9 Threats to Earth's Environmental Stability

The Earth's environment has been unusually stable for the past 10,000 years, but human actions now threaten that stability, say Johan Rockström and 28 colleagues in a recent article published in Nature.

This statement, by itself, is hardly shocking. Scientists began sounding alarms about climate change years ago. But Rockstrom et al present a new approach to the question of human sustainability. They list 9 boundaries that we are crossing and endangering Earth's ability to maintain the environment that enabled human development. Giving teeth to their thesis, they quantify 7 of these environmental boundaries.

The boundaries are:

• Climate change
• Rate of biodiversity loss (terrestrial and marine)
• Interference with the nitrogen and phosphorus cycles
• Stratospheric ozone depletion
• Ocean acidification
• Global freshwater use
• Change in land use
• Chemical pollution
• Atmospheric aerosol loading

The boundaries are interrelated, the authors say. For example, land-use changes in the Amazon could influence water resources in Tibet. And "transgressing the nitrogen–phosphorus boundary can erode the resilience of some marine ecosystems, potentially reducing their capacity to absorb CO₂ and thus affecting the climate boundary."

All boundaries must be addressed, according to the authors. We no longer have the luxury of concentrating on one at the expense of others.

The Nature article summarizes the full paper, "Tipping towards the unknown," available at the Stockholm Resilience Centre (where Professor Rockström is executive director). The paper's web page includes abundant complementary material, such as videos of some of the paper's contributors, the full 36-page scientific article and information for the press.