Environmental Biology BIOL 107
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Date Created: 10/05/15
Chapter FOOD AND AGRICULTURE FOOD AND NUTRITION In the last 40 years population growth averaged 17 but food production increased by an average of 22 Food supplies have kept up with population increase The amount of energy each person needs to remain active and healthy depends on body weight climate state of health stress level and basic metabolism 0 A small sedentary adult in a warm climate requires less than 2000 calday o A large muscular person living a very active life in a cold climate requires more than 6000 calday Food and Agriculture Organization FAO of the United Nations estimates that the average minimum daily caloric intake over the whole world is about 2500 calday CHRONIC HUNGER AND FOOD SECURITY Chronically undernourished people receive less than 2200 calories per day In the 1960s 60 of the population of developing countries was considered chronically undernourished At present it is estimated at less than 15 undernourished The UN Food and Agriculture Organization estimates that food production will continue to increase to provide 2800 calday in a near future and 3050 calday by the year 2030 About 850 million people don t have enough to eat 90 of the chronically undernourished are in developing countries Agricultural production has fallen in countries in transition eg former communist countries Poverty is the greatest threat to food security the ability to obtain sufficient food on a day to day basis Some analysts suggest that by reducing the world hungry the economic growth could greatly increase due longer healthier more productive lives for several hundred million people Hungry people are often excluded from the labor force because they are too weak to work Some countries like China Vietnam Nigeria Ghana and Peru have reduced chronic hunger by several millions Still other countries have increased their chronically underfed population eg lndia Women do 50 to 70 of the farm work in most of the world but rarely have access to control of the land capital and developmental aid Chronic hunger increases susceptibility to disease and leaves people feeling weak and lethargic reducing their ability to work This is reflected in economies and contributes to a devastating cycle of household hunger and poverty Vitamin and mineral deficiencies in children lead to stunted growth blindness and compromised mental development Iron deficiency anemia contributes to 20 percent of maternal deaths in Africa and Asia Source Food and Agriculture Organization fact sheet httpwwwfaovl quot 39 39 quot 39 quot 39 39 quot39 ndf httpwwwfao quot l39 39 html ACUTE FOOD SHORTAGES Famine is the acute food shortage that results in a largescale loss of life social disruption and economic chaos 0 Seed grains and breeding stock are eaten 0 Mass migration of starving people 0 Long time to recuperate after better conditions returned Causes of famine 1 Environmental conditions often triggerfamine eg drought pests 2 Political instability and economics also cause food shortages 3 Armed conflict is a major cause of famine Arbitrary political boundaries along with wars and land seizures by the powerful and rich block access to areas that once served as refuge during natural disasters Herding people into feeding camps is often the worst thing to do for them 0 Lack of sanitation 0 Lack of jobs 0 Social chaos and family breakdown o Often people can t replant when the situation returns to normal MALNUTRITION AND OBESITY In addition to calories we need specific nutrient in our diet 0 Proteins vitamins and minerals o Fats and carbohydrates provide calories needed for energy production in cells Some definitions Undernourished people who receive less than 90 of their minimum dietary needs Seriously undernourished less than 80 of the minimum dietary needs Overnutrition too many calories eg average daily intake in US is 3500 calday Malnourishment nutritional imbalance According to the US Surgeon General 62 of the US adult population are overweight and about 33 are seriously overweight or obese o Obese about 30 pounds above normal for an average person Lack of time for cooking and access to health food choices along with ready availability of fast food snacks and calorieladen drinks lead to dangerous dietary imbalances for many people Obesity is spreading around the world For the first time there is more overweight people than underweight lmbalance in the diet can lead to illness and even death Lack of iron leads to anemia lack of iodine leads to goiter Lack of proteins causes kwashiorkor anemic listless low resistance to diseases Marasmus is cause by lack of proteins and carbohydrates shriveled and very thin Vitamins are needed in very small amounts daily Some diseases associated with vitamin deficiency are scurvy pellagra and beriberi EATING A BALANCED DIET Generally it isn t necessary to take dietary supplements Eating a good variety of goods should give the person all the nutrients needed A diet low in meat dairy products fats and sweets is recommended New recommendation made by dietitians are 0 Eat little meat butter rice pasta potatoes and sugar 0 Nuts legumes beans peas etc fruit vegetables and whole grain should be eaten in abundance Unsaturated fats are recommended eg plant oils olive canola sunflower etc Transfats like those found in margarine are not recommended KEY FOOD SOURCES Our food comes mostly from about a dozen seeds and grains three root crops twenty or so fruit and vegetables six mammals two domestic fowl and a few fish and other forms of marine life Major crops 0 Primary Wheat rice and corn maize The majority of humanity depends on these three crops for their caloric and nutrient needs 0 Secondary oats rye barley and potatoes are important in mountainous regions and high latitudes These crops need a cool moist climate eg Northern Europe and Asia North America Cassava beans svaEt putatues yams and am m the trupms They gruvv m Warm Wet areas e g Amazuma Mmaneswa Snuth Paeme s ands Canooean We and surghum w my hmates They are mpunant w dry areas qufnca Abuut one two ufthe cerea oseo m the Worm guestu feed hves mck Meaty mm and seafuud North Amerma Eurupe and Japan make up 2m ufthe Worm pupu atmn and eonsome Buno of 3 the meat and WM m the Worm Fwsherwes eonmoote abuut 16 of mo quahty prutem eonsomeo Wonoywoe Pn anan Wmm FP ZHH and F39mhppmes remme sensmg PVHha e made shmg very Ef ment dep eted bythe UN senuus enyoonmemax pmb ems 5pm 55 chili 5mm Gmundnul pus hm Dry QuaIs beans Imn Mex man allnunsm coon FARM POLICY Much of the increase in food production over the past 50 years is the result of public support for agricultural education research and development projects such as irrigation systems transportation networks and crop insurance Agricultural subsidies can distort markets and cripple production in developing countries Agricultural subsidies encourage surpluses and allow farmers to sell their products overseas at as much as 20 below the actual cost of production This makes imported food cheaper than locally grown crops in many developing countries The FAO argues that ending distorting financial support in the richer countries would have a far more positive impact on food supplies and livelihoods in the developing world than any aid program SOIL A RENEWABLE RESOURCE Soil is an ecosystem and an essential component of the biosphere Soil can be used sustainably and enhanced under careful management There are about 15000 different types of soil in the United States In order to feed the world on a sustainable basis we need to know how the soil is formed how it is lost and what can be done to protect and rebuild good agricultural soil 0 Young soils have not been weathered for long and are rich in nutrients o In old soils rainwater has washed away minerals and organic matter and left behind clay and rustcolored oxides With care soils can renew and replenish indefinitely SOIL COMPOSITION WHAT IS SOIL Soil is a mixture of mineral matter organic matter water air and organisms INORGANIC MATTER Weathering breaks down the bedrock into small particles Particle size Gravel 264 mm Sand 0052 mm Silt 0002005 mm Clay less than 0002 mm Particle size affects the character ofthe soil Sandy loam organic matter clay and sand mixture is the best for agriculture Humus is the partially decomposed bodies of plants and animals 0 Humus coats mineral particles and holds them together in loose crumbs making the soil spongy Spongy soils hold water and nutrients needed by plants Maintains spaces for root hairs to grow SOIL ORGANISMS Soil is an ecosystem with its peculiar community of animals plants algae fungi and microorganisms Most animals stay close to the surface Burrowing animals and plant roots contribute to the turn over and aeration of soil There are many decomposers that return nutrients to the soil Mycorrhizal symbiosis is an association of between the roots of plants and certain fungi 0 Plant provides food to the fungus o Fungi absorbs water and minerals and transfer them to the plant 0 A mutualistic relationship where both partners benefit Plant roots penetrate the soil and draw water and mineral from it the roots also secrete acids that decompose mineral particles Fallen plant litter adds new organic material to the soil returning nutrients to be recycled SOIL PROFILES Most soils are stratified into layers called horizons 1 horizon surface litter made of fallen leaves twigs and other debris 2 A horizon topsoil made of organic matter humus organisms inorganic matter 3 E horizon zone of leaching where dissolve material moves downward by percolating water 4 B horizon subsoil low in organic matter and high concentration of minerals iron aluminum 5 C horizon weathered parent material broken rock fragments often brought to the place by geologic forces wind water and glaciers 6 R horizon bedrock impenetrable Soils are classified according to the texture color and composition of its horizons Because climate plays an important role in soil formation soils differ widely from one major climatic zone to another Tropical climates with their high temperature and rainfall yield deep strongly weathered and leached soils with low nutrient contents The lush vegetation is almost the only source for replenishing nutrients Arid climates with low precipitation and high evaporation give rise to soils that contain variable amounts of easily soluble components such as calcium carbonate or gypsum that is left behind after evaporation of water from the soil In temperate climates soi formation to a large extent a chemical process is more or less restricted to the warmer part of the year resulting in less weathered and less deep sois as compared to tropical regions In arctic climates soi formation is even m r restricted Moreover it is strongly influenced by freezingthawing processes and the presence of permanently frozen subsoil permafrost Source httpwwwisricnl Additional information httpWWW fan quot 39 cdraspurl filedocrepNV8594EW8594E00htm SOIL TYPES Alfisols are produced under moist deciduous forests Mollisols are formed under grasslands Both are very fertile Histosols are formed in waterlogged places where there is a lot of partially decayed plant material WAYS WE USE AND ABUSE SOIL Only about 11 of the earth39s land area is currently in agricultural production Constraints to agriculture steep slopes shallow soil poor drainage low nutrient level metal toxicity excess salts and acidity LAND RESOURCES Arable land is unevenly distributed around the world Worldwide the cropland available for agriculture is shrinking The current ratio is 021 hectares of croplandperson o 1 ha 247 acres Current population projection is that by the year 2025 the average cropland per person will decline to 042 acreperson In Asia the average will be 022 acre person 95 of the recent agricultural growth has come from improved crop varieties increased fertilization irrigation and pesticide use Productivity per unit of land has increased Largest increases in cropland have occurred in South America and Oceania where forests are being converted to agriculture Asia and Europe have little opportunity to open new cropland The soils of tropical Asia Africa and South America are old and generally infertile Most of the nutrients are in the standing plants and not in the soil LAND DEGRADATION Land is considered degraded when the soil is impoverished or eroded water runs off or is contaminated more than is normal vegetation is diminished biomass production decreased or wildlife diversity diminishes This results in 0 Lower crop yields in farmlands 0 Fewer livestock can be supported per unit of area in ranchlands 0 Fewer species in nature reserves In the past 50 years some 19 billion ha 1 ha 246 ac of agricultural land has been degraded This area is greater than that now in production 0 300 million are strongly degraded o 910 million are moderately degraded this area is about the size of China Causes vary from wind erosion water erosion salinization waterlogging nutrient depletion and toxic chemicals Every year 0 3 million ha of cropland are ruined by erosion o 4 million ha are turned into deserts o 8 million ha are converted to nonagricultural uses roads shopping centers housing etc No degradation Light soil degradation Moderate soil degradation Severe soil degradation Source httpwwwisricnl Photos of soil degradation httplwwwfaoorgIandandwateraglIlphotolibtoc ehtm httplwwwfaoorgdocrep003w2612ew2612eMap12epdf EROSION It is a natural process that redistributes the products of weathering and it is part of soil formation and soil loss It is a disaster only when it occurs in the wrong place at the wrong time A thin layer of top soil is removed every year until eventually nothing is left but poorquality subsoil that requires more fertilizer and water to produce any crop at all It is estimated that 25 billion tons of soil are lost from croplands each year due to wind and water erosion 1 of the cropland per year Erosion causes siltation of rivers reservoirs estuaries wetlands and offshore reefs and banks Erosion could reduce agricultural production by 25 in Central America and Africa and 20 in South America by the year 2003 Mechanisms of erosion 0 Sheet erosion layers of soil are removed from the surface Rill erosion rivulets or small channels of running water Gully erosion large channels of running water Streambank erosion washing away of soil from stream and riverbanks often removing trees Plowing fields or overgrazing is responsible for exposing the soil to the action of water and wind United States has one of the highest rates of soil erosion in the world o It exceeds soil formation on cropland by 40 0 About 12 of the soil that existed before the Europeans came has been lost 5 tons per acre is generally considered the maximum tolerable rate of erosion Erosion in some areas of British Columbia can be as high as 30 tons of topsoil per hectare Continuous monoculture cropping can increase soil erosion crop rotation tends to diminish erosion Worldwide about 25 ofthe land has potential use for agriculture About twice as much as we now use EROSION HOTSPOTS China India Russia and Ethiopia have high erosion rates It is estimated that China loses soil at a rate 20 times that of the United States The Huang Yellow river carries 700 kg of silt per cubic meter or 50 by weight The Ganges is next after the Huang in annual sediment load Some experts say that Haiti has no topsoil left Population pressure is responsible for the cutting of trees and plowing the grasslands with great effect on soil and loss of biodiversity Large expanses of land could be used more intensely with the proper input of fertilizers high yield crops and technology OTHER AGRICULTURAL RESOURCES Agriculture is also dependent upon water nutrients favorable climates productive crop varieties and upon the mechanical energy to tend and harvest the crops WATER Efficiency of irrigation water use is rather low in most countries High evaporation rate and seepage may cause the loss of up to 80 of the water intended for irrigation Waterlogging or salinization is the result of overwattering o Waterlogged soil is saturated with water and plant roots die from lack of oxygen 0 Salinization occurs when mineral salts accumulate in the soil it occurs particularly when soils in dry climate are irrigated with saline water lrrigation problems are a major source of land degradation and crop losses worldwide FERTILIZER Nitrogen potassium and phosphorous often limit plant growth Calcium and magnesium are often limited in areas of high rainfall Overfertilization often occurs because farmers are not aware of the nutrient content of the soil they farm Nitrates and phosphates are a major cause of aquatic ecosystem pollution Many countries have reported dangerous level of nitrates in ground water in farming areas eg France Germany Denmark and United States Eutrophication of lakes streams and ponds results from excessive nutrients in the water Some alternatives to chemical fertilizers are manure compost ashes crop residues leguminous crops ENERGY Farming in industrialized countries is generally energy intensive Fossil fuels supply most of the energy required in agriculture There is an indirect use of energy in the production of synthetic fertilizers and pesticides Additional food is used in food processing distribution storage etc Wind could become a source of energy Renewable energy sources are crops that can be converted into biofuels ethanol 0 Fuel crops are taken to be existing agricultural crops which can be used for fuel and energy as well as food eg wheat C225million hectares sugar beet C170000 ha potatoes 160000 ha and oilseeds C425 000 ha These crops are likely to be the serious feedstocks for biofuelling road transport 0 By products are taken as fuel feedstocks available in addition to the main crop ie straw forestry waste oil seed meals brewer39s grains sugar beet pulp and in the case of biodiesel glycerol Also in the case of biodiesel recycled cooking oils I I I Source httn39lwww hindiesel r n uknress on 39 htm NEW CROPS AND GENETIC ENGINEERING Most of the food in the world comes from 16 species of plants GREEN REVOLUTION The term was coined in 1968 by William Gaud director of the US Agency for International Development It is a movement to increase agricultural yield by using new cultivars fertilizers pesticides irrigation and mechanization Most countries have to depend on the agricultural land they have at present A few subSaharan African and Latin American countries have open new land to agriculture Europe and the former Soviet Union have lost agricultural land due to degradation After the WWII the Ford and Rockefeller Foundations set up agricultural research stations to breed tropical wheat and rice varieties that could provide substantial yield gains New strains of rice and wheat have triple or quadruple yields per hectare 22 acres in the tropics The new breeds respond more efficiently to increase in fertilizer and water than traditional breeds The are called quothigh respondersquot Under poor conditions these quothigh respondersquot often due worst than traditional varieties Throughout the world native varieties are being replaced by the new types and their genetic resource is in danger of being lost Seed banks are being set up to store many seed varieties for future breeding Mediterranean climate and savannas have produced about half of the thirty major food crops used by humans worldwide These biomes have long dry seasons and plants tend to store energy in their seeds roots and tubers Plants that originated in these two biomes produce 23 of our annual food supply 0 Middle East Fertile Crescent wheat barley oats rye figs peas apples grapes melons o and onions 0 Mesoamerica corn tomatoes beans chilies and squash 0 North China rice sorghum apricots peanuts yams peaches About 3000 plants have been used for food but only 16 plants are widely used for food For additional information visit httpwww arches una 39 quot 39 htm An interesting evaluation of the Green Revolution is found at httpWWW fnndfirqt quot 39 quotmom m m u hfml GENETIC ENGINEERING The development of genetically modified organisms GMOs by introducing genes of other species is called genetic engineering 0 Transgenic organisms Genetic engineering is common in agriculture Research is now underway to improve yields and create crops that Resists drought frost and disease Tolerate salty waterlogged or lownutrient soils Produce their own pesticides that will reduce the use of pesticides O O O 0 Higher vitamin and protein content Animals are being genetically modified to grow faster gain weight on less food and produce pharmaceuticals such as insulin in their milk Criticism 0 Pest resistance could be transferred to wild plants creating quotsuper weedsquot that are resistant to herbicides or to insect pests o Constant presence of pesticides in plants could accelerate pesticide resistance in insects or leave toxic residues in soil or food 0 GMO crops are relatively expensive and are criticize for enriching the rich multinational companies and make farmers dependent on them for seeds 0 Unanswered questions about possible health problems About 70 of the processed foods contain transgenic products including tomatoes potatoes corn and oils GMO in the United States 0 82 of soybeans o 71 of cotton 0 25 of maize PEST RESISTANCE Bacillus thuringiensis Bt a bacterium makes toxins lethal to members of the butterfly and beetle families of insects These insect families are responsible for most of the crop damage caused by insects Genes of Bt have been transferred to cotton corn and potatoes This new technology has reduced the use of pesticides by farmers Criticism o Entomologists worry that plants will produce the toxins regardless of level of infestation and eventually produce resistant strains 0 The problem of nontarget species being affected by the toxins is another criticism Monarch butterfly caterpillar dye if they eat pollen containing Bt toxins WEED CONTROL The most popular transgenic crops are not insectresistant but those engineered to tolerate high doses of herbicides Crops containing these genes can withstand heavy herbicide spraying to kill weeds growing in between the crop plants Criticism The creation herbicide resistant super weeds Domestic crops can interbreed with wild relative and pass these genes to the progeny IS GENETIC ENGINEERING SAFE Critics worry about irresponsible use of this technology or unforeseen consequences arising from new combinations of genetic material The public opinion has remained skeptical about GM plants 0 Health risks antibiotic resistant crops could help spread antibiotic resistant germs o The believe that itjust not right to mess with naturequot We have been moving genes around by hybridizing and selecting mutations for centuries Are GMO the same as those organisms developed in traditional practices Biotechnology may be more precise in creating novel organisms than normal breeding procedures biotechnology moves one or few known genes rather than a whole host of genes Would GMO help to feed the world or will help to consolidate corporate power and economic disparity o Unfair competition between rich agribusiness companies and poor farmers who cannot afford the transgenic seeds SUSTAINABLE AGRICULTURE It is also known as regenerative farming Agriculture has changed dramatically in the last 60 years Although these changes have had many positive effects and reduced many risks in farming there have also been significant costs Prominent among these are topsoil depletion groundwater contamination the decline of famil farms continued neglect of the living and working conditions for farm laborers increasing costs of production and the disintegration of economic and social conditions in rural communities Source httpwww saren urdavis 39 htm Sustainable agriculture agroecology or regenerative farming all aim to produce food and fiber on a sustainable basis and to repair damage caused by destructive practices Three goals of sustainable agriculture are 1 Environmental health 2 Economic profitability 3 Social and economic equitability Soil conservation Soil can be renewed and replenish indefinitely with careful practices 1 Managing topography o Contour plowing reduces water runoff and erosion 0 Strip farming is the planting of different crops in alternating strips along the land contours When one crop is harvested the other is still present to protect the soil 0 Terracing prevents erosion of steep hillsides In Indonesia and the Philippines some rice paddies have been cultivated for 2000 years 0 Planting perennial species in unstable soils on sloping sides eg tea fruit trees coffee Providing ground cover Mulch is a general term for a protective ground cover that can include straw wood chips manure leaves etc Annual crops generally cause high erosion rate Crop residues left on the ground Cover crops planted afterthe harvest and plowed under later on Mulch heavy paper or plastic sheets lnterplanting two different crops eg corn and beans Reduced tillage system Plowing helps to control weeds reduces competition brings nutrients to the surface improved drainage and aerated the soil Less plowing preserves the soil improves water management saves energy and increases crop yields Minimum till uses a chisel plow creating ridges on which the seeds can be planted Conservtill uses a sharp disc to cut a slot on the soil surface making a very narrow furrow for planting the seeds Notill drills the seed into the ground directly without plowing Lowinput sustainable agriculture Lowinput farming methods use fewer chemicals involve more crop rotation and use less energy but the total revenue is less but the net income per acre is often higher It is an alternative to industrial chemically intensive agriculture Lowincome farming is generally more sustainable Should the small farmer be considered or left at the mercy of multinational agricultural conglomerates 0 Energy intensive o Monoculture 0 Chemical and hormone intensive
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