Effects on the Environment

The most direct desired effect of perennial polyculture farming is to address many of the environmental problems that are evident in today's annual monoculture approach. These include soil erosion and degradation, water depletion, and water contamination from fertilizers, herbicides, and pesticides. In thinking about replacing current annual, monoculture farming with perennial polyculture farming, it is important to understand what areas of the world are currently under cultivation. Figure 2 shows areas in which at least 30 percent of the landscape is under cultivation. The specific potential effects of perennial polycultures on the main types of environmental degradation throughout the world's cultivated lands follow.

Erosion. In the perfect archetype of the "reengineered prairie," a perennial polyculture would provide year-round ground cover, leading to a significant drop in soil erosion by both water and wind. Human-induced water and wind erosion are serious, worldwide problems for agriculture, primarily during the fallow periods of annual monoculture (and polyculture) farming. Figures 3 and 4 give some indication of the problem. Figure 3 shows those areas of the world that are vulnerable to water erosion. Figure 4 shows those areas of the world that are vulnerable to wind erosion. The most vulnerable regions in both maps are in red. A comparison of Figures 3 and 4 with Figure 2 suggests that a significant fraction of the world's land under cultivation is subject to water and wind erosion.

Figure 3

Water Erosion Vulnerability

^ RiskofHuman-InducedWaterErosion

Figure 3

Water Erosion Vulnerability

^ RiskofHuman-InducedWaterErosion

SOURCE: U.S. Department of Agriculture, Natural Resources Conservation Service, December 27, 2005. As of April 13, 2007: http://soils.usda.gov/use/worldsoils/mapindex/.

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SOURCE: U.S. Department of Agriculture, Natural Resources Conservation Service, December 27, 2005. As of April 13, 2007: http://soils.usda.gov/use/worldsoils/mapindex/.

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For comparison, in the United States, soil erosion from water declined between 1982 and 2001, from 4.0 tons/acre to 2.7 tons/acre, and soil erosion from wind fell from 3.3 tons/acre to 2.1 tons/acre in the same period.5 Total soil erosion of 4.8 tons per acre would result in the loss of an inch of topsoil from the average acre of cropland roughly every 25 years. This compares with typical soil formation rates of 300 to 1,000 years per inch.6 Erosion in less developed countries is typically much greater than it is in the United States.

Besides providing year-round cover for croplands, perennials send their roots much deeper into the soil than do annuals, adding protection against soil erosion from water.

Soil Degradation. Land degradation more broadly refers to soil that has been eroded, that has lost its fertility through depletion of minerals and other nutrients, that has become salinized through a variety of mechanisms, or that has become contaminated by pesticides,

5 Figures are based on U.S. Department of Agriculture, Natural Resources Conservation Service, National Resources Inventory: 2001 Annual NRI, July 2003. As of April 13, 2007: http://www.nrcs.usda.gov/technical/ land/nri01/nri01eros.html.

6 See Judith D. Soule and Jon K. Piper, Farming in Nature's Image, Island Press, Washington, D.C., 1992, p. 13.

Figure 4

Wind Erosion Vulnerability

<ù 'tÊiÊf"~ Risk of Human-Induced Wind Erosion

Figure 4

Wind Erosion Vulnerability

<ù 'tÊiÊf"~ Risk of Human-Induced Wind Erosion

SOURCE: U.S. Department of Agriculture, Natural Resources Conservation Service, December 27, 2005. As of April 13, 2007: http://soils.usda.gov/use/worldsoils/mapindex/.

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SOURCE: U.S. Department of Agriculture, Natural Resources Conservation Service, December 27, 2005. As of April 13, 2007: http://soils.usda.gov/use/worldsoils/mapindex/.

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herbicides, or other means.7 Figures 5 and 6 show two different views of worldwide land degradation. Figure 5 is from the Food and Agriculture Organization of the United Nations (FAO), and Figure 6 is from the International Soil Reference and Information Centre in the Netherlands. Exact measures of soil degradation and erosion are arguable, but the maps in Figures 3-6 indicate that agriculture that provides year-round cover, that requires much less pesticide and herbicide, and that provides much of its own nutrients would seriously reduce soil degradation worldwide.

Water Depletion. According to the American Association for the Advancement of Science (AAAS):

More than 60 percent of the water used in the world each year is diverted for irrigating crops . . . . In Asia, which has two thirds of the world's irrigated land, 85 percent of water goes for irrigation. A worldwide doubling in the area under irrigation to more than 260 million hectares underpinned the "green revolution" that kept the world fed in the late 20th

7 For more on land degradation, see, for example, Sara J. Scherr and Satya Yadav, "Land Degradation in the Developing World, Issues and Policy Options for 2020," 2020 Brief, No. 44, International Food Policy Research Institute, June 1997. As of April 13, 2007: http://www.ifpri.org/2020/briefs/number44.htm.

Figure 5

Human-Induced Soil Degradation

Figure 5

Human-Induced Soil Degradation

SOURCE: Food and Agriculture Organization of the United Nations (FAO), Dimensions of Need: An Atlas of Food and Agriculture, FAO, Rome, Italy, 1995. Used with permission. As of April 13, 2007: http://www.fao.org/documents/show_cdr. asp?url_file=/docrep/u8480e/u8480e0d.htm.

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SOURCE: Food and Agriculture Organization of the United Nations (FAO), Dimensions of Need: An Atlas of Food and Agriculture, FAO, Rome, Italy, 1995. Used with permission. As of April 13, 2007: http://www.fao.org/documents/show_cdr. asp?url_file=/docrep/u8480e/u8480e0d.htm.

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century. Almost 40 percent of the global food harvest now comes from the 17 percent of the world's croplands that are made productive in this way.8

Figure 7 shows the locations of the 17 percent of croplands that are made productive by irrigation (compare it with Figure 2). Again, according to the AAAS, "[m]ost irrigation schemes around the world are extremely inefficient. Typically, less than half the water reaches crop roots" (see footnote 8). This does not, however, mean that the other 83 percent of croplands use water efficiently. One measure of the efficient use of water for agriculture and other uses is the Water Poverty Index (WPI) developed at the Centre for Ecology and Hydrology in the UK. The WPI combines five factors: resources (the physical availability of surface and ground water), access (the extent of access to water for human uses), capacity (the effectiveness of the people's ability to manage water), use (the ways in which water is used—including agriculture), and environment (a measure of environmental integrity related to water).9

8 Peter H. Gleick, The World's Water: The Biennial Report on Freshwater Resources, Island Press, Washington, D.C., 1998. Quoted in Paul Harrison, Fred Pearce, and Peter Raven, AAAS Atlas of Population and Environment, "Population and Natural Resources: Freshwater," American Association for the Advancement of Science and University of California Press, Berkeley, Calif., 2000. As of April 13, 2007: http://www.ourplanet.com/ aaas/pages/natural03.html.

9 For more on this topic, see Natural Environment Research Council (NERC), Centre for Ecology & Hydrology, "The Water Poverty Index," NERC, Swindon, UK, not dated. As of April 13, 2007: http://www.ceh.ac.uk/ sections/ph/WaterPovertyIndex.html.

Figure 6

Soil Degradation

GLOBAL ASSESSMENT OF THE STATUS OF HUMAN-INDUCED SOIL DEGRADATION (1990)

Figure 6

Soil Degradation

GLOBAL ASSESSMENT OF THE STATUS OF HUMAN-INDUCED SOIL DEGRADATION (1990)

SOURCE: International Soil Reference and Information Centre (ISRIC), Wageningen, Netherlands, 1990. Used with permission. As of April 13, 2007: http://www.isric.org/UK/About+ISRIC/Projects/track+record/GLASOD.htm.

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SOURCE: International Soil Reference and Information Centre (ISRIC), Wageningen, Netherlands, 1990. Used with permission. As of April 13, 2007: http://www.isric.org/UK/About+ISRIC/Projects/track+record/GLASOD.htm.

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Combined with Figure 7, Figure 8 suggests that efficient use of water is a serious problem in most developing countries and in some developed countries as well.

Efficient use of water in agriculture, then, is important not only in countries that are wasting a lot of irrigation water, but also in countries that do not have a lot of water to waste. Perennial polycultures, with their constant ground cover (to take advantage of water whenever it falls) and deep roots (to capture more water than annual plants do) are more efficient at water usage than annual plants—and, in some cases, much more efficient.

Water Contamination. Freshwater systems are contaminated throughout the world. Agriculture is not the only source of freshwater contamination, but it is a major one. The FAO identifies agriculture "as the single largest user of freshwater on a global basis and as a major cause of degradation of surface and groundwater resources through erosion and chemical runoff."10 Common contaminants in freshwater systems from agricultural runoff include phosphorus,

10 Edwin D. Ongley, "Control of Water Pollution from Agriculture," FAO Irrigation and Drainage Paper 55, FAO, Rome, Italy, 1996. As of April 13, 2007: http://www.fao.org/docrep/W2598E/w2598e04.htm#water% 20quality%20as%20a%20global%20issue.

Figure 7

Global Map of Irrigated Areas

Figure 7

Global Map of Irrigated Areas

Center for Environmental Systems Research University of Kassel, Germany April 1999

SOURCE: Petra Doll and Stefan Siebert, A Digital Global Map of Irrigated Areas: Documentation, Kassel World

Water Series, Report No. 1, University of Kassel, Center for Environmental Systems Research, Kassel, Germany,

2001. Used with permission. As of April 13, 2007:

http://www.geo.unifrankfurt.de/ipg/ag/dl/f_publikationen/1999/doell_siebert_kwws1.pdf.

NOTE: The map shows the fraction of each area that was equipped for irrigation in 1995.

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Center for Environmental Systems Research University of Kassel, Germany April 1999

SOURCE: Petra Doll and Stefan Siebert, A Digital Global Map of Irrigated Areas: Documentation, Kassel World

Water Series, Report No. 1, University of Kassel, Center for Environmental Systems Research, Kassel, Germany,

2001. Used with permission. As of April 13, 2007:

http://www.geo.unifrankfurt.de/ipg/ag/dl/f_publikationen/1999/doell_siebert_kwws1.pdf.

NOTE: The map shows the fraction of each area that was equipped for irrigation in 1995.

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nitrogen, metals, pathogens, sediment, pesticides, salt, and trace elements (e.g., selenium). The agricultural sources of those contaminants are primarily fertilizers, pesticides, and herbicides.

Maps of freshwater contamination would not tell the story of water contamination by agriculture because of the contributions from industry and other sources. There is one area, however, in which the agricultural contribution to water contamination is reasonably clear. That is in the dead zones in the world's oceans. A dead zone in the ocean is created by nitrogen and phosphorus (found in fertilizers) that wash down rivers and flow into the ocean. The nitrogen and phosphorus ignite algae and phytoplankton blooms. When these blooms die, they drop to the ocean floor and decompose, using up the oxygen of the deeper water. This severe depletion of oxygen—known as hypoxia—kills every oxygen-dependent sea creature in the area.

There are now some 146 dead zones in the oceans of the world, and they cover a total area measured in tens of thousands of square miles. The circles in Figure 9 are the major dead zones (as of2002). The colors indicate whether the dead zones are annual (red), episodic (blue), periodic (pink), or persistent (yellow). Most are annual dead zones that appear in the summer and autumn and disappear over the winter. From the map, it is clear that most of the dead zones are related to intensive agriculture in developed countries, although there are now dead zones in such developing countries as China, Brazil, and Mexico. With continued emphasis

Figure 8

Water Poverty Index

The information illustrated here represents results of work in progress and must not be taken as definitive

The information illustrated here represents results of work in progress and must not be taken as definitive

Water Poverty

(The lower the score the bigger the problem) | High t 1 Medium

I Low

SOURCE: Natural Environment Research Council (NERC), Centre for Ecology & Hydrology, "The Water Poverty Index World Map," NERC, Swindon, UK, 2003. Used with permission. As of April 13, 2007: http://www.ceh.ac.uk/sections/ph/documents/WPIworldmap_2.pdf.

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on fertilizers for improving productivity of agriculture in developing countries, dead zones are likely to continue to appear and to grow.

Agriculture's contribution to dead zones has been measured for some areas. Sources of nitrogen from the Mississippi River basin, for example, are estimated to include commercial fertilizers (41 percent); legumes (33 percent); animal manure (16 percent); atmospheric deposits (8 percent); and municipal and domestic wastes (1 percent).11 Clearly, if perennial polycultures could significantly reduce (or eliminate) the amount of commercial and animal fertilizers required for food production, the contaminants in freshwater basins would be reduced and the oceans' dead zones would be significantly reduced.

We know that fertilizers, herbicides, pesticides, and other chemicals used in modern farming cause further contamination of ground water and waterways, but it is more difficult to

11 Donald A. Goolsby and William A. Battaglin, "Nitrogen in the Mississippi Basin: Estimating Sources and Predicting Flux to the Gulf of Mexico," USGS Fact Sheet 135-00, December 2000, figure 5. As of April 13, 2007: http://ks.water.usgs.gov/Kansas/pubs/fact-sheets/fs.135-00.html. See also "Reducing Nutrient Loads, Especially Nitrate-Nitrogen, to Surface Water, Ground Water, and the Gulf of Mexico," Topic 5 Report for the Integrated Assessment on Hypoxia in the Gulf of Mexico, NOAA Coastal Ocean Program, Decision Analysis Series No. 19, May 1999.

Figure 9

Ocean Dead Zones

Figure 9

Ocean Dead Zones

SOURCE: United Nations Environment Programme (UNEP), Global Environment Outlook (GEO), GEO Year Book 2003, "Emerging Challenges—New Findings," UNEP, Nairobi, Kenya, 2002, p. 58. Used with permission. As of April 13, 2007: http://www.mindfully.org/Water/2004/Oxygen-Starved-Zones1jan04.htm.

NOTES: The 146 zones (shown as circles) are associated with either major population concentrations or watersheds that deliver large quantities of nutrients to coastal waters. Annual (red): yearly events related to summer or autumnal stratification; episodic (blue): events occurring at irregular intervals greater than once per year; periodic (pink): events occurring at regular intervals shorter than once per year; and persistent (yellow): all-year-round hypoxia.

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SOURCE: United Nations Environment Programme (UNEP), Global Environment Outlook (GEO), GEO Year Book 2003, "Emerging Challenges—New Findings," UNEP, Nairobi, Kenya, 2002, p. 58. Used with permission. As of April 13, 2007: http://www.mindfully.org/Water/2004/Oxygen-Starved-Zones1jan04.htm.

NOTES: The 146 zones (shown as circles) are associated with either major population concentrations or watersheds that deliver large quantities of nutrients to coastal waters. Annual (red): yearly events related to summer or autumnal stratification; episodic (blue): events occurring at irregular intervals greater than once per year; periodic (pink): events occurring at regular intervals shorter than once per year; and persistent (yellow): all-year-round hypoxia.

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say how much the situation would improve if those sources were significantly reduced because of the multisource nature of most water contamination. Nevertheless, in the best of scenarios, perennial polyculture farming could go a long way toward eliminating water and wind erosion, soil degradation, water depletion, and water contamination.

Loss of Biodiversity.12 In its simplest form, biodiversity refers to the number and diversity of species, the genetic material of those species, and the natural communities, ecosystems, and landscapes of which those species are part. Biodiversity includes animal as well as plant species. It has been recognized as extremely important by the environmental and scientific communities because of its numerous benefits, and the current rate at which we are losing it is alarming. Increased human activities and a rapidly growing global population are threatening the Earth's biodiversity. Worldwide, numerous plant and animal species are becoming extinct every year, at an estimated loss of species in the tens of thousands per year.13 Worldwide animal extinc

12 This subsection draws heavily on material provided by RAND colleague Beth Lachman, whose careful review has improved the paper in general.

13 Robert Leo Smith and Thomas M. Smith, Ecology and Field Biology, Prentice Hall, Upper Saddle River, N.J., 6th ed., 2001, p. VII-A.

tion rates are estimated to be 1,000 to 10,000 times higher than natural extinction rates.14 With these extinctions, natural systems that humans depend upon are degraded or lost, and the effects may be significant. Given current scientific knowledge, it is unclear at what point current biodiversity loss rates could lead to natural systems breaking down and critical problems; however, evidence of causes for concern already exists. For example, in California, habitat alterations and pesticide use have degraded natural ecosystems to the extent that few wild bees are left. California farmers, who have always relied on wild bees for pollination, must now rent bees to pollinate key agricultural crops.15 Evidence of the global importance of biodiversity can be found in the signing of the Convention of Biodiversity by over 150 nations at the 1992 United Nations Earth Summit and the attention given to biodiversity conservation at the summer 2002 World Summit on Sustainable Development in Johannesburg, South Africa. A conservative estimate of the annual economic and environmental benefits of biodiversity in the United States is $300 billion, and worldwide $3 trillion.16 Other estimates of the worldwide economic benefits of biodiversity range as high as $33 trillion per year.17

In a natural prairie, there can be more than 200 plant species in a given area and perhaps several times that number of microscopic soil animals that are important to efficient prairie operation. A true reengineering of the prairie would dramatically increase the biodiversity over a monoculture on the same plot of land. However, any less-ambitious reengineering of the prairie that includes a variety of plant species in a perennial polyculture would contribute to the diversity of plant life over a monoculture and promote biodiversity more widely.

There are other ways in which perennial polyculture farming could help the environment (e.g., polycultures produce more plant material in the ground, thus sequestering more carbon dioxide), but the five areas outlined above represent the primary worldwide agriculture-induced environmental problems that could be mitigated.

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