Coral reefs are a crucial oceanic ecosystem, providing a home to approximately 25% of all marine species occupying less than 0.1% of the ocean floor. These sensitive ecosystems are under extreme threat due to anthropogenic climate change. Shallow tropical coral reefs have declined by 50% since 1950 and could decline by 70-90% by 2050 if global warming is not limited to 1.5°C (2.7°F) above pre-industrial values. Global warming causes ocean temperatures to warm, leading to ocean acidification, which puts stress on corals leads to coral reef bleaching. Coral reef bleaching occurs when the coral polyps become stressed because the stress causes them to expel the algae inside them (called zooxanthellae), providing most of their energy through photosynthesis, and giving the corals their color. This algae is crucial for the coral’s survival and proper function; however, if environmental conditions improve, corals may begin taking up algae again and recover.

Many efforts are underway to restore and protect these important ecosystems. One restoration strategy includes growing corals in nurseries by creating “Coral Trees” in the ocean and then reintroducing them to carefully selected reef sites in the wild when they are healthy enough to survive on their own (after two years of monitoring). Since 2017, a group called Coral Gardeners has planted 221,212 corals, with an 80% survival rate. The progress of these sites is then monitored by photomosaics, meaning an image is generated by thousands of smaller images combined into one. These mosaics allow changes in coral coverage to be monitored over time without having to continually revisit the site and potentially cause disturbances. 

Although there have been successful restoration efforts, the best thing for the future of these corals would be to reduce ocean acidification. The ocean acts as a carbon sink and absorbs 31% of carbon dioxide emissions, and consequently, most of the excess heat from global warming. Reducing carbon emissions is the best way to ensure that coral restoration is successful and stress on coral reefs is reduced.