Other ways we mess with the land
This presentation is the property of its rightful owner.
Sponsored Links
1 / 29

Other ways we MESS with the Land! PowerPoint PPT Presentation


  • 85 Views
  • Uploaded on
  • Presentation posted in: General

Other ways we MESS with the Land!. 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. Overgrazing.

Download Presentation

Other ways we MESS with the Land!

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Other ways we mess with the land

Other ways we MESS with the Land!


1 overgrazing

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


Overgrazing

Overgrazing

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

Figure 8.21


Overgrazing1

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


Degraded rangelands

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


Public lands

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


Why are rangelands overgrazed

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


Solutions to overgrazing

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


2 deforestation

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


Forests are cut at alarming rates

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


Animal agriculture livestock and poultry

Animal agriculture: Livestock and poultry

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

Figure 9.15


3 feedlot agriculture

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


Feedlot agriculture environmental impacts

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?


Food choices energy choices

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.


Grain feed input for animal output

Grain feed input for animal output

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

Figure 9.17


Land and water input for animal output

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


4 aquaculture

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


Aquaculture

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


Benefits of aquaculture

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


Environmental impacts of aquaculture

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.


Environmental impacts of aquaculture1

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


Other ways we mess with the land

Trade-Offs

Aquaculture

Advantages

Disadvantages

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

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


5 fish harvesting

5. Fish Harvesting


Other ways we mess with the land

Spotter airplane

Trawler

fishing

Fish farming

in cage

Purse-seine

fishing

trawl flap

sonar

trawl

lines

fish school

trawl bag

fish caught

by gills

Drift-net fishing

float

buoy

Long line fishing

lines with

hooks


Other ways we mess with the land

100

80

60

Catch

(millions of metric tons)

40

20

0

1950

1960

1970

1980

1990

2000

Year

Total World Fish Catch


Other ways we mess with the land

25

20

15

Per capita catch

(kilograms per person)

10

5

0

1950

1960

1970

1980

1990

2000

Year

World Fish Catch Per Person


Other ways we mess with the land

800

80

Abundance

70

Harvest

600

60

Abundance

(kilograms/tow)

50

Harvest

(thousands of metric tons)

400

40

30

200

20

0

1960

1970

1980

1990

2000

Year

10


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

Problems and consequences


  • Login