Water: the greatest ecosystem service. 2011. In Landscape Ecology and Ecosystem Services. C. Young, L. Bosongel, I. Hooper & K. Moreton-Jones (Eds.) pp. 129137.
WATER: THE GREATEST ECOSYSTEM SERVICE
S. M. Haslam, Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA
Water is necessary for all life and, coming from the earth, is the greatest service the ecosystems of the earth provide to humankind, as well as to all other animals and plants. All are made largely of water, and so water must be able to enter and leave. Water enters, ultimately, as precipitation in the form of fresh water, falling equally on land and water. The smaller amount falls on land and freshwater, providing the necessities of life for the biota and their habitat (soil, trees, lakes, etc.) in which they live and from which they draw their water. Ultimately, this fresh water, with or without many solutes added, runs to the salt water of the sea with all its inhabitants, from whence it evaporates into the sky and precipitates down once again. This paper is concerned solely with the small part of the cycle which is on land and characterised as fresh water, which is responsible for life on earth.
Keywords: Water, ecosystem service, natural capital, river
'WATER IS NOT A COMMERCIAL PRODUCT LIKE ANY OTHER BUT, RATHER A HERITAGE WHICH MUST BE PROTECTED, DEFENDED AND TREATED AS SUCH.' (EU Water Framework Directive.) This statement appears obvious, but is not. None of the EU countries, to which it is addressed, are willing or able to carry it out. Some individuals, rather than nations, realise its truth, but even they are likely to be reduced to hoping that new technology will bring more water before it runs out, or worse, that war will allow 'my' country to seize and drink 'your' water, and only 'your' country will die. For something so precious as water, and yet so difficult to conserve by turning off taps, irrigating with precision, etc., this has devastating potentialities.
Water, necessary for all life, crops and cities alike, is the greatest service the ecosystems provide to humankind. The sun is outside our ecosystems and unlike water is so far an inexhaustible resource. Water, unfortunately, is neither, and from increased demand and (often wilful) negligence, shortages are appearing.
The riverscape and the river are natural capital, interdependent, and share the sheet of water which covers the land, in whole or in part, permanently or intermittently. Rain falls: some evaporates; some sinks below the ground surface, gradually emerging as springs or flushes; and (usually) most runs downslope, gradually collecting in rivers and finally the sea.