Endangered Rainforest

When rainfall is high and evenly distributed throughout the year (at least 2000 mm/yr or 100 mm/month) evergreen rainforests develop. They form the core of the tropical swath along the equator. It rains there everyday and it is home to the world’s most luxuriant and diverse flora and fauna. Even though the tropical rainforest covers only some 11.5% of the world’s surface, it stores in its biomass over half of the world’s rainfall.

Three quarters of the soil in the Tropics is very low in nutrients. It is very old and therefore much of its mineral content is already washed out. The fact that luxuriant rainforests can exist despite infertile soil is due to a perfectly balanced recycling system. First, fallen leaves, dead animal and plant matter decompose on the topsoil. Countless small animals, fungi and bacteria seize upon the organic material and decompose and mineralize it in a short period of time so that plant roots can absorb the nutrients. In order to maximize absorption, many trees have a shallow and effective network of roots, some of which even grow upward. Fungi play a very important role in this recycling system. With the fine tree roots they enter into a symbiosis called Mycorrhiza. Together they form an extremely effective circulation system of nutrients that maintains the minerals in circulation too. The Fungi make it easier for the tree roots to
absorb the minerals and in return they receive carbohydrates from the tree, produced in the leafs by photosynthesis The large-scale felling of trees leaves the filter of nutrients to become leaky: the Mycorrhiza is destroyed, the nutrients flow away and become forever lost to the system. How low the nutrient content of the soil is can be measured by the supply of nitrogen in the soil. In Central Europe 94% of the nitrogen supplies exist in the soil and only 6% are contained in the biomass. Quite the contrary in the Tropics: here more than half--58% to be precise-- is stored in the plants, while 42% is found in the soil.

High insolation year-round, favorable climate conditions, uninterrupted cycles and maximum biodiversity make our current tropical forests one of the ecosystems on Earth with highest volume of biomass. Tropical rainforests contribute 29% of Earth’s total foliage biomass.
Three out of four of the currently known 1.85 million species come from the Tropics. In one square kilometer of forest in Panama, 41,000 insect species were counted!

The tropical moist forests or seasonal rainforests link together the evergreen rain forests to the north and south. Dry periods and the characteristics of the seasons increase in intensity as one moves away from the equator. Seasonal rainforests have dry periods of 2 to 5 months.

As one moves towards the poles, the seasonal rainforests merge smoothly into seasonal dry forests. The dry periods last longer and the rainfall decreases. The seasons become more clearly defined.

Gradually the seasonal dry forests become superseded by savannas and forests of cactus. In coastal regions one finds a special type of tropical forest: the tidal forest or the so-called mangrove forest. The roots of the mangroves grow in sedimentary depositional environments. In the process, the mangrove’s dense network of roots acts as mechanism to catch the silt. Once the process is initiated, more and more silt accumulates. The process is impeded, above all, when sediment is washed away by tidal currents. Mangroves ultimately carve out their own ever-growing habitat.

48% of all forests are located in the Tropics or Subtropics.

The tropical forests are located between the tropics of Cancer and Capricorn, about 23.5 degrees north and south latitude, respectively. With around 18.5 million square kilometers, they cover around 40 percent of the tropical land area.

Primary rainforest refers to untouched, pristine forest that exists in its original condition. Their development has not been perceptibly influenced by man. Everything else is secondary rainforest, which has been disturbed in some way, naturally or unnaturally.

The rainforest receives between one quarter and, at most, one half of the water it requires from the hydrological cycle: clouds that form above the oceans move inland and there rain down. Part of the rainfall eventually ends up, through streams and rivers, back in the sea.

The rainforest receives the lion’s share of its water, however, from its own micro water cycle. In the rainforest, large amounts of water evaporate and form mighty rain clouds. These rain down over the forest and then evaporate anew.

Sufficient large and interrelated forest areas are needed in order for the micro water cycle to be self-sustaining. Model calculations assume that the micro water system functions as long as at least 50 % of the original forest area available was in existence before the start of deforestation.

Experts thus fear that a chain reaction could be triggered: if the micro water cycle is even delicately disturbed, it could completely collapse. The forests wouldn’t have the necessary water, which could accelerate the deterioration of tropical forests.
Tropical rainforests store vast amounts of the greenhouse gas carbon dioxide. It is stored in forest biomass as well as in the soil. Estimates start at 375 billion tons of carbon. Through burning and rotting, the carbon dioxide in the biomass is released into the atmosphere. It is estimated that through deforestation, tropical rainforests release between 0.6 and 2.6 billion tons of greenhouse gasses per year. Every year approximately 22 billion tons of carbon dioxide is emitted worldwide from various sources.

At the beginning of the 21st century, 39 million square kilometers of the Earth’s surface was covered with forest, some 19 million of which was tropical forest. In the middle of the last century the figure was almost double! And the loss of area continues: today, on average, over 415 square kilometers of tropical rainforest is deforested daily. That is equivalent to an area larger than the city of Munich. Between 1990 and 2000 alone, around 900,000 square kilometers of tropical forest was irretrievably lost. Commercial logging for lumber production, which is almost exclusively used for export, but also for firewood, is one of the most important factors causing deforestation. The exploitation
of the land for agriculture is another. On the one hand, plantations arise for the cultivation of highly exportable products (cash-crops) like soy, coffee, sugarcane, cacao, palm oil or oranges. On the other hand, grasslands are created for the farming of livestock. The traditional system of shifting cultivation itself exacerbates the problem. In its prevailing form nowadays, shifting cultivation hardly corresponds to the small-allotment slash and burn practice of the original inhabitants. Much more common today is the deforestation, by numerous landless settlers, of unregulated parcels of land in order to cultivate food for their own personal needs. Due to the quickly exhausted soils, which don’t permit lasting usage or
steady yields, the settlers move along after a short time to deforest still new areas. Various
infrastructure projects contribute likewise to the deterioration of tropical forests. The building
of settlements, transportation routes or industrial facilities is here analogous to the construction
of reservoirs for hydroelectric power stations. Likewise, it comes down to deforestation in
order to enable the reduction of mineral resources like copper, nickel, manganese, gold or iron
ore.

As measure to preserve valuable ecosystems and tropical rainforests, the designation of protected area has proven effective. At the turn of the century, around 12, 750 protected areas constituted over 12 million protected square kilometers, 30 % of which are national parks.