 15 biggest cities are on the coast and will be affected by sea-level rise. In the US alone, $500 billion worth of property could be below sea level by 2100.
The ocean has absorbed more than 90% of the excess heat and nearly 30% of the carbon dioxide released by burning fossil fuels. The extra heat absorbed by the ocean is buried deep underwater, with 35% of the additional warmth found at depths below 700 meters.. Far more heat is present in the deepest reaches of the ocean than 20 years ago.
4. CO2 & ACIDIFICATION
Ocean acidification is the ‘evil twin’ of climate change. The ocean currently absorbs approximately half of the CO2 produced by burning fossil fuel. The CO2 dissolves in seawater to form carbonic acid, decreasing ocean pH (i.e. increase acidity) by about 30% since the beginning of the industrial revolution.
19% of the world's coral reefs have been lost. At present rates, 60% of the world's coral reefs will be destroyed over the next 30 years. Beginning in 2014, we are in the midst of the third global bleaching event, the longest and most devastating in recorded history. Scientists believe that nearly half the coral on the Northern Great Barrier Reef for example was killed by bleaching in just 3months March-May 2016. Coral reefs are the crucial incubators of the ocean’s ecosystem, providing food and shelter to a quarter of all marine species, and they support fish stocks that feed more than one billion people.
Globally, low-oxygen areas in the ocean have expanded by more than 1.7 million square miles in the past 50 years. The occurrence of dead zones (hypoxic, low oxygen areas) have doubled in frequency every 10 years since the 1960s.
Plastic debris in the ocean is estimated at 5.25 trillion pieces of which 269,000 tons float on the surface. Around four billion plastic microfibers per square kilometer litter the deep sea.
8. SEABED MINING
1.2 million km2 of deep seabed have been licensed for exploration. The area is close to the size of Europe. Exploratory mining for polymetallic sulphides around hydrothermal vents is occurring in the EEZ of Papua New Guinea. Mining for cobalt crusts on seamounts is in the development stage.