TROPICAL RAINFOREST AND ITS DESTRUCTION

Extent of the Tropical Rainforest

The Tropical rainforest is a unique biosphere – 2 % of the earth’s surface, concentrated in a narrow equatorial belt is believed to contain 50 % of the world’s species. A map with the extent of tropical rainforests has been shown below.

Characteristics of the Tropical Rainforest

The tropical rainforest derives its name from the fact that it represents vegetation, which has resulted due to tropical rains. The rainforest is a complex community whose framework is provided by trees of many sizes. The tropical rainforest is characterised by dense vegetation, in a succession of layers. The microclimate under the canopy differs from that outside – there is less light, higher humidity and lower temperatures.
The great majority of plants are woody, with a thick undergrowth. A rainforest is also characterised by a large number of climbers – lianas and other epiphytes such as lichens, algae, mosses and orchids.

Trees have large buttress roots to support their immense size and roots run close to the surface in an attempt to intercept nutrients.
The plant species density is extremely high with as many as 150 different species per hectare of rainforest. As mentioned before, the forest follows a layered structure, with a great difference in the heights of trees, as they struggle to reach upwards for sunlight. The undergrowth is made up of shrubs, herbs and saplings of the trees.

The Canopy

The canopy, as the name implies is the uppermost layer of the rainforest formed as continuous foliage formed by the crowns of the trees. It is assumed that 70 % of species within the rainforest reside within the canopy.
The rainforest represents a symbiotic ecosystem. The trees and most of the other plants are rooted in the soil and draw nutrients and water from it. In turn their fallen leaves and twigs provide food for a host of invertebrates, such as termites, and also fungi and bacteria. Nutrients are returned to the soil via the decay of fallen leaves and branches and also by leaching from the fallen leaves by rainwater.

Within the forest canopy, especially in lowland forests, there are a large number of both vertebrates and invertebrates. These species either subsist on plant or animals, giving rise to complex inter-relationships: for example, in relation to the pollination of flowers and dispersal of seeds. The whole organic community and its immediate physical and chemical environment together make up the ecosystem of the rainforest. Over a sufficiently large area, the climax forest itself is in a state of dynamic equilibrium.

This means that while the forest is constantly growing and changing, there is no net increase in the overall number of living plants and animals; deaths are more or less balanced by replacements. Zaire is the richest country in Africa in terms of biodiversity and is one of the most biologically diverse countries in the world.

Many areas of montane forests are important but lack any protection at this time. This is especially critical in view of the increasing human population pressure in eastern Zaire. In many of these areas, reconciliation of human and conservation needs is central ² .

Destruction of Rainforest

‘The direct pressures of mounting human numbers, and the less direct but equally profound changes in the biosphere that result from human perturbation of biogeochemical processes, are altering the course and character of biological evolution’ ³ . 

‘Tropical rainforests are being destroyed at tremendous rates. The estimates vary but the earth is losing tropical rainforest at the rate of around 60,000 m2 per minute or approximately 1,000 m2 per second. Clear felling is being practised in order to clear areas for human activities and agriculture. This is resulting in the loss of species diversity and the loss of primary forest.

Estimated rates of species extinction have been presented in Table 2  ⁴

²  ‘Bio diversity in Sub Saharan Africa and its Islands’,  Occasional papers of the IUCN Species Survival Commission, Paper No. 6. Published by IUCN, Gland, Switzerland   1990

³    Holdgate, Martin  in ‘Tropical Deforestation and Species Extinction’   eds. Whitmore T.C, Sayer J.A, IUCN, Chapman and Hall, London 1992

⁴   Reid, W.V.,  in ‘Tropical Deforestation and Species Extinction’ eds. Whitmore T.C, Sayer J.A, IUCN, Chapman and Hall, London 1992 

Fig 7 : Equatorial tropical rainforests shown as green patches

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Fig 8 : Buttress roots typical of a rainforest

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Fig 9 : Rainforest Canopy    

 Fig 10 : River through rainforest with a view of the thick undergrowth

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FOREWORD

Why this page was published

AIMS AND METHODOLOGY     

What are we trying to prove?

INTRODUCTION

The violent world of Biosafety level 4 viruses

WHAT IS A VIRUS?

THE EBOLA VIRUS

The shepherd’s crook

LIFECYCLE OF THE EBOLA VIRUS

The nature of the beast

- Pathology-

VARIANTS OF THE EBOLA VIRUS

THE HIV VIRUS

Comparison of Ebola with the deadly AIDS virus

RESERVOIR SPECIES

Where does the virus hide?

HISTORY OF OUTBREAKS

Comprehensive list of outbreaks till date

TREATMENT

Current stage of research

THE TROPICAL RAINFOREST AND ITS DESTRUCTION

GIS ANALYSIS

Overlay of deforestation and Ebola outbreak areas

CONCLUSION

Is the human race headed for destruction?

Estimate

% Global loss 
per decade

Method of
Estimation

Reference

One million species between 1975 and 2000

  4

Extrapolation of past exponentially increasing trend.

  Myers 1979

15 – 20 % of Species between 1980 and 2000

  8 – 11

Loss of half the species in area likely to be deforested by 2015.

  Lovejoy 1980

25 % of species between 1985 and   2015 

  9

Estimated species area curve, forest loss based on Global 2000 projections.

  Raven 1988 a,b

At least 7 % of plant species

  7

Half of the species lost over the next decade in 10 ‘hot spots’ covering 3.5 % of the forest area.

  Myers 1979

0.2 – 0.3 % per year

  2 -3

Half of rainforest species assumed lost in tropical rainforests to be local endemics and becoming extinct with forest loss.

  Wilson 1988,  1989