The Common Sense Environmental Fund


Species Diversity and Stability




A growing number of scientists and activists are convinced that the way to protect our environment is through the preservation of entire ecosystems and biospheres: areas in which the complex interactions between life forms in their natural habitat are restored and protected.


Species Diversity and Stability


Some ecologists assert that ecosystem stability is influenced by species diversity. Roughly speaking, species diversity is a measure of the number of species living in a community. The higher the diversity, the greater the stability. Observations that extremely complex ecosystems, such as tropical rain forests, remain unchanged almost indefinitely if undisturbed support this idea. Simpler ecosystems, such as tundra, are less stable, that is, they experience sudden, drastic shifts in
population size. Other simplified ecosystems, such as fields of wheat and corn are also extremely vulnerable to change, and they deteriorate rapidly if biotic factors shift very much.


To understand why ecologists think there may be a connection between stability and diversity, consider the food webs in simple and complex ecosystems.  The number of species in a food web in a mature ecosystem is large.  So is the number of interactions among these organisms.  In a complex ecosystem, the elimination of one species would probably have little effect on the ecosystem.  In sharp contrast, the number of species in the food web of a simple ecosystem is small.  The elimination of one species could have repercussions on all other species.


In the frozen northern regions of Canada and Alaska, species diversity is low.  Heading south, diversity increases until one reaches the tropics of Central America, where diversity is highest. The relationship between latitude is also found in plants and virtually all other kingdoms.  Latitude, therefore, is an important factor affecting species diversity. The connection between latitude and species diversity is climate.
Quite clearly, the milder the climate, the more species live there.


Simplifying ecosystems by reducing species diversity makes systems less stable and more vulnerable to outside influences.  Some researchers maintain that populations and ecosystems rarely, if ever, return to equilibrium once disturbed.  Returning to equilibrium, if possible, would depend in large part on the nature and severity of the disturbance.  Evidence suggests, that ecosystems can recover from small perturbations, such as changes in rainfall or short-term drought. 

More severe alterations, such as deforestation of the tropics, may render a system unable to recover.


The Common Sense Environmental Fund researches, analyzes, assists and invests in organizations conducting research, conservation and restoration work that is protecting our planet's biodiversity. To save our planet for future generations we need your help. The Common Sense Environmental Fund is a 501(c)(3) non-profit organization. Your contribution is tax-deductible to the fullest extent of the law. To make a donation please click here.



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