In an era where environmental concerns are being met with harsh realities, the concept of Planetary Boundaries has emerged as a guiding framework for measuring and ensuring the sustainable coexistence of humanity and the planet. Developed by the Stockholm Resilience Centre, this framework identifies key Earth system processes that, if disrupted beyond certain thresholds, could lead to irreversible environmental changes.
The concept has evolved over the years, with pivotal publications in 2009, 2015 and now 2023 marking significant milestones in our understanding of planetary boundaries and our impact as a civilization.
2009: A Safe Operating Space for Humanity
The journey of Planetary Boundaries began with the publication of "A Safe Operating Space for Humanity" in 2009. This foundational work identified nine key planetary boundaries. These boundaries were critical limits beyond which human activities could cause abrupt and irreversible environmental changes:
Climate Change: The concentration of greenhouse gasses in the atmosphere, primarily carbon dioxide (CO2).
Biosphere Integrity: The rate of species extinction, driven by human activities such as deforestation and habitat destruction. Split between Genetic diversity and Functional Integrity.
Ocean Acidification: The increasing acidity of the oceans due to elevated CO2 levels.
Stratospheric Ozone Depletion: The depletion of the ozone layer, primarily due to the release of chlorofluorocarbons (CFCs).
Atmospheric Aerosol Loading: The presence of human-made particles in the atmosphere, which can impact climate and health.
Biogeochemical Flows: The excessive release of reactive nitrogen and into the environment, leading to pollution and ecosystem disruption. The excessive release of phosphorus into aquatic systems, causing eutrophication and dead zones.
Novel Entities: The impact of synthetic chemicals.
Land Use Change: The conversion of natural habitats for agriculture, urbanization, and infrastructure development, deforestation.
Freshwater Use: The excessive extraction and use of freshwater resources. 'Blue water' is water in rivers and lakes, groundwater and the water frozen in glaciers and the polar ice caps. Freshwater is also found in plants, the soil and rain – experts call this ‘green water’.
This groundbreaking work was met with widespread recognition and set the stage for a more profound exploration of the interplay between human activities and planetary stability.
2015: Refining Boundaries and Assessing Limits
In 2015, the Stockholm Resilience Centre, in collaboration with international scientists, revisited the Planetary Boundaries framework. This update aimed to provide a more detailed understanding of these boundaries and their interactions. Importantly, the research assessed which of these boundaries we were approaching or even crossing.
The findings from the 2015 research were a wake-up call. It revealed that several of these planetary boundaries were being pushed dangerously close to their limits. And 4 limits had been crossed (Biodiversity loss, Land-System Change, Climate Change and Biochemical Flows). Here are some key results:
Climate Change:
The research highlighted that we were approaching the boundary for climate change. The concentration of greenhouse gasses in the atmosphere, primarily carbon dioxide (CO2), was steadily rising, posing a significant risk.
Biodiversity Loss:
The boundary for biodiversity loss was another concern. The rate of species extinction, driven by human activities such as deforestation and habitat destruction, was accelerating.
Ocean Acidification:
Ocean acidification, caused by elevated CO2 levels, was also approaching the boundary. This posed a threat to marine ecosystems and biodiversity.
Freshwater Use:
Excessive extraction and use of freshwater resources were leading us closer to the boundary for freshwater use, risking water scarcity in many regions.
2023: Crossing Boundaries and Time for Action
Six of these boundaries are now being crossed, and the pressure on all of them is on the rise. The six are, biogeochemical flows, climate change, biosphere integrity, novel entities, land system change and freshwater change.
"This update on planetary boundaries clearly depicts a patient that is unwell, as pressure on the planet increases and vital boundaries are being breached. We don't know how long we can keep transgressing these key boundaries before combined pressures lead to irreversible change and harm," warns Johan Rockström, Director of the Potsdam Institute for Climate Impact Research.
Earth's Vital Signs
Lead author Katherine Richardson likens Earth to a human body, with planetary boundaries acting as indicators of its health. Just as elevated blood pressure raises the risk of heart problems, exceeding these boundaries poses increasing risks to both humanity and the ecosystems we depend on.
While some progress has been made, such as the recovery of the ozone layer thanks to global initiatives like the Montreal Protocol, other boundaries are deteriorating rapidly. To highlight 4 areas of concern:
Atmospheric Aerosol Loading: This boundary, although not yet transgressed, shows rising pressures in areas affected by air particle pollution, impacting monsoon systems.
Novel Entities: This boundary, which includes pollutants like microplastics, pesticides, and nuclear waste, has been transgressed. The introduction and accumulation of these chemical compounds pose significant risks.
Freshwater: Both green water (held in soil and plants) and blue water (visible water in rivers and lakes) boundaries have been transgressed, highlighting the precarious state of Earth's water resources.
Biosphere Integrity: A new approach to assessing the integrity of ecosystems reveals that this boundary was crossed during the late 19th century, coinciding with the expansion of global agriculture and forestry.
Beyond Climate Change
The researchers emphasize that Earth's resilience is not solely about climate change. The planetary boundaries framework provides a tool to track and communicate how increasing pressures destabilize our planet. As Sarah Cornell from the Stockholm Resilience Centre explains, Earth's unpredictability makes it crucial to engage with policymakers, businesses, and society to mitigate pressures on all boundaries.
Modeling the Future
Advanced computer models and simulations played a significant role in this study, allowing scientists to project the consequences of environmental changes over hundreds of years. This approach helps understand both rapid and slow Earth system processes that influence the outcomes of today's actions.
Urgent Call to Action
The world is witnessing extreme climate events, but the researchers are even more concerned about dwindling planetary resilience. Crossing these boundaries brings humanity closer to tipping points, jeopardizing our ability to limit global warming to the critical 1.5°C threshold.
The 2023 planetary boundaries assessment underscores the intricate interdependence between humans and the planet. It serves as a foundation for systematic efforts to protect, recover, and rebuild Earth's resilience. Ultimately, it reminds us of our responsibility as stewards of this planet.
The time for action is now, for the sake of our planet and future generations.
(All information and images credit to: Azote for Stockholm Resilience Centre, Stockholm University. Based on Richardson et al. 2023, Steffen et al. 2015, and Rockström et al. 2009)
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