The diversity of starfish species means that some species populations are doing better than others. However, all are vulnerable to ocean pollution. Starfish are often regarded as “keystone species” which scientists can use to determine the overall health of a given environment.
The star-like shape of starfish has led them to be collected, dried, and sold as souvenirs in many coastal towns. This has harmed starfish populations of some species that were once plentiful, and in some areas the local species have become endangered due to overcollection.
In some areas, starfish can cause damage as invasive species, or when their population grows too quickly (which is known as an “irruption”). The Great Barrier Reef in Australia has been greatly harmed by the irruption of the crown of thorns starfish, which consumes coral and, when its population grows out of control, can severely damage coral reefs.