“Sustainability” involves the ability to endure. From the standpoint of a biological community, the diversity of species and their productivity over time are important determinants of the stability of a community and its longevity.

What about human communities? What determines the sustainability of the human species on Earth? The answers to these questions have been the subject of much scientific research and controversy over the years. Now critical work on the subject has been completed that helps shed light on these vital questions.

The first article I recommend reading is entitled “Managing Earth’s Future” which is featured in the April 2010 issue of “Scientific American” and summarizes the work of a worldwide team of scientists including Dr. Jonathan Foley, Director of the Institute of the Environment of the University of Minnesota. Their method involves the review of numerous interdisciplinary studies of physical and biological systems and the identification of nine environmental processes that determine sustainability. Their next goal is to determine “threshold boundaries” or tipping points for each process, which, once exceeded, compromise the ability of the Earth to sustain human life.

The nine processes fall into three groups. The first group includes Aerosol Use and Chemical Pollution which have threshold boundaries that are yet to be determined. A second group of processes have threshold boundaries that are currently measurable and which we are rapidly approaching. These include Land Use, Freshwater Use, Stratospheric Ozone Depletion and Ocean Acidification.

A third group of processes have all exceeded their threshold boundaries. Biodiversity Loss exceeds its boundary by one hundred fold (100x) and has the potential to result in the 6th Great Extinction with threats to over 50% of the world’s species by the end of this century. Nitrogen is at 3 times its threshold boundary due to industrialized agricultural practices, which annually transfer 133 million tons of nitrogen from the atmosphere into bodies of water. This is creating vast dead zones in lakes and oceans.

Finally, the most popularly familiar process is the concentration of Carbon Dioxide in the atmosphere, measured in parts per million (ppm). Dr. Foley and his colleagues agree with Dr. James Hansen of NASA, the world’s foremost climatologist, that carbon dioxide not only exceeds its threshold boundary of 350 ppm at its current level of 387 ppm, it is rising at an unacceptable rate of 2 ppm annually. As Dr. Hansen convincingly argues in his recent (2009) book, Storms of My Grandchildren, the cause of this rise is the continued burning of fossil fuels, in particular coal, which is unsustainable from the standpoint of human habitability. What is not widely understood is that exceeding this boundary has the potential to end all life on Earth.

Personally, this last statement shocked me. Until recently the discussion of climate change has centered on sea level rise, drought, economic disruption, etc. Dr. Hansen and his colleagues are warning that the stakes are much higher than previously believed. This means that the boundary rate of carbon dioxide at 350 ppm is not only the most important number in humankind’s history, it is critical for all life on Earth.

The reason is that human induced climate change is creating an effect, or “forcing”, that is ten thousand times that seen during the Paleocene-Eocene Thermal Maximum (PETM). This forcing has the potential to suddenly release a time bomb of methyl “clathrates” (a complex of methane which is a gas with 21x the potency of carbon dioxide in terms of its “greenhouse gas” effect). These clathrates are stored under the ice caps and in coastal zones and their release would, in a positive feedback loop, transform the Earth’s climate into one similar to that of Venus, where the surface temperature is 850 degrees F., hot enough to melt lead!

If the threat is this severe, why aren’t our leaders making this their first priority and taking appropriate action? Dr. Hansen explains why and has suggestions regarding what each of us can do about it. His book is clear, comprehensive and very action oriented. I highly recommend reading Storms of Our Grandchildren as well as the April 2010 issue of “Scientific American” and the April 2010 issue of “National Geographic” with its special issue on “Water, Our Thirsty World”. This represents a primer on human sustainability.

Education is a great start, but urgent action is also required! Dr. Hansen suggests we ask President Obama to commission the National Academy of Sciences to review the current data on climate change, and have them present their findings to the American public in terms we can understand. Action points would include a comprehensive price on carbon and measures to end the burning of coal. He also suggests we join Bill McKibben’s organization www.350.org to multiply our effectiveness.

What else can we do? How can local action be important when the issues seem so huge? In his most recent book, Eaarth: Making a Life on a Tough New Planet, author Bill McKibben contends that the most important action on sustainability is local. We must consume less and transform our economies into more “distributed” and durable ones. He points out that “beginning with ourselves, globalization is reversible based upon the next purchase we make”. Labeling products to reflect their total ecological cost, and buying appropriately, can have an immediate effect that sends a global message. For instance, we can reduce both nitrogen and fossil fuel pollution by purchasing local and organically grown agricultural products through a community supported agriculture (CSA) cooperative. Organic community and home gardens have a similar and complementary effect.

Another local action would be to join the worldwide “transition town” movement that is helping many communities dramatically reduce their dependence on fossil fuels. This has reached hundreds of cities worldwide and has now reached Nevada City. We could bring it to our own community.  Since environmental education is key, we can expand the Conservancy’s education programs and base them around a model community or “ecovillage” which demonstrates best practices and acts as a training resource for the entire community.

The issue of human sustainability is clearly both important and urgent and requires us to act simultaneously at every level: as individuals, in our communities, as Americans and as a species. What better place to start than locally? After all, moving to another planet is not an option for any of us.

See you on the river,
Scott Underwood

Reprinted from “The Current” the American River Conservancy Informational Newsletter for June, July, August 2010 edition.