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Crossing Planetary Boundaries (PB)—a concept that defines nine potential ecological “tipping points”—could spell doom for the planet’s ecosystems and humanity’s future.
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Of these PBs, people have already crossed six of the nine thresholds.
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Now, scientists argue that there is potentially a tenth frontier that has remained unrecognized, involving global water deoxygenation in lakes, reservoirs, oceans and other bodies of water.
“Climate change” is a terrifying, catch-all term that sums up all the anthropogenic degradation humans are causing to the planet. It’s really just climate change one of the many threats facing the planet.
First introduced in 2009, the Planetary Boundary (PB) concept identifies nine unique thresholds that could spell disaster if humanity crosses them. While climate change is one of the nine boundaries, the list also includes things like the integrity of the biosphere, ozone depletion, ocean acidification, freshwater alteration, and more. (Of course, what we think of as climate change exacerbates all of these problems, so in a sense it remains Public Enemy No. 1.)
Now, in a new study, scientists argue that a 10th frontier could be added to the list – water deoxygenation. Some bodies of water in the world (such as the basins of the Black Sea, the Baltic Sea, and various fjords) are naturally anoxic, meaning they contain little or no oxygen. But widespread deoxygenation is different because it affects previously oxygenated bodies of water globally and to varying degrees.
According to the researchers, over the past 45 years, lakes and reservoirs have lost 5.5 percent and 18.6 percent of oxygen, respectively, and the oceans have decreased by 2 percent, which is a huge amount of oxygen when you consider the total size of the oceans. . One of the most dramatic examples of deoxygenation is in midwaters off the coast of California, where oxygen levels have dropped by a staggering 40 percent since 1960. The results of this study were published in the journal Ecology and evolution of nature.
Andreas Oschlies – study co-author and professor of marine biogeochemical modeling at the GEOMAR Helmholtz Center for Ocean Research in Kiel, Germany – details in a press release how rising temperatures and land (dis)use can cause this species to rapidly deoxygenate:
The cause of water oxygen loss is global warming due to greenhouse gas emissions and nutrient input due to land use. As the temperature of the water increases, the solubility of oxygen in the water decreases. In addition, global warming increases the stratification of the water column, as warmer, less saline, lower-density water lies above the cooler, saltier deep water below. This prevents the exchange of oxygen-poor deep layers with oxygen-rich surface water. In addition, nutrient inputs from the soil support algal blooms, leading to more oxygen consumption as more organic material sinks and is decomposed by microbes at depth.
Animals living in the oceans needed oxygenated water to survive, and as such these deoxygenated waters can significantly affect fish, shellfish and crustaceans. This is subsequently reflected in the food chain and threatens ecological collapse. And if that wasn’t enough, deoxygenated water can produce nitrous oxide and methane—two notoriously terrible greenhouse gases—through microbiotic processes. In other words, the loss of oxygen in the Earth’s water bodies can unleash an absolute flood of climate disasters that could spell doom for our planet.
“Dissolved oxygen regulates the role of marine and freshwater in modulating Earth’s climate. Improving oxygen concentrations depends on addressing the root causes, including climate warming and runoff from developed landscapes,” Kevin Rose, a professor at Rensselaer Polytechnic Institute in New York and lead author of the study, said in a press release. “Failure to address water deoxygenation will ultimately affect not only ecosystems, but also economic activity and society on a global scale.”
Humanity has already crossed six of the nine frontiers listed in the original PB concept, and now a tenth frontier could quickly be added to this notorious club. Fortunately, there is a solution, and it doesn’t matter it has been with us for over a century—eliminate emissions, save the planet.
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