A team of researchers from Princeton University discovered that our planet’s oxygen supply has dropped by 0.7 percent over the last 800,000 years. This discovery was made after studying air bubbles trapped inside ice cores collected in Greenland and Antarctica. These samples revealed that something has disrupted the Earth’s oxygen cycle, and geochemists are at a loss for a concrete explanation.
According to their recent publication in Science, the decrease in oxygen levels might have to do with a erosion that took place between 8 and 2.5 million years ago of silicate rock, which can release oxygen as it erodes:
This record indicates that PO2 declined by 7 per mil (0.7%) over the past 800,000 years, requiring that O2 sinks were ~2% larger than sources. This decline is consistent with changes in burial and weathering fluxes of organic carbon and pyrite.
Naturally, climate change and human activity has been cited as a possible cause. Given that urban development, mining, and erosion have decreased the Earth’s supply of oxygen-releasing silicate rock, there might be a strong case for blaming this dwindling oxygen on humankind.
However, Daniel Stolper, a Princeton geochemist and lead author of the published data, told Live Science that because there is no data about the oxygen cycle before the industrial age, it is difficult to determine the level of influence human activity might have had on oxygen levels:
There was no consensus on whether the oxygen cycle before humankind began burning fossil fuels was in or out of balance and, if so, whether it was increasing or decreasing.
Luckily for humans and all of the other living things on Earth, the decline is so far slight enough to not have a major effect on life cycles. However, fluctuations in oxygen levels have been previously found to affect or even trigger evolutionary changes. Thus, the fact remains that it is currently unknown what effects this change in oxygen might be having on the Earth’s ecosystems and life, and that has some environmental scientists concerned.