Unique in South-East Asia because its north-south axis extends some 1800km from mainland to peninsular South-East Asia, Thailand provides potential habitats for an astounding variety of flora and fauna.
As in the rest of tropical Asia, most indigenous vegetation in Thailand is associated with two basic types of tropical forest : monsoon forest (with a distinctive dry season of three months or more) and rainforest (where rain falls more than nine months per year). Natural forest area - defined as having crowns of trees covering over 20% of the land - covers about 25% of Thailand's land mass. According to the United Nation's World Development Report, Thailand ranks 44th in natural forest cover worldwide, ahead of Cambodia but behind Laos regionally, or tied with Mexico on a global scale.
Monsoon forests amount to about a quarter of all remaining natural forest cover in the country ; they are marked by deciduous tree varieties that shed their leaves during the dry season to conserve water. About half of all forest cover consists of rainforests, which are typically evergreen. Northern, Eastern North-Eastern and Central
Thailand contain monsoon forests mainly, while Southern Thailand is predominantly a rainforest zone. There is much overlap of the two - some forest zones support a mix of monsoon forest and rainforest vegetation. The remaining quarter of the country's forest cover consists of freshwater swamp forests in the delta regions, forested crags amid the karst topography of both the North and South and pine forests at higher altitudes in the North.
The country's most famous flora includes an incredible array of fruit trees, bamboo (more species than any country outside China), tropical hardwoods and over 27,000 flowering species, including Thailand's national floral symbol, the orchid.
As with plant life, variation in the animal kingdom closely affiliates with geographic and climatic differnces. Hence, the indigenous fauna of Thailand's northern half is mostly of Indochinese origin while that of the South is generally Sundaic (ie typical of Malaysia, Sumatra, Borneo and Java). The invisible dividing line between the two zoogeographical zones is across the Isthmus of Kra, about halfway down the Southern peninsula. The large overlap area between zoogeographical and vegetative zones - from around Prachuap Khiri Khan on the Southern peninsula to Uthai Thani in the lower north - means that much of Thailand is a potential habitat for plants and animals from both zones.
Thailand is particularly rich in birdlife, with over 1000 recorded resident and migrating species - approximately 10% of all world bird species. Coastal and inland waterways of the Southern peninsula are especially important habitats for South-East Asian waterflow. Loss of habitat due to human intervention remains the greatest theat to bird survival in Thailand ; shrimp farms along the coast are robbing waterfowl of their rich intertidal diets, while in the South the over-harvesting of swiftlet nests for bird's nest soup may threaten the continued survival of the nest's creators.
Indigenous mammals, mostly found in dwindling numbers within Thailand's national parks or wildlife sanctuaries, include tigers, leopards, elephants, Asiatic black bears, Malayan sun bears, gaur (Indian bison), banteng (wild cattle), serow (an Asiatic goat-antelope), sambar deer, barking deer, mouse deer, pangolin, gibbons, manaques, tapir, dolphins and dugongs (sea cows). Forty of Thailand's 300 mammal species, including clouded leopard, Malayan tapir, tiger, Irrawaddy dolphin, goral, jungle cat, dusky langur and pileated gibbon, are on the International Union for Conservation of Nature (IUCN) list of endangered species.
Herpetfauna in Thailand numbers around 313 reptiles and 107 amphibians, and includes four sea-turtle species along with numerous snake varieties, of which six are venomous : the common cobra (six subspecies), king cobra (hamadryad), banded krait (three species), Malayan viper, green viper and Russell's pit viper. Although the relatively rare king cobra can reach up to six metres in length, the nation's largest snake is the reticulated python, which can reach a whopping 15m. The country's many lizard species include two commonly seen in homes and older hotels or guesthouses, the 'tuk-kae' ( a large gecko) and the 'jing-jok' (a smaller house lizard), as well as larger species like the black jungle monitor.
Insect species number some 6000, while the country's rich marine environment counts tens of thousands of other species.