Rainforest Diversity


July 27, 2006

Tropical rainforests support the greatest diversity of living organisms on Earth.

https://mongabay-images.s3.amazonaws.com/1200/indonesia/sumatra_9236.jpg Although they cover less than 2 percent of Earth's surface, rainforests house an estimated 50 percent of all life on the planet's land masses.

No one knows exactly how many species live in the world's tropical rainforests — estimates range from 3 to 50 million species — rainforests are the undisputed champions of biodiversity among the world's ecosystems, containing far higher numbers of species on a per-area basis relative to sub-tropical, temperate, and boreal ecosystems. For example, whereas temperate forests are often dominated by a half dozen tree species or fewer that make up 90 percent of the trees in the forest, a tropical rainforest may have more than 480 tree species in a single hectare (2.5 acres). A single bush in the Amazon may have more species of ants than the entire British Isles. This diversity of rainforests is not a haphazard event, but is the result of a series of unique circumstances.

Comparison of biodiversity for selected groups between the United States and Indonesia

What is biodiversity?

Biodiversity -- short for biological diversity -- is the the number and types of organisms in an habitat, ecosystem, region or environment. It can refer to genetic, species, or habitat variation at any scale.

Portraits of Diversity

Countries with the Highest Biodiversity

Sumatran elephants in Bukit Barisan Selatan National Park. Photo by Rhett A. Butler

Review questions:

  • Most of the plant and animal species live in what level of the rainforest?
  • What are epiphytes?
  • What is an example of an epiphyte? (Hint: think of a popular kind of flower)
  • What are lianas?
  • What is a symbiotic relationship?
  • What is a keystone species?
  • Why are agoutis important in the rainforest ecosystem?

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Continued / Next: Role of Climate, Solar Energy, and Stability

  • The opening quotation comes from The Song of the Dodo (New York: Scribner, 1996) by David Quammen.
  • In his The Diversity of Life (Cambridge, Mass.: Belknap Press, 1992), E.O. Wilson eloquently depicts rainforest diversity using the example of the number of ants in a bush: a single bush in the bush in the Amazon may have more species of ants than the entire British Isles.
  • The "Mean Net Primary Production by Ecosystem" table is derived from Holdgate, M. ("The Ecological Significance of Biological Diversity," Ambio Vol. 25, No. 6, Sept. 1996).
  • E.O. Wilson demonstrates the Increase in Diversity Towards the Tropics using the number of bird species in locations of similar size (The Diversity of Life, Cambridge, Mass.: Belknap Press, 1992).
  • The box, "Portraits of Rainforest Diversity" is derived from several sources: plant species (E.O. Wilson, The Diversity of Life, Cambridge, Mass.: Belknap Press, 1992); butterflies (Robbins, R.K. and Opler, P.A., "Butterfly Diversity and a Preliminary Comparison with Bird and Mammal Diversity," p 69-75 in Biodiversity II. Reaka-Kudla, Wilson, Wilson, eds., Joseph Henry Press, Washington D. C. 1997); and insects (Didham, R.K. and Stork, N.E., "Rise of the Supertramp Beetles," Natural History, Vol. 107, No. 6. July/August 1998).