Earth’s Disastrous 10th Tipping Point Has Been Identified

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• Crossing Planetary Boundaries (PB)—a concept that defines nine potential ecological “tipping points”—could spell doom for ecosystems and humanity’s future on the planet.

• Of these PBs, humans have already crossed six of the nine thresholds.

• Now, scientists are arguing that there’s potentially a tenth boundary that’s gone unrecognized, which concerns worldwide aquatic deoxygenation in lakes, reservoirs, oceans, and other bodies of water.

“Climate change” is a scary, catch-all term that summarizes all the anthropogenic degradation humans are inflicting on the planet. In reality, climate change is only 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 biosphere integrity, ozone depletion, ocean acidification, freshwater change, and more. (Of course, what we think of as climate change exacerbates all of these issues, so in a sense, it remains Public Enemy No. 1.)

Now in a new study, scientists are arguing that a 10th boundary could be added to the list—aquatic deoxygenation. Some bodies of water in the world (such as basins in the Black Sea, the Baltic Sea, and various fjords) are naturally anoxic, meaning that they contain little or no oxygen. But widespread deoxygenation is different, as it affects previously oxygenated bodies of water globally and to varying degrees.

According to the researchers, lakes and reservoirs have experienced oxygen losses of 5.5 percent and 18.6 percent respectively in the past 45 years, and the oceans have dropped by 2 percent—a jaw-dropping amount of oxygen when you consider the collective 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 Nature Ecology & Evolution.

Andreas Oschlies—co-author of the study and professor of Marine Biogeochemical Modelling at GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany—gives a detailed description in a press release about how rising temperatures and land (mis)use can cause this kind of rapid deoxygenation:

Ocean-dwelling animals needed oxygenated water to survive, and as such, these deoxygenated waters can significantly impact fish, mussels, and crustaceans. This subsequently reverberates up the food chain and threatens ecological collapse. And if that wasn’t enough, deoxygenated water can also produce nitrous oxide and methane—two notoriously terrible greenhouse gasses—via microbiotic processes. In other words, losing oxygen in Earth’s bodies of water can unleash an absolute deluge 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 the Rensselaer Polytechnic Institute in New York and lead author on the study, said in a press statement. “Failure to address aquatic deoxygenation will, ultimately, not only affect ecosystems but also economic activity, and society at a global level.”

Humanity has already crossed six of the nine boundaries enumerated in the original PB concept, and now a tenth boundary could be quickly joining that notorious club. Luckily, there is a solution, and it’s one that’s been with us for more than a century—eliminate emissions, save the planet.

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