The mountain ridges which defined the physical look of the Mu Koh Chang National Park are covered by dense tropical green forest. They are mostly made up of trees endemic to the place which include species of Dipterocarpus alatus, D. turbinatus, Anisoptera costata, Hopea odorata, Irvingia malayana, Podocarpus neriifolius, Diospyros spp., Castanopsis spp., Croton spp., Oncosperma horrida, Caryota mitis., Daemonorops spp., Korthalsia grandis, Bauhinia bracteata, Freycinetia sumatrana, Platycerium coronarium, Amomum spp., Boesenbergia pandurata and Kaempferia pulchra. Around the villages of Salak Phet, Salak Khok, Khlong Son and Khlong Phrao Bay are areas of Beach Forest. The dominant tree species here are Terminalia catappa, Calophyllum inophyllum, Melaleuca leucadendra, Eugenia grandis, E. spicata, and Pandanus odoratissimus.
In the more sheltered spots, especially where freshwater enters the sea to produce brackish water, fairly large areas of mangrove forest exist. These mangrove forests consists of a combination of tree species including Rhizophora mucronata, R. apiculata, Ceriops decandra, C. tagal, Bruguiera gymnorrhiza, B. parviflora, Avicennia alba, Xylocarpus granatum, X. moluccensis, Hibiscus tiliaceus and Cerbera odollum. Mostly along the coastlines especially in the island of Koh Chang are coconuts which offer a unique and distinct tropical or Asian setting to many resorts and hotels.
Koh Chang Bamboo forest
Within Mu Koh Chang National Park, there are 29 wildlife species presently recorded.Animals seen include wild pig, barking deer, slow loris, stump-tailed macaque, silvered langur, eastern mole, small Indian civet, Javan mongoose plus several species of bats, squirrels, rats and mice.
The bird list for the park currently numbers 74 species of which 61 are resident. More common sightings include pacific reef-egret, yellow-vented bulbul, Nightjar, Pacific swallow, White-breasted waterhen, Green imperial pigeon and Oriental pied hornbill. Migratory bird visitors to the islands include little heron, greater sand-plover, white-winged tern, brown noddy, black-naped oriole, pale-legged leaf warbler, arctic warbler and barn swallow.
Two common breeding visitors to the islands are the blue-winged pitta and the hooded pitta, both of which have very distinctive whistling calls often heard early in the morning and in the evening. Commonly seen passage migrants include blue-throated flycatcher, blue-and-white flycatcher and the eastern-crowned warbler. Also discovered are 42 species of reptiles and amphibians. More commonly seen of which are Malayan mud turtle, Indian monitor lizard, water monitor lizard, white-face blue garden lizard, Tokay gecko, East Indian brown sided grass skink, python, racer, rat snake, king cobra, common Asiatic toad, green rice field frog, common tree frog, bulter’s chorus frog and rugosed frog. An endemic species found here and nowhere else is the aptly named Koh Chang frog (Rana kohchangae).
It was also observed that though the national park has a suitable environment for gibbons, park management personnel and residents did not experience any kind of encounters or sightings of gibbons. Nevertheless, there are still many unnamed species thriving in Mu Koh Chang which are waiting to be discovered but continuing to contribute and maintain the balance of nature.
Considering the biodiversity of Mu Koh Chang National Park, rainforests are regarded in the virgin state, mostly preserved and protected.