Planetary Boundaries: a safe world for humans.


On #WorldEnvironmentDay we focus on the concept of planetary boundaries. What are they about? They represent conditions that enable humans to live safely and comfortably on the planet. In other words, they help to define "a safe operating space for humans".

Text: © Kathelijne Bonne 

It is not about war vs. peace, or poverty vs. prosperity (not unrelated and they also require urgent action). It is about conditions that are favorable for our body to function on Earth, in a safe environment, with sources of food, drinking water, clean air, bearable temperatures, and generally a healthy natural habitat. 

The concept of planetary boundaries is based on the idea that the planet has limits, when faced with environmental burdens. The concept was proposed by scientists working in the Stockholm Resilience Center in Sweden. The idea is that planetary boundaries are used as a framework for an improved stewardship of the planet. 

What is a planetary boundary?

The boundary or limit can also be described as a tipping point or threshold: The value at which a very small increment for a variable (e.g. a small increase in CO2) triggers a larger, possibly irreversible catastrophic change in the response variable (e.g. global warming). It is the moment at which the Earth system cannot absorb a change anymore, without undergoing profound change. It is literally the straw that breaks the camel's back. 

Stability and resilience

In 2009 the Stockholm scientists defined nine processes that regulate the stability and resilience of the Earth system. They proposed measurable planetary boundaries within which humanity can continue to develop and thrive for generations to come.

The nine processes and the way they are measured are: 

  1. Climate change (in CO2, in parts per million)
  2. Biodiversity loss (number of species per million per year)
  3. Biogeochemical cycles (nitrogen removed from the atmosphere, and phosphorous going to the oceans, in millions of tonnes per year)
  4. Ocean acidification (measured by calcium carbonate saturation state)
  5. Land use (percentage of land surface converted to cropland)
  6. Freshwater (human consumption, in cubic kilometers per year)
  7. Ozone depletion (stratospheric ozone concentration)
  8. Atmospheric aerosols (particulate concentration)
  9. Chemical pollution (Concentration of toxic substances, plastics, endocrine disruptors, heavy metals, and radioactive substances)

Today, we are still in safe operating space for five of these nine planetary boundaries. The idea is to get back into safe operating limits for all processes. 

It is well known that Earth systems, including climate, temperature, ocean acidity and atmosphere oxygen levels, oscillate over long timespans. It means they can change, an argument often used by skeptics that prefer 'business as usual' over changes to be made for a more sustainable way of life. Even with the long-term climate changes, life has shown to be resilient because it has prospered for 4 billion years. That required a certain overall stability: The Earth systems did indeed change over time, but within limits that are safe for life as a whole to prosper and thrive. 

We know that sometimes species have died out. That happens because the naturally changed operating space is almost never safe for all species. For example, global ocean acidity has been responsible for the extinction of 90% of all species at certain times in the geological past. 

Human actions

Human actions have increased the rate at which Earth systems undergo change. Especially CO2 in particular is produced at an unnatural rate. But Earth is an interconnected system, and the system tries to absorb the excess CO2. That is, it is increasingly absorbed by the oceans. As a consequence, global water bodies become increasingly acid. This could push the Earth systems out of the safe limits (for humans and the ecosystems we depend on) and causing irreversible change. 

Luckily for is, some countries and many scientists, are scrutinizing the details of the planetary boundaries. We can only keep our fingers crossed that they will make it to policy makers in time. And for now, as citizens, we can think about what can be done, and implement small actions for a better future. 

Source: The website of the Stockholm Resilience Center