Ocean Deoxygenation

Ocean deoxygenation is one of the most pernicious, yet under-reported side-effects of human-induced climate change. The primary causes of deoxygenation are eutrophication (increased nutrient run-off from land and sewage pollution) and nitrogen deposition from the burning of fossil fuels, coupled with the widespread impacts from ocean warming. Oxygen loss from warming has alarming consequences for global oceanic oxygen reserves, which have already been reduced by 2% over a period of just 50-years (from 1960 to 2010).

Oxygen decline will impact marine ecosystems and the dependent human population. Even the smallest fall in oxygen levels, when near already existing thresholds, can create significant issues with far-reaching and complex biological and biogeochemical implications.

Ocean deoxygenation: A wake up call to save our suffocating seas Photo: IUCN

At a global-scale, warming-induced oxygen loss is driving progressive persistent changes in nutrient cycling and recycling, species distributions, marine ecosystem services and habitat availability. Whereas at a regional scale, the formation of low oxygen zones and harmful algal blooms become more frequent. In a ground-breaking new report, IUCN, in partnership with leading scientists, explore the causes, consequences and socio-economic implications of ocean deoxygenation, and discusses how we, as a planet, must react.

Ocean deoxygenation: Effects on pelagic sharks, billfish and tuna Photo: IUCN