Land and Food Resources I

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Land and Food Resources I

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Potential Test Questions

• What five ecosystem services are provided by
  natural areas. Discuss.
• 2. Discuss the tragedy of the commons, the ways
  in which we have commons in the United States,
  and solutions to the tragedy.
• 3. How can overgrazing affect desertification.
  (Make sure to explain why grasslands can tolerate
  grazing, how overgrazing effects grasslands, and
  what desertification is).

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Potential Test Questions
4. Discuss tropical deforestation and its causes.
Explain swidden agriculture in your
discussion. 5. What are the BLM and USFS? What
policies have they had in place that are harmful
to U.S. ecosystems. Explain.
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Ecosystem Services of Natural Areas

• Wildlife habitat (protect species)
• Flood and erosion control
• Soil formation/maintenance
• Groundwater recharge
• Recycle wastes (nutrient cycles) and break down
  pollutants

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Pasture and Open Rangeland
Predominantly grasses with a fibrous root system.
Rangelands occupy about 26 of the worlds land
surface.
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Pasture and Open Rangeland
There is twice as much permanent grazing land as
area given to agricultural crops in the world.
Much of the western Great Plains and the Prairie
provinces of Canada fall in this category.
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Pasture and Open Rangeland
Carefully managed, grazing can be sustained in
grasslands (with the loss of a few
grazing-intolerant plant species), because most
species are tolerant of being grazed.
For the U.S., rangeland/prairies have more
species of plants, and more threatened species of
plants, than any other biome type.
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Pasture and Open Rangeland
Benefits of grazing include Hooves create
seed-to-soil contact Natural grazers break soil
crusts that keep seeds from growing Grazers
trample standing vegetation into mulch Grazers
act like living compost piles, turning vegetation
into high-quality fertilizer By pruning stale
growth, they keep forage plants at peak
production
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Pasture and Open Rangeland
Effects of overgrazing grazing include Compacti
ng soil thus preventing seeds from germinating
and water from seeping into soil. Overfeeding
on plants not allowing them time to recover and
adequately root.
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Overgrazing
Overgrazing is when plants are consumed such that
the plant community does not quickly recover.
1/3rd of the worlds range is severely degraded
by overgrazing, making it the largest cause of
soil degradation.
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Overgrazing
The first symptom of overgrazing is the loss of
palatable species of herbs and grasses.
Continued overgrazing compacts the soil, strips
the ground bare, and leads to erosion.
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Desertification
Continued degradation leads to a fertile land
becoming more desert-like.
Without plants to hold soil moisture, surface
runoff increases, wells dry, the microclimate
becomes inhospitable for plants, and deserts
occur.
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Desertification
In Africa, deserts have increased by 50 million
hectares, and humid or semiarid lands have
decreased by that amount. Is human activity
responsible?
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Remember the Tragedy of the Commons
Any commonly held resource becomes degraded or
destroyed because the narrow self-interests of
individuals tend to outweigh the public interests.
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U.S. Rangelands
Bureau of Land Management (BLM) 200 million
acres U.S. Forest Service (USFS) 50 million
acres 60 of rangeland is privately owned.
55 of public rangelands are in poor condition
(sage, mesquite, cheatgrass, and
cactus). Grazing fees grazing permits on BLM or
USFS land was 1.35 per animal. It costs them
3.21 per animal to administer grazing. This
equals a loss of of 32 million. Few people hold
most of these permits welfare for rich
cattlemen.
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Forests and Forest Products
The amount of fuel wood consumed by each person
in developing countries is roughly equal to that
used as paper products by each American. Demand
for fuel wood will be twice the available supply
in just 25 years.
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The Rates of Deforestation Are Increasing
Consider Costa Rica, an environmental success
story. Lost 75 of its primary forests in the
last 60 years due to timber harvest, Del-Monte
plantations, cattle grazing (mostly for export).
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Costa Rica (the Green Republic)
Costa Rica contains more biological diversity
than all of North America combined.
Costa Rica encompasses only.03 of the worlds
landmass, but it contains and supports 5-6 of
the entire worlds biodiversity.
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Costa Rica Policies
Costa Rican Government has been a front runner in
conservation policy - 90 of its remaining forest
is protected, and it has the largest percentage
of land dedicated to national parks in the world.
Emphasis has been on sustainability. Along
with a strong conservation policy, the Costa
Rican Government has enacted incentive programs
to promote reforestation projects. These
incentive programs include such things as
residency status and various tax exemptions.
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Causes of Tropical Rainforest Destruction
Commercial Logging tropical forests harvested
for timber. Subsistence agriculture slash and
burn tactics (also called swidden or milpa
agriculture). Cattle ranching After commercial
harvesting or after subsistence agriculture, or
on its own.
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Slash and Burn (Swidden or Milpa Agriculture.

• Farmers clear a small plot (2 acres), burn the
  dried plants to provide a burst of nutrients (and
  ash is basic, increasing the release of minerals
  from clay).
• On field, they practice polyculture (using some
  perennials). Banana/plantain, papayas, cassava
  and sweet potato (root crops), beans (increase
  nitrogen), and maize (plots hold the soil because
  there is a variety of roots).
• In time, the plot is given over to encroaching
  forest because the fertility has decreased, and
  the farm begins in a new area.

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Milpa Agriculture
Depends on land to rotate through. If the farm
remains long term, the productivity of the land
declines. Higher populations are increasing
the pressure on the land and not allowing enough
time for recovery.
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Cattle Ranching
Ranching often introduced after commercial
harvesting or after subsistence agriculture, or
on its own.
Tropical soils are Oxisols and ultisols - soils
that are highly leached and nutrient
poor. Minerals are locked up in the vegetation
if vegetation is lost, minerals are lost. So,
it is hard to go from a pasture back to a forest
again.
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Logging in the U.S.A.
Kinds of cutting

• Clear cutting removal of all wood in a
  compartment.
• Strip cutting harvesting strips within a
  compartment on a rotational basis.
• Selective cutting planned removal of individual
  trees or small groups of trees within a forest
  stand.

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Clear Cutting
Cost effective because large machines can be
used, making it easier to fell, trim and skid
logs. But 1. Eliminates almost all habitat
2. Increases soil erosion greatly 3. Favors
early succession tree species and deer (game)
4. Increases soil and water temperatures.
Sometimes seed trees or nurse plants left
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Clear Cutting
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Clear Cutting
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Strip Cutting
1. Reduces erosion compared to clear
cutting 2. Provides seed sources for
establishment,
But strip cutting still favors early successional
tree species and edge animals.
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Selective Cutting

• Favors the more shade-tolerant trees like red
  spruce, sugar maple and hemlock because the shade
  is not broken.
• 2. Provides a continuing supply of food and cover
  for wildlife throughout the life of the forest.
• 3. An uneven-aged stand is particularly favorable
  to birds.

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Selective Cutting
Need intensive skilled management to prevent
degradation of the remaining stand (genetically
superior trees are likely to be
removed). Management and skidding costs are
likely to be higher, road construction and
maintenance must be more extensive.
High grading - taking out the few choice trees
for profit and leaving the rest. Lowest impact,
but requires other skidding techniques.