what causes the accumulation of mountain coral reefs

Coral reefs are ecosystems that are very important for marine life, because coral reefs are home to millions of marine ecosystems that are also very important for the survival of human life and other living things. in the past few decades, coral reefs have begun to enter difficult times because of the damage that has been so fatal that we can even find a pile of mountain coral reefs on the coast. Is it human activity or changes in the sea climate that makes thousands of coral reefs die suddenly and accumulate on the coast.

I found this picture on the coast of the island of Breuh which is part of the Pulo Aceh district, located at the end of the country of Aceh which borders on international shipping lanes ... in the yard of people's homes, dead coral reefs are used as material for soil soils on the page it is not flooded during the rainy season. really a very painful sight to see our sea conditions like that