Many interactions among plants and animals in the rocky intertidal zone take place over much longer periods than days or weeks. These changes are so slow that it's hard to see that things are changing. Also, so much time may elapse between observations that it's hard to make a comparison because you might not remember what you saw before.

Change can take place over seasons, years, or even longer periods. Scientists who wish to observe this kind of change may not be able to put a time-lapse camera out in the field for such a long time.

To document change over longer time intervals, researchers use a tool called a photoquadrat. A photoquadrat is a rectangular marker of a known size that is placed in a fixed location over time. Photographs of the photoquadrat area are taken intermittently and then compared.

A photo preserves details that a person might not remember in detail. Comparisons of photos reveal longterm change. The rectangular marker ensures that the same area is being compared from time-to-time and that the actual dimensions and orientation of the area are known.

Longterm monitoring is important in order to get an idea of the full range of change that ecosystems might experience. A human lifetime may not be long enough to experience the full range of change that the natural word has in store for us. If we can anticipate the range of change, we can be prepared.


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Because it takes so long and such persistence is required, it is remarkable that scientists such as Pete Raimondi make long term observations. Take a look at the sequence of tidepool images that Pete Raimondi took of a photoquadrat area in a rocky intertidal area near Santa Barbara, California.

Get a glimpse of ecosystem changes over 12 years. What might have caused these changes? If we didn't have these long term observations for comparison, we wouldn't be able to decide whether this ecosystem is in good health today or not.