According to Shark Savers, sharks are important because of the role they play in the oceans. Sharks have a positive effect on food webs, ocean populations and habitat health.
Sharks are efficient eaters, typically consuming fish that are older, slower or sicker. This improves the health of the overall population of the fish that sharks feed upon. Additionally, sharks serve as a kind of population control because they make sure the populations they prey upon do not grow large enough to threaten the ecosystem. For this reason, sharks are considered a keystone species within their food webs, and the reduction or removal of sharks can lead to the loss of many other species of sea life within that food web.
In addition to feeding on the older, slower and sicker fish, sharks also consume dead carcasses in the ocean. This prevents the spread of disease that would negatively affect other ocean life.
Finally, sharks help to keep certain ocean habitats healthy through intimidation. Without sharks to scare them off, certain ocean life would overgraze certain areas, such as turtles destroying a habitat in the absence of the sharks that would prey upon them. The presence of sharks scares those turtles away and ultimately keeps them from destroying these habitats and negatively affecting the ecosystem.