Other ways we MESS with the Land! 9/29/2013 Guru IBESS SOIL SYSTEM 1
May 25, 2015
Other ways we MESS with the Land!
9/29/2013 Guru IBESS SOIL
SYSTEM 1
1. Overgrazing
• When livestock eat too much plant cover on rangelands, impeding plant regrowth
• The contrast between ungrazed and overgrazed land on either side of a fenceline can be striking.
Figure 8.22 9/29/2013 Guru IBESS SOIL
SYSTEM 2
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SYSTEM 3
Overgrazing
• Overgrazing can set in motion a series of positive feedback loops.
Figure 8.21 9/29/2013 Guru IBESS SOIL
SYSTEM 4
Overgrazing • Livestock graze on grasslands and cleared forest
slopes – 65% of drylands are grasslands
• Land is often overgrazed – Barren land is eroded and degraded
• In the 1800s American buffalo (bison) were slaughtered – Rangelands stocked with cattle were overgrazed
– Leading to erosion and growth of unpalatable plants
• U.S. western rangelands produce less than 50% of the forage they produced before commercial grazing – Yet 20% of rangelands remain overstocked
9/29/2013 Guru IBESS SOIL
SYSTEM 5
Degraded rangelands
• The National Public Lands Grazing Campaign
documents harmful effects of livestock grazing
– Competition of livestock with native animals for food
– One-third of endangered species are in danger due to cattle-
raising practices (predator control, fire suppression)
– Wooded zones along streams are trampled and polluted
– Polluted streams make fish species the fastest-disappearing
wildlife group
• Desertification impacts 85% of North America’s
drylands
– The most widespread cause is livestock grazing
9/29/2013 Guru IBESS SOIL
SYSTEM 6
Public lands
• Overgrazing occurs because rangelands are public lands
– Tragedy of the commons: the incentive is for all to keep grazing, even though the range is being overgrazed
• The U.S. Bureau of Land Management (BLM) and Forest Service leases grazing rights on 2 million km2 of land
– Federal land is owned by taxpayers
– Animal unit = one cow-calf pair or five sheep
– The grazing fee ($1.35/animal unit/month) is 10% what would be paid on private land
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SYSTEM 7
Why are rangelands overgrazed? • The 1934 Taylor Grazing Act prohibits reducing
grazing levels or keeps grazing fees below market
level
– The U.S. government lost $115 million in 2004
– $500 million more was lost in ecological costs (to
watersheds, streams, wildlife, endangered species)
• When Congress and the BLM try to raise fees,
western congressmen threaten to cut the BLM
budget
9/29/2013 Guru IBESS SOIL
SYSTEM 8
Solutions to overgrazing • Better management could restore rangelands
– Benefiting wildlife and cattle production
• Conservation Stewardship Program (NRCS) – Provides information and support to land-owning ranchers
to burn woody plants, reseed land, rotate cattle
• The government could buy up some of the 26,000 permits – Retire rangelands
– Generously pay ranchers for their permits
– Use the land for wildlife, recreation, watershed protection
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SYSTEM 9
2. Deforestation • Porous, humus-rich forest soil efficiently holds
and recycles nutrients
– Also absorbs and holds water
• Converting a forested hillside to grassland doubles the amount of runoff and increases nutrient leaching
• When forests are cut and soils are left exposed
– Topsoil becomes saturated with water and slides off the slope
– Subsoil continues to erode
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SYSTEM 10
Forests are cut at alarming rates • 13 million hectares (32 million acres) are cut per year
– Mostly in developing countries
• Cutting tropical rain forests causes acute problems
– Heavy rains have leached soils of minerals
– Parent material is already maximally weathered
– So tropical soils (oxisols) lack nutrients
• Clearing rain forests washes away the thin layer of
humus
– Leaving only the nutrient-poor subsoil
– Very poor for agriculture
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SYSTEM 11
Animal agriculture: Livestock and
poultry
•Consumption of meat has risen faster than population over the past several decades.
Figure 9.15 9/29/2013 Guru IBESS SOIL
SYSTEM 12
3. Feedlot agriculture •Increased meat consumption has led to animals being raised in feedlots (factory farms), huge pens that deliver energy-rich food to animals housed at extremely high densities.
Figure 9.16 9/29/2013 Guru IBESS SOIL
SYSTEM 13
Feedlot agriculture: Environmental
impacts •Immense amount of waste produced, polluting air and water nearby •Intense usage of chemicals (antibiotics, steroids, hormones), some of which persist in environment •However, if all these animals were grazing on rangeland, how much more natural land would be converted for agriculture?
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SYSTEM 14
Food choices = energy choices
•Energy is lost at each trophic level. •When we eat meat from a cow fed on grain, most of the grain’s energy has already been spent on the cow’s metabolism. •Eating meat is therefore very energy inefficient.
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SYSTEM 15
Grain feed input for animal output
•Some animal food products can be produced with less input of grain feed than others.
Figure 9.17 9/29/2013 Guru IBESS SOIL
SYSTEM 16
Land and water input for animal output
•Some animal food
products can be
produced with less
input of land and
water than others.
Figure 9.18 9/29/2013 Guru IBESS SOIL
SYSTEM 17
4. Aquaculture
•The raising of aquatic organisms for food in controlled environments •Provides 1/3 of world’s fish for consumption •220 species being farmed •The fastest growing type of food production
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SYSTEM 18
Aquaculture
•Fish make up half of aquacultural production. Molluscs and plants each make up nearly 1/4.
•Global aquaculture has been doubling about every 7 years.
Figure 9.19 9/29/2013 Guru IBESS SOIL
SYSTEM 19
Benefits of aquaculture
•Provides reliable protein source for people, increases food security
•Can be small-scale, local, and sustainable
•Reduces fishing pressure on wild stocks, and eliminates bycatch
•Uses fewer fossil fuels than fishing
•Can be very energy efficient
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SYSTEM 20
Environmental impacts of aquaculture
•Density of animals leads to disease, antibiotic use, risks to food security.
•It can generate large amounts of waste.
•Often animals are fed grain, which is not energy efficient.
•Sometimes animals are fed fish meal from wild-caught fish.
•Farmed animals may escape into the wild and interbreed with, compete with, or spread disease to wild animals.
9/29/2013 Guru IBESS SOIL
SYSTEM 21
Environmental impacts of aquaculture
•Transgenic salmon (top) can compete with or spread disease to wild salmon (bottom) when they escape from fish farms.
Figure 9.20 9/29/2013 Guru IBESS SOIL
SYSTEM 22
Highly efficient
High yield in small volume of water Increased yields through cross- breeding and genetic engineering Can reduce over- harvesting of conventional fisheries Little use of fuel Profit not tied to price of oil High profits
Advantages
Large inputs of land, feed,
And water needed
Produces large and concentrated outputs of waste Destroys mangrove forests Increased grain production needed to feed some species Fish can be killed by pesticide runoff from nearby cropland Dense populations vulnerable to disease Tanks too contaminated to use after about 5 years
Disadvantages
Trade-Offs
Aquaculture
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SYSTEM 23
5. Fish Harvesting
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SYSTEM 24
Spotter airplane
Fish farming in cage
Trawler fishing
Purse-seine fishing
sonar trawl flap
trawl
lines
trawl bag
Long line fishing
lines with
hooks
Drift-net fishing
fish caught by gills
float buoy
fish school
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SYSTEM 25
100
80
60
40
20
0 1950 1970 1960 2000 1990 1980
Catc
h
(millio
ns o
f m
etr
ic t
on
s)
Year
Total World Fish Catch 9/29/2013 Guru IBESS SOIL
SYSTEM 26
25
20
15
10
5
0 1950 1970 1960 2000 1990 1980
Per
cap
ita c
atc
h
(kilo
gra
ms p
er
pers
on
)
Year
World Fish Catch Per Person 9/29/2013
Guru IBESS SOIL SYSTEM
27
800
600
400
200
0
1960 1970 1980 1990 2000
Year
80
70
60
50
40
30
20
Harv
est
(th
ou
san
ds o
f m
etr
ic t
on
s)
Ab
un
dan
ce
(kilo
gra
ms/t
ow
)
Abundance
Harvest
10
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SYSTEM 28
Problems and consequences
• Problem – Overgrazing
– Water Pollution • Slaughter
• Wastes
• Riparian grazing
– Land use • Fencing, deforestation
– Uses more water
• Consequence – Desertification, erosion nutrient
loss
– Groundwater contamination, ^BOD, Eutrophication, etc
– Habitat loss & fragmentation, decreased biodiversity
– Water shortages / depletion
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SYSTEM 29