Biodiversity in Rainforests

Rainforests are the most biologically diverse areas on Earth. It is estimated that rainforests, which cover merely 6% of the Earth’s surface, contain between one half and three quarters of the world’s species. The most biologically diverse rainforests are lowland forests in regions with evenly distributed rainfall. It has even been proven that rainfall levels are more important to biodiversity than soil fertility.

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Causes of Reduced Biodiversity

The foremost reasons behind reduced biodiversity now are changes in land use, alternation of climate, pollution, introduction of exotic species, human activity etc.  For rainforests, the primary factor is land conversion.  Habitat destruction is the primary cause of loss of rainforest biodiversity and is directly related to human population growth.  Deforestation is primarily responsible for the destruction of natural habitat.  Logging of rainforest leads to forest fragmentation.  Forests are being reduced to smaller size, creating many consequences, some of which are even unanticipated. For example, most animal species are not so tolerant to these changes.  Animals, particularly large ones, cannot maintain themselves in small fragmented forests.  Additionally, their migrations may be interrupted by fragmentation.  Warming is also another major concern in tropical rainforests as it affects evapotranspiration as well as soil fertility.  Increased moisture due to warming also increases infectious diseases.  Many species of frogs and lizards have declined or disappeared, perhaps because of the increase in parasites occasioned by higher temperatures.  Rainforests are losing biodiversity, not only because of the disappearance of natural habitat, but also because essential ecological processes are being interrupted by forest fragmentation caused by deforestation.

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Deforestation

Deforestation Maps and Graphs

This disproportionate world map shows deforestation rates. The largest areas are the areas with the highest deforestation rates. As you can see, the largest areas are Brazil, sub-Saharan Africa and South Asia, which have the World's most diverse rainforests.

This graph shows annual deforestation rates in the Amazon. As you can see, the area deforested fluctuates. We are currently experiencing a dip in deforestation, but judging by the trend of the graph, we should expect a spike in deforestation in the next few years. 

Impacts on Biodiversity I

Current extinction rates are estimated to be between 1000 and 10000 times the ‘natural’ rate. 50% of the world’s species are either extinct or in danger of becoming extinct. This can be attributed to human activity. Much damage has been done, as rainforests occupy only half of the area that they once did as a result of mass deforestation. Despite the alarming statistics, this detrimental behaviour shows no signs of slowing. Humans continue to deforest at such a high rate, that all rainforests outside of Government-protected reserves are projected to be cut down by the 22^nd century.

Deforestation in the Amazon Tropical Rainforest threatens many species of tree frogs, which are very sensitive to environmental changes.

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Impacts on Biodiversity II

Extinction does not necessarily mean the end of a species of animal, it can also mean the end of a species of plant.  Due to rapid deforestation, many plants in the Amazonian tropical rainforests are being exploited.  As canopy trees are logged, plants dependent upon them for shade or support or moisture vanish.   As a result, many plants like Terminalia acuminata, are extinct from the wild.   These plants are only known to exist in captivity as a naturalized population outside its historic range.  Some 338 species of plants are facing extinction in Brazil, according to a report compiled by IUCN - International Union of Conservation of Nature.  Deforestation, especially in southeastern Atlantic Amazonian tropical rainforest is blamed for this phenomenon.

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