The State of the Earth — What are we doing?

Posted by on August 27, 2012
Facebooktwittergoogle_plusredditpinterestlinkedin

Two recent papers in the prestigious journal Nature caught my eye.  That scientists are even publishing such papers, and that journals of the caliber of Nature publish them, says a lot about the state of our world.  I’ll deal first with one on the health of the oceans, and then discuss the one on the risk of planet-scale state shifts that I briefly mentioned last time.

Ben Halpern, of the National Center for Ecological Analysis and Synthesis, based in Santa Barbara CA, has teamed up with 32 colleagues from various US, and Canadian universities to produce a paper called “An Index to Assess the Health and Benefits of the Global Ocean.”  It was published on line on 15th August, but has not yet appeared in a print issue of the journal.  Its citation currently is Halpern et al, Nature doi:10.1038/nature11397.  The goal was to develop an objective and quantitative tool that would measure the status of our oceans.  Such an index can be recalculated in the future to see whether the oceans are getting better or worse, which is the same thing as seeing whether we are doing a good or a poor job of managing them.  (Actually, they restrict themselves to the oceans falling within the EEZ of any country, excluding the high seas for which there are too few data available.)

When people set out to invent an index, it is inevitable that certain assumptions, or explicit decisions will be made.  An index of something like ocean health will also likely be based on many value judgements, and that is certainly the case here.  These authors have done a pretty good job of detailing how they made decisions that created their index, however, I am not very comfortable with all the decisions they have made.  For example, the index is based on 10 sub-indices measuring different aspects of the ocean such as its delivery of food, its offering of tourism and recreation, and its provision of coastal livelihoods on the one hand, and its water quality and biodiversity on the other.  These apples and oranges then get weighted equally, each contributing 1/10 of the total index which ranges from 0 to 100.   One can quibble with the choice of aspects to quantify, the details that yield each sub-index, and the decision to weight them as equally important to the overall index.  Whether this index will become as ubiquitous as the Fahrenheit or Celsius temperature scales, or pH, or even the Grade A, Grade AAA, and so on system for evaluating eggs, I do not know.  It would be nice if we had a probe that could measure ecosystem health and this index is an attempt to produce that probe.

The more interesting thing to me about this paper is what Halpern and friends found out about the oceans.  The following figure shows index value for the global ocean on the left, and a suite of values for the EEZ of each of several countries. (They do not provide a figure for Canada but apparently Canada scored 70 on their index.  I think we should wait until the Harper government and the multinationals have got the Arctic coastline of Canada thoroughly mined and invite a re-assessment.)

 Index scores (inside circle) and individual goal scores (coloured petals) for global area-weighted average of all countries and for several representative countries.

The ten sub-indices are arrayed around the circle (four of them are split into values for two sub-sub-aspects).  The distance of the color out from the center shows the value for that sub-index (thus Tourism and Recreation gets a score of 10, while Clean Water gets a score of 78).  (The gray segments for Jarvis Island, a tiny, remote speck, represent aspects for which a score would not be relevant.)  Total scores range for 38 (Ivory Coast and Democratic Republic of the Congo, tied) to 86 (Jarvis Island), but I am still undecided what these scores mean precisely.  Despite the details of the scores, the fact that the oceans log in at 60 out of a possible 100, and the fact that ‘food provision’ and ‘tourism and recreation’ both score so poorly suggests to me that we are not coming close to using the oceans sustainably.  But perhaps we knew that already?

The second paper is one that was published in the 7th June issue of Nature.  Anthony Barnosky of UC Berkeley teamed up with 21 friends from universities in the US, Canada, Chile, and several European countries to publish “Approaching a State Shift in Earth’s Biosphere”.  In it they examine the types of changes that happened to the biosphere during phase shifts such as the five great mass extinction events in the Earth’s geological past, and the less extreme transition that occurred about 10,000 years ago when the last Pleistocene ice advance came to an end.  They then look at the kinds of pressures humanity is placing on the Earth, and focus in particular on rate and extent.  Their main conclusion is that we are currently, or in the very near future, placing pressures on the biosphere that are every bit as large as those experienced at the times of these earlier massive changes in ecological state.

They discuss the theory of ecological phase shifts and point out that the typical state shift involves a relatively sudden switch from one quasi-stable state to a very different, but also quasi-stable state.  One characteristic of phase shifts is that once the shift has occurred it can be very difficult or impossible to return to the previous state – in the fancy words of this field of ecology, there is a bifurcation.  In their diagram (below) they represent the state shift as the dotted line in a path that represents the changing state of the planet:

Quantifying land use as one method of anticipating a planetary state shift.

Here the growth of the human population, and the progressive conversion of terrestrial ecosystems into ones supporting our agriculture, urban centers and other uses, become the stressors that at some point trigger a sudden shift (the vertical downward arrow) to a new state.  Even if one freed up some of the land to natural habitat again, and reduced the size of the population, the planet would track back along the lower path, perhaps for quite some way until perhaps following the dotted path back to its original state.  The question marks on the figure could have been put anywhere – we simply do not know how close we are to a sudden global ecological change.  But the comparisons with past events are definitely scary.  Here is what they write close to the end of the paper:

Humans have already changed the biosphere substantially, so much so that some argue for recognizing the time in which we live as a new geologic epoch, the Anthropocene. Comparison of the present extent of planetary change with that characterizing past global-scale state shifts, and the enormous global forcings we continue to exert, suggests that another global-scale state shift is highly plausible within decades to centuries, if it has not already been initiated.

As a result, the biological resources we take for granted at present may be subject to rapid and unpredictable transformations within a few human generations. Anticipating biological surprises on global as well as local scales, therefore, has become especially crucial to guiding the future of the global ecosystem and human societies. Guidance will require not only scientific work that foretells, and ideally helps to avoid, negative effects of critical transitions, but also society’s willingness to incorporate expectations of biological instability into strategies for maintaining human well-being.

So, I like this article far more than the one by Halpern et al.  But in liking it, I also recognize they are talking about very troubling things.  I’d have been a lot happier if they said we were only 60% of the way towards a phase shift.

 

Comments are closed.