Forests
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Forests: Types, Benefits, Cover, Loss, and Importance for Biodiversity, Slides of Geology
Information about forests, their types, benefits, and the extent of forest cover and loss. It highlights the importance of forests for biodiversity and discusses the impact of human activities on forests. The document also includes details about tropical rainforests, terry erwin's experiment, and reasons for the high species richness in the tropics.
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2012/2013
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Forests
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Forests – Tropical, Temperate, Boreal
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Forest Cover and Loss
- 8000 years ago about 50% of the earth was forest.
Today about 30% of the planet is forested (FAO,
- That’s a total loss of about 40%. Primary (“virgin”)
forests are 65% gone!
- Many of today’s forests are modified by humans
(second- or third-growth).
Source: FAO, 2005.Docsity.com
Forest Cover and Loss
- Primary forests account for 36% of forest area - but
6 million hectares are lost or modified each year
- Wide variation in number of native tree species:
from 3 in Iceland to 7,780 in Brazil!
Source: FAO, 2005. Docsity.com
Tropical Humid Climates
- Between 3 and 5% of Earth’s total surface (found between 20 ºN to 20 ºS)
- Consistently warm (all months > 18ºC/64.4 ºF) – Never hot; Never cold.
- High rainfall all year!
- Daily temp range exceeds annual temp range!
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Tropical Rainforest
- Region/Distribution: Within 10-20 degrees of Equator
- Vegetation : Three-tiered; Thousands of
species, highest density of species, tall trees,
many canopy layers, evergreen, broadleaf
trees, epiphytes, lianas (vines), climbers,
stranglers, ferns
- Fauna: More species than all other biomes combined, colorful insects, amphibians, reptiles, and birds, few large animals, high density of biomass and incredible species diversity
- Other: Among most threatened biomes
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● 1 Panamanian tree species: 1100 species of beetles
collected!
● Of these, 160 believed to live only in the canopy of that
species of tree
● There are 50,000 known tropical tree species
● How many beetle species are there in all tropical tree
species?
● How many insect species?
Erwin's results and extrapolation
Details of Erwin's experiment from: Biodiversity and Conservation: A Hypertext Book by Peter J. Bryant [http://darwin.bio.uci.edu/~sustain/bio65/Titlpage.htm] Docsity.com
W hy are there so m any species in the tropics?
- Stability
- Energy
- Area
- Time Since Disturbance (glaciations)
- 'Evolutionary Speed' (Energy,Temperature)
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© the regents of the University of Michigan
Deforestation in the United States
was massive in scale, but is now essentially complete. In fact, today’s maps show that some areas are recovering. Massachusetts now is 75% forested. At the time of Henry D. Thoreau’s writings it was 25% forested!
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Forest Change by Region
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Why should we care?
- Where did your breakfast originate?
- 200 food crops derived from 250,000 species of flowering plants; 80% of food supply is from only 20 plants.
- Many crops (wheat, cotton, tobacco, sugar cane, bananas, potatoes, safflower, corn) are hybrids from wild and domesticated plant species.
- Many of these crops originate in the tropics, along with:
- Oranges (SE Asian tropics); coffee (Ethopian highlands), chocolate (S. American tropics), ...
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Agents Links to Deforestation
slash-and-burn farmers - clear forest to grow subsistence and cash crops
commercial farmers
- clear the forest to plant commercial cash crops, sometimes displace slash-and-burn farmers who then move to the forest
cattle ranchers
- clear the forest to plant pasture, sometimes displace slash-and-burn farmers who then move to the forest
livestock herders
- intensification of herding activities can lead to deforestation
loggers
- remove commercial timber, logging roads provide access to other land users
commercial tree planters
- clear mostly forest fallow or previously logged forests to establish plantations to supply fibre to the pulp and paper industry
firewood collectors
- intensification of firewood collection can lead to deforestation
mining and petroleum industrialists
- roads and seismic lines provide access to other land users, localized deforestation related to their operations
land settlement planners
- relocation of people into forested areas as well assettlement projects displacing local people who then move to the forest
infrastructure developers
- new access for other land users from road and highway construction through forested areas, flooding by hydroelectric dams
Why Remove the Forests?
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Timber is extracted from public and
private land
- Timber is extracted by private companies, even on public land
- Forest Service employees plan and manage timber sales and build roads
- The companies log and sell the timber for profit
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Harvesting forests
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