15:15-17:00 Session IVb Coral Reef and Human Existence
Ecosystem function and human activities in coral reefs
Makoto Tsuchiya
Faculty of Science, University of the Ryukyus, Japan
Several functions or roles in coral reefs such as 1) Fishery ground, 2) Providing for the coexistence of diverse species, 3) Environmental purification system, 4) Landscapes, 5) Disaster prevention, 6) Carbon dioxide cycle in global environment, and 7) Sites for education and research, have been emphasized in the discussion of their management or conservation. Today I am talking about them again with reference to the human activities. One of the most important roles of coral reefs is the role as food resources for people who rely and collect a lot of fishes, edible shell fishes and seaweed for their livelihood. In order to maintain their activities, biomass of marine organisms for fisheries needs to remain constant. In this regard, we have several problems, 1) overexploitation of resources, which may destabilize the coral reef structure, affect their reproduction, and result in their disappearance or diminishment. For example, there are conspicuous fluctuation in catches of octopus, sea urchins and giant clams during last 35 yrs., and 2) aquaculture, which means a sudden increase in the population size of cultured species. Eutrophication is widespread, caused by the accumulation of feces produced by cultured animals and food scraps. Design of the aquaculture is important, because aquaculture ignoring coral reef functions will cause unprecedented changes in the structure of coral reef ecosystems.
Effect of several serious disturbance events, i.e. Acanthaster outbreak, inflow of huge amount of fine particles (reddish clay), and intensive coral bleaching, on the ecosystem function should be discussed with reference to human activities. Damage caused by the fine particle inflow or coral bleaching has been serious and recovery from these events is not observed yet. Particularly the topic on the coral bleaching must be discussed with the global warming, because the speculation that it derives from rapid temperature increase caused by human activities is not off the point.
Beautiful landscapes give us unfathomable peace of mind. Related economic function including increase of tourists, their influence on reef environment, and construction of resort hotels should be taken into consideration.
We can easily understand that these functions are maintained by healthy biological activities and all functions are deeply interwound. Unbalanced relationships among coral reef organisms is a serious warning by coral reefs for us. It is our responsibility to recover the coral reefs from the disturbance caused by human activities.
