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23 Cards in this Set

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  • Back
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What are environmental refugees? What are some causes?
People seeking refuge abroad due to environmental problems at home.
Water scarcity, depleted soils, deforestation, desertification, or environmental calamities.
pg 124
Which biomes are more easily impaired, and take longer to recover?
Tundra, desert, tropical rain forest, and arid grasslands.
pg 125
What are some factors responsible for land degradation?
-Overgrazing of livestock herds
-Faulty agricultural practices
pg 125
What is the biggest factor, and what are some causes of it?
-When livestock managers increase the # of livestock beyond a certain size
-When livestock managers introduce types of grazing animals foreign to a particular plant community.
pg 125
Describe the process of land degradation from overgrazing on land and near water.
The resulting pressures of overgrazing leads to an unraveling of the ecosystem. As plants are eaten and disappear, invader weed species take over. Since these weeds are inferior to native plants in nutritive qualities, the vitality of the herd is affected. The weeds may be trampled and are reduced in coverage, then the soil is exposed to the forces of wind & water, may be worn away, leaving a barren mud flat or rocky hillside, devoid of any plants.
Near water, animals trample & eat vegetation, pollute the water, and damage stream bank stability. Soil erodes, & sedimentation may result in stream beds becoming shallower, warmer, and more turbid, affecting the aquatic life.
pgs 125-126
What is soil erosion?
When the amount of topsoil lost exceeds that of new soil formed, then the layer of topsoil becomes thinner & thinner until it disappears, leaving only the unproductive subsoil or bare rock.
pg 126
What contributes to soil erosion? Give an example.
Poor agricultural practices
-When traditional practices of crop rotation were abandoned in favor of continuous cropping to increase production, erosion greatly increased because the soil surface doesn't have any plant cover during a considerable portion of the year.
-Fall plowing contributes to substantial amounts of erosion by both wind & water during winter & early spring when fields are bare.
-Compaction & crusting of soils, which depletes soil nutrients.
-Salinization or water-logging of soils from irrigation.
pgs 126-130
What is the T-value or "T" of soil?
The amount of organic matter (the topsoil layer)
pg 126
Discuss using chemicals as an approach for areas experiencing soil erosion?
Chemicals can replace nutrients lost through erosion, however they can't substitute the lost organic material necessary for maintaining a porous, healthy soil structure.
pg 126
What is conservation tillage? What are some benefits?
A cultivation practice that involves leaving 30% or more of the soil surface covered with the previous year's crop residue.
-Reduces erosion
-Increases crop yields
pgs 128-129
What are some reasons we cut & burn woodlands? What are some consequences of the ever-increasing pace of this?
Additional farmland, fuel, and building materials.
We have less area of the earth covered by forests & the quality of the remaining woodlands is decreasing.
pg 130
What are frontier forests?
Undisturbed, extensive areas that remain ecologically intact.
pg 131
What does the rate of forest loss also affect?
As it goes up, so do pressures on ecosystems in the form of species loss, soil erosion, even climate change.
pg 131
What is deforestation?
The permanent decline in crown cover of trees to less than 10% of its original extent.
pg 131
Large areas of temperate old-growth forests have been replaced by tree plantations. Discuss the pros & cons.
-Can reduce erosion.
-Can regenerate degraded soils.
-Often contain only 1 species so they are biologically less diverse.
pg 134
What is the largest cause of deforestation? What about in poor countries?
Population growth & its demands....but really:
The clearing of land for agriculture.
The gathering of wood for fuel.
pgs 134, 138
What are some consequences of deforestation?
(Especially in semiarid regions), the land is left bare, exposed to erosion. The productive capacity of the land rapidly decreases but also severe flooding can occur.
-Also, as the supply of fuelwood decreases, people are looking for other things to burn (leaves, grass, etc), further robbing the soil of natural fertilizers.
-Excessive erosion rates decrease the soil's water-absorbing capacity, increasing the amount of flooding & transforming the land into desert-like conditions, or producing climate change.
pgs 134, 136
Discuss commercial lumbering...its causes? its consequences?
Done to supply the increasing demands of industrial nations for furniture, plywood, and paper pulp.
Causes extensive soil damage & deforestation. Also, where there are indigenous forest people, their livelihood may be harmed, further increasing their impoverishment.
pg 135
How does cattle ranching contribute to deforestation?
When tropical soils wear out, ranchers move on, burning and cutting down trees in the next area.
pg 136
How does soybean production contribute to deforestation?
Clearing more acres for planting.
pg 136
What is desertification? Where is it most likely to happen?
Land degradation in arid, semiarid, and dry sub-humid areas, resulting from various factors including climatic variations & human activities.
Around water holes when nearby pastures are heavily grazes & trampled, and around towns when people denude adjacent lands in search of fuelwood.
pg 139
What are some causes?
(Usually) climatic fluctuations & abusive land-use practices
Also population pressures
pg 139
What are wetlands?
Ecosystems characterized by soils that are inundated or water-saturated for at least part of the year, and have water-loving plants.
pg 140