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THE NATURAL ECOSPHERE


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OVERVIEW

The ecosphere comprises the spheres of life (biosphere), water (hydrosphere), soil
(pedosphere) and air (atmosphere). The biosphere consists of all living things that interact
with each other to form communities and with their surroundings to form ecosystems.
Organisms have specific roles in communities – some produce organic matter, others consume
it, and yet others feed on the dead remains, so forming food webs. Interaction with the
environment and movement of materials through food webs creates grand cycles of
chemicals – biogeochemical cycles.

The hydrosphere is the waters of the Earth, which are linked through the hydrological or water cycle – evaporation, condensation, precipitation, runoff. The pedosphere (soil) sits at the interface of the atmosphere, hydrosphere, lithosphere and biosphere. It is a complex entity resulting from physical, chemical and biological processes.

Climate, organisms, relief and substrate strongly influence its character. The atmosphere is a shell of dusty gas. Its composition is unique among terrestrial planets due to the action of organisms. Air constantly moves in grand convective overturnings and great swirling eddies, collectively called the general circulation of the atmosphere.


LEARNING OUTCOMES

The basic nature, form and function of these spheres is revealed in this chapter, which should
help you understand:

• How living things interact with each other to form communities and with their surroundings
  to form ecosystems and biogeochemical cycles
• The global water cycle and the nature of aquatic life
• Soil-forming process and soil biogeochemical cycles
• The composition and processes of the atmosphere.

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SUMMARY

The ecosphere is formed by the interaction of life (the biosphere), water (the hydrosphere), soil (the pedosphere) and air (the atmosphere). The biosphere consists of all life on Earth. Individual organisms interact with each other to form communities. Globally, nine basic community types correspond to nine climatic zones. Individuals and communities interact with their life-supporting
environment – air, water and soil – to form ecosystems. Organisms play different roles in ecosystems. Some are producers or autotrophs, others are consumers or heterotrophs. Yet others are decomposers and detritivores that feed on the waste-products of life.

The uptake and release of biochemicals by living things creates biogeochemical cycles, examples of which are the carbon and nitrogen cycles. The hydrosphere is the totality of the Earth’s waters – the seas and oceans, rivers and lakes, ice caps and ice sheets, glaciers and snowfields and all other stores of water. The hydrological cycles link these water bodies through the process of
evaporation, condensation, precipitation and runoff. The soil (pedosphere) is a complex organic and inorganic system formed by the interaction of air, water, rocks and life. Its nature varies from place to place owing to differences in climate, organisms, topography and substrate.

The atmosphere is a highly mobile shell of dusty gas. Its composition is unique among terrestrial planets due to the action of organisms. It has both a vertical and horizontal structure. Atmospheric processes produce the weather and climate experienced by other systems of the
ecosphere.

QUESTIONS

1. What is an ecosystem? To what extent     have humans altered the world’s natural     ecosystems? 4. How important is soil within iogeochemical    cycles? 2. How cyclical are biogeochemical cycles? 5. How important is atmospheric composition    in understanding climatic change? 3. Why do evaporation and precipitation vary     from place to place?

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FURTHER READING

• Arnell, N. (2002) Hydrology and Global Environmental Change. Harlow: Prentice Hall.
  An excellent text on water. Particularly useful because it is up-to-date and takes a global perspective.
  
• Barry, R. G. and Chorley, R. J. (2003) Atmosphere, Weather and Climate, 8th edn. London: Routledge.
  Deservedly known as a classic and enormously popular. An excellent introduction to the subject.
  
• Bridges, E. M. (1997) World Soils, 3rd edn. Cambridge: Cambridge University Press.
  A good starting point for studying soil and soil processes.
  
• Davie, T. J. A. (2002) Fundamentals of Hydrology. London: Routledge.
  An accessible introduction to the study of hydrological processes.
  
• Huggett, R. J. (2004) Fundamentals of Biogeography, 2nd edn. London: Routledge.
  An introduction to past, present and future individuals, communities and ecosystems.