UNITED NATIONS DEVELOPMENT PROGRAMME: Tremendous – and deserved – attention has been paid for the last few years to the scourge of ocean plastics pollution, which we now know reaches the farthest depths of the ocean and can have impacts on ocean life from the smallest plankton to the largest whales. We know (Jambeck et al., 2015) that some 4.8 million to 12.7 million metric tonnes of plastic enter the ocean each year. UN Environment has estimated the socio-economic costs of ocean plastics pollution at about US$13 billion per year. We are only beginning to explore and understand the potential human health impacts of plastics in the oceanic food chain.
There is however another major ocean pollutant the magnitude of which is, coincidentally, quite close to plastics at around 13 million metric tonnes per year (Seitzinger, 2010), and that is nitrogen. This includes a combination of fertilizer (4) and manure (4) run-off to rivers, untreated sewage (1), and atmospheric deposition (4). The dramatic increase in fertilizer production beginning in the 1950s led to the manufacture (using the Haber-Bosch process) of over 2 billion metric tonnes of reactive nitrogen and a 150 percent increase in the amount of nitrogen added annually to the environment, much of this reaching the ocean. Based on recent fertilizer prices, the ‘value’ of this unrecovered nutrient “waste” is about $15 billion per year. Models incorporating population and economic growth in ‘business as usual’ scenarios predict an additional doubling or more of nitrogen loads to the ocean, particularly in high growth regions such as South Asia, East Asia and Latin America.