It seems to me that one of the more interesting debates to be had around global environmental change and development is that of the nature of growth in the modern world.  There are those that argue (or at least implicitly argue) that growth is effectively unlimited by the biophysical world – the real barriers to growth around the world are capacity, governance, etc.  Operating from this assumption (or something near to it), the logical decision is to foster growth everywhere in the world, and to assume that the absence of growth is a symptom of problems with human capacity, attitudes and institutions that can and should be rectified.  At another pole are those that argue that our growth is fundamentally pinned to the biophysical world – this is the implicit assumption behind ecological footprint calculators, that we draw upon natural resource for growth in a manner that is fixed and measurable -and the measurements suggest, rather strongly, that growth is highly constrained by the biophysical world.
Like most people, I exist somewhere in the middle of this continuum.  Ecological footprint calculators, imperfect though they may be (for example, converting our resource use into acres of land is a problematic and weak process/proxy), demonstrate rather clearly that if we are to get everyone in the world up to the average standard of living in the United States, we would need the natural resources from around three Earths.  Many of the arguments about future policy built on these footprint calculations end up discussing rather steep resource and wealth redistribution curves if we want to see a more equal world.  However, there is a significant flaw in this reasoning – these measures (let’s just assume that they are reasonably accurate for the purposes of this argument) and the resultant policy prescriptions assume the per capita intensity of use to be a constant going forward into the future.  This discounts future technological developments that will, no doubt, lower the per capita resource use of those in the advanced economies, such as the US.
On the other hand, the news here isn’t all good – while the intensity of use might decrease over time, such decreases typically translate into the market in the form of reduced prices, which tend to spur increased production.  Put another way, 5 years in the future we may only use 75% of the resources we do today to make a shirt, thus lowering the footprint of that shirt and the person who buys that shirt.  However, the price of that shirt will likely decrease to remain competitive in the market, encouraging consumers to buy more shirts than they used to.  If the price drop of the shirt is such that the consumer who typically buys four shirts a year decides to buy five, we’ve already lost the decreased footprint created by increased efficiency to a larger footprint created by greater consumption.  In other words, improved resource efficiency related to growth won’t do us much good if it spurs the growth of consumption such that the per capita resource uptake remains constant or rises.
There is another bit of bad news here – even if those of us living in the advanced economies decided to freeze our amount of consumption, locking in our current standard of living while allowing increased resource use efficiency to translate into greater availability of goods and services in the Global South, I don’t see a point any time in the near future where these benefits will be of a scope that will allow for a real closing of the gap in the material standard of living between the developing and the developed.  We’re looking at differences of orders of magnitude right now, accrued over several centuries of differential political economic activity when the Earth’s population and total resource uptake was much, much smaller.  So if we want a truly equal world, those of us in the advanced economies are going to have to give something up.
While I am an indefatigable optimist (hey, I am writing this post but I still work in development), this doesn’t absolve me from a serious consideration of reality – so maybe I am a constrained optimist.  The size of the global population today, coupled with our current regimes of resource use, have taken most, if not all of the slack out of the global resource/growth equation.  No, we are not yet at a zero-sum world where growth in China means loss somewhere else, like the US – it is still possible to see growth in multiple sites, as technological advances create a bit more space for growth via increased efficiency.  But there will come a day where we will cross this curve – where our inability to make things more efficient as quickly as our increased demand on resources rises will finally come to a point where the resources themselves become the restrictor plate on growth – the world will effectively become a zero-sum economy.
In my work on the Millennium Ecosystem Assessment, I saw trends that make the math above a lot more pressing.  The rates of resource degradation around the world are astonishing.  Not everything is getting worse, of course – temperate forests, for example, are doing pretty well – but an astonishing percentage of the resources we rely upon for our standard of living are under threat right now, not in some distant future.  So our current use of the environment (much of this use in the name of growth, incidentally), with its various impacts, is hastening the day when we cross the curve into a zero-sum economy.  Some might argue (or hope?) that we will generate enough wealth and capacity between now and then as to come up with some sort of a solution for this – or to put back the damage that we have done to our environment, thus uncrossing the curve for a while longer.  This strikes me as a hell of a gamble*, where the stakes on a bad bet are getting larger and larger.  Meanwhile, the nature of this bet has been shifting from betting one’s house on red to betting one’s house on red 16 . . .
No, we are not there yet.  But, barring a remarkable revolution in our ability to generate energy and food (I won’t rule these out, but the sort of revolution we need is on the order of fusion, which isn’t all that close right now), zero-sum is coming.  But what should we call this not-quite-zero-sum world we are living in?  Surely someone has a name for this already . . .
*in the case of extinctions, this is a pointless gamble – there is no putting back extinct, and anything that goes extinct will have effects (some obvious, others difficult to discern) throughout ecosystems . . . and often there will be one or more impact parts of that ecosystem that humans see as useful. or necessary.