Chemical Pollution
Pollutants result from rearing and feeding
animals but also from processing them.
Livestock excreta contains considerable
amounts of nitrogen, phosphorous, potassium,
drug residues, heavy metals and pathogens
(disease causing bacteria) and these pose
serious threats to the environment.
In 2004, it is estimated that 135 million
tonnes of nitrogen and 58 million tons of
phosphorous were produced globally from
manure – cattle accounting for 58 per cent,
pigs around 32 per cent and poultry seven
per cent. To this has to be added the vast uncontrollably. When they die and decay, the
amounts of nitrogen used as chemical water can be robbed of oxygen, suffocating
fertiliser on fodder crops. fish and other organisms (eutrophication).
The damage extends to estuaries and inshore
Of these nutrients the most pressing concern waters too, where most fish breed.
is over nitrogen which, although a nutrient
essential to all forms of life, is now produced Partly enclosed seas such as the Baltic Sea,
in massive overabundance. The amount has Black Sea and Mediterranean have been hit
doubled since the 1940s because of huge hard by eutrophication and a dead zone has
quantities used to grow animal fodder, the developed in the Gulf of Mexico off the
burning of fossil fuels and large-scale mouth of the Mississippi River. In fact, 150 of
clearing of forests. these dead zones have been identified –
some the size of small countries. The United
Excess nitrogen can seriously damage the Nations Environment Programme (UNEP)
environment, destroying heathland and many believes they will soon damage fish stocks
grasses. In humans it can produce blue baby even more than overfishing.
syndrome, a potentially fatal destruction of
red blood cells in new-born children. It is estimated that global livestock produce
in excess of 13 billion tonnes of excreta a
The gases nitrogen produces – nitric oxide year. Apart from its threat to the
and nitrous oxide – play a major role in environment, more than 40 diseases can be
causing smog, ozone depletion, global caught by humans from manure.
warming and acid rain – for which they carry
65 per cent of the blame.
Only 50 per cent of nitrogen fertiliser is taken Tony Wardle’s detailed
up by vegetation, the remainder evaporating report on the
or being washed into groundwater or environment – Diet of
watercourses, posing one of the greatest Disaster – is available
threats to the aquatic environment. from Viva! for £3.50
(inc p&p).
Water plants and algae can grow almost
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