Transcript Soil Erosion - Lakeland Regional High School

Issues and Impacts of Agriculture
• Our ability to produce enough food
to feed to world depends on 3 things:
About 10% of Earth’s land surface can be
– land
used for agriculture (arable land)
– water
– and energy
About 70% of
Earth’s water is used
for agriculture
About 24% of GHG
emissions come
from agriculture
Main Topics - FYI
 Methods of producing food
 Increasing food production
 Environmental effects of food production
 Issues of sustainability
A World of 9 Billion
• Famine – widespread
starvation due to a shortage
of food
• By 2050, 9 billion people
will need to be fed
– Feed a nutritious diet is
difficult
– Food production can be
increased without
permanently harming the
environment
MALNUTRITION –
• lack of sufficient calories or
• lack of essential nutrients
What do we eat?
DIET – type and amount of food eaten
Worldwide – most people eat grains
Diet Around the World
How do the diets of people in developed countries
compare with the diets of people in developing
countries?
Their diets are higher in calories,
especially from fats and proteins.
Sources of food worldwide
 Of 30,000 edible plants, only 15 species
supply 90% of our food
 Primary plants:
wheat, corn, and rice
Provide > ½ calories people consume
 Primary animals:
cattle, pigs, and chicken
 Secondary: eggs, milk &
cheese
• A food crop that produces a large amount of
food with little negative environmental
consequences is ideal
– 1 Calorie of animal food uses more energy, water
and land than plant food
– 90% energy loss up the food chain
– Land can produce more food when used to grow
plants than animals
– Meat provides more nutrients per gram than plants
More Efficient Foods Less Waste
World Food Problems
• There is enough food to feed up to 10 billion
people
– However, most of us consume ~1/3 of our calories
from animals
– We need more food every year
• Today’s malnutrition results from poverty
– Lack of enough water for irrigation
– Income less than $1/day
– Africa, Asia & mountainous South America
World Food Problems FYI
• Fewer people living in poverty since 1980
• However :
World Food Problems
• To feed the people of 2050
– We will need to produce more food
– We will need to abolish poverty
• HOW?
– Increasing subsistence farmer productivity
• Irrigation
Agriculture History - FYI
• In early agriculture,
people began planting
seeds from plants
they liked most
• Agriculture and
livestock provided a
stable food supply,
which allowed the
development of
modern civilization
Types of Agriculture
• Traditional
–
–
–
–
Plowing – bio-powered
Fertilizer – organic manure
Irrigation – ditch
Pest control – manual
removal
• Modern
–
–
–
–
Plowing – fossil fuel powered
Fertilizer – synthetic chemicals
Irrigation – sprinklers & drip
Pest control – synthetic
chemicals
Ecology of Food
• Different kinds of agriculture have different
environmental impacts
Major Types of Agriculture
Traditional subsistence
Shifting cultivation
Nomadic herding
Traditional intensive
Plantation
Industrialized
Land
Labor
Capital
Land
Labor
Capital
Shifting cultivation
in tropical
forests
in developing
countries
Nomadic
herding in
developing
countries
Land
Labor
Capital
Industrialized
agriculture
in developed
countries
Fossil fuel
energy
Land
Labor
Capital
Fossil fuel energy
Traditional
intensive
agriculture
in developing
countries
World Food Production
Industrialized agriculture
Plantation agriculture
Shifting cultivation
Nomadic herding
Intensive traditional agriculture
No agriculture
THE GREEN REVOLUTION – a large increase in crop
production using modern agricultural techniques,
new crop varieties, and farming practices in
developing countries in the mid- to late 1900s
Green Revolutions
First green revolution
(developed countries)
Second green revolution
(developing countries)
Major International agricultural
research centers and seed banks
Producing Food by GreenRevolution Techniques
 High-input monoculture
 Selectively bred or genetically-engineered
crops
 High inputs of fertilizer
 Extensive use of pesticides
 High inputs of water
THE GREEN REVOLUTION – a large increase in crop
production using modern agricultural techniques,
new crop varieties, and farming practices in
developing countries in the mid- to late 1900s
• PROS –
– Large yields produced
• New varieties of grain (if enough water, fertilizer and
pesticides)
– Saved millions of people from starvation in India and
Pakistan
– Reduced the price of food
– Improved lives of millions
– Prevented some deforestation and habitat loss by
increasing yields on cultivated land
THE GREEN REVOLUTION
• CONS –
– Increases mostly on large farms
– Led to a 7000% increase in energy used by agriculture
– Worsened erosion, salinization, desertification,
eutrophication, and pollution
– Subsistence farmers do not have the money for water
and chemicals required by new crops varieties
– Does not meet the needs of subsistence farmers who
need:
• Small-scale irrigation
• Cash crops (fruits and vegetables)
Results of Green Revolution: Mixed
• Higher yields per acre when fertilizers and
pesticides available
• Lower yields when fertilizers and pesticides
unavailable
• Increased dependence on cash economy
• Increased dependence on fossil fuel
• Increased imports of fertilizers and pesticides
Food Production since the Green
Revolution
Rapid increases in total production
Prices decreasing
Shortages in developing countries
Approaching limits on meat production
Unintended consequences: Killer Bees
Mild-mannered, low honey producing Italian bee
X
Aggressive, high honey producing African bee?
Hope for a mildmannered, high
producing bee
Instead, got an
aggressive, low
producing bee
Worse yet – it escaped, and is interbreeding with other
bees making them aggressive & low producing too!
Environmental Effects of Food
Production
Biodiversity loss
Soil degradation
Air pollution and climate effects
Water pollution
Human health
Biodiversity Loss
Loss and degradation of habitat from
clearing grasslands and forests and
draining wetland
Invasive species out competing natives
Killing of wild predators to protect
livestock
Loss of genetic diversity from
replacing thousands of wild crop
strains with a few monoculture strains
Soil
Erosion
Loss of fertility
Salinization from irrigation
Desertification
LAND DEGREDATION
• Soil Erosion
• Desertification
• Soil Salinization
Causes of Soil Erosion
Wind
Water (#1)
People
Erosion Facts
• ~ ½ the original topsoil has been lost in the US
over the past 200 years
• Most farming methods increase the rate of soil
erosion
– Plowing loosens soil an removes plants that hold
soil in place
– Runoff from irrigation carries soil with it
Soil Erosion: A Global
Problem
Soil Erosion
• Often occurs faster than soil is formed,
depleting fertile topsoil
• Crops, trees, and other plant communities
protect soil from erosion
Did You Know?
More than 19
billion hectares
(47 billion acres)
of the world’s
croplands suffer
from erosion
and other forms
of soil
degradation
resulting from
human
activities.
Impacts of Soil Erosion
• Loss of soil fertility
• Sediment runoff causes
problems in surface water
(pollution, clog ditches,
boat channels, reservoirs)
• #1 source of U.S. water
pollution
• Renewable only on LONG
timeframes (200-1,000yrs.
for 1 inch)
What time of year do you think
most farm fields in U.S. are
vulnerable to erosion?
That’s right - SPRING
On Agricultural land in U.S. today, soil is
eroding 16 times faster than it is created
Desertification
When land in arid or semi-arid regions
becomes more desert-like due to
agricultural practices
Some estimates predict that 50 million people could be
displaced in the next 10 years due to desertification.
Africa's Ambitious "Great Green Wall"
SOIL SALINIZATION
• Major problem in areas of low rainfall and
naturally salty soil (CA, AZ, Africa, Near &
Middle East)
• Irrigation water saltier than rainwater
• Evaporation leave behind salts
REMEDIATION
• Line irrigation canals
• Water soil heavily to wash out salts
Soil Salinization
Soil Conservation (Farming
Practices That Reduce Erosion)
• Terracing: Steep slopes
turned into “steps”
• Contour Plowing: plowing
across the slope
• Intercropping: Different
crops mixed together
• Drip Irrigation: minimize
use of water
Contour and Strip Cropping
Soil Conservation (Farming
Practices That Reduce Erosion)
• Crop rotation: Crops are
alternated
• Shelterbelts: Tall plants block
wind
• Conservation tillage: Soil
turnover is reduced
• No-Till Farming: crop harvested
without turning over soil
Air & Climate
Greenhouse gas emissions from
fossil fuel use
Other air pollutants from fossil fuel
use
Pesticide drift from spraying
Dust / airborne particulates
Weather alteration from large scale
clearing
Water
Aquifer depletion
Water diversions
Increased runoff and
flooding from land cleared
to grow crops
Sediment pollution from
erosion
Fish kills from pesticide
runoff
Surface and groundwater
pollution from pesticides,
fertilizers & livestock
Overfertilization
(eutrophication) of lakes
and slow-moving rivers
from runoff of nitrates and
phosphates from
fertilizers, livestock
wastes, and food
processing wastes
Human Health
Nitrates in drinking water
Pesticides residues in drinking water,
food, and air
Contamination of drinking and
swimming water with disease
organisms from livestock wastes
Bacterial contamination of meat
Farm worker exposure & working
conditions
Controlling Pests
• Pests affect crop production
– Worldwide 33% of potential food harvest
• PEST – any organism that occurs where it is
not wanted or occurs in large enough numbers
to cause economic damage
• Weeds, insects, fungi
PESTICIDES
• Chemicals to kill insects, weeds & other crop pests
Pests and Weed Control
• Chemical pesticides: Effective and
cheap, but can lead to resistance
PESTICIDE – HUMAN HEALTH
CONCERNS
• Pesticides are designed to kill organisms – what is
the effect on humans?
–
–
–
–
Cancer rates in children higher than national average
Workers in pesticide factories become ill
Accidental chemical leaks (Bhopal, India-1000’s die)
Users must follow safety guidelines
PESTICIDES - PERSISTENT
• Do not break down rapidly
into harmless forms
• 1950's DDT video
• DDT banned in the US in the
1970’s
– Still detected in environment
– Effects -
Soil Pollution
• Too much, or carelessly
timed irrigation can
Evaporation
Evaporation
Transpiration
waterlog crops and lead to
salinization—a buildup of
salts in upper soil horizons.
• Toxic persistent pesticides
can remain in soil for a long
time, eventually filtering to
groundwater.
Waterlogging
Less
permeable
clay layer
Pests and Weed Control
• Biological Pest Control: using living
organisms to control pests
Pests and Weed Control
• Pathogens: organisms that cause disease
• Most common – Bacillus thuringiensis (Bt)
– Kill pest caterpillars (but can kill unintended
targets
Pests and Weed Control
• Plant Defenses: varieties of plants bred
to have defenses against pests
• Chemical compounds that repel pests
• Physical barriers to impede pests
Pests and Weed Control
• Plant Chemicals: uses plant’s defensive
chemicals
• Chrysanthemum plants
– Less harmful to humans and pets
– Biodegradable
Pests and Weed Control
• Growth Regulators: interference with pest life
cycle
• Pheromones: chemicals that affect the behavior of
pests
• Sterilization: eggs produced that do not develop
Pests and Weed Control
•Biological pest control:
Permanent solution, but
can harm non-target
organisms
•Integrated pest
management: combines
chemical and biological
pest-control methods
• goal – minimize
economic loss from pest
damage
Cactus moth larvae are
used to control prickly pear
cactus, but also threaten
many rare, native cacti
around the world.
Integrated Pest Management
Combination of farming methods, biological
pest control and chemical pest control
Increasing World Crop Production
 Crossbreeding and artificial selection
 Genetically modified organisms (GMOs)
 Continued Green Revolution techniques
 Introducing new foods
 Working more land
Sustainability
• Sustainable agriculture conserves natural
resources
– Minimizes the use of energy, water, pesticides &
fertilizers
– Involves planning productive, pest-resistant crops
that require little energy, pesticides, fertilizers &
water
Alternative Solutions:
Sustainable Agriculture
Low-input agriculture
Organic farming
Non-meat alternatives
Research in sustainable techniques
In Summary:
• Supplying food for the world’s growing population
was and still is an issue.
• Policy and research play a big role.
• Efforts to increase production have focused on:
– Improved varieties thru breeding and genetic engineering
– Inputs, esp. chemicals (fertilizers & Pesticides), energy and
water
• Agriculture has multiple impacts on the environment
and human health
• Sustainable agricultural techniques are growing but
far behind conventional