Thanks to Shutterstock for the picture, and the forthcoming Rio +20 summit for providing the "atmosphere." This paper from PLoS ONE blows the top off arguments for development in these hard times. It's ecology that matters in the broadest sense and Joseph Burger and his fellow researchers know it.

Humans are constrained by the systems that operate within the planet earth's ecological framework. Despite our integration in the systems, we need to understand quickly our long-term effect on natural cycles and their associated events.

Exponential population growth and colonisation of almost every habitat has caused us to extract environmental resources and transform them for our needs. Instead of our early human subsistence, we now have a responsibility to sustain these resources. Politics and economics only rule us so far.

Ecology has always been a minor partner in human endeavours, but seems to be the crucial one for us now. This series of problems has recently come to be called macroecology, with its relevance within a sustainability science that studies Earth's limited resources.

Unfortunately, the thermodynamics of sustainability means that instead of concentrating on socio-economics and development, as we have done, much more relevance can be found within human ecology (our relationships with our environment).

The planet has a capacity for primary production on land, of which we appropriate 20-40%. Fresh water and marine fisheries have been over-harvested by a vast amount while some finite resources were assessed as being "mined-out" several years ago. According to the Brundtland Report, as long ago as 1987,we were aiming to, "avoid compromising the capacity of future generations to meet their own needs."

This means that the energy, matter and information we exchange are all subject to simple and fundamental scientific principles, unaffected by politics or economics, although they influence these areas. Our problem with this is our outstanding scarcities of resources.

As thermodynamics involves the simple conservation of energy and mass, the flows and transformations required for our societies just need to be maintained. Economic growth however is limited by scarcity of energy as our rate of energy use grinds upward. Joseph R. Burger and his colleagues from the University of New Mexico, the US Geological Survey, the Santa Fe Institute, the University of Arizona and the Instituto de Ecologia, Universidad Nacional Autà ³noma de Mexico use several specific examples of sustainable action to illustrate how the earth's resources have to be treated as finite (because they are!).

In Alaska, Bristol Bay salmon fishery is an apparent success as far as sustainable fisheries are concerned. Sockeye salmon form 95% of a 70% catch of the overall numbers from a natural wild salmon run, and no decline has caused the management to suspect that their operation is unsustainable.

Upstream from the fishery, material loss and subsequent energy changes take place. The 30% of the fish left to spawn cannot supply the same predators and indigenous people. These predators use the salmon as a highly significant dietary item. Missing 83,000 metric tonnes of biomass means that 12,000 tonnes of carbon, 2,500 of nitrogen and 330 of phosphorus are lost. The marine "source" has been lost for the terrestrial "sink" in the Bristol bay watershed.

Credit: Credit: PLoS ONE/doi:10.1371/journal.pbio.1001345.g001

Pictorial illustration of important flows of salmon and contained biomass, energy, and nutrients within and out of the Bristol Bay ecosystem. Brown arrows depict the flows within the ecosystem, green arrows depict inputs due to growth in fresh water or the sea, and red arrows represent human harvest. Seventy percent of salmon are extracted by humans and are no longer available to the Bristol Bay ecosystem.

The diagram colourfully shows why one lake within the watershed area has created only one-third of its primary production achieved before commercial fishing began. While 70% of the biomass and nutrients disappears to Asia, Europe and the rest of the US, the so-called sustainable salmon fishery does not comply with energy or mass maintenance, even within the local area.

Global economies are even more involved in non-sustainable actions with great emphases on waste production and massive energy input in, for example, major cities. Sustainability is a myth, based on the provision of more healthy life-styles and minimal environmental impact in the immediate area. Even these cities are embedded within a much larger ecologically-based system.

Credit: PLoS ONE/doi:10.1371/journal.pbio.1001345.g002

Pictorial illustration of important flows of resources into and wastes out of Portland, Oregon. This "most sustainable city in America" depends on exchanges with the local, regional, and global environments and economies in which it is embedded.

Portland is a small city, with its surrounding Multnomah County, but has a great reputation. Bike paths, farmers' markets and recycling do not a an ecosystem make, however. A massive total of 1.25 billion litres of gasoline, 28.8 billion MJ of natural gas, 31.1 billion MJ of electricity, 136 billion litres of water, 0.5 million tonnes of food are input while you may not relish the output - 99 billion litres of liquid sewage, 8.5 million tonnes of CO2, and 1 million tons of solid waste have to be dealt with by the environment. The 24 million tons of traded goods with the rest of the earth is in fact average for a similar-sized US city.

The answer to the problem? OK. Cut off this unfortunate part of Oregon. Let it be under siege conditions, as still happens in less fortunate parts of the world. Thirst, starvation and disease are taken as said, so, far from being sustainable, the residents would not survive longer than a month (sorry ppl, but you could always take over a farm!). Such a vindictive god, this ecology is!

We reckon in our economic theories with a giant flux of energy and materials, to and fro. With Portland's ever-increasing importations, combined with all others, the globe we live in is transforming. As resources of rare metals worldwide disappear, they and all the other resources control how sustainability will work. If we can maintain the current human usage of resources and recycle all the waste, which is doubtful, how can we continue to "grow" and sustain our environment in the future? More resources cannot be found until we have a spare planet (which the economists may have already considered).

Climate change is a useful guide to this global problem. Each decade, the temperature rises ominously as we seem to have overwhelmed the Earth's capacity to absorb our CO2 emissions. If you are, like those unfortunate citizens of Portland, Oregon, one of the areas which suffers from this global problem (eg. a coastal city such as Dhaka), your sustainable economy in your own area will not help you. The whole earth is involved in these macro-eco-systems! Which is of course why the gloom and doom merchants have a field day considering these potentially drowning cities.

In 2007, we may have exceeded the available land area needed for our burgeoning population by more than 50%( estimated by the Global Footprint Network). Now that places the Portland citizens' problem in perspective. Portland we could solve. But 50% of the population?

But we have indeed exceeded the biosphere's capacity to provide for us.

(My apologies to the wonderful city of Portland for the terrible siege attack on their beautiful environmentally-friendly city. Perhaps they were chosen for that reason?)