Well, turtles are an important member of several marine communities, from coral reefs to seagrass beds, they need clean nesting beaches, and impact-free open oceans. Green sea turtles feed on sea grasses. If they were to disappear, who would eat the seagrass?
Also, the cropping of seagrasses is important in maintaining the seagrass health. Hawksbills eat sponges on coral reefs. If they were no longer around, reefs might get overrun with sponge and we’d have no great corals and fishes around.
Every animal on this planet has an important role to play. The decline of turtles has been accelerated by mankind, and it is our responsibility to do whatever we can to restore them to their previous numbers.