Ten years on, the Concrete Substrates for Accelerated Coral Restoration project in the southern Philippines has grown considerably. Precast concrete structures act as a substrate onto which juvenile corals are planted. The calcium bicarbonate in concrete is biologically friendly to coral growth, and the design of the structure allows optimal sunlight penetration. Corals grow as their calcareous (calcium carbonate) skeletons are deposited and bound to the coral colony. 

Living hard coral polyps secrete calcium carbonate skeletons from their basal plates to form protective cups in which they then sit. As coral polyps ‘bud’ (a form of asexual reproduction), new coral polyps develop, forming additional basal plates from which further calcareous skeletons are secreted. These platforms allow new corals to settle and grow over their predecessors. These processes lead to gradual growth of the coral reef framework. Coral growth rates are highly variable between species. In optimum conditions, some coral species, such as the branching Acropora cervicornis, can display fast growth rates of between 10-20 cm per year while other species, such as Porites, grow much slower at around 1 cm per year. The coral reef ecosystem accounts for around 25% of all marine life including more than 2 million species of fish, crustaceans, molluscs, sponges, sea cucumbers and seaweeds.

The reefs support subsistence and commercial fishing and contribute towards poverty alleviation by providing essential food, income and employment for communities in developing countries. As well as supporting marine biodiversity, reef ecosystems provide a number of ecological services and goods to human populations on a local, regional, and national level as they play an important role in coastline and habitat protection, nitrogen fixing, sand supply, climate records, medicine, recreation and tourism.