This is a big topic and I may split it into a couple of blogs. There are so many facets to sustainability.
Sustainability is acting to avoid  the depletion of natural resources in order to maintain an ecological balance. Oysters are naturally a great source to maintain the marine biodiversity because they are filter feeders. They pump gallons of water through their bodies and filter sediment along with chemical contaminants in the water.
Many pearl farms are sustainable, but not all. Sustainability is based on 5 principles:
Protect and repair the biosphere.
Sustainable use of natural resources.
Production transparency and disclosure.
Develop and operate farms in a socially and culturally responsible manner.
Manage a commitment to local law compliance .
Sustainable pearl farms have close links with the surrounding villages and employ numerous locals at different levels of pearling activities. They need to protect the environment for the health of the pearl oyster growth.