3.  Forests have been destroyed for centuries  Cleared for agriculture and farming.  Building materials  Fire wood  Living space

4.  In 1950, over 10% of Earth’s land was covered by rain forests.  Currently only 6%, and decreasing.

5.  Sustained yield  A balance between net growth and harvest.  Maximum sustained yield  The level of consumption at which the population declines if exceeded.

6.  Most plant and animal biodiversity on Earth.  As a result of deforestation, animals’ habitats are also destroyed.

7.  succession can take several hundred years to restore a climax community.  The required time for succession to reach climax community takes longer when biodiversity is greater.  Succession may not be possible if large stands are destroyed

9.  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.

11. 

12.  Replanting efforts with Monocultures  Low tree biodiversity = few animal niches = low animal biodiversity  Low biodiversity ▪ Ecosystem is more fragile.

14.  Have not been logged as extensively as other forest types  But, the growing need for wood has led to increased harvesting  Countries in need of money are selling large stretches of forests to domestic and foreign companies.

17.  Recall:  Little Biodiversity.  Short growing season.

18.  Very fragile  Low biodiversity = simple food webs  Short growing season = slow succession

19.  Until recently, the tundra was relatively undisturbed by humans  Our growing need for oil increases human activity in tundra ecosystems

20.  Global climate change  The largest warming trends are in the tundra.  Warming ▪ Thaws the permafrost.

22.  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 Human agriculture ▪ Native grasses are replaced with species specialized for agriculture ▪ Native animals have been replaced by herds of grazing cattle and sheep.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

24.  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.

25.  Midwestern United States in 1930s

26.  People from all over the world are dependent on plants & animals in their environments.

27.  We attempt to maintain these resources by balancing population recruitment and harvest.  Recall: sustainable yield.  Overharvesting can threaten the existence of populations.

28.  Threatened:  Threatened species are vulnerable to endangerment in the near future.  Endangered:  An endangered species is one which has been categorized as likely to become extinct.  Extinct:  Species or populations which no longer exists.