The jungle comprises a substantial portion of the earth’s land mass. Jungle environments consist of tall grasslands; mountains; swamps; blue and brown water; and single/double-canopy vegetation. Jungle environments are prominent in South America, Asia, and Africa. High temperatures, heavy rainfall, and oppressive humidity characterize equatorial and subtropical regions, except at high altitudes. At low altitudes, temperature variation is seldom less than 50º F (10º C) and is often more than 95º F (35º C). At altitudes over 4,921 feet (1,500 meters), ice often forms at night. The rain has a cooling effect, but stops when the temperature soars. Rainfall is heavy, often with thunder and lightning. Sudden rain beats on the tree canopy, turning trickles into raging torrents and causing rivers to rise. Just as suddenly, the rain stops. Violent storms may occur, usually toward the end of the summer months. The dry season has rain once a day and the monsoon has continuous rain. In Southeast Asia, winds from the Indian Ocean bring the monsoon but the area is dry when the wind blows from the landmass of China. Tropical day and night are of equal length. Darkness falls quickly and daybreak is just as sudden. Leaders must consider several jungle subtypes and other factors when performing duty and surviving in the jungle:
4-19. There is no standard type of jungle. Jungle can consist of any combination of the following terrain subtypes:
Semi-evergreen seasonal and monsoon forests.
Scrub and thorn forests.
TROPICAL RAIN FORESTS
4-20. The climate varies little in rain forests. You find these forests across the equator in the Amazon and Congo basins, parts of Indonesia, and several Pacific islands. Up to 144 inches (365.8 centimeters) of rain falls throughout the year. Temperatures range from about 90º F (32º C) in the day to 70º F (21º C) at night. There are five layers of vegetation in this jungle. Sometimes still untouched by humans, jungle trees rise from buttress roots to heights of 198 feet (60 meters). Below them, smaller trees produce a canopy so thick that little light reaches the jungle floor. Seedlings struggle to reach light, and masses of vines twine their way to the sun. Ferns, mosses, and herbaceous plants push through a thick carpet of leaves, and fungi adorn leaves and fallen trees. The darkness of the jungle floor limits growth, which aids in movement. Little undergrowth is present to hamper movement, but dense growth limits visibility to about 55 yards (50 meters). You can easily lose your sense of direction in a tropical rain forest, and aircraft have a hard time seeing you.
4-21. Secondary jungle is very similar to rain forest. Prolific growth, where sunlight penetrates to the jungle floor, typifies this type of forest. Such growth happens mainly along riverbanks, on jungle fringes, and where Soldiers have cleared rain forested areas. When abandoned, tangled masses of vegetation quickly reclaim these cultivated areas. You can often find cultivated food plants among secondary jungles.
SEMI-EVERGREEN SEASONAL AND MONSOON FORESTS
4-22. The characteristics of the American and African semi-evergreen seasonal forests correspond with those of the Asian monsoon forests:
Their trees fall into two stories of tree strata.
–Upper story 60 to 79 feet (18 to 24 meters)
–Lower story 23 to 43 feet (7 to 13 meters)
The diameter of the trees averages 2 feet (0.5 meter).
Their leaves fall during a seasonal drought.
4-23. Except for the sago, nipa, and coconut palms, the same edible plants grow in these areas as in the tropical rain forests. You find these forests in portions of Columbia and Venezuela and the Amazon basin in South America; in southeast coastal Kenya, Tanzania, and Mozambique in Africa; in northeastern India, much of Burma, Thailand, Indochina, Java, and parts of other Indonesian islands in Asia.
TROPICAL SCRUB AND THORN FORESTS
4-24. Tropical scrub and thorn forests exist on the West coast of Mexico, on the Yucatan peninsula, in Venezuela, and in Brazil; on the Northwest coast and central parts of Africa; and (in Asia) in Turkistan and India. Food plants are scarce during the dry season, and more abundant during the rainy season. The chief characteristics of tropical scrub and thorn forests include–
They have a definite dry season.
Trees are leafless during the dry season.
Ground is bare, except for a few tufted plants in bunches
Grasses are uncommon.
Plants with thorns predominate.
Fires occur frequently.
4-25. South American savannas occur in parts of Venezuela, Brazil, and Guiana. In Africa, they occur in the southern Sahara (North central Cameroon and Gabon, and Southern Sudan); Benin; Togo; most of Nigeria; the Northeastern Republic of Congo; Northern Uganda; Western Kenya; and parts of Malawi and Tanzania, Southern Zimbabwe, Mozambique, and Western Madagascar. A savanna generally–
Exists in the tropical zones of South America and Africa.
Looks like a broad, grassy meadow, with trees spaced at wide intervals.
Has lots of red soil.
Grows scattered, stunted, and gnarled trees (like apple trees) as well as palm trees.
4-26. Saltwater swamps are common in coastal areas subject to tidal flooding. Mangrove trees thrive in these swamps, and can grow to 39 feet (12 meters). In saltwater swamps, visibility is poor, and movement is extremely difficult. Sometimes, raftable streams form channels, but foot travel is usually required. Saltwater swamps exist in West Africa, Madagascar, Malaysia, the Pacific islands, Central and South America, and at the mouth of the Ganges River in India. Swamps at the mouths of the Orinoco and Amazon Rivers, and of the rivers of Guyana, offer plenty of mud and trees, but little shade. Tides in saltwater swamps can vary as much as 3 feet (0.9 meter). Advice for this terrain is, try to avoid the leeches, the various insects, including no-see-ums, and crocodiles and caimans. If you can, avoid saltwater swamps. However, if they have suitable water channels, you might be able to traverse them by raft, canoe, or rubber boat.
4-27. Freshwater swamps exist in some low-lying inland areas. They have masses of thorny undergrowth, reeds, grasses, and occasional short palms. These all reduce visibility and make travel difficult. Freshwater swamps are dotted with large and small islands, allowing you to get out of the water. Wildlife is abundant in freshwater swamps.
4-28. Success in the jungle depends on your level of applicable knowledge and preparation.
TRAVEL THROUGH JUNGLE AREAS
4-29. With practice, you can move through thick undergrowth and jungle efficiently. Always wear long sleeves to avoid cuts and scratches.
4-30. To move easily, you must develop a "jungle eye." That is, look through the natural breaks in foliage rather than at the foliage itself. Stoop down occasionally to look along the jungle floor.
4-31. You may find game trails you can follow. Stay alert and move slowly and steadily through dense forest or jungle. Stop periodically to listen and reorient on your objective. Many jungle and forest animals follow game trails. These trails wind and cross, but frequently lead to water or clearings. Use these trails if they lead in your desired direction of travel. However, they may also be favorite enemy points for ambushes and booby traps.
4-32. Use a machete to cut through dense vegetation, but avoid cutting too much, or you will tire quickly. If using a machete, stroke upward when cutting vines to reduce noise, because sound carries long distances in the jungle.
4-33. Use a stick to part the vegetation and to help dislodge biting ants, spiders, or snakes. Never grasp brush or vines when climbing slopes, because they may have irritating spines, sharp thorns, biting insects, and snakes.
Power and Telephone Lines
4-34. In many countries, electric and telephone lines run for miles through sparsely inhabited areas. Usually, the right-of-way is clear enough to allow easy travel. When traveling along these lines, be careful as you approach a transformer and relay stations, because they may be guarded.
4-35. Although water is abundant in most tropical environments, you may have trouble finding it, and when you do, it may not be safe to drink. Vines, roots, palm trees, and condensation are just a few of the many sources of water. You can sometimes follow animals to water. Often you can get nearly clear water from muddy streams or lakes by digging a hole in sandy soil about 3 feet (1 meter) from the bank. Water will then seep into the hole. Remember, you must purify any water you get this way.
4-36. The proportion of poisonous plants in tropical regions is no greater than in any other area of the world. However, it may appear that most plants in the tropics are poisonous, due to preconceived notions and the density of plant growth in some tropical areas.