The concept of planetary boundaries is a scientific theory that describes the nine bio-physical boundaries of the Earth’s environment that must not be overcome if we are to preserve our planet and ensure a sustainable future for humanity. These limits were defined by a group of scientists in 2009 and updated in 2015 in an article published in the scientific journal Nature.
The nine global boundaries are:
- Climate change: the concentration of carbon dioxide (CO2) in the atmosphere must not exceed 350 ppm.
- Acidification of the oceans: the pH of the oceans must not decrease by more than 0.2 units compared to pre-industrial levels.
- Loss of biodiversity and biosphere integrity: biodiversity loss must not exceed the natural rate of extinction (about one species every one million years).
- Disruption of the nitrogen and phosphorus cycle (biogeochemical flows): nitrogen and phosphorus levels must not exceed natural limits.
- The use of fresh water: the use of fresh water must not exceed the rate of renewal of fresh water resources (consumption should be less than 4000 km3/year).
- Deforestation and land use change: the conversion of natural land must maintain 70% of forest area before human clearing.
- Depletion of the stratospheric ozone layer: the ozone layer must be reduced by no more than 5% compared to pre-industrial levels.
- Air pollution: particulate levels in the air must not exceed natural levels.
- The accumulation of endocrine disruptors and toxic substances in ecosystems (novel entities): concentrations of toxic chemicals must not exceed natural levels of the environment.
These limits are interconnected and overcoming them may have cascading effects, with serious consequences for the planet and its inhabitants: environmental impacts can accumulate and reinforce each other, creating potentially more serious consequences than individual effects. For example, deforestation can lead to a decrease in biodiversity, an increase in greenhouse gas emissions and a decrease in the availability of fresh water. This in turn can contribute to increasing desertification and reducing the capacity of ecosystems to regulate climate. One problem can cascade in several new problems.
The concept of planetary boundaries is important because it provides a scientific framework for understanding and assessing the impacts of human activity on the planet. By understanding the Earth’s bio-physical boundaries, we can better assess environmental risks and take action to reduce the negative impacts of human activity on the environment. It highlights the interconnections between different aspects of the environment, and underlines the need for a systemic approach to addressing environmental problems.
Several global limits have already been exceeded. The concentration of carbon dioxide in the atmosphere surpassed the limit of 350 parts per million (ppm), reaching a level of over 415 ppm in 2021. The extinction rate of species is hundreds to thousands of times higher than the natural rate, resulting in rapid biodiversity loss worldwide. In many parts of the world, freshwater use exceeds the rate at which freshwater resources are replenished, resulting in a decrease in freshwater resources available to populations and ecosystems. Levels of toxic chemicals in the environment exceed natural levels, resulting in pollution of water, air and soil. The conversion of natural land for agriculture, urbanization and industry has exceeded the capacity of land regeneration, resulting in land degradation, loss of vegetation cover and loss of ecosystem capacity to provide ecosystem services.
The future of these planetary boundaries will largely depend on the actions taken now. If we do not quickly reduce our environmental impacts and actively work to meet global limits, the consequences could be severe. Although planetary boundaries have been exceeded in many areas, there is still hope for the future. More and more people are becoming aware of the importance of protecting the environment and start to understand that once boundaries are passed, there may be no coming back. This translates into increasing pressure on governments and businesses to act in favor of the environment.
The concept of planetary boundaries has already had a significant impact on environmental policies and global awareness of the urgent need to protect the environment. In the future, the concept is likely to continue to play an important role in environmental decision-making and in finding sustainable solutions. Monitoring global limits is increasingly integrated into government policies, international agreements and businesses, and it is likely that this will continue to strengthen in the future. Scientific data and analysis on planetary boundaries also continues to improve, contributing to a better understanding of environmental impacts.
By Jade Pannetier