Orangutans love a good Durian fruit. If the orangutans aren't there to eat them, then the population of Durian fruits will skyrocket.
Leopards love eating apes. Especially orangutans, something about that hair makes them go loco. Anyways, if the tsunami kills the orangutans then the leopards might have to look for another food source and that food source might begin to dwindle because it's all that the leopard is eating. You could look at it another way too. If the orangutan population goes down and the leopards are eating the ones that are left, the population will decrease even more and ecause the orangutans take forever to repopulate it wouold take awhile to even have the population to start going up.
Orangutans have numorous parasites, some among the many are: nemotodes, hookworms, and ticks. If there aren't alot of orangutans then the parasite population might go down, although that might not be a completely bad thing. Also, if the parasite population goes down then the remaining orangutans might be the healthiest orangutans around and orangutan population might start to go back up.
Wasps pollinate figs, and lay their eggs in the fruit. Orangutans eat the fruit and then distribute the fertile seeds in their feces, insuring reproduction of the figs throughout the rainforest.
Orangutans eat bark but the tree doesn't care.