PowerPoint-PräsentationEnvironmental Science
Doni Prakasa Eka Putra
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Changing Role of Human Impact
As human population grew, and tools became more advanced, the impact a single human could have on surroundings increased.
Environmental modifications allowed larger, dense human populations to arise.
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Historical Basis of Pollution
Pollution—Anything released into the environment that affects an organism’s survival and reproduction.
Two primary factors affect the amount of damage done by pollution:
Size of the population
Level of technological development
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When the human population was small, waste products were generally biodegradable.
Human-caused pollution is produced when waste is generated faster than it can be degraded, especially as people began to congregate and establish cities.
Throughout history, humans fought ecosystem degradation with technology.
Short-term solutions.
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Renewable and Nonrenewable Resources
Natural Resources—Structures and processes humans can use, but not create.
Renewable—Can be formed or regenerated by natural processes.
Soil, Vegetation, Wildlife
Non-Renewable—Not replaced by natural processes, or, rate of replacement is ineffective.
Minerals, Fossil fuels
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Economic—Monetary costs necessary to exploit the resource.
Energy—Energy expended exploiting the resource.
Environmental—Environmental effect of resource exploitation (often deferred).
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Impact of Agriculture on Natural Ecosystems
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Manipulative experiments
Yield the strongest evidence But, lots of things can’t be manipulated
Natural or correlational tests show real-world complexity
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Because of increasing human population growth, forested areas are under increasing pressure to provide wood products and agricultural land.
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Purchasing or leasing land.
Building roads
Harvesting
Transportation
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Modern forest management practices involve a compromise that allows economic exploitation while maintaining some of the environmental values of the forest.
Forested areas effectively reduce erosion.
Loss of soil (nutrients) reduces soil fertility.
Road building in forests increases erosion.
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Environmental Implication of Harvesting
Clear Cutting—Removal of all trees in an area. Economical but increases erosion, especially on steep slopes.
Patch-Work Clear Cutting—Clear cutting in small, unconnected patches; preserves biodiversity.
Selective Harvesting—Single-tree harvesting. Not as economical, but reduces ecosystem damage.
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Plantation Forestry
Many lumber companies maintain forest plantations as crops and manage them in the same way farmers manage crops.
Plant single species, even-aged forests of fast growing hybrid trees.
Competing species are controlled by fire and insects controlled by spraying.
Mature rate as low as 20 years (vs. 100).
Quality of lumber reduced.
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Tropical forests have greater species diversity than any other ecosystem.
Not easy to regenerate after logging due to poor soil characteristics.
Deforestation Concerns
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Managing Rangeland Ecosystems
Rangelands—Lands too dry to support crops, but received enough precipitation to support grasses and drought-resistant shrubs.
Wildlife are usually introduced species.
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Environmental Costs of Utilizing Rangelands
Management techniques and selective grazing of animals may lead to the elimination of non-preferred species.
Important to regulate number of livestock on rangelands, especially in dry areas.
Desertification—Process of converting arid and semi-arid land to desert.
Over-grazing
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Many areas in the world have had minimal human impact.
Some are remote and may have harsh environmental conditions.
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Environmental costs related to utilizing marine ecosystems fall into two categories:
Over-fishing
UN estimates 70% of world’s marine fisheries are over-exploited.
Capacity should be reduced by 30%.
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Sunlight penetration—shallow—warm
Nutrient deposition from land
Wind/wave action stirs nutrients
Trawls—nets dragged along bottom.
Large by-catch
Disturbs seafloor
Environmental Costs Associated with Utilizing Freshwater Ecosystems
Two primary human alterations:
Exotic Species—Introduced species
Many North American freshwater fisheries are primarily managed for sport fishery.
Fisheries managers must balance:
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Aquaculture
Fish farming is becoming increasingly important as a source of fish production.
Currently, about 60% of all aquaculture production is from freshwater systems.
Problems
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Animals have highly specific habitat requirements that change throughout the year.
Once habitat requirements are understood, steps can be taken to alter habitat and improve species success.
Fire to eliminate poor habitats.
Kirtland Warblers—Jack Pine stands.
Encourage growth of certain plant species.
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Hunting regulation is crucial.
Seasons usually occur in the fall to take advantage of surplus animals.
When populations get too small, artificial introductions can be implemented.
Native species for augmentation.
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Predator and Competitor Control
At one time it was believed populations of game species could be increased if predators were controlled.
Still used in some situations.
But, in many cases, human modification of habitat has a greater impact than natural predation.
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Migratory Waterfowl Management
North in spring to reproduce.
South in fall to escape cold temperatures.
International agreements necessary to maintain appropriate habitat.
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Extinction and Loss of Biodiversity
Small, dispersed populations are more prone to extinction.
Successful breeding more difficult.
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Wherever humans have become the dominant organisms, extinctions have occurred.
Food
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Useful to Humans:
Medical—Less than 1% of tropical rainforest plant species have been tested for pharmaceutical use.
Food Resources
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Extinction Prevention
Endangered—Very low populations, could become extinct in very near future.
Threatened—Still exist in large numbers in current range, but are declining in most areas.
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Less-developed and developing countries have both highest population growth and the majority of the world’s species.
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