Along the Great Barrier Reef, a creature long cast as villain may be something more ambiguous — a disruptor whose presence, in measured doses, quietly sustains the very ecosystem it is blamed for destroying. New research from the University of Sydney finds that crown-of-thorns starfish, when held at low densities by healthy predator populations, selectively prune dominant corals and open space for slower-growing species to take hold. The finding does not absolve the starfish of the devastation wrought during population explosions, but it reframes the question: not whether the starfish belongs,