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productivity
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Productivity is the growth rate of the living part of an ecosystem; the animals, plants and other organisms.

Productivity

Productivity is the growth rate of the organisms living in an ecosystem. It determines how fast we can use an ecosystem’s resources. When we take them faster than they are produced, the ecosystem loses biomass, diversity and productivity. We can maintain sustainable ecosystems by balancing the rate we take resources with the rate they are made.

 What influences productivity?

The basic level of productivity is influenced by two main factors:

  • the availability of the resources needed for photosynthesis
  • the diversity of the ecosystem.
 How the resources needed for photosynthesis affects productivity.

Most organisms gain the energy they need to live from the sun. Solar energy is either gained directly by photosynthesis or indirectly by eating other organisms.

Photosynthesis requires:

  • Sunlight
  • Carbon dioxide
  • Water
  • Nutrients (especially nitrogen and phosphorous and iron)

The productivity of an ecosystem depends on the abundance of these resources (as well as the diversity and abundance of primary producers). The lack of any one of these factors limits productivity.

Efficient nutrient recycling can help overcome low nutrient levels in an ecosystem. Water, carbon and the other nutrients required for photosynthesis cycle through an ecosystem. A diverse ecosystem is able to recycle these nutrients more efficiently making them available for photosynthesis faster increasing productivity.

 How diversity affects productivity

Diversity influences productivity by:

  • ensuring the efficient use of resources
    Different species use an ecosystem's resources in different ways. Having many species usually means that resources are used efficiently with little waste. The efficient use of these resources help them cycle through the ecosystem faster making them available for reuse by other organisms.
  • complimentary interactions between species
    Some species are thought to interact and use resources in ways that increase productivity for each other. For example, reef-building coral give zooxanthellae algae shelter and get food in return (see “What is a coral?” for more information). If one of these species is lost the other is much less productive.
  • the presence of architecture species
    Some species have enormous impact on the make up of an ecosystem by providing habitat. For example, coral reefs are 100 times more diverse than a nearby tropical ocean ecosystem. The reef supplies habitat and resources for hundreds of different species.
  • increasing ecosystem resilience  
    Disturbance events, like storms or fires, occur naturally in an ecosystem. A diverse ecosystem increases the chances that it will be able to resist or bounce back quickly from disturbance.
 Conclusion

Sustainable use of an ecosystem relies on not using resources faster than they are made. Productivity relies on the diversity of the ecosystem to ensure efficient cycling of resources, and loss of diversity lowers ecosystem productivity. Unsustainable use of resources feeds back on itself and the ecosystem loses productivity, and less can be taken from the ecosystem in the long term.

 References

Cardinale, B. J. (2006). Effects of biodiversity on the functioning of trophic groups and ecosystems. Nature 443: 989-992.

Hatcher, B.G. (1997). Organic Production and Decomposition. In Life and Death of Coral Reefs. Birkeland, C. (ed.). Chapman and Hall, New York.

Hooper, D. U. et al. (2005, February). Effects of biodiversity on ecosystem functioning: A consensus of current knowledge. Ecological Monograph 75(1). Retrieved 23 May 2008 from http://www.esajournals.org/perlserv/?request=get-document&doi=10.1890%2F04-0922

Odum, E. P. & Barrett, G. W. (2005). Fundamentals of Ecology (5th ed.). Thomson, Brooks/Cole: Australia.

Pommes. L. (1988). Energy flow and Trophic Structure. In Concepts of Ecosystem Ecology (Pomeror, L. R. & Alberts, J. A. eds.). Springer-Verlag: New York.

Science Encyclopedia. (2008). Ecological Productivity. Net Industries. Retrieved 25 June 2008 from http://science.jrank.org/pages/2257/Ecological-Productivity.html

Tait, R. V. & Dipper, F. A. (1998). Elements of Marine Ecology (4th ed.). Butterworth-Heinmann: Oxford.

Waide, R. B. (1999). The Relationship between Productivity and Species Richness. Annual Review of Ecology and Systematics 30: 257-300. Retrieved 23 May 2008 from http://www.jstor.org/stable/221686

Wikipedia . (2001, April 1). Algae. Wikipedia. Retrieved 23 May 2008 from http://en.wikipedia.org/wiki/Algae

Wikipedia. (2002, February 25). Plant. Wikipedia. Retrieved 23 May 2008 from http://en.wikipedia.org/wiki/Plants

Wikipedia. (2002, November 10). Food chain. Wikipedia. Retrieved 23 May 2008 from http://en.wikipedia.org/wiki/Food_web

Wikipedia. (2003, April 10). Wikipedia. Retrieved 25 June 2008 from http://en.wikipedia.org/wiki/Primary_production

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