Mass application of nutrients causes pollution
The world is facing a fertiliser crisis, with far too little in some
places, and far too much in others, a new report from the United Nations
says.
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 crop-lands 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. 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. He said: "Our analysis shows that by
improving the management of the flow of nutrients we can help protect
the environment, climate and human health, while addressing food and
energy security concerns."
- The Independent
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