The Effects of Agriculture on WildlifeBy Sarah Langan

Pesticides• Include insecticides and

herbicides• Routinely applied by farmers

to increase crop yields• Ariel spraying• Ground spraying• Granules

• Wildlife is exposed to pesticides by• Breathing them in • Ingesting them through contaminated

food and water• Absorbing them through their skin or feathers

Insecticides• Eliminate crop pests by attacking their central nervous systems• Direct affects on wildlife include• Sickness • Behavioral changes• Diminished reproductive abilities• Death

DDT• Persists in the environment, insoluble in

water, and accumulates in runoff• Fat solubility permits bioaccumulation • Effects bald eagle, osprey, peregrine falcon, and other birds• Causes the shells of the birds’ eggs to become so thin that they

are crushed when the parents try to incubate them• Banned in the United States in 1973 • Banned worldwide in 2006, except in African countries where

it is used to kill mosquito vectors of malaria

Diazinon• Negative impacts on birds• Decreases the number of eggs laid• Decreases survival rates of eggs and hatchlings• Increases embryonic deformities

• One granule can kill five house sparrows • Banned from use on farms and golf courses in 1988• Still widely used as home pest control

• 2001 estimates show that six million pounds are applied annually

Herbicides• Most commonly used pesticides on farms• Direct effects• Paraquat: causes abnormal embryonic bird growth and reduces

rates of hatching in waterfowl eggs• Indirect effects• Destroys habitat and food sources

Solutions - Pesticides• Ground application • Use most effective pesticide that is least detrimental to

wildlife• Microbial insecticides• Bacteria, viruses, and fungi that selectively attack a single species

or group of target insects• Do not harm mammals, birds, or fish

• Crop pest parasites and predators• Leave some areas untreated• Drainages, bottomlands• Field borders, fencerows, ditch banks

• Cover granules completely with soil• Develop more pest resistant crops

Run off• Chemicals from pesticides and nutrients from fertilizers build

up in the soil• Soil erosion deposits nutrients into aquatic ecosystems• Sedimentation• Build up of suspended soil particles• Direct affects

• Suppresses plant development• Limits sight-feeding fishes’ ability to

find food• Clogs fishes’ gills and limits oxygen

intake• Smothers eggs and larvae

Eutrophication• Excess nitrogen and phosphorous create low

oxygen conditions in aquatic ecosystems• Increases plant and animal biomass but decreases diversity

and changes the dominant biota • Algal blooms• Block sunlight from reaching aquatic plants

• Destroys habitat for fish and depletes food for waterfowl • Dead blooms sink to the bottom and are consumed by bacteria

• Bacteria use large amounts of dissolved oxygen when multiplying

Dead Zones• Aquatic areas of unlimited algae growth and

<2 ppm of dissolved oxygen• Gulf of Mexico• 6000 – 7000 square miles• Caused primarily by runoff from the Mississippi

River Valley• Gulf of California• Yaqui Valley irrigations are followed by

large blooms of red and brown tides• 19 – 223 square miles• Causes paralytic shellfish disease

Solutions – Runoff• Use fewer fertilizers• Decrease the rate of application• Animal waste control or conversion into fuel for electricity and

heating• Limit the amounts of nutrients, organic matter, and harmful

chemicals in waste from manufacturing facilities

Deforestation• Primary cause is agriculture• Destroys habitat and food sources• Increases competition for limited resources• Increases risk of extinction

• Endemic species• Populations that cannot adapt

Solutions – Deforestation • Stop clear-cutting• Replace trees that are cut down• Governmental regulations

Species that Benefit from Farming• Traditional farming practices in developing countries create

grassland habitats for threatened birds

Organic Farming• No chemical pesticides• Hedgerows and ditches provide habitat for natural predators

• No artificial fertilizers• Strictly manure

• Antibiotics only given to livestock as needed• Crop rotation• Mixed farming• Spring sowing

Pros• Known to increase

biodiversity on the farm• 2010 University of

Leeds study: 12.4% increase• 2012 University of

Oxford study: 30% increase

• Lower crop yields• 2010 University of Leeds

study: 55% decrease• 2012 McGill University and

University of Minnesota study: 25% decrease overall, 13% decrease with improved management techniques• Cereal crops have worst yield

decrease• Legumes, soybeans, and

fruits yield almost as much as conventional farming

and Cons

Shade-grown coffee• Introduced by the Smithsonian Migratory Bird Center in 1996• Coffee grows in the shade of native trees maintained by the

farmer

Pros• Creates suitable

habitat for many avian species• Natural pest control by

birds, bats, and predatory insects• Higher soil quality than

sun-grown coffee

• Lower yield than sun-grown coffee• Farmers profit from

fruit, firewood, medicinal herbs, building materials, and ecotourism

and Cons

Questions?