Which effect does overgrazing by sea urchins have on kelp forests?

Overgrazing by sea urchins has a significant negative impact on kelp forests. When sea urchin populations increase, often due to the reduction of their natural predators, they can feed excessively on kelp, which is essential for maintaining these underwater ecosystems. This overgrazing can lead to a decline in kelp biomass, resulting in the degradation of the marine habitat that provides shelter and food for a variety of marine organisms. As kelp forests diminish, the associated biodiversity is also threatened, as many species that rely on this habitat may struggle to survive without the kelp's structural support and nutrient availability. The health of kelp forests is crucial for maintaining the ecological balance in marine environments, and their decline can have cascading effects on marine life and local fisheries. Therefore, the answer accurately reflects the detrimental effects that excessive grazing by sea urchins has on kelp forests.