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Poo to You
The simple acts of rearing, feeding and processing animals into meat produces pollution. Livestock excreta contains considerable amounts of nitrogen, phosphorous, potassium, drug residues, heavy metals and disease causing bacteria (pathogens) and together they pose a serious threat to the environment. And there's a lot of it!
About 135 million tonnes of nitrogen and 58 million tons of phosphorous came from the global manure heap in 2004 – cattle accounting for 58 per cent, pigs around 32 per cent and chickens and other poultry seven per cent.
On top of this are the vast amounts of nitrogen used as chemical fertilizer on fodder crops - the plants grown for animals to eat.
There's a great deal of concern over nitrogen. Although it's essential to all forms of life the world is now produicing far too much of it. In fact, the amount we produce has doubled since the 1940s because of the huge quantities used to grow animal fodder, burning of fossil fuels and the mass felling and burning of forests.
Too much nitrogen can seriously damage the environment, destroying heathland and many grasses. In humans it can produce something called blue baby syndrome - the destruction of red blood cells in new-born babies which can be fatal.
Nitrogen also produces gases – nitric oxide and nitrous oxide – and these play a big role in causing smog, ozone depletion, global warming and up to 65 per cent of all acid rain.
Out of Control
Only 50 per cent of nitrogen fertilizer is taken up by the plants it's used on, the rest evaporating or being washed into groundwater, ponds, streams and rivers and seriously threatening the plants and animals that live there.
Water plants and algae can grow totally out of control but eventually they die and decay. When that happens, the water is robbed of oxygen and fish and other creatures can be suffocated (eutrophication).
Rivers carry the nitrogen into estuaries and the sea around the coast and cause similar problems. This is where most fish breed.
Partly enclosed seas such as the Baltic Sea, Black Sea and Mediterranean have been hit hard by eutrophication and a dead zone has developed in the Gulf of Mexico off the mouth of the Mississippi River.
In fact, 150 of these dead zones have been charted – some as big as small countries. The UN believes they will soon be even more damaging to the survival of fish than overfishing (United Nations Environment Programme - UNEP).
It's estimated that all the world's livestock produce more than 13 billion tonnes of excreta a year between them. Apart from its threat to the environment, more than 40 diseases can be caught by humans from manure.