Dinheiro gasto em fertilizantes e elementos químicos agrícolas em 1997 |
|
|
|
Produto |
# de Fazendas avaliadas |
$1.000 |
Ave. $ gasto (arredondado para o total $ amt.) |
Fertilizantes Comerciais |
1.190.733 |
9.597.128 |
8.060 |
Químicos Agrícolas |
941.136 |
7.581.424 |
8.056 |
Ave. Gasto Total |
|
|
16.116 |
Fig. 5. Essa tabela ilustra o gasto médio por fazenda em vários
produtos agrícolas.
Informação tirada de USDA 1999, p. 98.
Números sobre quanto desse gasto vem da indústria de agricultura animal não estão imediatamente disponíveis. Baseado no uso de terra, todavia, é possível fazer uma estimativa razoável através dos cálculos. Produtos de petróleo são provavelmente usados aproximadamente igualmente na indústria de colheita e indústria animal. Ambos os tipos de agricultura devem transportar seus bens, e ambos dependem pesadamente de maquinários para operar seus negócios. Como resultado, é provavelmente justo dizer que a agricultura animal usa um total de 57 por cento de terra agrícola nos Estados Unidos, este também utiliza 57 por cento dos produtos de petróleo na indústria, ou aproximadamente $15 bilhões. Certamente, terra fértil para cultivo requer muito mais fertilizante e outros elementos químicos agrícolas do que as fazendas de animais. Considerando esse fato, o dinheiro gasto nos elementos químicos agrícolas como parte da indústria animal é provavelmente próximo a 16 por cento (porcentagem de terra fértil usada para alimentar os animais) do total. Esse número é ainda um impressivo $5 bilhões. Embora que essas estimativas são aproximadas, eles oferecem algumas percepções para a extensão para o qual a produção de animais para comida contribui ao uso de petróleo e outros produtos químicos nos Estados Unidos. Por sua vez o uso desses produtos conduzem para a destruição da terra para sua extração, e a liberação de poluentes no seu consumo.
POLUIÇÃO
A mais freqüentemente estudada fonte de poluição de fazenda de animal não está relacionada com combustíveis fósseis, mas à orgânica, incluindo estrume, estratificação, alimento não consumido, e carcaças. Em um estudo, Copeland estima que agricultura animal nos Estados Unidos produz 112 milhões de toneladas de estrume seco a cada ano, tornando-o o mais abundante dejeto da indústria (2002, p. 187).
Quantia de estrume produzido por vários animais |
|
Tipo de animal |
Estrume produzido em lbs/yr/1,000 lb de massa animal |
Porcos |
80.000 |
Frangos |
30.000 |
Galinhas que botam ovos |
20.000 |
Criação de galinhas e perus |
30.000 |
Vacas leiteiras |
30.000 |
Fig. 6. Essa tabela lista a quantia de estrume produzido por cada tipo
de animal mostrado.
Informação não estava disponível para todos animais usados para comida.
É útil comparar esses dados com a Fig. 7 no Apêndice A,
que lista o número de animais em cada indústria, ainda que o peso deve ser estimado.
Informação tirada de EPA 2002, p. 6-3 até 6-23.
ARMAZENAMENTO DE ESTRUME
Colheitas de Fertilizantes
O EPA relata que aproximadamente 99 por cento das operações de fábricas de laticínios distribuem seu gasto sobre a terra, numa tentativa de fortificar o solo. Eles também notaram, todavia, que 36-61 por cento das pequenas leiteiras (200-700 vacas leiteiras) tem terra insuficiente para absorver os nutrientes de seus estrumes, enquanto 14 por cento não tem terra. Cinqüenta e um à sessenta e oito por cento das grandes instalações (>700 vacas leiteiras) tem terra insuficiente, e 22 por cento não tem terra (EPA 2002, p. 4-83). Essa discrepância é às vezes consertada pela distribuição de estrume na terra de outro fazendeiro, mas nutrientes de fezes animais muitas vezes excedem as necessidades regionais. Em 1998 Carpenter et al descobriu que "nutrientes que correm para ecossistemas aquáticos estão diretamente relacionados a densidades de armazenamento de animais, e sob altas densidades de gado, produção de estrume excede as necessidades das colheitas para o qual o estrume é aplicado" (p. 559). Nesse caso, nutrientes tornam poluentes e podem ser tóxicos aos sistemas vivos.
Lagoas
Lagoas são os depósitos mais comuns para a água por toda a indústria animal. Essas bacias capturam matéria orgânica e permitem que os decomponham anaerobicamente em compostos inofensivos. A confiabilidade das lagoas, no entanto, encontra-se sob sérias questões devido aos seus freqüentes fracassos estruturais, e conseqüente queda (Copeland 2002). Mallin et al estudou swine and poultry waste lagoon spills in North Carolina, and found in both cases that the spills caused harmful disturbances to water quality of the effected streams. The results showed changes to turbidity and dissolved oxygen, pollution levels of nitrogen (N) and phosphorous (P), dense phytoplankton blooms, and high fecal coliform concentrations. In a separate study conducted by Burkholder et al, a swine waste lagoon failure led to similar results, but in this case a fish kill of 4,000 individuals was also reported (Burkholder et al 1997). Copeland states that large-scale lagoon spills have occurred in almost every state in the U.S. (2002), and Mallin et al specifically note 30 reported spills from animal waste lagoons in 1995 and 1996 in North Carolina alone (1997).
Properly operating lagoons have also been studied for efficacy. In a 2002 Iowa study, Simpkins et al found that 50 percent of the earthen lagoon constraints in the study sample leaked at a rate greater than 1.6 mm/day, even under new state regulations. Furthermore, the researchers speculated that up to 5,000 unregulated lagoons existed in the state, and likely experienced far more substantial leaks. Whether functioning within required limits or not, animal waste lagoons often pose a serious threat to local environmental quality.
Efficacy of Controls
Many regulations are in place to curb the effects of pollution from animal farms, but inquiries into their efficacy have not been inspiring. Centner et al estimate that 80 percent of animal feeding operations in the United States are not permitted by the EPA, and therefore do not comply to its standards (2002).
Manure Contents and Effects on Ecosystems
The contents of animal manure is well documented, and the effects of these constituents on bodies of water is being thoroughly studied. The 2002 EPA report lists the "Key Pollutants in Animal Waste" as nitrogen (N), phosphorus (P), potassium (K), organic compounds, solids, pathogens, salts, trace elements, and volatile compounds (p. ES-7 – ES-8). These and other substances enter water bodies through leaks, infiltration through soil into groundwater, and directly through erosion and runoff and when animals have access to flowing water (EPA 2002). Agriculture is the number one cause of water pollution in the United States, and is responsible for roughly 70 percent of polluted waterways. Twenty percent of this 70 percent is said to originate from the animal production industry (Copeland 2002, p. 189). Furthermore, 16 percent of the pollution from crop raising comes from land used to grow fodder. In a smaller study, Nord et al judged that 66 percent of N and 78 percent of P output in one watershed originated from wasted animal feed and manure, when most of the farms in the study area split their land between growing cash crops and animal production (2003). Clearly, animal agriculture is a much larger polluter than is crop farming.
Once they have reached waterways, the pollutants in manure can cause a great deal of damage to aquatic and human life. A 2001 EPA report points to fish kills as the biggest problem associated with pollutants from manure (p. 1-5). Smith et al found that excessive amounts of P and N in fresh water causes excessive algal blooms, which adversely affect native populations by altering the chemical, thermal, and radiative aquatic environment. Accumulations of these nutrients in the ocean cause toxic phytoplankton blooms, which lead to fish kills (1999). Nitrogen can also become a global pollutant when released into the atmosphere, eventually settling back into distant water ways (Carpenter et al 1998; Aneja et al 1998).
Manure can be dangerous for people in a few forms. Organisms that are deadly to humans can make their way into the food supply through water contaminated with animal waste. Though direct contamination is not common, components of manure can also affect drinking water quality. These problems compound as practicality encourages animal operations to locate closer to heavily populated areas (EPA 2001). These facilities pose a serious threat to human health as well as to the health of local and global ecosystems.
Conclusion
The current world-wide growth in population and affluence is putting global resources under increasing pressure. Agriculture is a major consumer of land, water, and energy. Animal farming is responsible for roughly half of this resource exploitation and is a major source of pollution to natural systems. Although it is unreasonable to think that all Americans might become vegetarian, a simple reduction in the amount of animal products that this country consumes could mean enormous relief for non-renewable resources. This type of diet change has the capacity to decrease the United States' agricultural land, water, and petroleum needs by up to 50 percent. A diet that includes fewer animal products will also greatly decrease the amount of pollution in waterways, increasing the health of these ecosystems. Decidedly, one of the most profound and positive impacts an American can have on the planet comes from a simple change in eating habits.
Works Cited
Aneja, V.P., Murray, G.C., Southerland, J. (1998). Atmospheric nitrogen compounds: Emissions, transport, transformation, deposition, and assessment. Environmental Management, 48 (4), 22-25.
Burkholder, J.M., Mallin, M.A., Glasgow, H.B., Jr., Larsen, L.M., McIver, M.R., Shank, G.C., Deamer-Melia, N., Briley, D.S., Springer, J., Touchette, B.W., Hannon, E.K. (1997). Impacts to coastal river and estuary from rupture of large swine waste holding lagoon. Journal of Environmental Quality, vol. 26, no. 6, 1451-1466.
Carpenter, S.R., Caraco, N.F., Correll, D.L., Howarth, R.W., Sharpley, A.N., Smith, V.H. (1998). Nonpoint pollution of surface waters with phosphorous and nitrogen. Ecological Applications, 8 (3), 559-568).
Centner, T.J., Mullen, J.D.(2002). Enforce existing animal feeding operations regulations to reduce pollutants. Water Resource Management, vol. 16, no. 2, 133-144.
Copeland, Claudia (2002). Animal production, feedlots, and manure problems in the US. Encyclopedia of Global Environmental Change, vol. 7, 187-190.
EPA (2001). Environmental and economic benefit analysis of final revision to the national pollutant discharge elimination system regulation and the effluent guidelines for concentrated animal feeding operations, 1-3 through 1-6.
EPA (2002). Environmental and economic benefit analysis of final revision to the national pollutant discharge elimination system regulation and the effluent guidelines for concentrated animal feeding operations, 1-1 through 6-26.
Mallin, M.A., Burkholder, J.M., McIver, M.R., Shank, G.C., Glasgow, H.B., Jr, Touchette, B.W., Springer, J. (1997). Comparative effects of poultry and swine waste lagoon spills on the quality of receiving streamwaters. Journal of Environmental Quality, vol. 26, no. 6, 1622-1637.
Nord, E.A., Lanyon, L.E. (2003). Managing material transfer and nutrient flow in an agricultural watershed. Journal of Environmental Quality, 32, 562-570.
Simpkins, W.W., Burkart, M.R., Helmke, M.F., Twedt, T.N., James, D.E., Jaquis, R.J., Cole, K.J. (2002). Potential impact of earthen waste storage structures on water resources in Iowa. Journal of the American Water Resources Association, vol. 38, no. 3, 759-772 .
United States Department of Agriculture, National Agricultural Statistics Service (1999). 1997 census of agriculture: United States summary and state data (AC97-A-51).
United States Geological Survey (1990). Estimated use of water in the United States in 1990: Livestock water use. Retrieved from http://water.usgs.gov/watuse/tables/lvtab.huc.html October 29, 2003.
United States Geological Survey (1999). Water science map gallery. Water science for schools. Retrieved from http://ga.water.usgs.gov/edu/tables/dlir.html Dec. 7, 2003.
Apêndice A
Acres Irrigadas Pelo Tipo de Colheita |
|
Tipo de colheita |
Acres Irrigadas |
Corn for silage or green chops |
1.033.322 |
Sorghum for silage or green chops |
72.322 |
Hay (all types) |
9.564.336 |
Field seed and grass seed crops |
259.777 |
Alfalfa seed |
129.932 |
Total |
11.059.689 |
Fig. 2. This chart is simply available to illustrate the source of numbers cited in the report.
Information taken from USDA 1999, p. 40.
Fig. 3. This map clearly illustrates the correlation between arid regions and high levels of irrigation.
Figure taken from USGS Water science 1999.
Total census of animals in agriculture in 1997 |
|
|
|
|
Type of animal |
Number in millions |
|
Type of animal |
Number in millions |
Poultry |
|
|
Cattle |
|
layer hens |
367 |
|
cattle and calves |
99 |
"" |
314 |
|
cows |
43 |
pullets |
53 |
|
beef cows |
34 |
"" |
52 |
|
Total |
176 |
broilers |
1,103 |
|
|
|
turkeys |
307 |
|
|
|
Total |
2,196 |
|
Pigs |
61 |
|
|
|
|
|
Milk Cows |
|
|
Sheep |
7 |
cows |
18 |
|
|
|
cattle |
74 |
|
|
|
Total |
92 |
|
Total animals |
2,532 |
Fig. 7. This census was taken from the USDA Agricultural Census. Some information was listed repetitively in the USDA report and is shown in the same way here to avoid error (p. 21-34).