Health asessment of large and old trees in Ragunan Zoo, Jakarta

Taman Margasatwa Ragunan (TMR) or Ragunan Zoo in Jakarta is the largest zoo in Indonesia. The zoo has around 52,700 trees that serve as part of the landscape and shades for animals and visitors. However, the presence of the trees in zoo also carries some risks, such as broken branches or even falling trees, that may threaten the safety of the animals, visitors, and infrastructures. Because most of the trees are large and old with high historical and ecological values, their health needs to be evaluated regularly. A study was conducted to evaluate it with around fifty selected trees, particularly the ones that were old and located closest to the targets (i.e. animals, visitors, infrastructures). The evaluation used visual observation as well as integrated with sonic tomography technology. The result showed that five trees (10%) were healthy and safe, 31 trees (62%) were healthy and fairly safe, 12 trees (24%) were less healthy and fairly dangerous, and the rest trees were unhealthy or dangerous and very dangerous. The most common defects found in them are poor tree architecture (62%), root problems (58%), and codominant trunks or branches (40%). Therefore, it is vital to take care of the tree health in Ragunan Zoo. Trees with the risk of endangering its surroundings need to be cut off immediately. Biomechanics on sloping trees with codominant trunks need to be strengthened with the help of dynamic bracing sling system and support.