As we saw in the article "Economic Growth or Environmental Sustainability?" , some people believe that economic growth is infinite. But the reality is somewhat different. Economic growth is based on the exploitation and use of the natural resources our planet offers. However, these resources are limited , and their rate of regeneration must be lower than the rate of exploitation in order to continue using them. When exploitation exceeds the capacity for regeneration, we say that we have reached planetary boundaries.
The context of planetary boundaries
The concept of planetary boundaries was first proposed in 2009 by a group of 28 scientists led by Johan Rockström of the Stockholm Resilience Center. The framework identifies nine fundamental processes that regulate the Earth’s stability and resilience. If any of these processes are disrupted beyond certain thresholds, it could lead to a drastic change of the Earth system, moving us away from the current conditions that support life as we know it.
The nine proposed planetary boundaries encompass the interplay of complex biophysical processes that maintain global climatic and ecological balance. Since the Industrial Revolution , however, humanity has intensified the exploitation of natural resources to the point where six of these planetary boundaries have now been exceeded , significantly increasing the risks to life on Earth.
The nine planetary boundaries
The nine proposed planetary boundaries are described below:
- Climate Change: This limit is measured by the concentration of CO2 in the atmosphere and radiative forcing. To ensure a safe climate, a threshold of 350 ppm (parts per million) of CO2 in the atmosphere was set, but we have now exceeded 417 ppm, which has already caused global temperatures to rise by more than 1,2°C since the Industrial Revolution.
- Integrity of the biosphere: This limit is reflected in the extinction of species and the destruction of the ecosystem. The accelerated loss of biodiversity is driving what many scientists consider the sixth mass extinction.
- land use:The transformation of natural ecosystems, especially deforestation in the Amazon, has altered natural climate and nutrient cycles, exceeding the planetary limit for biospheric stability.
- Biogeochemical fluxes of nitrogen and phosphorus: These elements are essential for life, but their excessive use in fertilizers has generated serious imbalances in aquatic ecosystems, causing the proliferation of dead zones in the oceans and seas due to eutrophication.
- Ozone layer depletion:Although this limit was exceeded in recent decades, measures taken under the Montreal Protocol have partially reversed the damage, stabilizing the ozone layer.
- Changes in freshwater use (blue and green water): Water extraction for agriculture and other human activities has affected water availability in many regions. It is estimated that we have exceeded the safe limit in several areas of the planet.
- ocean acidification:This limit is close to being exceeded due to the massive absorption of CO2 by the oceans, which is causing pH levels to decrease, mainly affecting marine ecosystems such as corals.
- Atmospheric aerosol loadingAerosols, such as soot and other particles released during industrial activities and forest fires, affect cloud formation and precipitation. Although this limit has not yet been surpassed globally, regions such as India are already experiencing serious disruptions due to air pollution.
- New chemical entities: Microplastics, pesticides and other man-made chemicals have been released into the environment without a full assessment of their long-term impacts. This limit has also been surpassed.
Climate change: the most critical planetary boundary
Climate change is undoubtedly the most critical planetary boundary, as its effects are more visible than ever. The increase in extreme weather events such as droughts, wildfires, hurricanes, and heat waves are just some of the direct consequences of climate change. Furthermore, glaciers are melting at an alarming rate, contributing to rising sea levels and endangering coastal populations.
Exceeding 1,5ºC of global warming is considered to be a point of no return. However, we are already on track for a scenario of up to 2ºC warming if drastic action is not taken immediately.
To mitigate climate change, it is imperative to reduce greenhouse gas emissions, especially CO2, methane and nitrous oxide. International efforts such as the Paris Agreement seek to limit global warming, but stricter measures will be needed to achieve these goals.
Biodiversity loss: the sixth mass extinction
The loss of biodiversity is another planetary boundary that has been crossed. This is not only serious because we are losing thousands of species every year, but also because biodiversity plays a crucial role in the balance of ecosystems. The loss of key ecological functions, such as insect pollination and disease regulation, jeopardizes agriculture and human health.
We are in the midst of what many scientists consider the sixth mass extinction , a crisis unprecedented in Earth's history since the extinction of the dinosaurs. The intensive use of land for agriculture, mining, and urbanization is destroying the habitats of numerous species, accelerating their disappearance.
The impact of land use and deforestation
The conversion of forests into agricultural or urbanized land is one of the main causes of biodiversity loss. The Amazon rainforest, for example, has lost a vast amount of land area in recent decades due to deforestation, which not only decreases biodiversity but also affects the global climate by releasing large amounts of CO2 stored in trees.
Unsustainable land use not only affects biodiversity, but also disrupts the water cycle, contributes to soil erosion and affects local communities that depend on natural resources for their livelihoods.
A transformation towards more sustainable agricultural practices and a reversal of deforestation is urgently needed, especially in critical regions such as the Amazon and Southeast Asia.
Biogeochemical flows: the case of nitrogen and phosphorus
Nitrogen and phosphorus are essential for plant growth and life in general. However, modern agriculture has introduced massive quantities of fertilizers containing these elements, causing serious imbalances in ecosystems.
When nitrogen- and phosphorus-rich fertilizers seep into water bodies, they fuel algae blooms, which dramatically reduce oxygen levels and create dead zones where aquatic life cannot survive. This has led to environmental crises in lakes, rivers and oceans around the world, exacerbating biodiversity loss and the collapse of marine ecosystems.
Furthermore, the gases released by these same fertilizers contribute to global warming, since nitrogen oxides are powerful greenhouse gases.
Ozone layer depletion: a success story
The depletion of the ozone layer is one of the few planetary boundaries that has been successfully managed. In the 1980s, scientists discovered that chemical compounds known as chlorofluorocarbons (CFCs) were destroying stratospheric ozone, increasing Earth's exposure to the sun's harmful ultraviolet rays. This raised the risk of skin cancer and affected countless species.
Thanks to the Montreal Protocol (1987), countries agreed to phase out the use of CFCs. As a result, the ozone layer has shown signs of recovery, becoming a success story when concerted and decisive action is taken globally.
Changes in freshwater use
Freshwater use is closely linked to agricultural production and human expansion. Blue water (surface and groundwater) and green water (present in soil moisture and absorbed by plants) are essential for the functioning of ecosystems and agriculture. However, excessive water use has led to scarcity in several regions of the world, affecting millions of people and jeopardizing food production.
River diversion, over-extraction of aquifers and the construction of hydraulic infrastructure have altered natural water flows, contributing to the degradation of wetlands and other aquatic ecosystems. In many areas, available freshwater has already exceeded the limit of safe use.
ocean acidification
Ocean acidification is one of the planetary boundaries that has not yet been fully crossed, but we are very close. As the oceans absorb more carbon dioxide from the atmosphere, pH levels decrease, severely impacting marine species such as corals, mollusks, and crustaceans, whose survival depends on the presence of carbonates in the water to form their shells and skeletons.
This phenomenon also has implications for human food systems, as the loss of marine species affects fisheries and the development of aquatic food chains.
Atmospheric aerosol loading
Atmospheric aerosols , such as soot and particulate matter, affect both climate and human health. It is estimated that millions of people die each year as a result of respiratory illnesses associated with air pollution. In addition, aerosols can interfere with local weather patterns, affecting cloud formation and precipitation.
Aerosol levels in regions such as South Asia and China have reached dangerous levels, further complicating the global fight against climate change.
Although this limit has not yet been surpassed at a global level, it is critical that measures be taken to reduce emissions of pollutants.
New chemicals: an uncertain boundary
Finally, the threshold for new entities , which includes chemicals already present in the environment such as microplastics, pesticides, and radioactive waste, is one of the most uncertain. Despite this, it has clearly been exceeded, and although we don't know precisely what the long-term consequences of this accumulation of new chemicals in the atmosphere and ecosystems will be, its negative impact is already evident in water pollution and the health of marine ecosystems.
Immediate measures are needed to regulate the production and distribution of these substances to avoid an irreversible impact on ecosystems and human health.
Humanity has already exceeded six of the nine planetary boundaries established by the scientific community, which represents a significant risk for the future of life on Earth. While it is still possible to reverse some of the damage, it is essential to take coordinated measures, both locally and globally, to preserve the planetary balance on which we depend for our survival.