Think about the plants and animals you see in your area. Do you see many different species or few? Do you see these organisms frequently, or not very often? All the organisms that you see are part of an ecosystem. Ecosystems are communities of living organisms that interact with one another and with the nonliving parts of their environment.

Each species in an ecosystem has a role -- some spread the seeds of plants, some break down dead matter, and some are food for others. When organisms are fulfilling their roles adequately, an ecosystem can flourish. For example, many woodland ecosystems depend on earthworms for breaking down detritus, or dead organisms, into nutrients for the soil. While changes and fluctuations are normal in ecosystems, even an unexpected, small change can have a lasting impact on an ecosystem and the organisms that live there.

What are the ways that ecosystems change? What happens to organisms when their environment changes? Can these changes be reversed? Let’s visit some ecosystems across the globe to find the answers to these questions!