A Safe Operating Space For Humanity

Hello dashing readers,

I thought after my initial introduction it would be a good idea to show you some actual proposed thresholds/boundaries. This will hopefully make everything a little less conceptual and more real. John R Rockstrom et. al. (et. al. meaning all the other authors involved) wrote a great report for the Stockholm Resilience center that was summarized in Nature (one of the main scientific journals) a few years back. The title of the article is the title of this post.

The report and article proposed that to meet the challenge of maintaining a Holocene state, a framework based on ‘planetary boundaries‘ would have to be established.. These planetary boundaries define the safe operating space for humanity with respect to the Earth system and processes (climate circulations, chemical pollution etc.).

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    Thus Rockstrom and his colleagues made three key points: -

1. A new approach for defining preconditions for human development.
2. Crossing certain biophysical thresholds could have disastrous consequences for humanity.
3. Three of nine interlinked planetary boundaries have already been overstepped.

 

Although Earth’s complex systems can respond smoothly to change this is likely to be an exception and one would more likely expect an abrupt, non-linear change. Particular sensitivity will be experienced approaching a threshold, as well of the possibility of irreversible change as we have previously discussed last week (a tipping point). An example would be the impact on the monsoon system. Many people heavily rely on these periods of inundation, as with out crops will likely fail. The monsoons have historically been expected over certain areas at certain points in the year, if this were to be altered too drastically then it is likely many people would suffer, even to the point of starvation.

Some of these thresholds are easier to define than others i.e. can be defined by one control variable. An example would be CO2 concentrations described in parts per million (ppm). You may remember earlier in the year when CO2 surpassed 400ppm (temporarily due to seasonality issues, it’s currently at 393ppm) and the consequential fuss about global warming that was made (rightly so). Other thresholds for land and water degradation make it harder to draw a red line at a certain point due to it being intertwined with other aspects of our landscape,.

Figure 1 below displays the 9 processes that Rockstrom et. al. felt if crossed, could generate unacceptable environmental change.

Figure 1: The inner green shading represents the proposed safe operating space for nine planetary systems. The red wedges represent an estimate of the current position for each variable. The boundaries in three systems (rate of biodiversity loss, climate change and human interference with the nitrogen cycle) have already been exceeded.

Table 1 below builds on figure 1, giving detailed description of the boundaries, the earth system process being impacted and the analyses behind them.

From table 1 we can see that humanity is, in addition to the three boundaries transgressed already, soon to surpass the boundaries for global freshwater use, change in land use and ocean acidification also.

The planetary boundaries are described in terms of individual quantities and separate processes, but the boundaries are tightly coupled. If one boundary is broken, then other boundaries are also under serious risk. For instance, significant land-use changes in the Amazon could influence water resources as far away as Tibet (That’s more than 11,000 miles away). Or the climate-change boundary depends on staying on the safe side of the freshwater, land, aerosol, nitrogen–phosphorus, ocean and stratospheric boundaries. Infringing on 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. Think of poor Nemo and friends….

As you can see it can get very complex very quickly given the huge number of factors and dynamic nature of the relationships. Thus although some boundary breaks are headline grabbing, they are all a concern.

It is worth noting that the authors took a conservative approach to quantifying the boundaries. This was due to a sensible risk-averse approach and baring in mind the large uncertainties over the true position of many thresholds, as gaps in our knowledge base exist. Most interesting of these currently being the allowed overshoot time of our already transgressed boundaries before positive feedback loops take hold (X produces more of Y which in turn produces more of X), so we might not be able to return back to safe prior levels.

Large criticisms can be thrown at this paper over some of the proposed boundaries. We aren’t actively monitoring on a large/long enough scale many of the processes influencing our thresholds. Thus due to the difficulty of making global estimates the authors took their best educated guess in some areas. The links between these somewhat unknown systems further complicating the situation, as they can’t be studied in isolation. Despite all this we still widely agree that the best scenario for humanity is below the limits set (so we need to backtrack), where long-term social and economic development can occur.

Thanks for reading, if you are interested in the full reports I’ve put the links to the pdf files below. I would particularly recommend the 2^nd link, lots of great simple to understand graphs to enjoy.

‘Remember if you meet someone, tell them about global warming, it’s a real icebreaker’.

PDFs

http://www.nature.com/nature/journal/v461/n7263/pdf/461472a.pdf

http://www.uu.nl/SiteCollectionDocuments/GEO/UCAD/rockstrom2.pdf