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ANEA 1102

Alam Sekitar dan Manusia

Kuliah 24

Ekosistem sebagai Sumber

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I. Why Do We Want to Use Resources Sustainably?

A. Resources provided by ecosystems sustain life.

B. There are a limited number of resources in an

ecosystem.

C. Ecosystems are limited in their ability to cycle

resources.

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II. Ecosystems and Their Goods and Services

A. The Goods (Resources)

a. Wood: buildings, paper, furniture

b. Food: meat, grains, vegetables, fruits, oils

c. Minerals: phosphorus and nitrogen (for farming),copper (electrical wire), aluminum (cans, cars), iron,

silver, gold, platinum, titanium

d. Fuel: wood, petroleum, dung, alcohol

e. Clothing: cotton, rayon, nylon, polyester, fur, leatherf. Plastics: petroleum, trees (rayon)

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B. The Services

1. Maintenance of Hydrologic Cycle: water infiltratessoil and is absorbed by plants.

Water evaporates from soil or evapotranspires from

plants. Evaporated water condenses in the atmosphereand falls to the earth as precipitation. Flooding is

prevented by the functioning of dynamic ecosystems

because precipitation is absorbed by the ecosystem and

slowly released.

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B. The Services

2. Modification of Climate: Water absorbs aconsiderable amount of energy from the sun as itevaporates. This energy is released when the watercondenses. Heat is moved around the planet in water.

3. Erosion Control and Soil Building: Plant and detrituscontrol erosion by absorbing the impact of precipitation, and make a greater surface area availablefor the absorption of water. Plants, animals, andmicroorganisms found in terrestrial ecosystems createsoil.

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4. Maintenance of Oxygen and NitrogenCycles: Photosynthesis releases oxygen. Nitrogen fixingmicroorganisms in the soil maintain soil fertility.

5. Waste Treatment: Water is a universal solvent. Manywater-soluble pollutants (sediments, excess nutrients) areremoved from the water in wetlands.

6. Transformation of Toxic Chemicals: Microorganismstransform many toxic chemicals, both organic and inorganic,into harmless products. [The opposite is true also. TheMinamata Bay disaster resulted when organic mercury wasreleased in industrial effluent and transformed by

microorganisms into organic mercury].

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7. Pest Management: Predators for the organisms we

consider pests exist. When predators are maintained,

pest management is provided by ecosystems.

8. Carbon Storage and Maintenance of the Carbon

Cycle: Carbon is cycled through the atmosphere,

biomass, and soil. The biomass of the forest contains500 billion metric tons of carbon more than is found in

the atmosphere. Even more carbon is found in the

organic matter of soil

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Fig. 12.4 Worth more than $100,000 a year for just one acre, these services

are lost when wetlands are bulkheaded and converted for vacation homes.

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B. Monetary Benefit of Ecosystems

1. A 1997 study estimated that the world's ecosystemsprovide $33 trillion worth of goods and services per

year.

2. One acre of wetlands does the equivalent of $100,000 per year of water purification and fish

propagation services.

3. We undervalue the services of ecosystems because

their services are provided free of charge.

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4. We notice the services when they are gone:

a. The eutrophication of Chesapeake Bay is a result of wetland loss and an increase in the added nutrients

within its watershed.

b. Flooding in Bangladesh is a result of deforestation inIndia; consequently, the monsoons cause great loss of

human life and devastation of crops.

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III. Patterns of Use of Natural Ecosystems

A. Consumptive versus Productive Use

1. In consumptive "people harvest natural resources in

order to provide for their needs for food, shelter, tools,

fuel and clothing."

2. "Productive user refers to the exploitation of

ecosystem resources for economic gain."

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B. "A natural ecosystem will receive protection only if the

value society assigns to its natural function is higher than

the value the society assigns to exploiting its natural

resources."

1. This is a conflict between individual gain from and

societal loss of the goods and services provided by anecosystem.

2. This conflict also occurs between those who use public

land for private gain (ranchers, loggers, miners, etc.) andthose who want the ecosystem conserved in a way that

produces the greatest good for the largest number of

organisms (humans included.)12

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C. Maximum Sustained Yield (MSY): "The highest

possible rate of use that the system can match with its

own rate of replacement or maintenance."

1. How does MSY works?

At low population size the rate of population growth will

increase because the environmental resistance factorsare low.

At low population size, the rate of population growth

will increase until environmental resistance factors

begin to limit population size. This point is MSY.As the population size becomes larger than the MSY, the

rate of growth population decreases and the number of

individuals that can be extracted does not increase.13

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2. MSY is the point where the highest rate of recruitment

can occur. The highest rate of harvesting can occur at the

point where the highest recruitment occurs.

3. The difficulty with MSY is determining it. We typically do

not know the point at which the highest recruitment

occurs.

4. For example, North Sea cod were overfished because we

do not understand MSY.

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Fig. 12.8 Maximum sustainable yield occurs not at the maximum population

level, but rather at a lower, optimal population level.

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D. Tragedy of the Commons: When a resource is held in

common or by no one, it is known as a commons.

1. Grasslands (grazing, mining)

2. Coastal and open ocean (fishing, mining)

3. Groundwater (urban and agricultural use)

4. Woodlands and forests (logging, mining)

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IV. Ecosystems Under Pressure

A. Forests and Woodlands

1. Threat: Total Removal

2. Consequences: loss of biomass, reduced productivity,

reduced biodiversity, soil erosion, changed hydrologiccycle, loss of carbon dioxide sink

B. Ocean Ecosystems

1. Threat: Overexploitation

2. Consequences: Reduced productivity and reduced

biodiversity 17

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C. Grasslands

1. Threat: Total Removal

2. Consequences: Loss of biomass, reduction in

biodiversity, loss of carbon dioxide sink, changed

hydrologic cycle, and soil erosion

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Fig. 12.10 In the U.S. only 17% of wood is used for fuel.

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Fig. 12.13 This figure shows cod landings from Georges Bank, 1982-96.

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FiFig. 12.14 This method of harvesting groundfish has been compared to

clear-cutting forests because of degradation of the bottom.g. 12.13 This figureshows cod landings from Georges Bank, 1982-96.

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V. Solutions

A. Private Ownership of Land

B. Regulation of Commerce (national parks and wildlife

refuges, etc.)

C. Land Trusts

D. Preservation

E. Conservation

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VI. When We Have Gone Too Far Restoration Ecology

A. Restoration Ecology: Repairs a damaged ecosystemso that normal functioning returns and the native

flora and fauna are again present.

B. Difficulties

1. Lack of Knowledge

2. Disturbed Soils

3. Accumulated Pollutants

4. Exotic Species Have Achieved Dominance

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C. Examples:

1. Prairie Restoration at Fermi Labs, Illinois

2. Wetlands Restoration at Stone Lake on the

Consumnes River, California

3. Riparian Habitat Restoration by the Nature

Conservancy along the Sacramento River, California

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VII. Public and Private Land in the United States

A. Federal, State and Local Land

1. What do they provide us?

2. Who benefits from them?

3. Why do we have them?

B. Private Land

1. Land Trusts

2. Individual Ownes

3. Corporate Owners26

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Fig. 12.16 Because the East and Midwest were settled first, federally-owned

lands are concentrated in the West and Alaska.

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Fig. 12.17 The National Park is the center of a much larger ecosystem

receiving attention from the Greater Yellowstone Coalition

anea1102_kuliah_25

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