If emissions from greenhouse gases continue, species losses from warming and oxygen depletion of ocean waters could eclipse all other human stressors on marine species by around 2100. Tropical waters would experience the greatest loss of biodiversity, while polar species are at the highest risk of extinction
New research shows that a wide variety of marine animals — from vertebrates to crustaceans to mollusks — already inhabit the maximum range of breathable ocean that their physiology will allow. The findings provide a warning about climate change: Since warmer waters will harbor less oxygen, some stretches of ocean that are breathable today for a given species may not be in the future.
Historical observations collected off California since the 1950s suggest that anchovies thrive where the water is breathable — a combination of the oxygen levels in the water and the species’ oxygen needs, which are affected by temperature. Future projections suggest that the waters off Mexico and Southern California could be uninhabitable by 2100.
New research from the University of Washington and Stanford University combines models of ocean conditions and animal metabolism with published lab data and paleoceanographic records to show that the Permian mass extinction in the oceans was caused by global warming that left animals unable to breathe. As temperatures rose and the metabolism of marine animals sped up, the warmer waters could not hold enough oxygen for them to survive.
In a paper published Aug. 31 in the journal Science, a team led by scientists at the University of Washington reports that insect activity in today’s temperate, crop-growing regions will rise along with temperatures. Researchers project that this activity, in turn, will boost worldwide losses of rice, corn and wheat by 10-25 percent for each degree Celsius that global mean surface temperatures rise.
Polar oceans pump organic carbon down to the deep sea about five times as efficiently as subtropical waters, because they can support larger, heavier organisms. The finding helps explain how the oceans may function under climate change.
Warming temperatures and decreasing levels of dissolved oxygen will act together to create metabolic stress for marine animals. Habitats will shift to places in the ocean where the oxygen supply can meet the animals’ increasing future needs.
Predictions that the lowest-oxygen environments in the ocean will get worse may not come to pass. UW research shows climate change, by weakening the trade winds, will shrink these extremely low-oxygen waters.