Presentation on theme: "LAND & WATER USE (10-15 %). Agriculture Feeding a growing population Human nutritional needs: – 2000-2500 calories/day, less is undernourishment (famines."— Presentation transcript:
Agriculture Feeding a growing population Human nutritional needs: – 2000-2500 calories/day, less is undernourishment (famines are acute incidents of undernourishment catalyzed by war or environmental devastation) – In US, avg. is 3500 calories/day = overnutrition * 1/3 Obese – Malnourishment (pg. 285-287)– shortage of adequate vitamins/minerals: » Kwashiorkor – lack of protein = swollen abdomen » Marasmus – lack of protein/calories = skeletal thinness/wrinkled skin » Anemia – lack of Iron = low energy/fatigue » Ariboflavinosis – Vit. B2 deficiency (one of the most common in the US) = skin problems, sore mouth » Goiter/Hyperthyroidism – iodine deficiency » Rickets – Vit D deficiency (not enough Calcium) » Vit. A deficiency = poor vision » Scurvy – Vic. C deficiency = loose teeth/black and blue skin
Types of agriculture– two types: – Industrialized – uses large amounts of fossil fuel energy, water, fertilizers, pesticides to produce large quantity of a single crop (monoculture), 25% of all cropland (mostly developed countries) – Types of include: » Plantation agriculture – in tropical developing countries, growing cash crops (bananas, coffee, soybeans, etc.) on monoculture plantations for sale in developed countries – Traditional agriculture, practiced by 44% of world, in developing countries, provides 20% of world’s food supply – two types: » Traditional subsistence – crops for family farm survival (uses human labor/animals) » Traditional intensive – increase # of humans/animals/fertilizer = higher yield, farmer can feed family and sell for income.
Green Revolution– uses 8% of oil output – Since 1950, caused increase in global food production from increased yields/unit area of cropland (called first green revolution) – Three steps: » Developing/planting monoculture, selectively-bred, high-yield varieties of key crops: rice, wheat, corn. » Large amount of fertilizer, pesticides, water to produce high yields » Increase # of crops grown/year on land w/multiple cropping (2-3 crops a year on same land) – Since 1967, second green revolution b/c of fast growing dwarf varieties of rice/wheat = greater yield. Genetic engineering and crop production
Deforestation – taking out the natural (water- absorbing) trees/vegetation to make way for timber, fuel, livestock grazing, farming – causes nutrients to leach from topsoil, erosion of topsoil, runoff causing flooding, guillies / landslides.
Irrigation – 57% of irrigation water doesn’t get to crops, most water is used for agriculture – types include. – Drip-irrigation (efficiency = 90-95%) (Best) – above/below ground pipes/tubes deliver water to individual plant roots – Center-pivot (eff. = 80-90%) – water pumped from underground, sprayed from mobile circling sprinklers – Gravity flow (eff = 60-80%) (Worse) – water fills ditches in crop field, much is lost **this can also be called flood-irrigation
Sustainability Agriculture – organic fertilizers – high-yield polyculture plants – biological pest control – integrated pest management – efficient irrigation – soil conservation
Controlling pests Types of pesticides – Insecticides » Chlorinated hydrocarbons (DDT) – high persistence (HP), biologically magnified (BM) » Botanicals (from plants - Rotenone, pyrethrum, camphor), LP, not BM » Microbotanicals (bacteria, fungi, protozoa), LP, not BM – Herbicides – Fungicides ………etc……..… First generation – natural pesticides (though certainly toxic, like metals/arsenic) Second generation – DDT and man-made chemicals (*we don’t know true effects because we have not studied these significantly)
A threshold is the exposure level or dose of an agent above which toxicity or adverse health effects can occur, and below which toxicity or adverse health effects are unlikely. For example, taking aspirin is therapeutic and not dangerous up to a contain dose, but above that dose it can cause nausea, brain damage, bleeding, and, eventually, death. The LD50 is the dose that kills half (50%) of the animals tested (LD = "lethal dose").
Costs and benefits of pesticides use – Benefits: » save human lives – from malaria (mosquitoes), bubonic plague (rat fleas), typhus (body lice/fleas), sleeping sickness (tsetse fly) » increase food supplies/lower cost – losses from pests would be worse without pesticides » increase profits for farmers » work faster/better than alternatives » when used properly/risks are less than benefits – Risks: » **BIGGEST PROBLEM: Accelerate development of genetic resistance to pesticides – insects can develop immunity w/in 5-10 years through directional natural selection » Broad-spectrum insecticides also kill natural predators/parasites which help control pest populations » Pesticides don’t stay put – 2% gets to crops during aerial spraying (go into air, surface water, groundwater, food, etc.) » Some harm wildlife (wiped out 20% of honeybee colonies, kill 67m birds and 6-14m fish/year) » Can threaten human health – 3m in developing countries are poisoned by them each year.
Integrated pest management – important for pollution prevention (could drop pesticide risks by 75%), crops are evaluated as part of a ecological system; controlled by: cultivation, biological, chemical methods: Goal is to reduce crop damage to an acceptable level: Relevant laws – FIFRA (1947) – Federal Insecticide, Fungicide, and Rodenticide Act – requires EPA approval for use of all commercial pesticides » EPA sets tolerance level specifying amount of toxic pesticide that can remain on crops that people eat » Banned: most chlorinated hydrocarbons, several carbamates/organophosphates.
Forestry Old Forest- 100 + years old. New Forest Even Aged- tree farms Uneven Aged- Natural Forest Deforestation- removal of trees * Slash and Burn Fragmentation- disruption of habitat Person
Tree Harvesting SELECTIVE CUTTING- best for the environment SHELTER WOOD CUTTING SEED TREE CUTTING * CLEAR CUTTING- most devastating STRIP CUTTING
– Sustainable land-use strategies Forests – Grow timber on long rotations (100-200 years) – Selective cutting of individual trees, strip cutting (NOT clear cutting) – Minimize fragmentation of remaining forests – Reduce road-building in remaining forests – Use logging/road-building that minimizes soil erosion.
Forest Fires Ground Fires- Chaparral (California) * rainy season followed by drought. Crown Fires- * Benefits- Return nutrients, rid of pest & disease
– National forests– forests cover 30% of US land, provide habitats for 80% of wildlife, supply 2/3 of water runoff; there are 156 national forests, good b/c: Economic: $4B worth of oil/minerals, 3M cattle graze on it, 19% of US forest area Ecological: habitat for 200+ endangered species, habitat for $4-7B pollinators, provides clean drinking water for 60m people Recreational: hunting, fishing, camping
Public and federal lands Management – best way to preserve biodiversity – more than 17,000 areas (10% of world) is protected – conservationists want to protect 20% - would need funding by national governments and cooperative ventures with businesses (** #1 reason for extinction is habitat destruction) Wilderness areas– provide mostly undisturbed habitats for wild plants/animals, provide a natural lab to discover how nature works…preserves biodiversity, protect them as centers of evolution National parks – National Park System established in 1912, has 55 national parks (most in the west) – most are too small to sustain large species, many suffer from invasion from non- native species – pollution is the biggest problem Wildlife refuges– Teddy Roosevelt established first Wildlife Refuge in 1903, now 524. Visited to hike, hunt, fish. 75% are wetlands and protect migratory birds, protect 20%+ endangered species (have helped many recover). Wetlands - important for biodiversity, Federal Wetlands Law: requires a permit to fill or deposit material in a wetland (cut wetland loss by 80%); goal is zero net loss (does allow for mitigation banking. Estuaries- rivers meet the sea- important breeding grounds.
Rangelands – Overgrazing– too many animals graze on grassland for too long and exceed the carrying capacity of the grassland (mostly caused by excessive feeding of livestock animals; leads to: Lower NPP (net primary productivity) of grasslands Erosion of grassland by wind/water Compaction of soil (decreases water holding capacity) Invasion of grassland by shrubs MAJOR cause of Desertification!!
Urban land development Planned development three models: – Concentric circle model – sprawl develops outwards from a central business district; example: NYC – Sector model – pie-shaped wedges of commercial/industrial/housing districts – Multiple-nuclei model – many independent cities very close together; example: LA, California
Suburban sprawl – growth of low-density development on the edges of cities (encourages the dependence on cars); leads to loss of cropland/forest/wetlands, pollution of drinking water/air, greenhouse gas emissions, etc.
Urbanization – number of people living in cities w/greater than 2500 people: – Advantages: populations live longer/lower infant mortality, better access to medical care/family planning/education, recycling is more feasible, helps preserve wildlife habitats (occupy 2% of earth’s land) – Disadvantages: not self-sustaining, consumes 75% of earth’s resources, lack trees, produce little of their own food, can have water supply problems Urban Blight- run down urban areas- “projects”
Transportation infrastructure Canals and channels– artificial waterways used for travel, shipping, or irrigation, often narrows or straightens natural streams, can increase flow of water increasing erosion and flooding, reducing habitats for wildlife Ecosystem impacts of roads – cutting down forests for roads can lead to erosion, and runoff Mass transit Advantages: More energy efficient than cars, produce less air pollution than most cars, require less land than roads and parking areas for cars, cause fewer injuries/year, reduce car congestion in cities Disadvantages: expensive to build/maintain, cost efficient only in densely populated areas, can cause noise
Land conservation options Preservation – set aside land for protection – John Muir was an early leader of the preservationist movement he also founded the Sierra Club Remediation – (repair) similar to decontamination - removal or neutralization of chemical substances from a site to prevent any adverse effects. Mitigation– means “trade off” – mitigation banking is when destruction of existing wetland/land is allowed as long as an equal area of the same type of wetland/land is created or restored (not always successful – but better than nothing) Restoration– trying to restore a degraded habitat or ecosystem to a condition as close as possible to the pre-degraded state
Mining Surface mining safer than sub-surface – Open-pit mining: machines dig holes and remove ores – Dredging: chain buckets/draglines scrape underwater mineral deposits – Area strip-mining – strip away overburden and remove minerals (used on flat surface) – Mountain top removal Sub-surface mining – dangerous, removes deep deposits, disturbs less land/produces less waste material. * Shaft, Tunnel, Slope – Room and pillar – machine out all but a pillar to hold up mine roof – Longwall mining – steel props support mine roof
– Relevant laws and treaties General Mining Law of 1872 – allows mining companies to take minerals from public land without paying royalties Surface Mining Control and Reclamation Act (SMCRA), 1977 – regulates the environmental effects of coal mining (sets standards)
World Wide 1 billion people depend on fish as their main source of food. 1 million employed in fishery industry. 125 million ton harvested annually - 75 % consumed as food. FISHERIES
Blue Revolution Overfishing Bycatch Magnuson Fishery Conservation and Management Act. (1976) Sanctuaries- Dry Tortugas
Fig. 10-17, p. 216 Buoy Trawler fishing Drift-net fishing Purse-seine fishing Long line fishing lines with hooks Sonar Fish farming in cage Spotter airplane Deep sea aquaculture cage Fish caught by gills Float Aquaculture