Transcript Biome-Human Impact

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Forests have been destroyed for centuries
 Cleared for agriculture and farming.
 Building materials
 Fire wood
 Living space
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In 1950, over 10% of Earth’s land was covered
by rain forests.
Currently only 6%, and decreasing.
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Sustained yield
 A balance between net growth and harvest.
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Maximum sustained yield
 The level of consumption at which the population
declines if exceeded.
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Most plant and animal biodiversity on Earth.
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As a result of deforestation, animals’ habitats
are also destroyed.
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succession can take several hundred years to
restore a climax community.
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The required time for succession to reach
climax community takes longer when
biodiversity is greater.
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Succession may not be possible if large
stands are destroyed
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Harvested for farms, orchards, and urban
development.
Two factors driving exploitation of deciduous
forests
 The rich soil is excellent for farmland.
 Hardwood trees are great material for furniture,
flooring, and fuel.
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Replanting efforts with Monocultures
 Low tree biodiversity = few animal niches = low
animal biodiversity
 Low biodiversity
▪ Ecosystem is more fragile.
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Have not been logged as extensively as other
forest types
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But, the growing need for wood has led to
increased harvesting
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Countries in need of money are selling large
stretches of forests to domestic and foreign
companies.
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Recall:
 Little Biodiversity.
 Short growing season.
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Very fragile
 Low biodiversity = simple food webs
 Short growing season = slow succession
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Until recently, the tundra was relatively
undisturbed by humans
Our growing need for oil increases human
activity in tundra ecosystems
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Global climate change
 The largest warming trends are in the tundra.
 Warming
▪ Thaws the permafrost.
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Steppes and Prairies
 Human agriculture
▪ Native grasses are replaced with species specialized for
agriculture
▪ Native animals have been replaced by herds of grazing
cattle and sheep.
 This greatly decreases biodiversity
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Humans and desertification
 Caused by
▪ Livestock overgrazing
▪ Poor farming practices
 Process
▪ Without plants, wind erodes topsoil.
▪ Recall: plant roots act as binding agent for soil.
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Midwestern United States in 1930s
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People from all over the world are dependent
on plants & animals in their environments.
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We attempt to maintain these resources by
balancing population recruitment and
harvest.
 Recall: sustainable yield.
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Overharvesting can threaten the existence of
populations.
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Threatened:
 Threatened species are vulnerable to
endangerment in the near future.
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Endangered:
 An endangered species is one which has been
categorized as likely to become extinct.
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Extinct:
 Species or populations which no longer exists.