What do "planetary boundaries" refer to?

The concept of planetary boundaries first emerged in 2009 in an article published in the famous scientific journal Nature. Its authors: a team of 26 researchers, including climate scientists, led by the Swedish specialist Johan Rockström, then director of the Stockholm Resilience Centre.

Their work was based on a systemic analysis of our planet and its dynamics. In practice, they studied the interactions between the different systems that sustain life on Earth: the atmosphere (in other words, air), the hydrosphere (water), the biosphere (different forms of life), the lithosphere (soil), etc.

Their conclusions are as follows:
1️⃣ nine major processes facilitate and regulate the Earth's system as it has existed for approximately 10,000 years;
2️⃣ these processes are today impacted by human activities;
3️⃣ there exists for each of these a limit beyond which the process will no longer produce the usual effects and lead to radical imbalances.

In simple terms, we could say that the planetary boundaries are a series of critical thresholds linked to the current major equilibrium on Earth. Below these thresholds, we remain within what these scientists call a "safe operating space for humanity". If, however, we go beyond these, we have to expect the worst given the overall balance will be disrupted.

We had already crossed three planetary boundaries in 2009: global warming, altered nitrogen cycles and biosphere losses. Since then, the situation has worsened, with 4 new limits officially declared as crossed. The most recent being: Land use change (in 2015), the introduction of new pollutants and freshwater use (both in 2022).

Humanity has, therefore, crossed six of the nine planetary boundaries leaving its "safe operating space for humanity", entering an area of risk.

A recent study published in the journal Science Advances has finally assessed all nine planetary boundaries. This is the third major update to this important scientific framework.

The bad news is that six of these limits have already been crossed. This means that human activities have exceeded critical levels for certain environmental processes. Fortunately, pressure on the ozone layer is showing signs of improvement.

The study also provides some interesting details. Thanks to new scientific data, researchers were able to quantify the atmospheric aerosol loading limit. According to the study, this limit has not yet been crossed, despite increasing pressure.

On the other hand, using a new approach to assess biosphere integrity, the team concluded that this limit had been crossed as early as the late 19th century.


In 2024, a seventh limit, ocean acidification, is set to be exceeded (Source: Potsdam Institute for climate impact research (PIK)).

The choice of nine boundaries, the exact values beyond which a threshold is crossed or even the measurement units selected… : the planetary boundaries concept is the subject of debate and discussion within the scientific community. It is nothing new, given the progress science makes by these exchanges of views and other controversies.

That said, the planetary boundaries have gradually established themselves as part of the environmentalist's fight to preserve life on Earth. As soon as 2011, the UN and the European Commission, for example, very quickly adopted this forecasting tool. In France, some, such as the Fondation pour la Nature et l’Homme (Nature and Humans Foundation), even advocate amending the Constitution.