What characteristic makes otters keystone species?

Otters are considered keystone species because they have a significant impact on their environment, which helps maintain the balance of their ecosystem. By preying on sea urchins, for example, otters help control the population of these herbivores. If otters are removed from the ecosystem, sea urchin populations can explode, leading to overgrazing of kelp forests. This shift not only affects the kelp but also the myriad of species that depend on kelp habitats for shelter and food. Therefore, the presence of otters promotes biodiversity and the stability of their environment, illustrating the crucial role they play as a keystone species.