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Env Sc Units 6, 7, 8
Terms in this set (74)
Why should we care about the earth's water supply?
- Produce food and electricity
- Dilute wastes and pollutants
- Water sources are unequally distributed
- Water sources are often polluted
- Low costs --> inefficient use
- Water shortages
What are five unique properties of water?
1. Hydrogen bonds
2. Surface tension
3. Unusually high boiling point
4. Universal solvent
5. Density of ice is lower than liquid water
What is the water cycle (hydrologic cycle) and why is it important?
The planet's fixed water cycle that is constantly recycled and purified
The conversion of liquid to vapor
The evaporation of water from plant leaves
The return of water from the atmosphere to the earth's surface
Water flowing off the land into bodies of surface water
Precipitation that does not infiltrate the ground or return to the atmosphere by evaporation or transpiration. Found in streams, rivers, lakes, and wetlands.
Water that sinks into the soil and is stored in slowly flowing and slowly renewed underground reservoirs
How is water purified?
How much of the earth's surface is covered by oceans?
What percentage of earth's water supply is available to us as useable freshwater? Where is most of this available freshwater stored?
0.024% and it is found in aquifers
Explain how aquifers are recharged and why they can be depleted.
They are recharged by precipitation sinking downward through exposed soil, or from the side by water seeping through the soil from streams and they can be depleted when we pump out water faster than the aquifers can be recharged
What is drought?
Extended period of below average precipitation and high evaporation
How is the freshwater that is used in the United States divided among agricultural, industrial, and home uses?
Agricultural - 37%
Industrial - 40%
Home uses - 13%
What are three factors in our increasing use of freshwater?
1. Population growth
2. Rising levels in consumption
3. Most countries and communities don't put a high priority on water conservation
A variety of strategies for getting the most use out any amount of water that we withdraw from the water cycle.
A measure of the water used to produce and deliver food and consumer products
An estimate of how much water it takes to meet annual water needs
Per capita water footprint
A measure of how much water it takes to meet the needs of an average person each year
A barrier across a river that blocks its flow
Artificial lake behind the dam
What are the major ways in which human activities have altered the hydrologic cycle?
- Transfer large volumes across land
What is reliable surface runoff and how much of it do humans use for drinking water and other purposes?
- The portion of the planet's total annual surface runoff from precipitation that is available for human use
- About one-third
List three problems that have resulted largely from the damming of rivers around the world.
1. It can reduce the downstream flow of water to a trickle and keep a river from reaching the ocean.
2. Land is flooded to create the large reservoirs behind dams.
3. As the flow of the river slows in the large reservoirs, it drops great amounts of suspended silt.
Why were the Colorado River dams and reservoirs were built?
- Provide low cost water
- Flood control
- Encourage settlement in this region
What are problems caused by the damming of the Colorado River?
- A modest flow of water
- Excessive withdrawal
- Prolonged drought
- Water rarely makes it to the sea
- Evaporation and leakage from reservoirs
What two major factors contributed to the problems with the damming of the Colorado River?
1. The river is in a very dry area
2. The government-built dams and reservoirs amount to a huge government subsidy
What three things are examples of how human activities contributed to the degradation of Lake Chad's ecosystem?
1. Rapid population growth in the four countries that surround the lake
2. Climate change
3. Inefficient irrigation
What are three harmful effects of overpumping aquifers?
1. It can disrupt urban and agricultural systems that depend on groundwater
2. It can disrupt natural ecosystems
3. It can sometimes cause the porous rock in aquifers to collapse
What are the benefits and problems resulting from the pumping of water from the Ogallala aquifer.
- Provides drinking water for people, animals and crops
- A large portion helps make ethanol fuel for motor vehicles
- Crops are no longer irrigated
- The water has been depleted even more
What are the major pros and cons of building more large dam-and-reservoir systems?
- Provide water for drinking, irrigation, and other uses
- Produce electricity
- Can control flooding
- Reservoirs flood forests and croplands
- Reservoirs displace people
- Can disrupt aquatic ecosystems
What are the major pros and cons of relying more on groundwater to expand water supplies?
- Groundwater is found almost everywhere
- Available year-round in most cases
- Renewable if not overpumped
- Land subsidence
- Saltwater intrusion into coastal freshwater aquifers
What are the major pros and cons of transferring water from water-rich areas to drier areas?
- Supply irrigation water to produce more food
- Provide water supplies for urban areas and indistry
- Discourage water conservation where water prices are low
- Can harm people and economies in areas where water is withdrawn
- Can disrupt aquatic systems in areas where water is withdrawn
Name and describe the two major types of desalination technology.
1. Distillation - saltwater is heated until it evaporates and leaves behind salts in solid form or in a salt-laden liquid. The water vapor is then cooled and condensed as freshwater.
2. Reverse osmosis/microfiltration - salt is removed by using high pressure to force saltwater through a membrane filter.
What are three major problems associated with desalination?
2. Pumping water and using chemicals can harm organisms
3. Produces salty wastewater which can threaten aquatic life and contaminate surface water
The earth's great variety of species and ecosystems.
Why should we care about species extinction hastened by human activities?
- The earth's biodiversity provides us with resources, ecological services, and because nature is beautiful and interesting.
- We are degrading ecosystems that are potential sites for the emergence of new species.
- Many people share the ethical view that wild species have a right to exist.
A group of organisms that have similar genetic and other characteristics that distinguish them from other groups of organisms.
Define extinction and describe two methods that scientist us to study historical evidence of extinction.
- Extinction - process by which a species ceases to exist on the earth.
- Scientists study extinction by analyzing fossils, and mineralized replicas of living matter found in some rocks.
Rate of extinction
Estimated number of species, or the percentage of known species, that go extinct during a certain time period, typically a year.
Background extinction rate
Historic extinction rate that existed before humans dominated the planet.
Scientific estimate of background extinction rate
1 out of a million species per year
Sharp rise in the extinction rate
Why do experts think the rate of extinction has risen steadily and will rise even more sharply during this century?
Because of the projected growth of the human population and the projected increase in rates of resource use per person during this century.
How do current and projected rates of extinction compare with the background rate?
The annual rate of extinction is now about 1,000 times the background rate that existed before modern humans appeared on earth. During this century, the extinction rate is likely to rise to at least 10,000 times the background rate.
A species whose total population is so small that it could soon become extinct.
Still exists in numbers high enough to survive in the short term, but because its populations are declining, it is likely to become endangered in the near future.
What are factors that can increase a species' chances of becoming extinct?
- Limited habitat area
- Extensive range, but modified by humans
- Island dwellers (limited immigration; isolated evolution free from competitors, predators and diseases and thus fewer defenses when introduced)
- Low reproductive rates
- Large (easily hunted)
List the six major causes of the endangerment of wild species.
- Habitat destruction, degradation and fragmentation
- Invasive species
- Population growth and rising rates of resource use per person
- Climate change
Eliminating animals' habitats
Habitat is damaged in such a way that organisms can no longer use it
A large, intact area of habitat is partially destroyed and divided into smaller, isolated patches, typically by roads, crop fields, logging, and urban development.
How can invasive species threaten native species and ecosystems in which they live?
- Crowd out native populations
- Take over an ecosystem where there are few or no natural predators
Why is human population growth a factor in the rising rate of extinction?
More people = more habitats and resources = less habitats and resources for organisms
What are ways in which climate change is likely to affect the rate of species extinction?
- Carbon dioxide emissions
- Flooding and droughts
How does the U.S. government protect habitat?
- 548 partially protected National Wildlife Refuges
- Passing laws to protect areas where endangered species live
Areas of land that are especially rich in highly endangered plant and animal species found nowhere else on the earth.
What are the pros and cons of the US Endangered Species Act?
- Protects species and their habitats
- Has successfully stabilized populations of 99% of species listed
- Helps protect species endangered by smuggling and illegal trade
- Species listed only when they are seriously endangered
- Listing and habitat protection take a long time
- Landowners cannot develop their protected land
Why is prevention the best approach to dealing with invasive species?
Because when a nonnative species is released into an ecosystem where conditions are favorable for its survival, it becomes next to impossible to reverse the impacts.
What are three ways to help prevent the spread of potentially harmful invasive species?
1. Research what makes invaders successful and ecosystems susceptible.
2. Conduct surveys to monitor invasions and model how they are likely to spread.
3. Strengthen and increase inspections of imported goods.
The removal of large expanses of forest for agriculture, settlements, mining, firewood, or other uses.
Why is tropical deforestation a special concern to many scientists?
- Reducing the earth's biodiversity by destroying the habitats of many of the plant and animal species found in these forests.
- Reducing the amount of vegetation that removes carbon dioxide from the atmosphere.
Explain how large-scale cutting of tropical forests can change the nature of these forests.
- Dehydrating the forest's soil
- Degrading the vital ecosystem they provide
How do new forest roads typically lead to forest degradation?
- Erosion and sedimentation
- Invasion by insects
- Diseases and non-native species
- Mining farming
- OHV use and other disturbances
How can clear-cutting harm a forest?
- Leads to greater runoff and erosion
- Removes all or most trees
What are two underlying causes of tropical forest degradation?
- Population growth and poverty
- Cutting/burning trees and building settlements
- Timber harvesting, cattle grazing, mining plantation cropping
Loss of soil moisture to the point where the land loses some or all of its productivity, or ability to produce vegetation.
What effect will projected climate change have on desertification?
It will expand desertification in dry areas of the world and could lead to a decline in food production and water shortages
What are three suggestions by researchers for how to use forests more sustainably?
- Loggers rely more on selective cutting and strip cutting
- Halt to any clear-cutting on steep slopes where erosion can be highly destructive
- Reduction of road construction in uncut forest areas
What are two underlying causes of deforestation?
- Forests undervalued
What are two ways in which we could reduce the demand for harvested trees?
- Reduce demand of wood
- Choose building materials made of recycled plastic that are fashioned to resemble wood lumber
Buffer zone concept
Drawing a line around an inner core of an area, then drawing more lines farther out from the center to create buffer zones around the inner core. In these buffer zones, local people can use resources, ideally in sustainable ways, without harming the inner core.
Why do some biologists believe biodiversity hotspots to be the best conservation strategy?
It would protect the largest number of endangered species per unit of land area protected
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