5. other ways we screw with agriculture! (good)

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


SYSTEM 3

Overgrazing

• Overgrazing can set in motion a series of positive feedback loops.


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


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


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


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


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


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


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


SYSTEM 11

Animal agriculture: Livestock and

poultry

•Consumption of meat has risen faster than population over the past several decades.


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.


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?


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.


SYSTEM 15

Grain feed input for animal output

•Some animal food products can be produced with less input of grain feed than others.


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.


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


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.


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


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.


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.


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


SYSTEM 23

5. Fish Harvesting


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


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


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


SYSTEM 29

5. other ways we screw with agriculture! (good)

Education

overgrazed land

input of land

grasslands land

reseed land

km2 of land federal

natural land

private land

guruibess systemsoil15