L 12 global effects of agriculture

Lecture 12Lecture 12Global Effects of AgricultureGlobal Effects of Agriculture

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Global Effects of AgricultureGlobal Effects of Agriculture

Agriculture is the world’s Agriculture is the world’s largest & oldestlargest & oldest industry industryThe production, processing, and distribution of food all The production, processing, and distribution of food all alter alter the environment.the environment.Because of the size of the industry large Because of the size of the industry large effects effects on the on the environment environment are unavoidableare unavoidable

On-site (primary) effectOn-site (primary) effect

Where the agriculture Where the agriculture takes placetakes place

Off-site (secondary) Off-site (secondary) effecteffect

Away from the Away from the agricultural site, agricultural site, typically downstream & typically downstream & downwinddownwind

Major environmental problems of Agriculture (Q)Major environmental problems of Agriculture (Q)

DeforestationDeforestation Desertification Desertification Soil erosionSoil erosion OvergrazingOvergrazing Degradation of water resources Degradation of water resources SalinizationSalinization Accumulation of toxic metals & toxic organic compoundsAccumulation of toxic metals & toxic organic compounds Water pollutionWater pollution EutrophicationEutrophication


Global EffectsGlobal Effects Changes in Changes in albedo albedo Evaporation Evaporation of waterof water RoughnessRoughness of the surface of 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 agriculture Modern agriculture by clearing landby clearing land and as a major user of and as a major user of

fossil fuelsfossil fuels increasesincreases the concentration of the concentration of carbon dioxidecarbon dioxide Affects Affects climateclimate through fire through fire


Fires associated with release of significant amount of Fires associated with release of significant amount of carbon carbon dioxidedioxide, and small , and small particulatesparticulates to the atmosphere to the atmosphere

Another global effect results from the production and use of Another global effect results from the production and use of nitrogenous fertilizernitrogenous fertilizer which leads to significant change in which leads to significant change in global biogeochemical cyclesglobal biogeochemical cycles

Agriculture affects Agriculture affects biodiversitybiodiversity The loss of competing ecosystems The loss of competing ecosystems reduces biodiversityreduces biodiversity IncreasesIncreases the number of the number of endangered speciesendangered species

Pests Pests are undesirable are undesirable competitors, parasites, or competitors, parasites, or predatorspredators

Major agricultural pests are Major agricultural pests are insectsinsects

NematodesNematodes BacterialBacterial and and 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 crop In terms of potential crop

loss weeds are the major loss weeds are the major problemproblem

There are about There are about 30,00030,000 species of weedsspecies of weeds

In any year a typical farm is In any year a typical farm is infested with between infested with between 10 10 and 50and 50 weed species weed species

Compete with crops Compete with crops for all for all resourcesresources

Pest Control and Agricultural ChemicalsPest Control and Agricultural Chemicals

PreharvestPreharvest losseslosses are from are from weedsweeds Post harvest lossesPost harvest losses are largely due to are largely due to herbivoresherbivores

Weeds

Pest

Symptoms of pest attack

Pest Control—PesticidesPest Control—Pesticides

Worldwide only about 100 species of weeds, insects, fungi and Worldwide 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 we are 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 were Earlier pesticides were broad spectrumbroad spectrum One of the earliest pesticides used was One of the earliest pesticides used was arsenicarsenic, a chemical , a chemical

element element toxic to all lifetoxic to all life including people including people


Development of more sophisticated pesticides began in Development of more sophisticated pesticides began in 19391939 when when Paul Muller discovered DDTPaul Muller discovered DDT

DDTDDT soon became the world’s soon became the world’s most usedmost used pesticidepesticide and and Paul Paul MullerMuller received the received the Nobel PrizeNobel Prize in in 19481948 for his discovery for his discovery

It appeared to have no short-term effect on people and It appeared to have no short-term effect on people and seemed to kill only insectseemed to kill only insect

Eventually Eventually three factsthree facts about DDT were discovered which about DDT were discovered which led to led to its banningits banning

1. 1. Long term effectsLong term effects on other on other desirabledesirable organisms organisms

2.2. Stored in oils & fats Stored in oils & fats and and concentrated as it passed up in food concentrated as it passed up in food chains— chains— biomagnificationbiomagnification

3. Storage in oils & fats allows it to be 3. Storage in oils & fats allows it to be transferred biologicallytransferred biologically Because of these problems DDT was considered as the Because of these problems DDT was considered as the

most notorious chemical of the last centurymost notorious chemical of the last century


Alternatives to DDTAlternatives to DDT With the banning of DDT With the banning of DDT low persistentlow persistent (length they (length they

remain deadly in the environment) remain deadly in the environment) organophosphatesorganophosphates, , carbamatescarbamates became prominent became prominent

These chemicals are These chemicals are more specificmore specific and and decay rapidlydecay rapidly in in the soilthe soil

They tooThey too, , are toxicare toxic and must be handled carefully and must be handled carefully

Perfect PesticidePerfect Pesticide

A A perfectperfect pesticide would have the following characteristics: pesticide would have the following characteristics: InexpensiveInexpensive Highly specificHighly specific Less persistentLess persistent Breakdown into harmless materials Breakdown into harmless materials

However, the perfect pesticide has not been inventedHowever, the perfect pesticide has not been invented

Problems of Pesticide Use—Impact on other organismsProblems of Pesticide Use—Impact on other organisms

A major problem is that broad-spectrum insecticides kill natural A major problem is that broad-spectrum insecticides kill natural predators and parasites that help control the population of pest predators 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 the of the insecticide applied to crops reaches the target peststarget pests

Less than 5% of herbicideLess than 5% of herbicide applied to crops reach the target applied to crops reach the target weedsweeds

Pesticides that miss their target pests end up in the air, both Pesticides that miss their target pests end up in the air, both surface & groundwater, bottom sediments, food, nontarget surface & groundwater, bottom sediments, food, nontarget organisms including humans & wildlifeorganisms including humans & wildlife

Problems of Pesticide Use—Impact on other organismsProblems of Pesticide Use—Impact on other organisms

Most pesticides can be toxic to humans causing genetic Most pesticides can be toxic to humans causing genetic mutations, birth defects, behavioral disorders, effects on the mutations, birth defects, behavioral disorders, effects on the immune systemimmune system

Can cause cancer and death to animals Can cause cancer and death to animals

Sensitive plants can show signs of growth irregularity, loss in Sensitive plants can show signs of growth irregularity, loss in biomass, or deathbiomass, or death

Contamination of soil and aquatic ecosystems reduce the Contamination of soil and aquatic ecosystems reduce the activity of beneficial microorganismsactivity of beneficial microorganisms

Extreme case of contamination can reduce the activity of Extreme case of contamination can reduce the activity of these microorganisms to essentially zerothese microorganisms to essentially zero

Integrated Pest Management, IPM (Q)Integrated Pest Management, IPM (Q)

An ecosystem approach to pest management that integrates a An 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, and parasites, 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 natural natural enemiesenemies of some pests in soil of 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

An alternative to pesticide use that relies on An alternative to pesticide use that relies on natural enemies to suppress pest natural enemies to suppress pest populationspopulations

It is just one component of IPMIt is just one component of IPM Control pest organisms by using natural Control pest organisms by using natural

ecological interactions including ecological 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 quantities eating pests It is possible to buy quantities of ladybugs for release in home gardens or of ladybugs for release in home gardens or farmsfarms

The hope is that these The hope is that these ladybugsladybugs will will feed on feed on pestspests and reduce their abundance and reduce their abundance

Biological control of Pests (Q)Biological control of Pests (Q)

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 to Since many moths are pests, synthetic odors can be used to

control themcontrol them Spraying an area with the pheromone confuses the males and Spraying an area with the pheromone confuses the males and

prevents them from finding females, which results in a reduced prevents them from finding females, which results in a reduced moth population the following yearmoth population the following year

Genetically modified cropsGenetically modified crops

Genetically modified cropsGenetically modified crops (GM crops, or biotech crops) are plants, (GM crops, or biotech crops) are plants, the the DNA of which has been modified using of which has been modified using genetic engineering techniques, to resist pests and agents causing harm to plants and to techniques, to resist pests and agents causing harm to plants and to improve the growth of these plants to assist in farmers efficiencyimprove the growth of these plants to assist in farmers efficiency

Genetically modified crops produce more food, but some worry it could Genetically modified crops produce more food, but some worry it could upset delicate ecosystemsupset 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 could harm Genetically modifying foods could harm

other organisms and upset the balance in the ecosystemother organisms and upset the balance in the ecosystem Creation of New Diseases: Creation of New Diseases: Some modification involves bacteria and Some modification involves bacteria and

viruses, so some people worry that this engineering could create new viruses, so some people worry that this engineering could create new diseasesdiseases

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L 12 global effects of agriculture

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