Graph of the Day: Fertilizers and Ocean Dead Zones

23 January 2012 (UNEP) – Industrially produced nutrient fertilizers (nitrogen, phosphorus) are essential to global food security and have been the main driver of dramatically improved agricultural yields over the last sixty years to feed a growing population. At the same time, excess nutrients from inefficient use in farming and insufficient treatment of nutrients in wastewater, have made their way into rivers, aquifers, coastal areas and oceans, leading to degradation of marine ecosystems and groundwater at a global scale. Nutrient loads from continents to oceans and the coastal zone have increased roughly three fold from pre-industrial levels, primarily from agricultural run-off and poorly or untreated sewage. Mainly due to the addition of manufactured nitrogen (from atmospheric nitrogen and natural gas), the amount of reactive nitrogen entering the earth’s biogeochemical system has increased by about 150% compared to pre-industrial times. A 2009 Nature Report, “A Safe Operating Space for Humanity”, determined that excess nitrogen in the environment was one of 3 of the 9 ‘planetary boundaries’ that had already been exceeded. In effect, mankind is ‘mining’ the atmosphere for nitrogen; with a practically limitless supply, this process could proceed for hundreds if not thousands of years leading to continually worsening conditions for coastal areas and groundwater. The environmental and socioeconomic impacts of nutrient pollution are massive and occurring over wide areas globally. The occurrence of coastal hypoxic zones caused by eutrophication has increased exponentially in recent years, and nitrate pollution is one of the main groundwater contaminants in the developed and also increasingly in the developing world. Coastal hypoxia impacts fisheries, tourism and various ecosystem services provided by healthy coastal ecosystems. For the EU alone, the economic costs of damage to the aquatic environment from excess reactive nitrogen are estimated at up to € 320 billion per year. Initial evidence from the EU and US suggests that the overall benefits from improved nutrient management exceed costs and that this cost/benefit calculus occurs in other parts of the world. A paradigm shift is needed in the way we produce, use and treat nutrients, from a dominantly ‘linear’ approach to a much more cyclic approach with substantial recovery of ‘waste’ nutrients. Without this change our oceans will continue to degrade through increased hypoxic zones with disastrous consequences to coastal communities dependent on marine resources for food and livelihoods. The ‘business as usual’ approach where we use sizeable fossil fuel energy resources to convert atmospheric nitrogen to fertiliser for production of food, and then use significant energy and infrastructure through conventional wastewater treatment to convert a portion of this reactive nitrogen back to atmospheric nitrogen, is highly wasteful. A move to a far more efficient and closed recycling approach to nutrients will not only protect the freshwater and ocean environment from pollution but will improve livelihoods through creation of new business and job opportunities and reduce fossil fuel energy consumption and associated greenhouse gas emissions.

Green Economy in a Blue World [pdf]