Transgressing the Earth's Boundaries

In preparation for my Sustainability Economics exam on Thursday, I decided to combine the necessary with the fun and write about a concept that I will hopefully remember come Thursday – the Planetary Boundary framework championed by Johan Rockström from the Stockholm Resilience Centre.

Rockström starts with arguing that the planet has moved into the Anthropocene, an era in which humans constitute the main drivers of change in the Earth’s system. Acknowledging that impact, his research team identified nine so-called Planetary Boundaries that constitute the limits of the planet’s capacity to absorb change. Actions that would lead to the transgression of these boundaries could “destabilize critical biophysical systems and trigger abrupt or irreversible environmental changes that would be deleterious or even catastrophic for human well-being”. 

So what are the nine boundaries we are talking about, and what importance do they have?

1. The most important boundary according to Rockström is clearly climate change. It is also a boundary that we have already breached, if we believe the researchers’ estimates. Even if we stabilize global warming and CO2-emissions, the loss of summer polar sea-ice is almost certainly irreversible. This can mean that temperatures will rise even more rapidly (as the ice sheets absorb less heat), and sea levels will be metres higher than at present. The ongoing destruction of terrestrial carbon sinks such as rain forests could accelerate this development even further.

2. Ocean acidification is also linked to CO2-emissions, since around a quarter of these emissions are finally dissolved in our oceans. This alters ocean chemistry and increases its acidity, making it harderfor organisms such as corals and some shellfish and plankton species to grow and survive. And if these disappear, the ocean ecosystems would change even further, leading to a likely decline in many fish stocks.

3.  Stratospheric ozone depletion might be one of the boundaries that show how change can be possible – some of you might remember the appearance of the Antarctic ozone hole because of the use of certain ozone-depleting substances like CFC. This thinning of the ozone layer led to increased levels of ultraviolet radiation, which is associated with higher rates of skin cancer in humans as well as other  damage to terrestrial and marine biological systems. Fortunately, the Montreal Protocol of 1989 phased out many of the harmful substances and in 2012, the ozone hole was at its second smallest in 20 years.

4. The fourth boundary is the combination of nitrogen and phosphorus cycles. It is intrinsically linked to agriculture, since its main origin is the development of chemical nitrogen and phosphorus-based fertilizers and their widespread application. Many of these nutrients are not taken in by plants and leak into waterways and coastal areas, where algae start to bloom and take oxygen out of the water – this creates dead zones where marine ecosystems struggle to survive, such as in the Gulf of Mexico. Nitrogen is another one of the boundaries already transgressed.

5. Another boundary that is strongly affected by our agricultural system is global freshwater use. According to Rockström et al., 25% of the world’s river basins run dry before reaching the oceans due to use of freshwater resources in the basins, and in 2050 half a billion people are expected to be under water-stress. Population growth, climate change and large-scale human interventions in river flows have a compounded impact on this boundary.

6. Change in land use include both agricultural and non-agricultural uses, but the researchers stress that forests, wetlands and other vegetation types have primarily been converted to agricultural land. These land use changes again influence a variety of other factors, including the reduction of carbon sinks, the reduction of biodiversity, changes in water flows, and nitrogen and phosphorus cycles.

7. Speaking of which, biodiversity loss is the third boundary that we already surpassed. According to estimates, we are currently in the sixth major extinction event the Earth has ever known – and the first knowingly caused by humans. Humans have increased the rate of species extinction by 100–1000 times compared to the Earth’s typical extinction rates, and currently around 25% of species in well-studied groups are threatened by extinction. This has deleterious effects on system resilience (if genetic material is lost, an ecosystem might not be able to adapt to external circumstance changes as well).

8. The last two boundaries were identified, but not quantified. Atmospheric aerosol loading refers to air pollution through the emission of pollutant gases as well as land-use changes that increase the amount of dust and smoke in the air. This has both direct effects on human health as well as being a major influence on the Earth’s climate system, such as cloud formation and global-scale and regional patterns of atmospheric circulation. Highly polluted environments in tropical region have already seen shifts in monsoon systems, for example.

9. Finally, chemical pollution through the dispersion of toxic compounds such as heavy metals, synthetic organic pollutants and radioactive materials in the environment is seen to have a dangerous effect on ecosystems. Reduced rates of fertility and the potential of persistent generic damage have already been observed in bird populations and marine mammals.

Pretty heavy, right? Except for the two last points, the researchers assigned some quantitative limits to each of the concepts and therefore were able to evaluate where the Earth was doing well and where we were dangerous close to  (or past) balance.

The concept has its share of critics too, which argue that some of these boundaries might be negotiable, or argue against the assignment of a quantitative boundary in cases where there is no evidence of a tipping point. For example, for land use changes or biodiversity loss, how should you assign a limit if you don’t even know what the impacts of transgressing it could be?  Wouldn’t that just be an arbitrary restriction to progress, development and to pragmatic policy-making? Furthermore, they contend that a global-scale concept like this only has limited regional applicability, and could even lead to adverse policy decisions, for example if nitrogen-based fertilizer were limited in parts of Africa, where it is currently underused and could contribute to significant yield increases.

Personally, I find it an illuminating – while scary – idea. I do agree with the worry, though, that it gives little in concrete policy-suggestions and might thus be shelved with other environmentalist awareness-raising efforts, never to be taken seriously – although its message certainly is very much so.

What do you think? Is it an alarmist idea with limited applicability or a crucial concept that showcases the real complexity of our environment? 

Bonus: Watch Johan Rockstöm explain his concept in an inspired TED-talk:

[youtube=http://www.youtube.com/watch?feature=player_embedded&v=RgqtrlixYR4]