The tragedy of the tragedy of the commons

Humanity is playing out the tragedy of the commons on a global scale. At present rates, each individual added to the global human population will annually consume about 0.5 tonnes of cereal grain, 0.05 tonnes of meat or fish, 1 million litres of water, 0.3 tonnes of wood, 4.5 barrels of oil, 0.3 tonnes of copper, and 0.2 tonnes of phosphate fertilizer, and each one will release about 5 tonnes of CO2 and 4 tonnes of solid and liquid waste into the environment. If these numbers seem large, multiply each of them by 2,000,000,000 to estimate the additional consumption by 2050 when the global population has grown from its current 7.1 billion to over 9 billion (UN 2010). The resulting numbers are almost incomprehensible. The bottom line is that enormous quantities of natural resources will need to be extracted from the earth to support projected population growth (e.g., Brown et al. 2011). Additional quantities, especially of energy and metals, will be required to increase overall standards of living and to reduce poverty and disease, especially in developing countries. How can these resources be obtained, and at what cost to the environment and biodiversity of the planet (e.g., Wackernagel and Rees 1998, IPCC 2007)? Several approaches have addressed these issues: limits to food supplies (e.g., Pauly et al. 2005, Godfray et al. 2010, Foley et al. 2011, Tilman et al. 2012), supply and distribution of fresh water (Gleick and Palaniappan 2010), availability of alternative sources of energy (e.g., Hall and Klitgaard 2011), and threats from chronic and pandemic diseases (Heymann 2003, Osterholm 2005). A few efforts been made to provide more comprehensive analyses of multiple limiting factors, perhaps most notably the ecological footprint approach of the group at the University of British Columbia (http://www.footprintnetwork.org/en/ index.php/GFN/) and the planetary boundaries analyses of Stockholm Resilience Center (Rockström et al. 2009). Nevertheless, most of the attention has been piece-meal—focused on specific problems such as greenhouse gas emissions, climate change, and the outbreak of the H1N1 influenza.