Quảng Bình Province is endowned with biodiversity, especially typical of Annamites eco-region.
According to the results of initial surveys, the primary tropical forest in Phong Nha-Kẻ Bàng is home to 140 families, 427 genera, and 751 species of vascular plants, of which 36 species are considered endangered and listed in the Vietnam’s Red Data Book. The most common tree species in this park are Hopea sp., Sumbaviopsis albicans, Garcinia fagraeoides,Burretiodendron hsienmu, Chukrasia tabularis, Photinia arboreum and Diospyros salletii. Seedlings can only grow in holes and cracks in the limestone where soil has accumulated, so in general regeneration after disturbance is slow. The forest type in this national park is dominated by evergreen tree species with scattered deciduous trees such as Dipterocarpus kerri,Anogeissus acuminata, Pometia pinnata and Lagerstroemia calyculata. In Phong Nha-Kẻ Bàng, the dominant plant families are the Lauraceae, Fabaceae, Theaceae and Rosaceae, with some scattered gymnosperms such as Podocarpus imbricatus, Podocarpus neriifolius, and Nageia fleuryi.
In the national park there is a 5000-ha forest of Calocedrus macrolepis on limestone (Calocedrus rupestris) mounts with about 2,500 trees, 600 per hectare. This is the largest forest of this tree in Vietnam. Most of these trees here are 500–600 years old. These trees are listed in group 2A (rare, precious and limited exploitation) of the official letter 3399/VPCP-NN dated 21 June 2002, an amendment to Decree 48 by the Government of Vietnam. Biologists discovered three rare orchid species. Orchids found here include:Paphiopedilum malipoense, Paphiopedilum dianthum, Paphiopedilum concolor. In 1996, IUCN classified these orchid species in danger of extinction in the near future.
Endemic species in Phong Nha-Kẻ Bàng National Park include: Burretiodendron hsienmu, Cryptocarya lenticellata, Deutzianthus tonkinensis, Eberhardtia tonkinensis, Heritiera macrophylla, Hopea sp., Illicium parviflorum, Litsea baviensis, Madhuca pasquieri,Michelia foveolata, Peltophorum tonkinensis, Semecarpus annamensis, Sindora tonkinensis.
The forests of Quảng Bình, particularly in Phong Nha-Kẻ Bàng, are home to at least 98 families, 256 genera and 381 species of vertebrates. 66 animal species are listed in Vietnam’s Red Data Book and 23 other species in the World Red Book of Endangered Species. In 2005, a new species of gecko (Lygosoma boehmeiwas) was discovered here by a group of Vietnamese biologists together with biologists working for the park, Cologne Zoo in Germany and the Saint Petersburg Wild Zoology Institute in Russia.
The gaur and one species of eel have been discovered in this park. 10 new species previously unknown in Vietnam were discovered by scientists in the park. Phong Nha-Kẻ Bàng is home as well to a significant population of primates in Vietnam, with ten species and sub-species. These include the globally vulnerable pig-tailed macaque, Assamese macaque, stump-tailed macaque and white-cheeked crested gibbon (Nomascus leucogenys and Nomascus leucogenys siki). The park is home to one of the largest populations of Francois’ Langur in Vietnam, including two different forms of the species. The area is known for its population of Hatinh and black langurs. 10 species of bats listed in the IUCN List of Threatened Species are recorded in this park. Of the 59 recorded reptile and amphibian species, 18 are listed in Vietnam’s Red Data Book and 6 are listed in the IUCN Red List of Threatened Animals. The 72 fish species include 4 species endemic to the area, including Chela quangbinhensis.
The park is home to over 200 bird species, including such rare birds as the chestnut-necklaced partridge, red-collared woodpecker,brown hornbill, sooty babbler and the short-tailed scimitar babbler. An initiative survey conducted by Russian and Vietnamese scientists from Vietnam-Russia Tropical Centre (funded by WWF) recorded 259 butterfly species of 11 families. Almost all major butterfly taxa in Vietnam can be found in Phong Nha-Kẻ Bàng.