Know Your Planetary Boundaries
In 2009, a paper under the title
The paper has received over 5000 citations since it was first published, thus showing it received a great deal of attention; its results extensively discussed among scientists. What is it about this paper, you ask? The study signals nine main threats to the stability of the Earth System and that any of them is capable of tipping the whole system to an unknown, volatile, dangerous new state. All but one of these threats are currently increasing, while three of them are in a dangerous zone — loss of biodiversity, climate change, and chemical fertilizers’ use (i.e., nitrogen and phosphorus). In 2015, the study was updated and the results further developed, but the fundamental message remained the same. In the new framework, land-use change is also highlighted as one of the most important threats. It is indeed contributing to climate change and biodiversity loss, as well.
What does this mean? The Earth was in a stable state for the last 10 000 years. This state provided a very stable climate that allowed us to develop agriculture, then cities, then complex societies. But if we were to lose this stability, the planet would not be able to support more than 7 billion people. The biosphere, like all complex adaptive systems, is capable of rapid fundamental changes — so-called regime shifts — that are transforming the governing processes of the system in a short time — often irreversibly. Within planetary boundaries, such change can be possibly avoided; outside of them, the probability of a regime shift increases dramatically.
In 1972, with the publication of Limits to Growth, the technical understanding of sustainability was that we must not overuse our renewable and non-renewable resources and that to do that, we need better technologies, less consumption and a controlled population. The Planetary Boundaries framework does not deny that, but it approaches the same problem in a different way: if we want to keep the system’s self-organizing power, adaptive capacity, resilience and, ultimately, its stability, we must stay inside the planetary boundaries. The same truth applies here as we have seen with regional regime shifts — like lake-eutrophication — slow variables must be kept under control and away from dangerous values in order to stay clear of the greatest dangers of the ecological crisis. Planetary boundaries are thresholds where global regime shifts could occur. As it is true for regional cases, the exact threshold cannot be defined — but we know where the danger zone is and what tendencies are harmful. We do not need to know exactly where the edge of the cliff is in order to avoid it.