Geography 2412 Class Notes
Chap 8: Agriculture and Food
Agriculture is the most widespread human
transformation of earth. Began evolving about 12K YBP, with domestication of
plants and animals, and increased control over biotic and abiotic
elements of the environment (e.g., plant and animal genetics; management of
water and soil). The food surpluses created by ag technology allowed rapid pop growth, sedentization and urbanization, and specialization of labor
and production/consumption systems.
We’ll look at:
•
agricultural
systems, their evolution and structure, and land uses
•
Environmental
effects of modern agricultural systems
•
Prescriptions for
sustainable systems
•
Food supply
issues (to be taken up in mostly recitation)
Evolution of agricultural systems:
–
Sedentary ag: permanent fields and villages,
The Great irrigation societies, and
other cropping systems in New and
–
Nomadic herding:
movement with animals to take advantage of seasonal grazing resource; movement
is key to collecting low density NPP across ;large
areas, typically grasslands especially well-developed long-distance nomadism on grasslands
of Africa and
–
Shifting cultivation: small plots
cleared from wet tropical forests, take advantage of fresh, but limited,
natural soil fertility, then move on, plot left to re-vegetate.
–
–
Commercial
agriculture: Commercial agriculture came to dominate, especially
Mechanization
Commercial
fertilizers
Hybrids
Pesticides
Large-scale
farms/corporate farms
Food Choices: What do we want of plants
and animals?
High yield: varieties bred and chosen to
yield.
High food value
Good storage characteristics:
This selection process has yielded five main
crops:
Wheat: good
mid-latitude, semi-arid crop, good nutrition.
corn (maize):
rice (good for tropics): well suited to wet tropical
climates, good nutrition.
casava (topical tuber) grows wlel in tropical areas,
can be stored in the grtound, and is pest resistent
potatoes (widespread tuber): another
(see maps 8.4 –
8.7, no map for cassava) Plus, of course, livestock production, that selected
for herding, docile milk, blood and meat-producing livestock. (also, draft power livestock, but less and less use din in
modern, mechanized agriculture). Modern ag system devote much of their
grain production to feeding livestock for meat protein, which critics say is
inefficient system.
Resource Characteristics of the Main Ag
Systems (Table 8.2):
Know Table 8.2.
Main points:
Intensive subsistence: uses multi-cropping, intercropping on relatively
small plots; , high labor inputs, low mechanization, high yield and output,
mostly used by producers themselves (subsistence), but some marketing
Shifting cultivation: small plots, but needs large land area available
over time for shifting sites; variety, w/ intercropping; relatively low labor,
no purchased inputs, no mechanization,. Low yield and
product. Used by producers.
Subsistence herding: needs large areas to move across; low labor, low
inputs, no mech; low yield and total product, mostly
used by producer with some trade.
Travis added in lecture: Commercial
herding (text subsumes under commercial ag but we
separated for discussion of a system widespread in western US: ranching and
grazing of cattle): large land needs; moderate labor input, low mechanization,
low purchase inputs (though more and more veterinary inputs); low yield per
unit area, but in concert with feedlot system that feeds cattle grained
produced by commercial grain farmers, has high total production of meat.
Commercial agriculture: varies in land demands, but should be considered
mostly large scale; low to moderate labor inputs; high purchased inputs
(hybrids, energy, fertilizers and pesticides); high mech;
mostly HIGH yield and high total food product, with almost no use by producers,
all for market.
Seciton 8.8: Ag and Environment
The main negative environmental impacts of
agriculture are all pretty well known, and most have been part of agriculture
since it evolved. They include:
Soil erosion: wind and water can transport soil particles off of
fields when plowing, planting, weeding, etc, disturb soil structure and leave
soil bare, usually after harvest. Wind erosion was key element of the 1930s
"Dust Bowl" in the US Great Plains, as poor cropping practices and
drought combined to create crop failure and soil erosion.
Salinizaiton and waterlogging: Salinization:
irrigated agriculture is practiced especially in arid and semi-arid climates,
so the applied water tends to evaporate and, depending on the source, will
leave behind salts that were originally in solution in the water. This problem
showed up in Tigris-Euphrates irrigation systems thousands of years ago, and
farmers have learned to flood fields to remove those salts (which then become a
pollutant in the runoff water). Waterlogging
occurs when the water applied builds up in the shallow water table and actually
starts to make the soil too wet for crops to thrive. Obviously, the solution to
both problems is to make irrigation more efficient, putting just what the corps
need on land, and not over-watering.
Ground Water Depletion: more and more irrigation now relies on wells, in
Africa, Asia and the
Surface water diversion and contamination:
Runoff from irrigated fields takes
soil particles (sediment), plus pesticide and fertilizer residues into the
surface water system.
Simplification and substitution of
ecosystems: This is a tough problem:
modern commercial ag works
most effectively with monocultures, and farmers try hard to suppress weeds and
other plants that compete with that monoculture. This spills over to ecosystems
near the fields as well. Grassland and wetland habitats in particular have been
reduced and simplified by ag.
Solutions: a more sustainable agriculture
Conservation tillage: strip cropping and contour plowing, terracing,
reduce soil erosion. Stubble mulching and other methods that retain some crop
residue on fallow fields reduce chances for wind and water to erode soil.
Crop rotations: crops in rotation help each other out—some fix more
nitrogen (reducing need for fertilizer) and fight weeds. But commercial ag is focused on mono-cultures for
obvious reasons: the equipment and inputs are all very specialized to a particular
crop (e.g., wheat, not sunflowers) so rotations mean more equipment some of
which sits idle in the rotation. This is a traditional practice that is being
brought back into commercial ag.
In a limited way, sometimes to improve fertility or as part
of Integrated Pest Management.
Conserving water, reducing chemical
inputs: efficiency really helps:
more efficient irrigation systems (drip and trickle) plus organic fertilizers
or even just more precision to use just the right amount of fertilizer.
Integrated pest management: The use of organic pesticides, other insects or
diseases that combat the pest (or target) insect or disease, even plants that
act as decoys and attract pest away from the main crop, are all part of a more
sustainable pest management, or IPM.
Many "new" approaches that can be
more sustainable, including growing a variety of corps that suit the
environment, actually are rather traditional approaches that need to be
harvested from older systems before they are completely lost, including intercropping,
rotations, IPM, and the variety of species and hybrids that are lost in
commercial specialization.
Chap 8: Food Supply and Famine
Food supply: has increased per capita!
Through:.
Famine, malnutrition: 1/6 (1.1 billion) of
population still malnourished. WHY?