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VOL. 12.3

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By Thom Henley

What Makes A Tropical Forest A ‘Rainforest’ And A Jungle Such A ‘God-Awful Jungle

Tourists returning from a hike or elephant trek through the choking vines and vegetation of logged-over lands are often bitterly disappointed their advertised ‘jungle trek’ included none of the magnificent trees, showy epiphytes, orchids and wildlife diversity they expected. More by accident, however, than design their tour company is technically correct in calling these secondary forests a ‘jungle’.

Scientists love classifications, sorting out this infinitely complex planet we live upon into neat little categories. As anyone who did not sleep their way through high school biology class can tell you, we have enough orders, phyla, families, species and subspecies to confuse the best of students. Few people other than botanists and foresters, however, are aware of the complex classifications for forest types.

South Thailand’s forests fit into five broad categories based on elevations: Montane Forest, Lower Montane Forest, Hill Forest, Lowland Forest and Mangrove Forest. At the highest elevations in the south (1500m and above) is the forest type fewest people ever see, the Montane or Cloud Forest. Here dwarfish trees struggling against high winds and cold temperatures, are almost perpetually bathed in wet fog and cloud. Somewhat lower (1000-1500m) the Lower Montane Forest is composed of large oak trees, ferns and begonias, creating quite a different type of woodland. Hill Forests (300-1000m.) are lower still and make up most of the protected forest areas in Thailand. Here a greater variety of tree species can be found with an abundance of palms and rare jungle orchids.

The greatest diversity of all is found in the Lowland Forest, which grows on the plain to a height not exceeding 300m. Finally, at sea level, along protected shallow shorelines, one finds the Mangrove Forest where a surprising number of tree species have adapted to the periodic inundation by the tides. Mangrove forests, which wed the land to the sea, are most pronounced along the Andaman coast, with the most extensive d displays of this type found near Ranong and Phang Nga Bay.

Sadly, the Lowland Tropical Forest, which blanketed the southern peninsula just 50 years ago, is virtually gone, replaced by millions of hectares of oil palm and rubber plantations. From the Isthmus of Kra to the southern tip of the peninsula at Singapore, one would be hard pressed to find even a few remnant patches remaining.

Khao Nor Chuchi, the protected Gurney’s pita reserve in the south of Krabi Province, is the one notable exception. It is a pitifully small reserve compared to the vastness of this peninsula where it was once the dominant forest type, but it does offer the visitor a botanical glimpse into the glory that once was. Huge emergent trees, with flared root bases big enough to hide an elephant behind, a wealth of woody liana vines, showy epiphytes and an astonishing variety of plant life thrill the increasing number of visitors who flock to this reserve.

While the Lowland Tropical Forest is largely a thing of the past there are still significant forest reserves in the south of Thailand at slightly higher elevations. These hill forests fall into two categories: Tropical Evergreen Forests and Tropical Rainforests. The first of these has a distinct dry season while the latter has rain falling in substantial amounts in every month of the year.

This may seem like hair-splitting to a lay person but scientists note distinct botanical differences between these closely associated forest types. While both Tropical Evergreen Forests and Tropical Rainforests display stratified layers, an abundance of lianas and the huge flared root bases of many emergent trees, there is a preponderance of bamboo species in the drier forest type and a greater species diversity in the true rainforest. It’s a general botanical rule that the greater the rainfall the greater the biodiversity and nothing on earth outside the coral reefs can match Tropical Rainforests for mega-diversity.

It is possible to find localised pockets of rainforest at the base of a waterfall, or deep in a shaded canyon of an otherwise Tropical Evergreen Forest. Khao Sok National Park in Suratthani Province for instance, has only 6% of its forest classified as true Tropical Rainforest, but that doesn’t stop tour operators from advertising all of Khao Sok as rainforest. Far better examples of rainforest can be found closer to the Thai-Malay border, but these are more than a day’s drive from the South’s premier tourist centre - Phuket, and there are other complications in visits to these sites.
Hala Bala Wildlife Sanctuary in Yala Province has been the scene of border skirmishes between Islamic Separatists and the Thai Border Patrol and is currently closed to the public (as this issue of the magazine goes to print – Ed note). Thale Ban National Park in Satun Province recently had its park facilities attacked and destroyed by angry villagers wanting to encroach further into the park. It has been slow in attracting more visitors.

What most people on eco-tours in the south of Thailand get to see then is jungle in the truest sense of the term. Webster defines it as: “a dense growth of rank and tangled vegetation.” The thick, nearly impenetrable growth of tall grasses, creepers and light-loving saplings which spring up after old growth forests are logged or burnt over, or as unused agricultural lands begin the long slow succession back to a forest state, is what scientists refer to as “a jungle.” Unlike an old growth or ‘virgin’ forest, where the upper and lower canopies result in a heavily shaded forest floor with little understory creating easy hiking conditions, a secondary tropical forest or ‘jungle’ is so dense with light-loving species all competing for a place in the sun, a machete must be used to literally hack a way through it.

This then is the jungle of Hollywood adventure films, teeming with deadly snakes, tigers and other large, dangerous animals — at least on the silver screen. The truth is one is unlikely to find much fauna here other than rats, a few squirrels and some adaptable bird species. There is always a huge loss in biodiversity as primary forests are converted to secondary forests or jungle; this is especially pronounced if the area of flower-peckers, barbets, fruit doves, hornbills, fruit bats, large squirrels, langurs and flying lemurs.

Below the upper canopy is a layer of forest formed by the crowns of shorter trees. This lower canopy has butterflies in abundance, tree frogs, gliding lizards, woodpeckers, trogons and flycatchers. The clouded leopard is found here as are the slow loris, civets, tree shrews and smaller squirrels.

The understory is made up of low growing ferns, palms, bamboo, herbs and young saplings. It provides habitat for large grazers and their predators: conversion is large and the area for conservation is small.

It is the stratified nature of the undisturbed tropical forest that makes it so extraordinarily rich in species compared to the single dense layer of vegetation in a jungle. Both Tropical Evergreen Forests and Tropical Rainforests display six levels recognized by research scientists:

Viewing such a forest in profile one can easily distinguish the top level, emergent trees: which are the tallest plants with the most massive bases in the forest. These are the preferred trees for gibbons when singing and sleeping. Emergent trees also provide nesting cavities for hornbills, and a wealth of fruit and seeds for arboreal and ground-loving birds and mammals.

Just below the emergents is the upper canopy: a continuous layer of tree crowns in a million shades of green. This is the preferred habitat of sunbirds, elephant, rhino, deer, tapir, bear, tiger, and other cats. The forest floor is the lowest level. It is largely reserved for insects and decomposers (beetles, scorpions, ants, millipedes, leeches) and insectivorous mammals like the scaly anteater and many species of snakes.

So there we have it, all the proper classifications and different Thai forest types. Now that you’re an expert on the subject challenge your Thai tour leader to show you a Lowland Tropical Forest, a Tropical Evergreen Forest, a true Tropical Rainforest and a Jungle. He or she will no doubt bless you with a big Thai smile and that classic, all-encompassing Thai response: “Same, same, only different.”

Your guide, as usual, will be absolutely right.