Transcript Understanding Our Environment

Chapter 09
Lecture Outline*
William P. Cunningham
University of Minnesota
Mary Ann Cunningham
Vassar College
*See PowerPoint Image Slides for all
figures and tables pre-inserted into
PowerPoint without notes.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1
Food and Agriculture
2
Outline
•
•
•
•
•
•
•
Food and Nutrition
Key Food Sources
Farm Policy
Soil
 Ways We Use and Abuse Soil
Agricultural Resources
 Water
 Fertilizer
 Energy
Genetic Engineering
Sustainable Agriculture
3
Food and Nutrition
•
World food supplies have more than kept up with
human population growth over the past two
centuries.
 During the past 40 years, population growth has
averaged 1.7% per year, while food production
increased an average 2.2%.
4
Chronic Hunger and Food Security
•
In 1960, 60% of the population of developing
countries was considered chronically
undernourished.
 Fallen to less than 14% today
•
Poverty is the greatest threat to food security (Ability
to obtain sufficient food on a daily basis).
 Operates on multiple levels
 Recognizing role of women in food production is
an important step forward.
5
Hunger Around the World
6
Acute Food Shortages
•
Famines are characterized by large-scale food
shortages, massive starvation, social disruption, and
economic chaos.
 Mass migrations often occur because productive
capacity has been sacrificed.
 Environmental conditions are immediate trigger,
but armed conflict and political oppression are
underlying causes.
7
Famines
•
Aid policies of rich countries often serve to
distribute surplus commodities and produce feeling
of generosity BUT
 Herding people into feeding camps is
counterproductive. Many die on the way, others
die in epidemics or from violence, and they
cannot replant their crops when weather returns
to normal.
8
We Need the Right Kinds of Food
•
Malnourishment - nutritional imbalance caused by a
lack of specific dietary components or an inability to
absorb or utilize essential nutrients
 3 billion people suffer from vitamin, mineral or
protein deficiency.
 Results in illness, reduced mental capacity,
developmental abnormality, stunted growth,
death
9
Nutritional Problems
•
Iron deficiency is the most common dietary
imbalance in the world.
 Leads to anemia, insufficient hemoglobin in
the blood
- Increases risk of death from hemorrhage in
childbirth and affects development
 Red meat, eggs, legumes, and green
vegetables are all good sources of iron.
10
Nutritional Problems
•
Lack of iodine leads to goiter as well as stunted
growth and reduced mental capacity.
•
Lack of vitamin A affects as many as 140 million
children and 350,000 go blind each year.
11
12
Protein Deficiency Diseases
•
•
Kwashiorkor - occurs mainly in children whose diet
lacks high-quality protein
 Reddish-orange hair, bloated stomach
Marasmus - “To Waste Away” - caused by a diet
low in protein and calories
 Very thin, shriveled
13
14
Key Food Sources
•
Three crops deliver majority of world’s nutrients:
 Wheat, Rice and Corn
- Potatoes, barley, oats and rye are staples in
cool, moist climates.
- Cassava, sweet potatoes, and other roots and
tubers are staples in warm, wet climates.
15
Overnutrition
•
•
•
•
People in rich countries eat too much meat, salt,
sugar and saturated fat and not enough fiber,
vitamins, and minerals.
On average, we consume 33% more calories
than we need.
 62% of Americans are overweight.
Obesity is spreading around the world as other
people adopt Western lifestyles.
New dietary pyramids recently published
16
Dietary Pyramids
17
Meat and Dairy
•
In the past, rich countries consumed the majority of
meat and dairy, however meat consumption in
developing countries is rising.
•
Modern breeding techniques provide cattle
resistant to heat and tropical diseases.
•
But carving pastureland out of tropical forests and
savanna reduces biodiversity and causes conflicts
as landless farm workers are forced into
shantytowns.
18
Meat and Dairy
•
Concentrated animal feeding operations - in North
America animals are fattened on grain in feedlots
 Local air and water pollution caused by
untreated waste
 Waste can contaminate soil and food.
- Recent spinach contamination
 High density of animals requires constant use
of antibiotics, leading to antibiotic resistance
in microbes.
19
Seafood
•
•
•
•
•
Seafood is an important protein source.
Since 1989, 13 of the 17 major fisheries in the
world have declined or become commercially
unsustainable.
If current practices continue, the world’s fisheries
will be exhausted by 2048.
Huge boats sweep large portions of the ocean and
kill birds, turtles, and other species as “by-catch”.
Aquaculture (growing aquatic species in pens) is
providing an increasing share of the world’s
seafood.
20
Seafood
•
•
Aquaculture supplies food, but it
 uses wild populations to stock and feed captive
populations
 destroys mangrove forests and wetlands used as
nurseries for all marine species
 allows the spread of disease
 releases large quantities of feces, antibiotics and
other pollutants
Polyculture of mixed species of herbivores or filter
feeders can help.
21
Farm Policy
•
Farm subsidies in many countries are protected by
powerful political and economic interests.
 Agricultural subsidies encourage surpluses and
allow American farmers to sell products
overseas at prices below production costs.
 Most aid goes to just a few crops such as corn,
wheat, soybeans, rice and cotton.
 Aid encourages intensive farming of land which
encourages erosion.
22
Soil: A Renewable Resource
•
Soil - a complex mixture of weathered minerals,
partially decomposed organic materials, and a host
of living organisms
 Many thousands of soil types worldwide
- Vary due to influences of parent material,
time, topography, climate, and organisms
 Can be replenished and renewed. However, in
many places we are using it faster than it can be
replaced.
23
Soil Composition
•
Particle size affects soil characteristics.
 Spaces between sand particles give sandy soil
good drainage and allow aeration.
- Can easily dry out
 Tight packing of small particles in clay soils
makes them less permeable to air and water.
 Sandy loam is best for farming.
 Humus - residue of decomposed plant and
animal material. Gives soil the spongy texture
that holds water and nutrients.
24
Soil Organisms
•
Activity of organisms living in soil helps create
structure, fertility, and cultivation suitability (tilth).
•
Micorrhizal symbiosis - an association between
roots of plants and certain fungi. Plant feeds the
fungus and the fungus provides water and
inorganic nutrients to the plant to enable it to grow
better.
25
Soil Ecosystems
26
Soils are Layered
•
Soils are stratified into horizontal layers called soil
horizons.
 Horizons taken together make up soil profile.
- O Horizon (Organic layer)
 Leaf litter, partially decomposed organisms
- A Horizon (Topsoil)
 Mineral particles mixed with organic
material
27
Soil Profiles
-
-
-
E Horizon (Leached)
 Depleted of soluble nutrients
B Horizon (Subsoil)
 Often dense texture from accumulating
nutrients
C Horizon or regolith (Parent Material)
 Weathered rock fragments with little
organic material
28
29
Soil Types
•
Soils are classified according to structure and
composition (12 Orders):
-
Mollisols
Alfisols
Spodosols
Oxisols
Ultisols
Aridosols
Andisols
Vertisols
Histosols
Inceptisols
Entisols
Gelisols
30
Ways We Use and Abuse Soil
•
•
Approximately 12.5% of the earth’s land area is
currently in agricultural production.
 Up to four times as much could potentially be
converted to agricultural use.
- Much of this additional land suffers from
constraints such as steep slope or poor
drainage.
Global climate change could alter weather patterns
and flood coastal areas so that world food
production could be seriously reduced.
31
Arable Land Unevenly Distributed
•
North America and Europe are particularly well
suited to growing while some other parts of the
world lack suitable soil, topography and water.
•
Available cropland is shrinking.
 Exceptions are South America and Oceania,
where forests are being converted to farms
•
Gains in agricultural production have come from
increased fertilization, pesticides and irrigation
rather than more land.
32
Land Resources
•
Many developing countries are reaching limit of
lands that can be exploited for agriculture without
unacceptable social and environmental costs.
33
Land Degradation
•
Estimated nearly 3 million ha of cropland ruined
annually via erosion, 4 million ha transformed into
deserts, and 8 million ha converted to nonagricultural uses.
 ha stands for hectare, which is 10,000 square
meters or about 2 and a half acres.
•
Over the past 50 years, 1.9 billion ha of agricultural
land has been degraded.
34
Land Degradation
•
Definitions of degradation are based on both
biological productivity and expectations of what
land should be like.
 Generally, land is considered degraded when
soil is impoverished or eroded, run-off is
contaminated, or biodiversity is diminished.
- Water and wind are the driving forces for vast
majority of soil degradation.
35
Soil Degradation in the U.S.
36
Erosion
•
Erosion is a natural process, resulting in
redistribution of the products of geologic weathering,
and is part of both soil formation and soil loss.

Worldwide, erosion reduces crop production by
equivalent of 1% of world cropland per year.

Erosion results in sediment loading of rivers and
lakes, siltation of reservoirs, and smothering of
wetlands and coral reefs.
37
Mechanisms of Erosion
•
Sheet Erosion - thin layer of surface removed
•
Rill Erosion - small rivulets of running water gather
together and cut small channels
•
Gully Erosion - rills enlarge to form bigger channels
too large to be removed by normal tillage
•
Streambank Erosion - washing away of soil from
banks of streams and rivers
38
Mechanisms of Erosion
•
•
Wind can equal or exceed water as an erosive
force, especially in a dry climate and on flat land.
Desertification - conversion of productive land to
desert
 Intensive farming practices responsible for
erosion:
- Row crops leave soil exposed.
- Weed free-fields
- Removal of windbreaks
- No crop-rotation or resting periods for fields
- Continued monoculture cropping can increase
soil loss tenfold.
39
Desertification
•
Conversion of productive lands to desert
 threatens 1/3 of the earth’s surface and 1 billion
people
•
Rangelands and pastures are highly susceptible
(overgrazing, soil degradation).
•
Africa and China are of particular concern.
 Rapid population growth and poverty create
unsustainable pressures.
 Removal of trees for fodder and firewood triggers
climate change that spreads desertification.
40
Desertification
41
Other Agricultural Resources
•
Water
 Agriculture accounts for largest single share of
global water use.
- Much irrigation water lost to seepage and
evaporation
- In some countries, low cost encourages overuse of water.
 Waterlogging
 Salinization - mineral salts accumulate
in soils; lethal to plants
42
Fertilizer
•
Lack of nitrogen, potassium, and phosphorus often
limits plant growth.
 Adding nutrients via fertilizer usually stimulates
growth and increases crop yields.
- 1950 - average of 20 kg/ha fertilizer used
- 1990 - average of 91 kg/ha fertilizer used
 Overuse causes water pollution.
 Manure and nitrogen-fixing bacteria are alternative
methods of replenishing soil nutrients.
 Fertilizer use could increase crops in Africa.
43
Energy
•
Farming in industrialized countries is highly energyintensive.
 Between 1920-1980, energy use rose directly
with mechanization of agriculture, and indirectly
with synthetic fertilizers.
 Altogether, U.S. food system consumes 16% of
total energy use.
- Most foods require more energy to produce,
process, and transport than we get from
eating them. Eating locally grown foods has
less environmental impact.
44
Biofuels
•
Usually corn or soy-based ethanol fuels in the U.S.
•
State of the art facilities to process them have a net
energy yield of 150%.
•
Diesel engines can use plant oils directly.
•
Plans to use fast growing trees, kenaf, switch
grass, and cattails in the production of biofuels
45
New Crops
•
•
Most of the world’s
food comes from only
16 species.
New crops possible
 Winged bean
 Tricale, a hybrid
between wheat and
rye
46
Green Revolution
•
•
Most major improvements in farm production have
come from technological advances and
modification of a few well-known species.
 Corn yields jumped from 25 bushels per acre to
130 per acre in last century.
- Most of gain accomplished through
conventional plant breeding
Green Revolution started by Norm Borlaug. Dwarf,
high yielding wheat and rice grown around the
world.
47
Green Revolution
•
•
•
Borlaug won Nobel Peace Prize.
Green revolution plants require fertilizers and
protection from pests. If these are lacking, modern
crops may not produce as well as traditional crops.
Poor farmers may be left out of the green
revolution.
Crops of green revolution grow in temperate
climates. Efforts underway to create new crops for
tropical climates.
48
Genetic Engineering
•
Genetic engineering - removes DNA from one
organism and splices it into the chromosomes of
another. Produces genetically modified organisms
(GMOs) with new traits.
- Can produce crops with pest-resistance and
wider tolerance levels to frost, drought, low
nutrient soils, salty soils, etc.
- Can improve protein or vitamin content of crop
- Can incorporate oral vaccines into foods such
as bananas for use in developing nations
- Animals can be modified to grow faster or
produce pharmaceuticals in their milk.
49
GMOs
•
•
Opponents worry that
 GMOs might produce superweeds resistant to
pesticides.
 Native biodiversity may be reduced.
 Novel toxins might be created.
 Technology may only be available to the rich,
making family farms uncompetitive and driving
poor nations further into poverty.
You are already eating GMOs as 60% of processed
food in the U.S. contains GMOs.
50
Pest Resistance and Weed Control
•
Biotechnologists have recently created plants
containing genes for endogenous insecticides.
 A gene from the bacterium Bacillus thuringiensis
(Bt) makes toxins that are lethal to butterflies and
beetles. These genes have been transferred
into corn, potatoes and cotton. Reduces
pesticide use and increases yield.
 Concern has arisen over several points.
- Spread of genes into wild populations leading
to resistance in pests
- Effect on nontarget species
51
Transgenic Crops
•
Genetically modified organisms are also called
transgenic organisms.
•
Transgenic crops can be engineered to tolerate
high levels of pesticides.
 Roundup Ready and Liberty Link are two most
popular. Crops can grow in the presence of the
pesticides (called Roundup and Liberty) while
weeds within the field are killed.
52
Is Genetic Engineering Safe?
•
Environmental and consumer groups have
campaigned against transgenic organisms.
 “Frankenfoods”
 European nations have bans on GMOs.
•
U.S. Food and Drug Administration declined to
require labeling of foods containing GMOs.
 New varieties are “substantially equivalent” to
related traditionally-bred varieties.
53
Is Genetic Engineering Safe?
•
•
•
•
GMOs tested so far do not survive well in the wild
and are no more invasive than unmodified plants.
Worry that genetically modified animals will escape
captivity and outcompete their wild relatives.
(Salmon with added growth hormone gene grow 7X
faster than their wild counterparts.)
We should err on the side of safety.
Will GMOs help feed the world or lead to more
economic disparity?
54
Sustainable Agriculture
•
•
Sustainable agriculture attempts to produce food
and fiber on a sustainable basis and repair the
damage caused by destructive practices.
Soil Conservation
 Managing Topography
- Contour Plowing - plowing across slope to
slow flow of water
- Strip Farming - planting different crops in
alternating strips along land contours
- Terracing - shaping land to create level
shelves of earth to hold water and soil
- Plant perennial species.
55
Sustainable Agriculture
56
Sustainable Agriculture
57
Soil Conservation
•
Providing Ground Cover
 Annual row crops cause highest rates of erosion
because they leave soil bare for much of the
year.
- Leave crop residue after harvest.
- Plant cover crops such as clover after harvest.
- Interplant two different crops in the same field.
Harvest one; the other is left to hold the soil.
Double harvests are an advantage as well.
- Mulch
58
Soil Conservation
•
Reduced Tillage
 Minimum Till - reducing number of times soil is
disturbed
 Conserv-Till - uses a disc called a coulter to
open a furrow just wide enough for seed
 No-Till - drilling holes in ground for seed
•
Often farmers using conservation tillage depend
relatively heavily on pesticides, which is a
disadvantage.
59
Low Input Sustainable Agriculture
•
•
•
•
•
•
Small scale, low input agriculture
No synthetic chemicals
Raising cows on pasture grass rather than grain
No antibiotics
Typically produces smaller yield, but production
costs are lower and prices are higher so net gain
is higher
Preserves rural culture better than factory farms
60
Consumers’ Choices are Important
•
•
•
•
Adopting a vegetarian or organic diet can reduce
environmental impact.
An even greater impact can be made by becoming
a locavore, a person who eats locally grown,
seasonal food.
Join a community supported agriculture program
(CSA) in which you make a payment to a local farm
in return for weekly deliveries of food.
Agroecology - sustainable farming using ecological
knowledge
61