2. Global Effects of AgricultureGlobal Effects of Agriculture
Agriculture is the world’sAgriculture is the world’s largest & oldestlargest & oldest industryindustry
The production, processing, and distribution of food allThe production, processing, and distribution of food all alteralter
the environment.the environment.
Because of the size of the industry largeBecause of the size of the industry large effectseffects on theon the
environmentenvironment are unavoidableare unavoidable
On-site (primary) effectOn-site (primary) effect
Where the agricultureWhere the agriculture
takes placetakes place
Off-site (secondary)Off-site (secondary)
effecteffect
Away from theAway from the
agricultural site,agricultural site,
typically downstream &typically downstream &
downwinddownwind
3. Major environmental problems of Agriculture (Q)Major environmental problems of Agriculture (Q)
DeforestationDeforestation
DesertificationDesertification
Soil erosionSoil erosion
OvergrazingOvergrazing
Degradation of water resourcesDegradation of water resources
SalinizationSalinization
Accumulation of toxic metals & toxic organic compoundsAccumulation of toxic metals & toxic organic compounds
Water pollutionWater pollution
EutrophicationEutrophication
4. Global Effects of AgricultureGlobal Effects of Agriculture
Global EffectsGlobal Effects
Changes inChanges in albedoalbedo
EvaporationEvaporation of waterof water
RoughnessRoughness of the surfaceof the surface
Rate of exchange of chemical compounds (CORate of exchange of chemical compounds (CO22, for example), for example)
produced and removed by living thingsproduced and removed by living things
Each of these can have regional and global effectsEach of these can have regional and global effects
Modern agricultureModern agriculture by clearing landby clearing land and as a major user ofand as a major user of
fossil fuelsfossil fuels increasesincreases the concentration ofthe concentration of carbon dioxidecarbon dioxide
AffectsAffects climateclimate through firethrough fire
5. Global Effects of AgricultureGlobal Effects of Agriculture
Fires associated with release of significant amount ofFires associated with release of significant amount of carboncarbon
dioxidedioxide, and small, and small particulatesparticulates to the atmosphereto the atmosphere
Another global effect results from the production and use ofAnother global effect results from the production and use of
nitrogenous fertilizernitrogenous fertilizer which leads to significant change inwhich leads to significant change in
global biogeochemical cyclesglobal biogeochemical cycles
Agriculture affectsAgriculture affects biodiversitybiodiversity
The loss of competing ecosystemsThe loss of competing ecosystems reduces biodiversityreduces biodiversity
IncreasesIncreases the number ofthe number of endangered speciesendangered species
6. PestsPests are undesirableare undesirable
competitors, parasites, orcompetitors, parasites, or
predatorspredators
Major agricultural pests areMajor agricultural pests are
insectsinsects
NematodesNematodes
BacterialBacterial andand viralviral diseasesdiseases
WeedsWeeds
VertebratesVertebrates : Rodents & birds: Rodents & birds
that feed on grain or fruitthat feed on grain or fruit
Weeds:Weeds:
In terms of potential cropIn terms of potential crop
loss weeds are the majorloss weeds are the major
problemproblem
There are aboutThere are about 30,00030,000
species of weedsspecies of weeds
In any year a typical farm isIn any year a typical farm is
infested with betweeninfested with between 1010
and 50and 50 weed speciesweed species
Compete with cropsCompete with crops for allfor all
resourcesresources
Pest Control and Agricultural ChemicalsPest Control and Agricultural Chemicals
PreharvestPreharvest losseslosses are fromare from weedsweeds
Post harvest lossesPost harvest losses are largely due toare largely due to herbivoresherbivores
9. Pest Control—PesticidesPest Control—Pesticides
Worldwide only about 100 species of weeds, insects, fungi andWorldwide only about 100 species of weeds, insects, fungi and
microbes cause about 90% damage to the crops we growmicrobes cause about 90% damage to the crops we grow
PesticidesPesticides are chemicals used to kill or control organisms weare chemicals used to kill or control organisms we
consider undesirableconsider undesirable
Common types of pesticides include:Common types of pesticides include: insecticides, herbicides,insecticides, herbicides,
fungicides, nematocides, rodenticidesfungicides, nematocides, rodenticides
Earlier pesticides wereEarlier pesticides were broad spectrumbroad spectrum
One of the earliest pesticides used wasOne of the earliest pesticides used was arsenicarsenic, a chemical, a chemical
elementelement toxic to all lifetoxic to all life including peopleincluding people
10. Pest Control—PesticidesPest Control—Pesticides
Development of more sophisticated pesticides began inDevelopment of more sophisticated pesticides began in 19391939
whenwhen Paul Muller discovered DDTPaul Muller discovered DDT
DDTDDT soon became the world’ssoon became the world’s most usedmost used pesticidepesticide andand PaulPaul
MullerMuller received thereceived the Nobel PrizeNobel Prize inin 19481948 for his discoveryfor his discovery
It appeared to have no short-term effect on people andIt appeared to have no short-term effect on people and
seemed to kill only insectseemed to kill only insect
EventuallyEventually three factsthree facts about DDT were discovered whichabout DDT were discovered which led toled to
its banningits banning
1.1. Long term effectsLong term effects on otheron other desirabledesirable organismsorganisms
2.2. Stored in oils & fatsStored in oils & fats andand concentrated as it passed up in foodconcentrated as it passed up in food
chains—chains— biomagnificationbiomagnification
3. Storage in oils & fats allows it to be3. Storage in oils & fats allows it to be transferred biologicallytransferred biologically
Because of these problems DDT was considered as theBecause of these problems DDT was considered as the
most notorious chemical of the last centurymost notorious chemical of the last century
11.
12. Pest Control—PesticidesPest Control—Pesticides
Alternatives to DDTAlternatives to DDT
With the banning of DDTWith the banning of DDT low persistentlow persistent (length they(length they
remain deadly in the environment)remain deadly in the environment) organophosphatesorganophosphates,,
carbamatescarbamates became prominentbecame prominent
These chemicals areThese chemicals are more specificmore specific andand decay rapidlydecay rapidly inin
the soilthe soil
They tooThey too,, are toxicare toxic and must be handled carefullyand must be handled carefully
13. Perfect PesticidePerfect Pesticide
AA perfectperfect pesticide would have the following characteristics:pesticide would have the following characteristics:
InexpensiveInexpensive
Highly specificHighly specific
Less persistentLess persistent
Breakdown into harmless materialsBreakdown into harmless materials
However, the perfect pesticide has not been inventedHowever, the perfect pesticide has not been invented
14. Problems of Pesticide Use—Impact on other organismsProblems of Pesticide Use—Impact on other organisms
A major problem is that broad-spectrum insecticides kill naturalA major problem is that broad-spectrum insecticides kill natural
predators and parasites that help control the population of pestpredators and parasites that help control the population of pest
speciesspecies
No more than 2%No more than 2% of the insecticide applied to crops reaches theof the insecticide applied to crops reaches the
target peststarget pests
Less than 5% of herbicideLess than 5% of herbicide applied to crops reach the targetapplied to crops reach the target
weedsweeds
Pesticides that miss their target pests end up in the air, bothPesticides that miss their target pests end up in the air, both
surface & groundwater, bottom sediments, food, nontargetsurface & groundwater, bottom sediments, food, nontarget
organisms including humans & wildlifeorganisms including humans & wildlife
15. Problems of Pesticide Use—Impact on other organismsProblems of Pesticide Use—Impact on other organisms
Most pesticides can be toxic to humans causing geneticMost pesticides can be toxic to humans causing genetic
mutations, birth defects, behavioral disorders, effects on themutations, birth defects, behavioral disorders, effects on the
immune systemimmune system
Can cause cancer and death to animalsCan cause cancer and death to animals
Sensitive plants can show signs of growth irregularity, loss inSensitive plants can show signs of growth irregularity, loss in
biomass, or deathbiomass, or death
Contamination of soil and aquatic ecosystems reduce theContamination of soil and aquatic ecosystems reduce the
activity of beneficial microorganismsactivity of beneficial microorganisms
Extreme case of contamination can reduce the activity ofExtreme case of contamination can reduce the activity of
these microorganisms to essentially zerothese microorganisms to essentially zero
16. Integrated Pest Management, IPM (Q)Integrated Pest Management, IPM (Q)
An ecosystem approach to pest management that integrates aAn ecosystem approach to pest management that integrates a
variety of techniques including:variety of techniques including:
Using natural enemies of pests—Using natural enemies of pests—parasites, diseases, andparasites, diseases, and
predatorspredators
Planting of a greater diversity of crops (Planting of a greater diversity of crops (crop rotationcrop rotation) reducing) reducing
the chance of finding a hostthe chance of finding a host
No-till or low-till agricultureNo-till or low-till agriculture, which helps build up of, which helps build up of naturalnatural
enemiesenemies of some pests in soilof some pests in soil
Application of highly specific chemicalsApplication of highly specific chemicals
Components of IPM includeComponents of IPM include
ChemicalsChemicals
Development of genetically resistant stockDevelopment of genetically resistant stock
Biological controlBiological control
Land cultureLand culture
17. An alternative to pesticide use that relies onAn alternative to pesticide use that relies on
natural enemies to suppress pestnatural enemies to suppress pest
populationspopulations
It is just one component of IPMIt is just one component of IPM
Control pest organisms by using naturalControl pest organisms by using natural
ecological interactions includingecological interactions including predation,predation,
parasitism and competitionparasitism and competition
Intentional introduction of predators,Intentional introduction of predators,
diseases, or other parasites of a pestdiseases, or other parasites of a pest
LadybugsLadybugs are predators of many plant-are predators of many plant-
eating pests It is possible to buy quantitieseating pests It is possible to buy quantities
of ladybugs for release in home gardens orof ladybugs for release in home gardens or
farmsfarms
The hope is that theseThe hope is that these ladybugsladybugs willwill feed onfeed on
pestspests and reduce their abundanceand reduce their abundance
Biological control of Pests (Q)Biological control of Pests (Q)
18. Biological control of PestsBiological control of Pests
Use of sex pheromones—Use of sex pheromones—chemical releases by female insectchemical releases by female insect
Can be synthesized & used as bait in trapsCan be synthesized & used as bait in traps
Be effective up to 4.3 kmBe effective up to 4.3 km
Since many moths are pests, synthetic odors can be used toSince many moths are pests, synthetic odors can be used to
control themcontrol them
Spraying an area with the pheromone confuses the males andSpraying an area with the pheromone confuses the males and
prevents them from finding females, which results in a reducedprevents them from finding females, which results in a reduced
moth population the following yearmoth population the following year
19. Genetically modified cropsGenetically modified crops
Genetically modified cropsGenetically modified crops (GM crops, or biotech crops) are(GM crops, or biotech crops) are
plants, theplants, the DNADNA of which has been modified usingof which has been modified using geneticgenetic
engineeringengineering techniques, to resist pests and agents causing harm totechniques, to resist pests and agents causing harm to
plants and to improve the growth of these plants to assist in farmersplants and to improve the growth of these plants to assist in farmers
efficiencyefficiency
Genetically modified crops produce more food, but some worry itGenetically modified crops produce more food, but some worry it
could upset delicate ecosystemscould upset delicate ecosystems
AdvantagesAdvantages
More FoodMore Food
Reduced Need for PesticidesReduced Need for Pesticides
Better Food QualityBetter Food Quality
Disadvantages of GM cropsDisadvantages of GM crops
Destabilization of Ecosystem:Destabilization of Ecosystem: Genetically modifying foods couldGenetically modifying foods could
harm other organisms and upset the balance in the ecosystemharm other organisms and upset the balance in the ecosystem
Creation of New Diseases:Creation of New Diseases: Some modification involves bacteria andSome modification involves bacteria and
viruses, so some people worry that this engineering could createviruses, so some people worry that this engineering could create
new diseasesnew diseases
