Understanding the Earth’s Limits: The Nine Planetary Boundaries

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Humans have created many systems on earth that aim to make things easier, such as agricultural systems, production systems, transportation systems, and consumption culture. The system may support human interests, but at the expense of the ecological system.

“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,” Center researcher and co-author, Johan Rockström, Director of the Potsdam Institute for Climate Impact Research (PIK) and Professor in environmental science at the Stockholm Resilience Centre at Stockholm University.

[Source: Population Connection]

Planetary Boundaries: What Do They Mean and Why Are They Important?

In 2009, Johan Rockström, then the director of the Stockholm Resilience Centre, and a team of 28 internationally recognized scientists proposed the concept of nine planetary boundaries.

The concept of planetary boundaries has been a helpful tool for understanding the impact of human activities on the Earth's ecosystems, ensuring that our actions do not compromise the integrity of the Earth's ecosystems and biosphere. To achieve this, two types of thresholds have been established: a safety threshold and a risk threshold. Exceeding the risk threshold can lead to significant and potentially irreversible climate disruptions, which are difficult to control. 

This is a stark warning, as we have already exceeded six of the nine planetary boundaries, putting our very survival at risk. The nine biophysical processes that make up these boundaries are interconnected and constantly interacting, highlighting the complex and interconnected nature of the Earth's systems.

Dive deeper into the 9 planetary boundaries

The 2023 update to the Planetary boundaries

[Source: Stockholm Resilience Center]

1. Climate change Climate change is the most widely recognized planetary boundary. The indicator of climate change is CO2 because it is a key driver of global warming. Carbon dioxide (CO2) is a greenhouse gas that traps heat in the Earth's atmosphere, contributing to the warming of the planet. The threshold for this boundary is set at 350 parts per million (ppm) of CO2 in the atmosphere, which corresponds to approximately 1° to 2°C of global warming. We have already exceeded this level, with current CO2 levels at around 417 ppm, and are on track for a 2-3°C temperature rise by 2100, which poses a high risk of triggering irreversible tipping points.
   

2. Change in biosphere integrity (biodiversity loss and species extinction) Biodiversity loss is another critical boundary because it undermines the Earth's ability to adapt to change, disrupts essential ecosystem processes, and increases the risk of catastrophic environmental and social consequences. The study estimates that over 10% of the genetic diversity of plants and animals has been lost over the past 150 years, and the extinction rate is accelerating. The boundary is measured by genetic diversity and functional integrity, which are both compromised due to human activities such as land use change and harvesting.
   

3. Stratospheric ozone depletion The concentration of ozone should not fall below 5% of pre-industrial levels.The study notes that ozone levels are within the threshold. Ozone depletion can lead to increased UV radiation and negative impacts on ecosystems. This can result in skin cancer, cataracts, and immune system suppression in humans, as well as damage to ecosystems and agricultural productivity.
   

4. Ocean acidification The mean surface seawater saturation state with respect to aragonite should not fall below 80% of pre-industrial levels. The study notes that ocean acidification levels are close to the threshold. Ocean acidification compromises the structural integrity of corals and shellfish. This can lead to the collapse of marine ecosystems, threatening the survival of many marine species and the services they provide, such as coastal protection and nutrient cycling.
   

5. Biogeochemical flows (phosphorus and nitrogen cycles) Biogeochemical flows refer to the cycling of nutrients such as nitrogen and phosphorus. The boundary for this process is breached due to significant changes in both blue and green water availability since pre-industrial times.  Industrial and agricultural fixation of nitrogen should not exceed 35 TgN per year, and the annual phosphorus inflow to oceans should not exceed 10 times the natural background weathering of phosphorus. Exceeding these thresholds can lead to ecosystem disruptions and environmental degradation. This can result in eutrophication, biodiversity loss, and the creation of oxygen-depleted "dead zones" in aquatic ecosystems, undermining water quality and fisheries.
   

6. Land-system change (for example deforestation) Land system change is measured by the preservation of forest cover. The boundary is defined as the preservation of a weighted average of 75% of the forest cover present in the Holocene. The study estimates that only 60% of global forest cover remains, with tropical, temperate, and boreal forest cover in several geographic areas significantly lower than the thresholds. Exceeding this threshold can lead to land degradation and loss of ecosystem services. This can result in habitat loss, biodiversity decline, soil degradation, and disruptions to the global carbon cycle, undermining ecosystem services and exacerbating climate change.
   

7. Freshwater use Freshwater use has increased significantly due to human population growth and agricultural expansion. The boundary for freshwater is breached, with a quarter of the global population now using at least 80% of their countries’ available freshwater every year. Novel ecosystems can disrupt ecosystems, bioaccumulate in food chains, and pose risks to human health and the environment. This can result in unpredictable and far-reaching consequences, threatening the integrity of Earth's systems and the well-being of present and future generations.
   

8. Atmospheric aerosol loading (microscopic particles in the atmosphere that affect climate and living organisms) Atmospheric aerosol loading refers to the presence of particles in the atmosphere. The boundary for this process is breached due to human activities such as burning fossil fuels and agricultural practices. The current Status of Atmospheric aerosol loading is not yet breached. Exceeding this threshold can lead to water scarcity and ecosystem disruption. This can have severe consequences for agriculture, human health, and economic development, as well as exacerbating social tensions and geopolitical conflicts over access to water resources.
   

9. Introduction of novel entities Novel ecosystems refer to the creation of new ecosystems through human activities. The boundary for this process is breached due to the widespread destruction of natural habitats and the creation of artificial environments. Novel ecosystems can disrupt ecosystems, bioaccumulate in food chains, and pose risks to human health and the environment. This can result in unpredictable and far-reaching consequences, threatening the integrity of Earth's systems and the well-being of present and future generations.

This Must be Fought For

Six of nine crossed planetary boundaries may increase pessimism about our Earth's future, but we can still take action to prevent further crossings. By implementing sustainable practices, reducing our environmental footprint and switching to renewable energy sources, we can mitigate the impact of our activities on the earth's ecosystem. This includes reducing carbon emissions by planting trees to combat climate change and conserving biodiversity to protect ecosystems. By making conscious choices and implementing policies that prioritize environmental conservation, we can work to restore the balance between human activities and nature, thereby ensuring a sustainable future for everyone.

Blue Carbon Ecosystem Restoration: An Initiative to Curb the Passage of Planetary Boundaries

[Source: CarbonEthics]

Blue carbon ecosystems, such as seagrass meadows and mangrove forests, are natural carbon sinks that capture and store carbon dioxide from the atmosphere. These ecosystems are highly efficient in carbon sequestration, compared to tropical forests, seagrass can absorb carbon 35x faster and mangroves can absorb carbon 10x more efficiently.

Understanding the Earth’s Limits: The Nine Planetary Boundaries | CarbonethicsRestoring and protecting blue carbon ecosystems not only help mitigate climate change but also provide numerous co-benefits to people and nature. This ecosystem serves as a habitat for a variety of marine and coastal species, protecting coastal waters from pollutants and reducing the impact of extreme weather such as storms and floods. Additionally, the blue carbon restoration initiative with CarbonEthics will improve local community livelihoods.

We can prevent worse changes together,  preserving ecosystems and supporting local communities. Collaborate with CarbonEthics to balance climate change through carbonethics.co/partnership

Reference:

Richardson, K. et al. (2023). Earth beyond six of nine planetary boundaries. Science Advances, 9(37).

Rockström, J.et al. (2009). Planetary boundaries: exploring the safe operating space for humanity. Ecology and Society, 14(2).

Wood. K., & Ashford, O. 2023. How Blue Carbon Can Tackle the Climate, Biodiversity and Development Crises. WRI.