How do ecosystems change?

Sometimes places change.  This may happen slowly.  A pond may fill in with dirt and dead leaves.  After many years, the pond is gone and the area becomes a meadow. 

Change can also happen quickly.  Lightning strikes and starts a forest fire.  In just a few days, trees and wildlife are gone.

Plant and animal populations change too.  Sometimes many members of a species die or are killed.  The species can become endangered.  This means very few are left.  If all the members of a species die, the species becomes extinct.

Diversity is the number of species in an area.  A rain forest can have thousands of species.  Diversity makes the ecosystem strong because small changes are less likely to affect the whole ecosystem.  If a disease attacks one kind of tree in the rainforest, that species would be the only one to die.  The disease might not harm other trees that are different.  The animals that depend on the trees can move to trees that are still living. 

Man can change an ecosystem.  Forests can be cut down, marshes filled in for houses, pollution dumped into rivers that kill the organisms living their, etc.  If man affects the environment in ways that cause damage ecosystems can be destroyed or greatly weakened.