Almost 15 years ago, a group of scientists proposed the concept of “planetary boundaries” to identify significant Earth systems that were at risk of instability due to human activities. They examined systems such as temperature, biodiversity, and freshwater to identify the limitations of civilization’s “safe operating space.” They did not, however, consider how exceeding these limitations may damage people, particularly the poor and vulnerable.
Crossing planetary boundaries
A substantial update, published today in the journal Nature, describes how much punishment nature can withstand before turning on humanity. The authors discover that humans have already crossed seven out of the eight global barriers.
The academics present their new work in the hope that businesses and governments will develop tools to align their practices with science-based thresholds.
“We simply need to have science-based targets well beyond climate for all the planetary boundaries, to have a stable and resilient Earth system – and also to handle the climate crisis,” said Johan Rockstrom, director of the Potsdam Institute for Climate Impact Research in Germany and a co-author of the new and original works.
The new research now contains justice criteria along three dimensions, affecting the many millions of people who are at risk today, the billions who will be affected in the future, and the world’s innumerable species and ecosystems.
The urgency for action and adaptation
This fairness approach necessitates more rigorous limits for some Earth systems, such as the climate than geophysical-stability factors alone would. The 1.5C warming limit entrenched in the Paris Agreement is already on life support, according to the authors, and is too high considering humanitarian considerations, as proven by tens of millions of people presently exposed to deadly heat.
Since industrialization, the world has warmed by 1.2 degrees Celsius. Scientists estimate that by 1.5 degrees Celsius, more than 200 million people, largely from poor, vulnerable, and disadvantaged populations, will endure unprecedented heat. Their goal is to keep the world average temperature increase below 1 degree Celsius, but because that’s not possible on a visible time scale, countries will have to deal with the consequences. And that means “adaptations and compensations to reduce sensitivity to harm and vulnerability will be necessary.”
The authors call for international compensation for poorer countries’ “loss and damage” sustained during extreme weather events, as agreed to at last year’s UN climate talks.
The scale of effort required to meet these challenges is unprecedented. “Nothing less than a just global transformation across all ESBs [Earth system boundaries] is required to ensure human well-being,” they write. Energy, food, cities, and other sectors require rebooted politics, economics, and technology. “It requires a leap in our understanding of how justice, economics, technology, and global cooperation can be furthered in the service of a safe and just future.”
The 51 authors are members of the Earth Commission, a group of natural and social scientists co-founded by Rockstrom to provide information that can advise organizations such as the Information Based Targets Network, which develops guidance for businesses and cities. The study aims to quantify global changes that are “primarily driven by social and economic systems that are based on unsustainable resource extraction and consumption.”
Global transformation
The new research builds on prior planetary boundaries studies as well as other analyses of social vulnerability to systemic change, such as the United Nations Sustainable Development Goals. According to the authors, a crucial advance in this article is the translation of social justice considerations into the same units of measurement as Earth systems, such as degrees Celsius for temperature or cubic kilometers for water use.
Nitrogen and phosphorus from farms, for example, leach into waterways and generate oxygen-depleted “dead zones” in rivers and seas, with ramifications for drinking water in some locations. According to the research, the global limit for excess nitrogen is 119 million metric tons per year, and the global limit for excess phosphorus is 10 million.
To combat air pollution, scientists set the goal of minimizing the difference in aerosol concentrations between the Northern and Southern Hemispheres while establishing an upper limit for dangerous small particle pollution. Aerosols from both natural and human sources, ranging from volcanoes to tailpipes, cause sickness and premature mortality worldwide.
They also propose two biodiversity indicators to reduce species and ecosystem degradation. The first specifies the percentage of natural ecosystems that should be preserved: 50% to 60%, which is higher than the current figure of 45% to 50%. To ensure that human-touched areas continue to play important roles, the authors propose that 20% to 25% of every square kilometer of urban, agricultural, and other land affected by people should preserve natural ecosystem characteristics. To prevent freshwater biodiversity loss, scientists propose that rivers and streams depart from natural monthly flows by no more than 20%.
Replicating Scientific Baselines
The new analysis is more tangible than past versions of planetary boundaries research, according to Kim Cobb, director of the Institute at Brown University for Environment and Society, who was not involved with the study. While there may still be scientific uncertainties about elements of these systems, “we don’t really have any uncertainties about the disproportionate impacts of climate change on the most vulnerable,” she said. “And so that’s something that I think should ground us in decision-making today.”
Essentially, the authors are attempting to replicate for the entire Earth system what has already occurred for climate change: Create scientific baselines that can be used by standard-setting organizations and governments to assist businesses, localities, and others in ensuring that their activities do not contribute to greater systemic environmental change or human harm. The boundaries may include but are not the same as, “tipping points,” or thresholds beyond which the world, with or without human intervention, continues to change.
“The ultimate definition of justice today is the right of every human being, particularly future generations, to have a stable planet – to be born on a planet which is at least as livable as the planet where his or her parents were born,” Rockstrom said.