on bali's menjangan reef, dustan worked with coral reef scientist carol milner. milner: the biodiversity in this area of southeast asia, within the coral triangle, is the highest in the world. we started this reef in 2011 and again in 2016 to make an objective, unbiased comparison of the reef at those times. we've used transects, so we lay a 50-meter tape measure, and every 50 centimeters, we record the substrate directly below-- whether it's live coral, whether it's dead coral; whether it's rock or sand, whether it's algae--to as much detail as we can. so for every tape measure we lay, we get a hundred points, and we can work out a percentage of coverage. we also go along one meter either side of that tape measure, so it's a 2-meter width that we look at the reef and record all the damage, all the disease, the crown of thorns, the recruits, the small babies, and any breakage of the live coral. woman: are we ready? narrator: the biosphere foundation brings student groups from around the asian pacific region to learn about various threats to coral reefs, from coas