SOME INTERESTING INFORMATION AND FACTS ABOUT RAIN FORESTS

TROPICAL RAIN FORESTS

Of all the many and varied natural environments to be found on the earth, perhaps the most awe-inspiring and popular are the tropical rain forests. Although it is the forests of the Amazon which spring most readily to mind, it is important to remember that they also occur in parts of North America, Asia, Australia, and Africa, for the most part within a narrow band 4 degrees either side of the equator. These forests, with their mighty trees and extraordinary flora and fauna constitute the planet's richest habitats, and one of our most precious natural resources.

In this section we look at some of the fascinating animals, plants and people which inhabit the tropical rain forests along the meridian line, and we consider some of the conservation issues affecting these biological treasure houses. But before we do this, let's first get an idea of what a tropical rain forest actually is.

Tropical rain forests are mainly the product of climatic interactions, particularly temperature and rainfall. In general, tropical rain forests occur where a mean monthly temperature of between 20 and 28 degrees C is combined with an annual rainfall of between 1.5 and 10 metres, evenly distributed throughout the year. This last proviso is very important because it is only to those tropical forests which experience little seasonal variation in terms of rainfall that the term rain forest can legitimately be applied.

AFRICAN FORESTS

Less than seven per cent of Africa’s surface is covered with tropical rain forest, and the majority of this is concentrated in the centre of the continent. The Democratic Republic of Congo, Gabon, Cameroon and the Central African Republic all have substantial forest coverage of various types. However, West Africa is not without its share of this type of vegetation. Ghana has over 15,000 sq. km of rain forest, most of which is found along the coast, Nigeria has nearly 40,000 sq. km, Cote D’Ivoire has some 30,000 sq. km and Togo has around 1300 sq. km.

Africa’s rain forests are not as rich in species as those found in South America and Asia, but they still surpass every other region in terms of both the diversity and the density of the wildlife to which they are home. Much of Africa’s forest cover has been lost due to human activity, and this is examined along with other conservation issues in greater detail in another section.

We will be concerned with those tropical rain forests which lie on the meridian line, and consequently our attention will be focussed upon Ghana and Togo. Nevertheless, much of what is said in relation to these countries will also apply to forests found elsewhere on the continent.

TREES

The diversity of trees found in the tropical rain forests is quite extraordinary, and far exceeds that of any other kind of forest, sometimes with as many as 100 tree species per hectare. Equally remarkable are the heights and diameters of the trees, which while not the tallest or most massive on earth, still dwarf those of most other forest systems.

For example, Khaya ivorensis, a member of the family of trees collectively known as African mahogany, can attain heights of up to 60 metres, and diameters of 1.8 metres.

Because of the constantly high temperatures and extreme humidity found in the tropical rain forests, bacteria and other micro-organisms thrive in the top layer of soil, feeding on the mass of decaying matter which falls from the canopy. The result is that there is little matter left to accumulate, so the top soil is very thin and poor in nutrients.

Under normal circumstances large trees send out masses of roots which can extend for several metres. These roots absorb nutrients from the soil and give the tree a firm foundation. rain forest trees have a large number of roots, but these can only extend a small distance into the thin soil, and cannot therefore provide stability. The solution is to employ buttress roots which work in much the same way as buttresses on citadels or Christian cathedrals, and these can grow up to 5 m up the trunk of a tree.

EPIPHYTES LIANES AND STRANGLERS

Lianes

Not all plants which thrust their way into the forest canopy are trees. Lianes, for example, have their roots in the forest floor, but rely for their support upon existing trees.

Often starting out as shrubs, the lianes put out long branches which attach themselves to tree trunks and climb up until they reach the sunlight, at which point they generate leaves and frequently create large crowns.

Epiphytes

Like the lianes, epiphytes do not provide their own support, but in contrast they are not rooted in the ground at all. Instead, they grow on the surface of the canopy trees, rooting in crevices where humus has accumulated. These roots, however provide only an anchorage, and the epiphytes do not draw their nutrients from the host tree. Exactly where these plants do obtain their nutrients varies from one species to another, some collecting falling plant matter, others receiving organic matter from the insects which pollinate them. Common epiphytes are orchids, bromeliads and ferns.

Stranglers

Found only in the tropical rain forests, stranglers start out as epiphytes, but at a certain point in their growth they produce roots which wrap around the trunk of the tree on which they live, and descend into the ground. This provides them with increased nutrients, allowing them to grow towards the canopy. Eventually the strangler surrounds its supporting tree with roots, which ultimately kills it. However, the trunk of the tree remains, and continues to support the strangler. Most stranglers are figs.

ANIMALS

The remarkable abundance and diversity of plant life in the tropical rain forest ensures that there is always plenty of food available for herbivorous animals. Because most vegetation is concentrated high up in the canopy, it is here that many of the forest's animals are to be found, some descending only rarely to the ground. Among the most numerous of these are primates, several species of which inhabit the rain forests of Ghana and Togo. These include monkeys such as the black and white colobus, the spot-nosed monkey, and the Diana monkey, as well as larger apes such as chimpanzees, and smaller primates such as bushbabies. Also living in the canopy are an enormous variety of birds such as hornbills, parrots, and turacos, some of which feed on plant matter. Others enjoy a diet of insects, which are exceptionally numerous in the rain forest.

The forest floor, although not home to as many species as the canopy, still has its share of interesting fauna. Hoofed mammals, including various types of duiker, reptiles such as the common hinged tortoise, and larger mammals such as the pygmy hippopotamus and forest elephant, are just a sample of the creatures to be found on the ground.

Where herbivores abound there will inevitably be carnivores to prey on them, and the west African rain forests are no exception. Leopards prowl on the ground and in the trees, Nile crocodiles lurk in the rivers and pools, and birds of prey soar overhead, carrying off rodents and small primates. The forests are complex ecosystems, delicately balanced with every animal and plant playing its own role in maintaining the equilibrium. From the smallest plants and the insects that pollinate them, to the carnivores right at the top of the food chain, nothing is dispensable.