A safe operating space for humanity: understanding the planetary boundaries

Are we pushing Earth too far? Our planet is like a spaceship hurtling through space, but we can't jump ship and easily find a new one if things go wrong. Here, we explore the 9 Planetary Boundaries we're crossing.

The Richat Structure or "The Eye of the Sahara" | Hodoyoshi-1 Satellite | Axelspace

Understanding the Earth's limits is crucial for our survival. In this article, Dr Claudia Luiza Manfredi Gasparovic, a researcher in Industrial Ecology at Nium, explores the concept of planetary boundaries and nine critical processes that maintain a stable and habitable Earth.

Imagine Earth as a safe zone for humanity. This zone, established over the past 10,000 years, allowed us to thrive. But our actions, from burning fossil fuels to polluting oceans, push us outside this safe zone. This article delves into:

  • What are planetary boundaries? These nine essential processes regulate Earth's stability.
  • Which boundaries have we crossed? Six, including climate change, freshwater use, and land-system change, are already in danger.
  • What are the consequences? From extreme weather events to ecosystem collapse, the impacts are already felt and could worsen significantly.
  • What can we do? The article emphasises the need to change course and return to the safe zone. This requires urgent action, from reducing greenhouse gas emissions to protecting biodiversity.

The article also highlights the role of clean ammonia in this critical equation. While it can play a part in decarbonising energy systems, its production and use must be carefully managed to minimise negative impacts on other planetary boundaries. This call to action urges us to understand the big picture and take responsibility for our planet's health. We can still secure a safe future for ourselves and future generations by working together.

Rupert Bay, natural tannin-stained river water mixes with seawater | NASA

Scientists have identified nine planetary processes that sustain life on Earth. We have already breached six of them - including climate change.

Humans need many things to survive. Water. Food. Air. Shelter. Thermal comfort. The list goes on. Now imagine if people didn’t realise this.

That’s what often happens with the planet. When we look at the climate crisis with a focus on carbon, we often don’t realise all the other systems the planet needs to sustain life. And since it’s the planet that provides us with water, food, air, shelter, and thermal comfort, it threatens our survival, too.

So, what does the planet need for us to be safe? And are we providing it?

That’s what Scientists from the Stockholm Resilience Center set out to answer.

What ‘safe’ means

The scientists realised that from the last ice age 10,000 years ago until not so long ago, the conditions of the planet, such as temperature, climate, and the cycles of carbon and nitrogen, had mainly stayed the same. These stable conditions throughout this period (called the Holocene) allowed humans to survive and thrive.

This “window” of opportunity led humans to settle down, grow our food, develop societies as we know them and ultimately burn fossil fuels and industrialise agriculture, therefore changing the Earth’s conditions more in centuries than in the previous thousands of years - changes enough to threaten life on Earth.

It led to the rise of the “Anthropocene”: the time we live in now, when human influence on the planet became determinant, changing the previous conditions so much that we are no longer in a safe space for survival.

Planetary boundaries

Scientists set out to determine precisely how we had changed the planet and which ones were most critical. They started with a set of questions:

  • What environmental processes regulate the stability of the Earth system? 
  • Do these processes have well-defined limits beyond which human survival is threatened? 
  • And what are these boundaries?

From ample scientific evidence, they devised the concept of ‘planetary boundaries’: nine processes are critical for maintaining the stability and resilience of the Earth system in conditions similar to the ones we have experienced throughout human existence.

Because the Holocene conditions are considered safe, they were used as a reference in defining the boundaries for the nine planetary processes.

These limits define the “planetary playing field” boundaries for humanity: a safe operating space for Earth and us; as long as we can keep the planet within that window, we should be good.

Transgressing boundaries

If we don’t keep these processes at these safe levels, we risk destabilising the Earth's state in which modern societies have evolved. We are incurring the risk of triggering non-linear, abrupt and unacceptable global environmental change from the point of view of sustaining humanity.

The problem: we have already crossed six of the nine boundaries.

Nine key Earth processes

The nine planetary processes the scientists identified cover the “biogeochemical cycles” (cycles of transport and transformation of chemical elements) of nitrogen, phosphorus, carbon and water; systems of circulation on the planet such as the climate, atmosphere, ocean; and biophysical features like biodiversity and land systems, which contribute to its capacity for resilience and keeping stable conditions all around. Moreover, two boundaries are associated with human activity: aerosol loading and chemical pollution by introducing novel entities.

They don’t exist separately but interact with each other, resulting in the overall state of the Earth system.

The state of each one of these processes is measured through a control variable, and each is assigned a boundary value (a limit).

In all, the Planetary Boundaries are:

  • Climate change: the extra amount of heat (energy) from the Sun retained on the Earth's system due to the “cover” of greenhouse gases emitted by human activities and the disruption it causes to Earth’s climate. Therefore, this boundary is controlled by the change in “radiative forcing” (the effect of this extra amount of energy) and atmospheric CO2 concentration. Both are beyond their boundary value, while the safe CO2 concentration levels are around 350 ppm, now at 419 ppm. It is considered a ‘core’ boundary because of how it interacts with all others.

  • Freshwater change: the amount of water used by human activities affects biodiversity, food, and ecological functions such as the provision of habitats, carbon sequestration, and climate regulation. Less freshwater available means less resilience of terrestrial and aquatic ecosystems. Freshwater use is controlled considering “blue water” (surface and groundwater) and “green water” (moisture in the soil or water available to plants), respectively, by the percentage of annual global ice-free land area with streamflow (movement of water) or root-zone soil moisture. Both have been transgressed a century ago, in 1905 and 1929.

  • Atmospheric aerosol loading: aerosols are tiny particles that, after emission from natural sources or human activities like combustion of fossil fuels and agriculture, are suspended in the atmosphere and affect both the climate and human health. It is controlled with the annual mean difference between hemispheres of a variable called ‘aerosol optical depth’ (AOD), a measure of overall reduction in sunlight that reaches Earth’s surface due to these particles absorbing and scattering light. The boundary is set at 0.1, and the current value is at 0.076. Though this boundary has not been breached, the impacts of aerosols are already felt today.

  • Ocean acidification: when CO2 from the atmosphere is dissolved in the oceans, it reacts and partially becomes carbonic acid, acidifying these waters. Due to the extra CO2 in the atmosphere, oceans are becoming much more acidic. This harms ecosystems and sealife, for instance, causing the blanching of coral reefs. It also diminished the oceans’ ability to absorb CO2, potentially causing climate change. Ocean acidification is controlled by carbonate ion concentration (a form of dissolved CO2) in surface seawater. The boundary is set at 80% of the preindustrial value, and a recent estimate places it at 81%, verging on outside of safe operating space. This trend is worsening as CO2 emissions continue to rise.

  • Land system change: this boundary focuses on three major forest biomes that play critical ecological roles: tropical, temperate, and boreal. The remaining forest cover controls it compared to the potential forest area in the Holocene. The boundary positions are at 85%/50%/85%, respectively. Continental average values for these biomes vary from 37.5%-83.9% for tropical forests, 34.2-54.3% for temperate forests, and 56.6-70.3% for boreal forests. Therefore, the boundary is breached in all biomes.

  • Terrestrial biosphere integrity: the biosphere is the area on the planet that sustains life, both above and below the Earth’s surface. It includes the air, the oceans, the land, and all the living beings and ecosystems in it, which make Earth a planet so different from all others. This boundary addresses the fundamental role that the terrestrial biosphere and its interactions with the geosphere (rocks and minerals) play in regulating the state of the Earth system. Integrity means that the biosphere changes in ways that preserve its overall dynamics and capacity for adaptation. It is measured by genetic diversity (how many different species there are), measured by the rate at which species are going extinct, and the planetary function, which is measured by how much of the biosphere production (net primary production, NPP) humans appropriate (HANPP). Limits are <10 extinctions/million species-years, and we are at over 100 E/MSY and <10% of HANPP, and 30% currently. It is also considered a ‘core’ boundary.

  • Stratospheric ozone depletion: a layer of ozone in the stratosphere helps protect Earth from the Sun’s UV radiation, which is dangerous to humans and affects processes like photosynthesis. Human release of substances like halocarbons from industry and nitrous oxides react with this ozone, weakening this layer and exposing Earth to UV rays. The boundary measure for this is the number of ozone molecules called Dobson units. It is set at least 276 DU, and the current value is 284 DU. Therefore, we are in the safe zone for this boundary.

  • Novel entities: a reference to the introduction, by human activity, of substances not found in nature, such as chemicals, microplastics, pollutants and medicines, and human modification of evolution, such as GMOs. They could have significant and persistent effects on Earth, especially the biosphere. The boundary is set at a zero release of these compounds unless they have been certified harmless and monitored. This boundary is transgressed because numerous untested and unregulated substances are released yearly.

Earth is now well outside of the safe operating space for humanity. Six boundaries have been breached, and another one is at risk!

Current status of control variables for all nine planetary boundaries. Source: Richardson et al. 2023

Finding our way back

Droughts decrease crop yields. Storms make people lose their homes and lives. Excess in nutrients pollutes water and destroys habitats. Acidic oceans and desertified forests no longer absorb carbon - further feeding this loop.

The Science is clear: we are changing the planet into a version of Earth that may not support us. The change in Earth’s climate is one of the most critical. But it is not the only one.

To guarantee that humans and all of life on Earth continue to survive, thrive, and evolve, we must pay attention to these changes, stop their current path, and ultimately reverse them.

The planetary boundaries framework should function as signposts, guiding human development on a changing planet.

The planetary boundaries framework does not dictate how societies should develop. These are political decisions, and they must consider human dimensions not incorporated in the framework, such as equity. Identifying a safe operating space for humanity on Earth contributes to decision-makers ability to define desirable courses for societal development and our shared future.

Securing a safe future for Earth (and all that reside here) requires looking at the big picture.

The role of clean ammonia

Ammonia is essential for food production today and could become an essential part of decarbonised energy systems in the future.

Clean ammonia can play a fundamental role in stopping climate change. But producing it requires water and land, and using it in fertiliser or to power ships impacts the biosphere. 

To secure a better planet for future generations, we must consider how clean ammonia and its value chain impact other planetary systems.

At Nium, minimising negative and maximising positive impacts on nature and people are central to our thinking.

To learn more about how we are leading the way in planetary-aware technology development, email hello@wearenium.com and get access to our 2024 Impact Reports for clean ammonia as fertiliser, energy vector and shipping fuel, where we use the Planetary Boundaries framework to anticipate all the ways our minion reactor and powerful nanocatalyst can impact the planet so we can deliver positive change from it.