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Humans Have Exceeded Six of the Nine Boundaries Keeping Earth Habitable
Scientists find we are “well outside the safe operating space for humanity” in a new study meant to assess the health of our planet

Tara Wu
Tara Wu

Reporter

September 18, 2023
two trucks on rocky ground in front of lush trees
A quarry in the Cerro Blanco Forest in southern Ecuador, which is facing threats from construction and deforestation. MARCOS PIN / AFP via Getty Images
Human activities have caused the Earth to exceed six of nine boundaries necessary for keeping the planet healthy, pushing the environment “well outside the safe operating space for humanity,” scientists warn in a new study published last week in Science Advances.

According to the paper, Earth’s ability to sustain human society depends on nine primary “planetary boundaries,” or global systems that are key indicators of its health. Of these nine limits, humans have blown past six: climate change, biosphere integrity (which includes biodiversity), freshwater availability, land use, nutrient pollution and novel entities (meaning human-made pollution, such as microplastics and radioactive waste). Only the categories of ocean acidification, air pollution and ozone depletion remain within the constraints.

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These boundaries are not “tipping points” that are impossible to return from. Instead, they signal humans’ impact on the environment, scientists say.

“Crossing six of the nine boundaries isn’t a guarantee of disaster,” Katherine Richardson, an Earth systems scientist at the University of Copenhagen in Denmark and lead author of the study, tells Mongabay’s Elizabeth Claire Alberts. “It’s a wake-up call; it’s like your blood pressure. If your blood pressure is [elevated], it doesn’t necessarily mean you’re going to have a heart attack. But it does tell you the risk is too high, and you try and put it down.”

The international group of scientists that conducted the research, which draws from 2,000 studies, calls it the “first scientific health check for the entire planet,” per the Guardian’s Damian Carrington. They say the “most worrying” finding is that all four of the biological boundaries, which cover living things, are already at or near the most dangerous levels.

Of note is the severity of nutrient pollution, namely the overabundance of phosphorus and nitrogen in Earth’s waters. These two elements are widely used as crop fertilizers and cause issues like algal blooms and ocean dead zones when they are released haphazardly into ecosystems...CONT...😟😒😞😎🥹😞