Basics of Environmental Science

By Michael Allaby | Go to book overview

3

Physical Resources
When you have read this chapter you will have been introduced to:
• the hydrologic cycle
• the life cycle of lakes
• salt water, brackish water, and desalination
• irrigation, waterlogging, and salinization
• soil formation, soil ageing, and soil taxonomy
• soil transport
• soil, climate, and land use
• soil erosion and its control
• mining and processing fuels
• mining and processing minerals

22

Fresh water and the hydrologic cycle

In the sense used here, a ‘resource’ is a substance a living organism needs for its survival. There are also non-material resources, such as social contact and status, which may be essential to a feeling of well-being or even to survival itself, but these are not considered here.

Non-humans as well as humans make use of the resources available to them; animals need such things as food, water, shelter, and nesting sites, all of which are resources, as are the sunlight and mineral nutrients required by plants. Human biological requirements are similar to those of other animals. Like them, we need food, water, and shelter, although we differ from other species in the means we have developed for obtaining them. It is because human and non-human requirements often coincide that sometimes we find ourselves in direct competition for resources with non-humans. It is not only we who find crop plants edible and nutritious, for example, and before we can build houses to shelter ourselves we must clear the land of its previous, non-human occupants.

Water is, perhaps, the most fundamental of the resources we require. Without water, as the cliché has it, life could not exist on land. Our bodies are largely water (by weight), and if you add together the ingredients listed on many food packets you will find they seldom amount to more than about half the total weight: the remainder is water.

It is not any kind of water we need, of course, but fresh water. Sea water is of only limited use to us, and out of reach for people living deep inside continents, and drinking it is harmful, although it can be rendered potable by the removal of its dissolved salts. For the most part, therefore, we humans must obtain all the water we need from rivers, lakes, and underground aquifers. In the world as a whole, it is estimated that by the year 2000 we will be using about 4350 km3 (4.35×1015 litres) of water a year. Of this, almost 60 per cent will be needed for crop irrigation, 30 per cent for industrial processes and cooling, and 10.5 per cent for domestic cooking, washing, and drinking (RAVEN ET AL., 1993, p. 273).

Of all the water in the world, 97 per cent is in the oceans, so our freshwater needs must be met from the remaining 3 per cent. It is not even that simple, however, because of all the fresh water,

-90-

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Basics of Environmental Science
Table of contents

Table of contents

  • Title Page iii
  • Contents v
  • Figures vii
  • Tables xi
  • Preface to the Second Edition xiii
  • How to Use This Book xv
  • 1 - Introduction 1
  • 2 - Earth Sciences 19
  • 3 - Physical Resources 90
  • 4 - Biosphere 137
  • 5 - Biological Resources 200
  • References 258
  • 6 - Environmental Management 261
  • Further Reading 296
  • Glossary 300
  • Bibliography 307
  • Index 316
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