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Ethiopia, the third largest country in Africa by population, has been hit by famine many times because of shortages of rain and depletion of natural resources. Deforestation has lowered the chance of getting rain, which is already low, and increased erosion. Berkeley Bayisa, an Ethiopian farmer, offers one example of why deforestation occurs.
Once abandoned, the plants of the rainforest will find it difficult to grow back in that area. [37] Forest fragmentation also opens the path for illegal hunting. Species have a hard time finding a new place to settle in these fragments causing ecological collapse. This leads to extinction of many animals in the rainforest.
Deforestation and forest area net change are not the same: the latter is the sum of all forest losses (deforestation) and all forest gains (forest expansion) in a given period. Net change, therefore, can be positive or negative, depending on whether gains exceed losses, or vice versa.
Douglas fir wanes as a dominant species, and the forest is primarily made up of western red cedar, Sitka spruce, and western hemlock. The Gulf of Alaska begins where the fjords of southeast Alaska end, and marks the transition into "sub-polar rain forest". Here the forest occupies only a very narrow strip between the ocean and the icy alpine zone.
A pioneer tree species, one that is able to quickly regenerate after a disturbance, may be able to reassert its role in the forest while a climax tree species may not. [10] Forest impacts can be divided into two phases: short-term physical disturbance caused directly by the pest, and long-term changes in ecosystem functions in response to the ...
An ecological cascade effect is a series of secondary extinctions that are triggered by the primary extinction of a key species in an ecosystem.Secondary extinctions are likely to occur when the threatened species are: dependent on a few specific food sources, mutualistic (dependent on the key species in some way), or forced to coexist with an invasive species that is introduced to the ecosystem.
Amazon River rain forest in Peru. Tropical rainforests are hot and wet. Mean monthly temperatures exceed 18 °C (64 °F) during all months of the year. [4] Average annual rainfall is no less than 1,680 mm (66 in) and can exceed 10 m (390 in) although it typically lies between 1,750 mm (69 in) and 3,000 mm (120 in). [5]
Amazonian evergreen forests account for about 10% of the world's terrestrial primary productivity and 10% of the carbon stores in ecosystems [94] – of the order of 1.1 × 10 11 metric tonnes of carbon. [95] Amazonian forests are estimated to have accumulated 0.62 ± 0.37 tons of carbon per hectare per year between 1975 and 1996. [95]