Chpt_10_Notes - Chapter 10 Sustaining Terrestrial...

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Chapter 10: Sustaining Terrestrial Biodiversity: The Ecosystem Approach Human Impacts on Terrestrial Biodiversity Human activities have negatively affected global biodiversity. A. Humans have disturbed from 50- 83% of the earth’s land surface. 1. We have logged about 95% of virgin forests in 48 states , 98% of tallgrass prairie has disappeared , and California has lost 99% of native grassland and 85% of original redwood forests. 2. Human use, waste, and destruction have affected 40% of the net primary productivity of earth’s terrestrial ecosystems. 3. Species extinction rate is now probably between 100-10,000 times what it was prior to human existence. B. Preservation of biodiversity is important for several reasons such as intrinsic or existence value and also because of its usefulness to humans. 1. Instrumental value consists of use values that benefit people for goods and services, scientific information, recreation, and ecological services. 2. Nonuse values are existences value, aesthetic value (the appreciation of wild species, or a view for beauty alone), and bequest value, the act of leaving natural capital for use by future generations. Managing and Sustaining Forests Managing and sustaining forests is a long-term commitment. A. Forests with at least 10% tree cover occupy about 30% of the earth’s surface, excluding Greenland and Antarctica. B. Forests are classified according to their age and structure into three major types. 1. Old growth/frontier forests are those, which have not been seriously disturbed by human activities/natural disasters for hundreds of years. These forests are storehouses of biodiversity because of the ecological niches they provide for wildlife species. 2. Second-growth forests develop in an area after human activities or natural forces have removed them. 3. Tree plantations/tree farms replant and clear-cut one species of tress in a regular cycle. C. Harmful effects of deforestation (temporary/permanently removing trees) are given below: 1. Deforestation reduces biodiversity and the ecological services that forests provide. 2. Deforestation can change regional climate and forests will not regenerate. 3. Deforestation emits carbon dioxide, which affects global climate change. 4. Research indicates that at least 200 years is needed to accumulate the same amount of carbon stored in the original forest. D. Deforestation is widespread across the planet and is continuing. 1. World Resources Institute surveys indicate that original forest cover has decreased by 20-50%. 2. Global deforestation is occurring by at least 0.2 – 0.5% per year, with 4/5 th of the losses occurring in the tropics. 3. If conditions don’t change, within the next 10-20 years, 40% of the world’s remaining forests will have been logged or converted to other uses. E. About half the wood harvested each year and three-fourths of that in developing countries is
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Chpt_10_Notes - Chapter 10 Sustaining Terrestrial...

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