Ecological Structures
Life and the Earth's Environment
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Materials for Life
Capturing Energy for Life
Evolution & the Environment
Disruptive Forces on Ecosystems
Measurement of Impact on Ecosystems
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Biodiversity is the ordered complex in which all species are harmoniously co-adapted. This is a good definition because we think of biodiversity as a resource that helps us to assess the impacts to that resource and gives us another measure of environmental impact. Just because an ecosystem exists does not mean it is healthy as evaluated by biodiversity. The following are the various environmental resources that are evaluated to determine if problems exist:

  • air quality = chemical concentrations, odor, visual
  • water quality = chemical concentrations, temperature, pH, flows, microbiology, taste, odor
  • soil quality = chemical concentrations, odor
  • biodiversity = indicator species

Just as we tried to model resource consumption, we need to measure biodiversity. The key to doing this is to recognize that not all species have the same role within the environment. Some species once removed have an obvious effect on the environment and are known as key or indicator species. An analogy is the removal of your tonsils versus your heart. You can think of your heart as a key organ, or an indicator organ. Can you think of any key species? One example is rabbits in a grassland. If the rabbits are eliminated, there will be significant changes to the grassland habitat.

Biodiversity is therefore measured, or assessed in terms of key indicator species. There are different types of losses of species as follows:

  1. Depletion of a once common species - the species is gone, but the habitat still exists and the species could be replaced though there is still some loss of the gene pool. Example: buffalo/cows
  2. Local or global species extinction - the species is gone forever and all current and potential adaptations are lost. This happens all the time. The concern is that historically losses occurred at a slow enough rate for ecosystems to adapt, however, anthropogenic induced losses are happening at a much faster rate. Example: the deforestation rate of extinction is now 10,000 times that before human civilization.
  3. Ecosystem disruption - this is the most serious of the three because not just 1 species is lost, but an entire ecosystem. Example: ecosystem lost as a result of 3 Gorges Dam in China.

The important point is that we may use the indicator/key species to identify losses that may be occurring and prevent them from occurring.

IV.1 Biodiversity as a Result of Evolution

IV.2 Importance of Biodiversity



  ©Copyright 2003 Carnegie Mellon University
This material is based upon work supported by the National Science Foundation under Grant Number 9653194. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.