One hundred thousand years ago the Earth lived on its natural wealth: rich soils produced food for plants that fed animals that fed predators. The hunting to extinction of large mammals was the first step towards the loss of the Earth's resources.
Domestication of grazing animals and the use of fire led to the destruction of forests and creation of pasture. Agriculture followed, giving rise to the growth of civilisations, beginning in Sumer in the Tigris-Euphrates river system. Sumer's richly productive irrigated land, however, eventually became saline and eroded. Over a span of 2,500 years the world's first culture rose, flourished, then disappeared from history. In our own time, the last 50 years in the US has seen 55 million acres lost to salination. The 'heartland' states, where intensified industrial agriculture dominates, are losing 5-10 tonnes of topsoil per acre each year.
Such an outcome is brought on by the 'cascade effect' of agricultural deterioration; all of which starts with nitrates, the key chemical fertiliser.
