The mass application of nitrogen, phosphorus and other nutrients needed for plant growth has had huge benefits for world food and energy production, but it has also caused a web of water and air pollution that is damaging human health, causing toxic algal blooms, killing fish, threatening sensitive ecosystems and contributing to climate change, says the report, Our Nutrient World.
However, in some parts of the world, insufficient access to fertilisers remains the problem, and still hampers food production and contributes to land degradation — even while supplies of some nutrients such as phosphorus are more and more seen to be limited.
The report calls for a major global rethink in how fertilisers are used across the world, so that more food and energy can be produced while pollution is lessened rather than increased.
It suggests that the attention long given to carbon dioxide because of its role in global warming should now be given to nitrogen and phosphorus products, because their mass use is playing its own role in substantially affecting the planet.
Since the 1960s, human use of synthetic nitrogen fertilisers has increased nine-fold globally, while phosphorus use has tripled; and further substantial increase of about 40 to 50 per cent in fertiliser use are expected over the next 40 years to feed the growing world population.
"While recent scientific and social debate about the environment has focused especially on CO2 in relation to climate change, we see that this is just one aspect of a much wider and more complex set of changes occurring to the world's biogeochemical cycles," says the report. "In particular it becomes increasingly clear that alteration of the world's nitrogen and phosphorus cycles represents a major emerging challenge that has received too little attention." A question to be decided, says the report, is what body should oversee a new attempt at globally managing fertiliser use.
Fertilising crops was originally a natural process, using plants which 'fix' nitrogen from the air, such as clover and other legumes, or by the application of animal manure. But since the development of modern agriculture in the 19th and 20th centuries, natural sources of nutrients have been insufficient and croplands have needed mined or manufactured fertilisers spread upon them – in increasingly large amounts.
As their use has intensified, so have the unintended side effects, especially eutrophication — the process which occurs when excess nutrients run off into water bodies and promote excessive plant growth, especially of algae.
The resulting algal blooms can be toxic to fish and other water life and even to people, and they are occurring across the world in rivers, lakes and the sea.
Contributors to warming
The large amounts of nitrogen being pumped into the environment are also contributing to air pollution and to global warming, as some oxides of nitrogen are greenhouse gases.
Phosphorus us mined from phosphate rock deposits, which occur in only a few countries; nitrogen fertilisers are produced by the famous Haber-Bosch process, developed in the early 20th century and now responsible for 500m tonnes of fertiliser a year.
Even, so, says the report, in Africa, Latin America and parts of Asia there are still wide regions with not enough access to nutrients. The lead author of the report is Professor Mark Sutton from the UK's Centre for Ecology & Hydrology. (Michael Mccharthy/The Independent)