Context:
- Six out of nine planetary boundaries that make Earth healthy and habitable have been transgressed due to human activities like greenhouse gas emissions and deforestation, according to a new study.
- The broken boundaries mean the planet’s life-support systems have been driven far away from the safe operating space for humanity that existed during the period between the last ice age (about 10,000 years ago) and the start of the Industrial Revolution. This period was characterised by relatively stable and warm planetary conditions.
What are planetary boundaries?
- The planetary boundaries are a framework, introduced in 2009, that identifies guardrails for humanity’s impacts on the processes critical for determining global environmental conditions. Current scientific understanding suggests respecting these guardrails would minimise the risk of human activities triggering a dramatic and potentially irreversible change in living conditions on Earth.
- We humans, just like all other living organisms, survive by using the Earth’s resources, but those resources are limited. When we acknowledge the Earth’s resources as the currency that supports us, then the planetary boundaries framework becomes a kind of bank statement. It tells us how much of various components (resources) of the Earth system we can allow ourselves to use, without greatly increasing the risk of dramatically changing the overall environmental conditions we enjoy.
- The planetary boundaries framework, then, sets limits on how much we can allow ourselves to impact not only the climate but also the other global processes that are critical for maintaining conditions on Earth that can support modern civilization.
How is the planetary boundaries framework formulated?
- A large group of independent scientists are working together to develop the framework – and to keep it up to date with the newest scientific understanding of both the Earth system interactions and the global impacts of human activities. Earlier in September, the third update of the framework was released.
- Underpinning the framework is the observation that, despite humans having been present on Earth in their current biological form for about 200-250,000 years, it was only during the last 10-12,000 years that modern civilizations evolved.
- This period coincides with a period in Earth’s history with quite stable and relatively warm conditions and many believe there is a connection between these Earth conditions and the rise of civilizations.
- In other words, we know that humanity can thrive under these Earth conditions but do not know for certain we can thrive under others. Humanity would, therefore, be foolish to knowingly risk dramatic changes in these Earth conditions.
- Guardrails or “boundaries” are established for nine component processes of the Earth system. Three relate to the resources humanity removes from the system, i.e., biodiversity, water, and land use. The remaining all relate to waste products humans release to the environment, i.e., greenhouse gases (climate and ocean acidification), ozone depleting chemicals, “novel entities” (plastic, concrete, synthetic chemicals, gene modified organisms, etc. that would not be found on Earth if we humans were not here), aerosols, and the release of reactive nitrogen and phosphorus via fertilisers.
- Control variables are selected for each process. Then, based on the current scientific understanding of how these component processes combine to create global environmental conditions and how they have behaved during the Earth’s history, i.e., under different climatic conditions, a guardrail for human perturbation of the process is established.
Earth’s current state of health?
- Planetary boundaries do not represent tipping points or thresholds. scientists think of them being more like blood pressure. If your BP is greater than 120/80, it is not a guarantee of your having a heart attack but it does increase the risk and the doctor, therefore, will try to bring it down. The “blood pressure-like” signals we are getting from patient Earth suggest that treatment is necessary to preserve the Earth conditions we are dependent upon.
What’s the significance of your findings in the context of an increasingly warming world?
- In our recent update of the framework, we conclude that six of the nine boundaries are transgressed and that the boundaries found to be transgressed at the time of the last update (2015) are further overstepped today. Furthermore, the study indicates that achieving the climate goals set by politicians will likely not be possible unless boundaries are respected for land use change.
- Nevertheless, deforestation continues to increase globally. Returning to the bank statement analogy helps us understand what this means. The owner of the bank account can continue to “party” even as the balance on the account declines, but the party cannot continue indefinitely. Such is the situation in which humanity finds itself.
Do we still have time to reverse the damage done to the Earth system?
- Yes, but we are already running great risk. No one knows when potentially irreversible and drastic changes may occur. But we do know that such change is inevitable at some point as transgression of the boundaries increases, and that the risk becomes greater as we increase transgression.