FOREST ECOSYSTEMS

• biodiversity = number of species present at any time
• Currently
• 1 to 1.4 million species catalogued
• Probably 5 to 100 million total on Earth



• Biodiversity depends on
• Balance between
• the rate of evolution
• The rate of extinction



• Natural change
• Past average life span of species: 100,000 to 1 million years



• 10 to 100 new species estimated to evolve each year

• Species lost due to inability to adapt to changing environmental conditions
• sudden, local natural disasters



• gradual change



• Forests
• serve the essential role of moderating soil erosion



• modulating the water cycle



• provide habitat for species



• regulates global CO₂





• Changes
• 45% of Ethiopia was forested in 1900; today only 1 - 3%



• 60% of Haiti was forested in 1920; today only 2%



• 93% of Madagascar has been deforested



• North America?





• Why? / Wood as a resource
• Debt payment



• Land Settlement



• Creation of pastureland



• Logging
• Asian nations supplied 2/3rd's of timber used in international trade in the 1980's



• By 2000 only 10% due to depletion



• Hydropower

• Fuelwood

• Effects
• Every year an average of 50,000 species becomes extinct because of deforestation problems
• Estimated extinction rate for plants and animals
• 24 to 400 species per day (>8000 per year!)



• Up to 100 -10,000 times faster than new species evolve!



• Because of this problem, rainforests cover less than two percent of the Earth's surface.



• An average of 2.47 acres of forestland (equal to two football fields) are destroyed per second
• making it 78 million acres per year. That is an area larger than the country of Poland



• While reading the above information, approximately 150 acres of rainforest were destroyed. Within the next few minutes, 6 species of animals and plants will become extinct.



• If deforestation continues at the current rate, scientists estimate nearly 80-90 percent of rainforests will be destroyed by the year 2020



• Link to global warming?



• Link to Desertification
• Process
• exposure and excessive stress dries out the soil



• native plant species decline, resulting in less production of organic matter



• soil hardens as fertility is reduced

• because less water can infiltrate the hardening of soil increases even more



• water runs off of landscape rather than infiltrating, causing scouring of the landscape, flooding, etc...



• deserts increase by about 27,000 mi² / year