. >> this is dinowad, photographed in 1988.he darker areas in the water show extending for around 100 meters. almost 20 years later, the coral is nearly all gone. >> waves, water, it erodes the land. there must be a protection, and the coral is the number one protection against that. >> with coral off shore, the incoming waves are broken up and diminished as they reach land. without the protection, the waves are stronger when they hit the shore, and climb higher up the beach. these waves are eroding the sand, and carrying it back out to sea. just how far back the beach has receded over the past two decades is evident from these aerial photographs. >> very good. >> dr. fortes also points out that development along the beach front has accelerated the problem. >> this one, especially. you know, if the structure is like that, and the waves strikes, the force is stronger once it goes down. if it is slanted like this, it is lesser. that's why the natural, it's flat. so that the waves driven by the wind will just go and then down. but