Coral reefs are no exception and they change due to natural and human factors.
Take a look at the comparative photos below taken of the same reef area except a year apart and you will see just how quickly the reef community can change. Documenting this change and explaining why a coral reef changed requires that reefs be monitored for the long-term and that a baseline or reference condition be established. In 1997, volunteers helped establish a baseline inside and outside of the Sanctuary's zones by participating in an international coral reef monitoring effort called ReefCheck. Establishing a baseline is essential because it gives managers a point of reference from which to gauge the change in our coral reef ecosystem. As long as monitoring methods are consistent from year to year than the baseline remains valid.