Planetary boundaries

Our planet has natural limits that keep it healthy. Scientists call these limits the planetary boundaries. These boundaries help describe how human activities affect the Earth system.

Staying within these limits keeps the Earth in a stable state. This stable period is called the Holocene. During the Holocene, the climate and nature were steady enough for human societies to grow. If we cross these boundaries, the Earth might not be able to regulate itself anymore. This could lead to sudden and big changes in our environment.

There are nine different boundaries that scientists watch closely. These include climate change and how much freshwater we use. Other boundaries cover things like ocean acidification and the loss of nature, called biosphere integrity. Scientists also look at how we change land and how we use nitrogen and phosphorus. They even watch for new human-made materials, which they call novel entities.

Each boundary has a specific number or measurement to track it. For example, they look at how much carbon dioxide is in the air. They also check how much of the world's forests remain intact.

A group of scientists first created this idea in 2009. They were led by Johan Rockström and Will Steffen. Many other experts helped them, including Nobel laureate Paul Crutzen. They wanted to find a "safe operating space" for all people. In 2015, the team updated their work with more data. They added new authors to help study the changes. They also changed some names to be more accurate. For instance, they renamed "loss of biodiversity" to "change in biosphere integrity." This shows that how nature functions is just as important as the number of species.

Many of these boundaries have already been crossed. In 2009, scientists said three boundaries were already past the safe limit. By 2015, they found that climate change and land system change were also crossed. Since then, more limits have been passed. In 2022, the limit for novel entities was crossed. In 2023, the boundary for freshwater change was passed. Most recently, in 2025, scientists documented that ocean acidification had also crossed its limit.

These numbers show how much the Earth is changing.

Understanding these boundaries is like knowing the rules of a playing field. If you stay inside the lines, the game stays steady. If you go outside, things can become very messy and hard to fix.

The framework helps governments and leaders make better plans. It moves us away from just trying to do less harm. Instead, it helps us find a way to live that stays within the Earth's safe zone. This helps ensure that humans can thrive for a very long time.