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11 - Changing biodiversity

Published online by Cambridge University Press:  05 June 2012

Frank Oldfield
Affiliation:
University of Liverpool
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Summary

Extinctions

Some 1.7 million species have been identified, but these probably comprise less than 15% of the total number of species thought to exist on Earth (Hammond, 1995). Of the major taxonomic groups, only in the case of plants and vertebrates have more than 80% of all the species been described and it is only for these groups that any direct assessment of rates of extinction can be calculated on a percentage basis. One of the few comparisons between regional extinction rates in birds, plants and insects – in this case, butterflies in Britain – suggests that extinction rates calculated for birds and plants may well be equally indicative of trends in insect populations (Thomas et al., 2004). Although the comparisons made are for a small area in global terms, and the populations and drivers of change involved may not be representative of those in the wider world, the results still lend some support to the view that groups of organisms for which data are sparse may be just as threatened by extinction as those studied more comprehensively.

Figure 11.1 shows estimates of the percentage of species of birds, mammals, fish and plants regarded as currently under threat of extinction (Pimm et al., 1995). McCann (2000) states that one third of the plant and animal species in the United States are at risk of extinction.

Type
Chapter
Information
Environmental Change
Key Issues and Alternative Perspectives
, pp. 190 - 196
Publisher: Cambridge University Press
Print publication year: 2005

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  • Changing biodiversity
  • Frank Oldfield, University of Liverpool
  • Book: Environmental Change
  • Online publication: 05 June 2012
  • Chapter DOI: https://doi.org/10.1017/CBO9781139165266.012
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  • Changing biodiversity
  • Frank Oldfield, University of Liverpool
  • Book: Environmental Change
  • Online publication: 05 June 2012
  • Chapter DOI: https://doi.org/10.1017/CBO9781139165266.012
Available formats
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Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

  • Changing biodiversity
  • Frank Oldfield, University of Liverpool
  • Book: Environmental Change
  • Online publication: 05 June 2012
  • Chapter DOI: https://doi.org/10.1017/CBO9781139165266.012
Available formats
×