Despite the critical importance of marine biodiversity to human well-being, the oceans have not always fared well at the hand of humans. Some species, from the great auk to the sea mink, are extinct; others, such as the great whales, have been hunted to fractions of their original populations. Marine and coastal ecosystems face many different threats, including:

• Overfishing, destructive fishing, and illegal, unreported and unregulated (IUU) fishing: Assessments indicate that, globally, around 50 per cent of marine fish stocks are fished around their maximum sustainable yield and 30 per cent are overfished.
  

• Loss of critical marine habitats, such as seagrasses, mangroves and coral reefs: Corals have shown the most rapid increase in extinction risk of all assessed taxonomic groups. More than 60 per cent of the world’s coral reefs face immediate direct threats.
  

• Pollution, such as marine debris, and eutrophication: Recent estimates indicate that more than 10 million tonnes of plastic waste are currently entering the oceans every year, killing fish, seabirds and other taxa that ingest and become entangled in it; pollution from excess nutrients used on land is creating areas of coastal waters that are almost devoid of oxygen.
  

• The release of greenhouse gases, including through burning fossil fuels and from habitat destruction, is changing global climate, causing ocean warming, sea-level rise, and increasing the acidity of the oceans, with wide-ranging consequences that we are only beginning to comprehend. For example, ocean acidification has increased by around 26 per cent since pre-industrial times, impacting the physiology, sensory systems and behaviour of marine organisms, and compromising the health of the oceans and their ability to provide important services to the global community.
  

• A rapid rise in underwater sound from anthropogenic activities, causing physical and behavioural effects for some marine species, including marine mammals, marine reptiles, fishes, diving birds and invertebrates.
  

These pressures are negatively impacting the health of marine ecosystems and undermining their ability to provide the services and resources that are not only critical to socio-economic well-being (including through food, livelihoods and medicines), but are also important to the healthy functioning of the entire planet. If urgent action is not taken soon to reverse global trends in biodiversity loss, the oceans will reach an ecological tipping point beyond which it will be nearly impossible to recover.