Asked by: Phil Friesen, Victoria, Canada
Oxygen makes up one-fifth of the air we breathe, but it’s the most vital component – and it does seem to be declining. The main cause is the burning of fossil fuels, which consumes free oxygen. Fortunately, the atmosphere contains so much oxygen that we’re in no danger of running out soon.
According to the Scripps Institution of Oceanography, monitoring stations point to an annual loss of just one oxygen molecule for every five million air molecules. They have also found hints that the ecosystem is compensating for some of the loss.
A more pressing problem may be the loss of dissolved oxygen in the water. ‘Dead zones’ with less than 5 per cent of the amount of oxygen needed for the majority of marine creatures are most common around polluted coastlines. But in April, researchers announced the discovery of dead zones in the North Atlantic – the first ever found in the open ocean. These appear to be linked to naturally-formed eddies, inside which oxygen-consuming plants can settle and grow. Whether such eddies will become more common with global warming is unclear.