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a Pine Lake Institute for Environmental and Sustainability Studies, Hartwick College, Oneonta, NY 13820-4020
b Dep. of Environmental Studies, University of Nevada, Las Vegas, NV 89154
* Corresponding author (drohanp{at}hartwick.edu)
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ABSTRACT |
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Abbreviations: EPA, Environmental Protection Agency • ESA, Endangered Species Act • IBA, Important Bird Area • NRCS, Natural Resources Conservation Service • SSSA, Soil Science Society of America • SSURGO, Soil Survey Geographic (SSURGO) database • STATSGO, State Soil Geographic (STATSGO) database • USDA, United States Department of Agriculture
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INTRODUCTION |
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Given the long history of protecting the various parts of nature that we have perceived to be endangered by our development activities, it is certainly reasonable to propose a formal process for recognizing natural (non-anthropogenically made) soils that are either rare or threatened. Soils, after all, are often described as the foundation of all life, and the unique structures and characteristics of various soils make them key support systems to the diversity of life on earth (Gibbons, 1984; Huston, 1993; Singer and Warkentin, 1996).
Just as we lose animal and plant species to extinction, so to are we seeing soils damaged or destroyed due to pressures from multiple anthropogenic practices; destruction that can put life at risk. Worldwide, the effects of global warming are predicted to lead to the disappearance of permafrost within 1000 yr (Pearce, 2006), which would result in the extinction of a whole order of soils–Gelisols, in the U.S. system of soil taxonomy, which cover approximately 8.6% of earth's ice-free land area. Many examples throughout history also exist of civilizations rising and falling in part due to their management of soil (Dale and Carter, 1955; Hyams, 1976; Hillel, 1992). The best soils for food production are often ideal for building sites, and their favorable characteristics attract intensive development (Elvidge et al., 2004; Lopez et al., 2001), often resulting in their degradation (Scherr, 1999; UNEP, 2004) and significant economic loss (Uri, 2001).
Given these circumstances, if soil degradation and destruction is occurring in a significant portion of a soil's known extent, we should be able to identify that soil as threatened in the same way that species are categorized as threatened under the ESA. The ESA defines a threatened species as "an animal or plant species likely to become endangered within the foreseeable future throughout all or a significant portion of its range" and an endangered species as "an animal or plant species in danger of extinction throughout all or a significant portion of its range" (Czech and Krausman, 2001; ESA, 1973). Certainly many parallels can be drawn between the plight of degraded soils and endangered species. Extinction of soils is certainly a viable concept, and the rehabilitation of degraded soils can be perceived as quite similar to the rebuilding of a population of a threatened or endangered species. Such management takes time, careful stewardship, and a special recognition of the causes of the problem by key constituents of the human population.
Soil degradation has been of concern to conservationists for many decades, but the concept of rare and threatened soils has only recently emerged in the scientific literature. In a 1998 article entitled "Do soils need our protection?," Amundson discussed the rapid spread of landscapes in the San Joaquin Valley of California with disturbed soils from agriculture or development, highlighting the potential loss to society of "unique soil types that may serve as scientific and educational resources for future generations" (Amundson, 1998). Guo et al. (2003) used the USDA Natural Resources Conservation Service (NRCS) State Soil Geographic (STATSGO) database to quantify the structure of soil taxonomy, the spatial distribution, and relative abundance of soils in the USA and from this identify rare soils (those of limited areal extent, according to STATSGO data). However, the coarseness of STATSGO data precluded the identification of many soils that might be considered rare or threatened (Guo et al., 2003). Amundson et al. (2003) used the same data as Guo et al. (2003) to refine the terminology of rare soils using two numerical parameters: series density (number of series per area in a state) and series abundance (total area of each soil series in a state). From these two parameters, Amundson et al. (2003) derived four classes of soil diversity that were used in the quantification of the STATSGO database. The composition and coarseness of the STATSGO data seem to limit their usefulness in this endeavor. Yet, until U.S. Soil Survey Geographic (SSURGO) data become contiguous for the continental USA, it will not be possible to derive a better estimate of soil diversity, using soil taxonomy, unless we accept the limits of soil taxonomy and soil taxonomy databases and focus on specific areas or other interpretations of rare, threatened, or important soils.
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A DEFINITION FOR RARE AND THREATENED SOIL |
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An important first step in identifying rare and threatened soils is to agree on general definitions for the terms. We identify a rare soil as one of limited areal extent, occurring in relatively small portions of the landscape; a threatened soil is one of greater areal extent undergoing a transformation that alters its characteristics and therefore function. Land uses leading to urbanization, such as inundation due to human-made dams, surface and subsurface mining, landfills, hazardous waste sites, poor agricultural management, and recreational areas such as playing fields and golf courses, can result in threatened soils. Each of these land uses is a threat to natural soils regardless of acreage because each changes the natural function of the soil in that landscape.
Developing a list of rare soils would be fairly straightforward because this could be done independently of land use or political boundary; rare soils merely occur in limited areal extents. Developing a list of threatened soils would not necessarily be straightforward because the designation depends on complicated factors (cultural, political, geographic, and others) and trying to rally support for protecting such soils would likely be politically challenging and potentially controversial. We have avoided using the "endangered" terminology found in the ESA specifically because we see no difference from the standpoint of threatened or endangered with respect to soil. Unlike a plant or animal, it is quite unlikely that soil, facing a situation in which it would be destroyed beyond original identification or function, can be brought back from the brink of extinction. Soil is generally slow to change. Although some soil processes take minutes to adjust, such as soil pH, most processes that lead to the development of a soil as an individual entity/body take hundreds, thousands, or millions of years.
We would like to stress the importance of distinguishing between a rare or threatened soil and a rare or threatened landscape. Although we propose in this paper that soils are the focus of the nomination process, we recognize that soil can contribute to the formation of, or occur in, unique landscapes, which in essence are inseparable from the soil. Monger and Bestelmeyer (2006) present an eloquent demonstration of such coevolution mechanisms for soils and landscapes in arid environments. Therefore, it is important for those looking for, or nominating, rare or threatened soils that they be aware that rare or threatened soils could encompass unique landscapes that may also be rare or threatened. We believe that this intricate relationship of soil and landscape further supports the argument for recognizing a rare or threatened soil, especially because unique soils and landscapes often support rare ecosystems and species. Examples of such unique soil-landscape assemblages might include wetlands, thermal spring areas, areas of salt-affected soils (Fig. 1 ), mound features such as the mima mounds of California (Fig. 1) and Washington state, high altitude environments, and the high percentage clay soils that result in gilgai features (Fig. 1).
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DEMONSTRATING THAT A SOIL IS RARE OR THREATENED |
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SSURGO data are also valuable for finding threatened soils and in tracking changes in soils. Iowa's organic-rich mollisols, which are mapped by the NRCS as "severely eroded" (specifically the Monona and Tama series soils [333 800 ha in east-central and eastern Iowa]), provide an example of threatened soils. Severely eroded soils have decreased productivity for agricultural production, may become unusable for non-agricultural land uses if erosion is severe enough, and may over time have to be classified by soil scientists as a different type of soil. Using SSURGO data to identify the extent of soils such as the Tama and Monoma series allows us to identify soils threatened to the point where agricultural production may be lost and where damage is severe enough over time that the soil classification changes and the ability to produce food jeopardized.
Therefore, at the suggestion of Iowa state soil scientist Mike Sucik, we used SSURGO data from several counties in Iowa to examine soils mapped by the USDA NRCS as moderately or severely eroded. SSURGO data indicate that 5100 ha of the Tama soil series (Typic Argiudolls) in Johnson County (3% of the county) is mapped as moderately or severely eroded (Fig. 1). SSURGO data for all soils in this county show that approximately 35% of the total land area is moderately or severely eroded. In Pottawattamie County, Iowa, SSURGO data show that 29 400 ha (12% of the county) of the Monona series (Typic Hapludolls) are mapped as moderately or severely eroded (Fig. 1). In this one county, 41% of the land area is moderately or severely eroded according to the NRCS. Erosion of Iowa's highly productive soils is quite troublesome because Iowa farms are essential to the state's and the nation's economic health and food production. In 2003 Iowa farms produced $6.56 billion dollars in grains and the state's livestock sales accounted for $6.07 billion dollars (Iowa Farm Bureau, 2005). In 2003, Iowa supplied approximately 19% of U.S.-grown grain corn and 14% of U.S. soybeans (Iowa Department of Agriculture and Land Stewardship, 2005).
Nationwide, the situation also appears troubling for the Tama and Monona series. Using nationwide data from the U.S. National Soil Information System (NASIS), 17.8% of the land area covered by the Monona series, which occurs only in Iowa, Kansas, and Nebraska, is eroded, 35.4% is moderately eroded, and 0.9% is severely eroded. For the Tama series nationwide, which occurs in Iowa, Illinois, Indiana, and Wisconsin, 3% of its land area is eroded and 14.9% is moderately eroded. For the future of agricultural production, it is important that we sustain the long-term productivity of these economically important soils. By recognizing such soils now as threatened, we can track their change over time and focus conservation efforts.
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FURTHER WAYS TO CLASSIFY RARE AND THREATENED SOILS: WHAT IS A SOIL'S VALUE? |
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Soil has an economic value to society derived from the continued function and characteristics that support certain human activities that generate revenues or protect human health. We grow food and textiles in soil, clean our waste via septic systems in soil, and purify our water in part through the movement of water through soil. Virtually every soil has some kind of economic value because soil is tied in some way to nearly everything we depend on economically. The Tama and Monoma series carry a high economic value, but this is now at risk due to the degradation of these soils over time. Losing the great agricultural productivity of these soils, or other such mollisols across the country, could indeed jeopardize future U.S. food security.
Even soil not being used for commodity production is important to ecosystem function, which in the big picture is important to humans through climate and ecosystem regulation. For example, recent research conducted on subaqueous soils by Demas and Rabenhorst (1999, 2001), Demas et al. (1996), and Bradley and Stolt (2003) led to the classification of sediment under up to 2.5 m of water (Soil Survey Staff, 1999; Bradley and Stolt, 2003) as soil according to U.S. soil taxonomy. Such soils are often important for supporting aquatic life, which in turn supports other aquatic fauna. Identification of these substrates as soil was an important step in the evolution of soil science and strongly stresses the importance of subaqueous soil environments and the valuable services they provide to society in the form of support for freshwater and estuarine fisheries around the world and support of marsh and wetland ecosystems important in flood protection. Around the USA, many subaqueous soils are experiencing substantial anthropogenic disturbance from surface runoff laden with pollutants and from dredging. United States Environmental Protection Agency (USEPA) research shows that nationwide recreational and commercial finfishing profits in estuarine environments, where subaqueous soils occur, totaled $30 billion annually (USEPA, 1992). In addition, estuaries provide habitat for 75% of the catch of all commercial fish species and approximately 28 million jobs nationwide (USEPA, 2005).
The ecosystem value of a soil pertains to those characteristics within a soil (hydrologic function, mineralogy, organic matter content) that support species's habitats. An example is provided by the serpentine soils (Fig. 1) in the eastern serpentine barrens of Pennsylvania and Maryland (Latham, 1993; Tyndall and Hull, 1999), which support the rare serpentine aster, Symphyotrichum depauperatum (Fern.) Nesom. In addition to hosting rare plant species, serpentine soils support populations of rare fauna such as nickel-resistant bacteria (Mengoni et al., 2001). If we were to lose these soils, we may then lose the ability to develop successful biotechnology-based solutions to pollution. The Hans Jenny Pygmy Forest Reserve in Mendocino, CA, provides another example of an area currently protecting three soils now experiencing local pressure outside the reserve from urban/suburban expansion: the Blacklock series (Typic Duraquods), the Aborigine series (Typic Albaquults), and the Ferncreek series (Plinthic Haplohumults) (Drs. M. Singer and R. Southard, personal communication, 2003). The California state soil, San Joaquin (Abruptic Durixeralfs), has been deep-ripped, leveled, and irrigated for row crop production (Dr. R. Southard, personal communication, 2003). Other examples of soils with ecosystem values exist, such as those in virtually any coastal environment, as well as soils on sites with very old and slow-growing plant species, such as bristlecone pine (Pinus longaeva) and giant sequoia (Sequoiadendron giganteum) trees.
Soils with special scientific value might represent unique landscape or pedologic relationships (e.g., helping the scientific community better understand the processes of soil formation); provide medical knowledge (e.g., the discovery of streptomycin produced from soil bacteria); or provide technological advances (e.g., wastewater treatment or the use of zeolite in water purification and softening). A familiar landscape example for soil scientists and geomorphologists would be the mima mound fields of Washington and California (Fig. 1). In the USA, these features have already been identified as worthy of local (Hogwallow Preserve near Exeter, CA) and national recognition (Miramar Mounds National Landmark, San Diego, CA). Mima mounds are literally soil mounds several meters in diameter (or linear in some instances) believed to have been formed by several potential processes: burrowing animals (Cox, 1984; Nelson, 1997), soil erosion collapse around mounds (Reider et al., 1999), or seismicity (Berg, 1990). These soils have been located in only a few locations around the world: California (Cox, 1984; Cox and Allen, 1987), Wyoming (Reider et al., 1999), Washington State (Dalquest and Scheffer, 1942; Nelson, 1997), the western Cape Province of South Africa (Lovegrove and Siegfried, 1986), and Kenya (Cox and Gakahu, 1985). Other examples of soils with special scientific value would be most hot spring environments (Fig. 1) and low temperature springs; wetlands; and unique ecotones such as the High Peaks Region of New York State and Webb's Mill Bog in New Jersey.
Soils of historic/cultural value reveal important information about previous human occupation and practices, such as the Cliffhouse soil series (Aridic Argiustolls) identified in Mesa Verde National Park, Colorado. This series was named after the "cliff houses" the Ancient Puebloans inhabited. The soil was identified by the NRCS as a series in part due to its eroded nature, which resulted from years of agriculture practiced by the Ancient Puebloans. In Nevada, the NRCS currently has pending a Histosol that once hosted a peat moss harvesting operation in the state (Swedesplace series [Sapric Haplohemists]). The series was identified as unique more for it being a rare Histosol in Nevada, but the associated historic land use also adds to the importance of the soil (Tom McKay, NV NRCS personal communication, 2006).
Finally, in addition to the above listed values, soils that are of extremely limited range have special value in their rarity and deserve protection. Similar examples of protection exist for many unique geological formations, such as Devils Tower National Monument, Wyoming, and the many stone arches in Canyonlands National Park, Utah. Soils derived from marl parent materials (Fig. 1) in Maryland, Virginia, and West Virginia, such as the Massanetta (Fluvaquentic Hapludolls), Warners (Fluvaquentic Endoaquolls), Lappans (Fluventic Calciudolls), and Fairplay (Fluvaquentic Endoaquolls) series, provide an example. Past research on marl derived soils (Shaw and Rabenhorst, 1997, 1999) has resulted in important knowledge of unique and locally rare soil formation processes. Marl derived soils in this region have also been identified to support rare, threatened, or endangered plant species (Bartgis, 1983; Bartgis and Lang, 1984). These rare soils and wetland communities are being encroached on by development and invasive species (Drohan et al., 2006). Using the NASIS database we find that the Fairplay series occurs on less than 1011 ha and the Lappans series on less than 567 ha in Maryland and West Virginia combined. The Massanetta series occurs on less than 1174 ha in Virginia and West Virginia combined and the Warner series occurs in five states on less than 4087 ha combined.
The awareness of rare soils and their important contributions is growing in the USA. In Nevada, the NRCS is now beginning to recognize soils of limited areal extent with important features related to land management (Tom McKay, NV NRCS personal communication). Currently pending example series include: the Bluegyp series (334 ha) (Leptic Haplogypsids), which was established due to it's high sulfate content; the Ashflat series (123 ha) (Vitrandic Argicryolls), which hosts a unique plant community and has a high volcanic ash content; the Bagval series (30 ha) (Typic Haploxererts), which hosts a unique riparian community; and the Wetbag series (28 ha) (Vertic Cryaquolls), which hosts a unique wetland community.
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PROBLEMS IN LISTING RARE OR THREATENED SOILS |
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Identifying rare or threatened soils by relying solely on existing digital soil databases may limit the success of the process. Across the USA, there exists a discrepancy in SSURGO data because of the order level of mapping. In several of the sparsely populated western states, soils are commonly mapped at the Order 3 level (1:20 000 to 1:63 360 scale), whereas in the eastern USA they are often mapped at the Order 2 level (1:12 000 to 1:31 680 scale) (Soil Survey Division Staff, 1993). Because of the coarseness of Order 3 mapping, unique soils could easily be missed by being too small or by being incorporated into mapping units as associations or inclusions.
Finally, it is likely that establishing legally binding classifications of soils and technically complicated criteria for identifying rare and threatened soils could hinder the process of using rare and threatened soils to educate the nation about the importance of soils in everyday life. If we become to legally specific in the classification of rare and threatened soils, we may lose the chance to protect soils that are quickly being degraded by human activities. Ultimately, the mission of recognizing rare and threatened soils is one of both conservation and education. We should consider how we can achieve both with greatest efficiency.
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GETTING THE POINT ACROSS WITHOUT LEGISLATION: EXAMPLES FROM WILDLIFE CONSERVATION |
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We believe the most promising alternative to legislation is the formalized recognition of soils identified worthy in one or more of the value categories discussed earlier—for example, soils that are important for food production or for plant and animal species habitat, or soils that have valuable characteristics due to scientific, historic, or cultural interest. This type of recognition is not uncommon in the USA and other nations. Three examples exist that we can use as models for identifying and potentially conserving rare and threatened soils: the BirdLife International/National Audubon Society's "Important Bird Areas" program, Conservation International's identification of biological "hotspots," and the United Kingdom's "County Wildlife Sites."
The BirdLife International/National Audubon Society's Important Bird Areas (IBA) program http://www.audubon.org/bird/iba/, verified 20 June 2006) identifies sites that are essential habitat for one or more species of bird. IBAs have no legally binding protection, but the designation does lend weight to land-use decisions made by planning commissions and governmental agencies. For example, New York Governor George Pataki signed a ground-breaking bird habitat protection bill in 1997 http://www.dec.state.ny.us/website/dfwmr/wildlife/bca/, verified 20 June 2006) modeled on Audubon's New York IBA program, using IBA criteria to identify and conserve state-owned lands. Site designation is a first step toward a worldwide conservation effort involving scientists and the general public.
Another popular method of bringing public attention to issues of conservation is the idea of biological hotspots, which are areas of special concern because of their unusual ecological qualities, assemblage of species supported, and/or the environmental degradation that is presently occurring or expected to occur there. Conservation International http://www.conservation.org/xp/CIWEB/home, verified 20 June 2006) has successfully managed a campaign that identifies biodiversity hotspots around the world. This campaign, by focusing attention on areas of vital concern, helps to direct resources to the natural habitats that need them the most. In some ways, it is a form of "triage" conservation, treating the most valuable and most severely threatened areas first. But the benefits of attracting public attention and appropriately targeting scarce financial resources are significant.
In the United Kingdom, a third example of a possible model for a soils protection system exists in the County Wildlife Sites [Local Sites] program, which includes sites considered to be especially important for wildlife in a county. Individuals or groups in counties identify sites that preserve a specific plant or animal and raise money to support their conservation (via owning an area or supporting management) through non government bodies like wildlife trusts http://www.wildlifetrusts.org/, verified 20 June 2006). Environmental organizations in the United Kingdom (such as the Royal Society for the Protection of Birds, National Trust, Woodland Trust, and English Nature) can help in identifying sites and in setting up their management plans. Once the site is identified, the local wildlife trust then helps citizens and land managers work together to manage the site. For example, many wetlands are of countywide importance and have been designated County Wildlife Sites. This is not a statutory designation but provides a layer of recognition to land-use planners (i.e., the designation should be taken into account when the planning authority decides on a land-use application). Designation also provides a great opportunity for public outreach about the value of the site.
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THE PROPOSAL: A FORMAL DESIGNATION PROCESS FOR RARE AND THREATENED SOILS |
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The process is not without its caveats. First, unlike the ESA, we do not presently see the possibility of removing a soil from the list once listed. Unlike a plant or animal listed under the ESA, a soil is unlikely to recover the spatial extent or function that initially led to its listing, even with human intervention. Therefore, careful consideration should be made before addition of a soil to the list.
Second, as we have proposed, the list will reflect soils that are rare or threatened according to the five values we describe. However, it is important to avoid listing soils that are not truly rare or threatened just because they meet one or more of the values identified above. If a soil is not rare or threatened, then it should not be added to the list. For example, a soil may be unique in being able to support certain crops, but may be spatially extensive. Values should be unique to a nominated soil rather than common to many. In some instances, a soil could be perceived as unique based on opinion. For example, some argue that a soil can help to impart a unique flavor to a wine, yet this process may not be documented in the scientific literature. Where opinion is interpreted to be the driver of the nomination rather than fact, the reviewing committee should reject the nomination. A nomination should also be rejected if an attempt is made to add further protections to already protected landscapes but without evidence of a rare or threatened soil. For example, Antietam National Battlefield in Maryland is federally protected and although the landscape is unique for what occurred there during the Civil War, the soils across the battlefield are common across the central Maryland, eastern West Virginia, and southern Pennsylvania area and therefore are not rare. In addition, the soils did not necessarily contribute anything to the battle and therefore are not culturally unique.
Third, at what extent does a soil become rare? For a plant or animal, one can distinguish at the species level differences between species due to the ability to interbreed, and thus examine that species's fitness; a decrease in a species's fitness in part can lead to a species being listed under the ESA. However with soil, boundaries can be diffuse and soil does not necessarily reproduce. As with the ESA, we do not propose to set a specific number that is used to define the minimum area for a soil before being listed as rare. In our opinion, such a number may constrain what is a flexible process to protect soils and to educate the nation about them. However, we caution those nominating soils, and the committee reviewing proposals, to not abuse the concept of rarity; avoid this by using the other values to add weight and importance to the nomination.
Fourth, what boundaries should be used to identify a rare and threatened soil? Many types of boundaries exist to map soils and these are often tied to different extents (spatial scales) and we would hope the committee evaluating nominations would be open to the wide variety of possibilities. The examples discussed earlier of the work by Amundson et al. (2003) and Guo et al. (2003) are one possibility. In addition would be those wishing to use the concepts of soil endemism (Bockheim, 2005) and pedodiversity (Ibáñez et al., 1998). The USDA has already developed maps and databases in paper and digital format, which we have shown to be suitable for identifying unique, rare, and/or threatened soils. We believe for a quick and widely accepted mechanism for the separation of soils, the USDA NRCS series or soil mapping unit concept would be suitable for nomination purposes. However, we also recognize that a different scale may be more appropriate, now or at a later time, such as a suborder of soil taxonomy or a special instance in which multiple series in an area are nominated exclusive of the traditional soil mapping boundaries for the area. For example, based on predictions of global warming and the loss of permafrost (Pearce, 2006) (and thus the soil Order Gelisols) should Gelisols now be considered a threatened soil? We believe so. However, the final decision of acceptance would rest with the nomination review committee; in the case of unusual circumstances though, the method for deriving the boundary should be clearly stated and justified by the nominee. As soil science progresses the concept of a soil's extent will evolve. Therefore, we suggest the committee should be open to new ways of viewing what a soil's extent is.
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THE NOMINATION PROCESS |
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BEYOND THE NOMINATION PROCESS |
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To enhance the conservation potential of the nomination process and encourage adoption of the process to promote greater awareness of soil, the SSSA should officially develop memoranda of understanding with organizations such as The Nature Conservancy, The Conservation Fund, Conservation International, the National Audubon Society and scientific societies. In the geographic area of the listed soil(s), and nationwide via the Internet map server, the SSSA would provide educational materials about the listed soils, which address their value and importance. Along with the nominators, the Society should also help promote awareness via cooperative media efforts (press releases, interviews with local and national soil scientists) in areas where the listed soils are located. For rare or threatened soils, such public attention would be very important for garnering support for additional protections. If the committee is successful in gaining the support of other conservation organizations, a duel or multi organization designation could be derived to cooperatively recognize the nominated and accepted rare soil. This would add more importance to the designation; we do not see such a multiorganization designation as too difficult to devise. Other possible approaches to protecting the nominated and accepted soils could include trying to acquire easements on the land or purchase the property outright in cooperation with a local and/or national land trust or conservation group such as The Nature Conservancy or The Conservation Fund.
Although the list of recognized state and national rare or threatened soils could eventually number in the hundreds, it would be useful to pick a smaller number (perhaps 15–20) of "ambassador" soils that could be used to educate the public and draw attention to the seriousness of the problem of soil degradation (Table 1). In the same way that certain animals and plants are used as "poster children" for the plight of endangered species and environmental degradation, so too could certain dramatic examples of the loss of valuable soils raise awareness of the importance of soil science and conservation.
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ACKNOWLEDGMENTS |
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Received for publication August 17, 2005.
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TOP
ABSTRACT
INTRODUCTION
