All ecosystems change over time. Sometimes the changes are
rapid. They may take only hours, days, or weeks to occur.
Sometimes the changes are slow and gradual. They may take
thousands or millions of years to occur.
Can you think of some examples of rapid changes?
Clearing the land of plants to build new homes or shopping
centers is a rapid change. Deforestation in tropical rain
forests is another type of rapid change. During deforestation,
people cut down trees for lumber and use the forest land for
building or farming. Volcanic eruptions, floods, and
tornadoes also cause rapid changes in ecosystems.
In contrast, gradual changes take a long time to occur.
The climate of an ecosystem may change slowly over millions
of years. The climate in an area may become warmer or
colder. It may become wetter or drier. Lakes or rivers may
gradually form in areas that were once dry.
When ecosystems change, the species that live there are
influenced. Some organisms will have traits that allow them
to live in the new environment. These organisms will
survive and reproduce. They will pass their successful traits
on to some of their offspring. After many generations, all the
members of the species will have these successful traits.
This process is called adaptation. Adaptation happens over a
long period of time.
When an ecosystem changes gradually, it allows
time for adaptation to occur. That is, species can
slowly adjust to the changes over time. Rapid
changes do not give species enough time to adapt.
Therefore, species may not survive when a rapid
change occurs. Species are less likely to survive
rapid changes than they are to survive gradual ones.
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