Human activities are causing dramatic effects on Earth’s environmental conditions. From logging to plastic pollution to greenhouse gas emissions, we're changing the living conditions on the planet. These actions, if unchecked, might result in an Earth unsuitable to sustain our current way of life. In fact, a sobering new study suggests that we may already be in the danger zone.
The study builds on a paper from 2009 that outlined nine planetary boundaries. Basically, if we start crossing these boundaries, humanity is in trouble. These are:
- biosphere integrity;
- climate change;
- freshwater changes;
- ocean acidification;
- ozone depletion;
- land use change;
- introduction of novel entities (pollution);
- biogeochemical flows;
- and aerosol loading.
All of these have been transgressed except three: ocean acidification, aerosol loading, and ozone depletion. In other words, we're crossing most of the environmental planetary boundaries that keep life on Earth safe.
This means that Earth’s life support systems are being significantly disrupted. The stable conditions that have been around for about 10,000 years, and which usually only change in geological time, have started since the shifting Industrial Revolution.
This doesn't mean impending doom, researchers say. But it does show we're headed for trouble.
“We can think of Earth as a human body, and the planetary boundaries as blood pressure. Over 120/80 does not indicate a certain heart attack but it does raise the risk and, therefore, we work to reduce blood pressure,” Katherine Richardson, lead author and oceanography professor at the University of Copenhagen, said in a news release.
The planetary boundaries
Climate change is one of the most evident breaches of the planetary boundaries. The researchers looked at the concentration of carbon dioxide (CO2) – now at 417 parts per million (ppm), a big jump from the 280 ppm when the industrial revolution started. They set the safe threshold at 350 ppm, a mark that was exceeded back in 1987. To make matters even worse, our greenhouse gas emissions are accelerating.
But climate change isn't even our worst transgression. Apparently, it's how we treat life on Earth.
Biosphere integrity -- essentially a market for how well different species and ecosystems are doing -- is under grave threat. We're destroying vast swaths of the natural world which is triggering high extinction rates. Experts agree we have now entered into a sixth mass extinction driven by human activity. About 40% of the land has already been converted for food production, recent reports show.
"Next to climate change, integrity of the biosphere is the second pillar of stability of our planet. Our research shows that mitigating global warming and saving a functional biosphere for the future have to go hand in hand," Wolfgang Lucht, co-author and researcher at the Potsdam Institute for Climate Impact Research, said in a news release.
Another big problem comes with phosphorus and nitrogen. These are extensively used as crop fertilizers to enhance performance and then run out into ecosystems, severely polluting them. The researchers found that humans are releasing more of these chemicals into the environment than the planetary limits that they calculated.
The study also looked at “novel entities” -- meaning artificial chemicals released in the environment, such as plastic waste and forever chemicals (PFAS), which are becoming a big problem around the world. We have also crossed this boundary, meaning that we are releasing chemicals into the environment at a hazardous level.
"Our study shows that humans are appropriating the equivalent of 30% of the energy that was available to support biodiversity before the Industrial Revolution," Katherine Richardson said in a news release. "Surely, the removal of so much of the energy that otherwise would have been available to nature must be a driver of biodiversity loss.”
Righting the course
The planetary boundaries are not irreversible tipping points, the researchers explained. It's not like you can't go back and improve things, at least not yet.
Crossing six boundaries, as we have done so far, does not necessarily imply a disaster but it’s a clear warning signal, the researchers said. In fact, we have one success story already. The fact that humans have been able to address and reduce ozone depletion, one of the nine boundaries that we haven’t crossed, shows humanity has the capacity to turn things around if we act fast.
Granted, turning things like pollution or climate change around is set to be much more difficult. But the study provides a “guide for action” to how we can return to sustainable limits, while also securing prosperity and equity. Researchers end by calling for a systemic effort to protect, recover and rebuild planetary resilience and said the international community should put more focus on the need to limit our impacts.
The study was published in the journal Science Advances.