Seagrass meadows

There are more than 500 species of sharks in the world’s oceans, from the 7-inch dwarf lantern shark to whale sharks that can grow to over 35 feet long. They’re found from polar waters to the equator, at the water’s surface and miles deep, in the open ocean, along coasts and even in some coastal rivers. With such diversity, it’s no surprise that sharks serve many ecological functions. For example, the largest individuals of some big predatory species, such as tiger and white sharks, can have an oversized role in maintaining balances among species. They do this by feeding on prey and sometimes by just being present and scary enough that prey species change their habits and locations. In a newly published study, colleagues and I surveyed decades of research on sharks’ ecological roles and considered their future in oceans dominated by people. We found that because sharks play such diverse and sometimes important functions in maintaining healthy ocean...