The goal of this paper is to act as a review of wetland science and legislation in answering the question of how adequately the needs of migratory birds are met by current legal measures. First I will present a very brief history of wetland-related legislation in the U.S. in order to provide a background for assessing conservation features of law. Then, in two separate sections, I will address how well the services wetlands provide to migratory birds are protected by law and how well the problems facing wetlands are addressed by legislation.
Early US legislation regarding migratory birds had a strong focus on protecting the birds rather than their habitat. The primary reason for this is that hunting was seen as the greatest threat to migratory birds at the time. The woes of habitat loss were overwhelmed by the urge to develop, and the problem of illegal hunting, with bird parts being sold to expensive restaurants and hat fanciers, was much easier to address (“Guide”). To counter the problem of illegal hunting of game birds, the Lacey Act was passed in 1900, making it explicitly prohibited to cross state borders with illegally taken game (“Guide”). Later this prohibition was expanded to include international trade.
Other laws addressing similar issues were passed during the same period, including the Weeks-McLean Law, passed in 1913, which put migratory birds under the jurisdiction of the federal government (“Guide”). Due to constitutional weaknesses of the law, it was later replaced with the Migratory Bird Treaty Act (MBTA) in 1918. The MBTA was an international treaty that was originally between the U.S. and Canada (via Great Britain), but which later included Mexico, Japan, and Russia. While none of these laws really addressed habitat concerns, they set the foundation for protecting migratory birds, paving the way for future legislation.
In 1929 the first of several laws to address habitat issues, the Migratory Bird Conservation Act, was introduced (“Migratory Bird Conservation Act”). Among other things, this law created a commission to oversee the purchase of lands specifically for migratory bird conservation and established a special Migratory Bird Conservation Fund. Between the years of 1935 and 2000, this conservation program produced almost $650 million dollars for the purchase of wetlands, which, by the end of 2000, had been used to protect close to 5 million acres of wetlands (“Migratory Bird Conservation Account”).
To help provide funds for this cause, a law that came to be known as the Duck Stamp act was enacted in 1934, requiring hunters over the age of 16 to purchase a hunting stamp put out by the US Post Office (“Migratory Bird Hunting”). The revenue from sale of these stamps was then deposited to the Migratory Bird Conservation Fund. To further expedite the setting-aside of wetlands for conservation purposes, several laws were passed increasing the amount of funds immediately available. The Wetlands Loan Act of 1961 approved a loan based on future sales of duck stamps to be utilized by the Migratory Bird Conservation Fund (“Wetlands Loan”). The Emergency Wetlands Resources Act of 1986 provided additional funds for the purchase of wetlands by authorizing use of Land and Water Conservation Fund money (“Emergency”). This act also provided additional revenue to the Migratory Bird Conservation Fund by authorizing the transfer to it of money equal to all duties from the import of guns and ammunition. As another source of revenue, it created an entrance fee to National Wildlife Refuges, which was to be split between the Migratory Bird Conservation Fund and actual refuge maintenance costs. Finally, it required the creation of a “National Wetlands Priority Conservation Plan,” which in turn was intended to aid in the selection of the most vulnerable wetlands for protection by establishing certain criteria (“National Wetlands”).
The measure known as the Food Security Act was passed in 1985 with provisions that prevent farmers who drain wetlands on their land from receiving federal aid (“Food Security”). This regulation is credited not only with greatly reducing the area of wetland destroyed for agricultural purposes but also with the setting aside of over 700,000 acres of wetlands through voluntary land easement (“Voluntary”).
The North American Wetlands Conservation Act was passed in 1989, creating an organization to administer and coordinate a North American Waterfowl Management Plan between the US, Canada, and Mexico. Working through a system of partnerships this program has invested over $1.7 billion to protect, restore, and “enhance” nearly 5 million acres of wetlands in the three partner countries (“North American”). Importantly, however, this plan focuses its efforts largely on the trends of breeding duck populations, though some attention is given to other species (“North American”).
Another important component of wetland protection lies in the regulation established by §404 of the so-called “Clean Water Act,” which gives the Army Corps of Engineers (ACE) authority to regulate deposit of dredged and fill material (“Section 404” ). This has allowed the ACE to limit wetlands destruction via a system of permits. Additionally, in 1986 the Army Corps made the statement that its permitting authority extends not only to navigable waters, but also to interstate waters that provide habitat for migratory birds (“Solid Waste” ). This was an extension from the previously accepted authority the Corps had over waters immediately adjacent to navigable waters.
In the recent (2000) Supreme Court decision in the Solid Waste Agency of Northern Cook County (SWANCC) v. USACE, however, the Supreme Court ruled that the US Army Corps of Engineers does not have authority to regulate all waters providing habitat for migratory birds, potentially removing habitat protection from “isolated” wetlands.
There are two basic capacities through which wetlands serve migratory birds: as major stopover sites en route to migration destinations (e.g., Chesapeake Bay, Rio Grande valley) and as summer breeding grounds (e.g., Prairie Pothole Region). I will consider both of these in turn and attempt to address how well their utility to migratory birds is addressed by current federal law.
As en route stopover sites, wetlands have the potential to be utilized by the greatest number of birds-both in terms of species and sheer numbers-because both landbirds and waterfowl frequent them. While there is still much to be learned, one emerging idea is that larger landscape contexts can be important for suitability to many migratory species (Naugle et al. 2001). There are several potential explanations for why this might be the case. For some birds this might simply be the case of needing to have a wide selection to ensure suitable stopover habitat despite the potential for great variability in water levels (Weller 127). Whatever the case, there is mounting evidence that migratory birds do utilize many different wetlands throughout a complex prior to and during migration (Plissner and Haig 2000). What this could mean in terms of habitat protection is that the landscape context in which wetlands are located would matter just as much as, if not more than, individual wetland quality. For species that tend to move among wetlands more readily (e.g., northern pintail, black tern), the importance of an individual wetland’s “quality” has been demonstrated to increase dramatically as the density of wetlands surrounding it decreases (Naugle et al. 2001).
Another more specific context in which wetlands serve as stopover sites for migratory birds is in arid regions, such as in the southwestern U.S. Birds migrating through these regions tend to follow the paths of rivers and streams where possible, concentrating in riparian habitats (Finch and Yong 2000). In such locations, habitat quality is directly linked to the survival of migrating birds: if the birds cannot find enough food prior to their migration across whatever obstacle awaits them (e.g., the desert, the Gulf of Mexico), their chances of survival will be greatly diminished (Finch and Yong 2000).
Unfortunately, legislation has of yet given little consideration to the value of wetlands as stopover sites to migratory birds. Most legally initiated conservation plans focus their policy decisions primarily on breeding birds, as opposed to stopover species. This is likely to be in part due to the fact that little information exists as to the exact importance of stopover functions. Another part of it is likely to be due to the fact that concrete values of breeding waterfowl are more easily quantified (via revenues from hunting) than the values of stopover species, which often spend little time in a region.
Since the Clean Water Act continues to govern navigable waters, adjacent waters, and tidal waters, much of the sub-set of stopover habitat in the arid southwest is likely to be protected (if only nominally), since wetlands occurring far away from rivers or other bodies of water are going to be rare. Stopover wetland habitat does not need to be completely destroyed to threaten the birds that rely on it, however, and fragmentation in this particular case is a very real concern in these particular cases.
Wetlands also serve as breeding sites for many birds. Breeding requirements are in some ways slightly easier to quantify than stopover requirements, if only for the fact that the birds spend more time in one area and are easier to track. Nonetheless, our knowledge about migratory birds (particularly nongame migratory birds) is quite limited. While large wetlands have been recognized as being important for a relatively long period of time, recognition of the importance of smaller patches of wetland is only beginning to occur (Weller 131). The benefits of large swaths of wetland are easy to quantify, because it is possible to cite numbers of species, whereas the benefits of smaller wetlands are difficult to compare. As components of larger landscape contexts, smaller wetlands provide valuable services to birds, whereas on a wetland-to-wetland basis, large wetlands appear to offer services to a greater number of species. The problem with making determinations based solely on the number of species frequenting a particular wetland, of course, is that as habitat small wetlands tend to attract different types of species of birds than large wetlands (Naugle et al. 2001). Enhancing this problem, “officially” listed breeding requirements for migratory birds emphasize a minimum feasible wetland size, prompting policy to recognize the importance of large wetlands while largely ignoring the potentially important functions served by small wetlands.
If policy is biased at all in the types of wetlands it protects-which it seems to be-it is biased in favor of large basin wetlands, which are easy to focus on and manage (as opposed to small isolated wetlands scattered around a landscape). For the period of 1986 to 1987, freshwater forested wetlands and freshwater emergent wetlands both declined, whereas freshwater ponds actually increased (Dahl 2000). Whereas many waterbirds rely on large areas of open water (and adjacent vegetated areas) for breeding, there are still species that are negatively affected by the decrease in forested and emergent freshwater wetlands. Additionally, conservation measures that merely satisfy breeding requirements may not ensure a species’ complete success, as other wetlands may be required for other life stages.
While wetlands have yet to be significantly addressed by law as stopover habitat for migratory birds, their status as breeding habitat for waterfowl is relatively well established. To that end, quite a few laws focus on the task of setting aside breeding habitat, whereas no law directly addresses the question of preserving stopover habitat. Preservation of breeding habitat does allow for the inadvertent preservation of stopover habitat, but does not ensure that all important stopover habitat is acknowledged.
At the turn of the century (and earlier), wetland loss was certainly a major threat to migratory birds, but given the protections of the time (i.e., virtually none), hunting was also a very real threat. Despite current legal measures in place now, however, habitat loss is a very real concern, especially considering the potential to build on a wetland allowed by the permitting process and the recent Supreme Court ruling deregulating federal protection of isolated wetlands. While there have been a wide range of problems facing migratory birds over the years, the most significant one is habitat loss. While it is true that not all migratory birds make use of wetlands, the number that do and the threatened state of wetlands make conservation all the more important to address.
Preventing wetland loss is obviously an important issue in the conservation of migratory birds. However, when it comes to actually preserving wetlands, several issues arise. First, there is the problem of saving fringe wetlands along the banks of rivers, not necessarily because of lack of legislation but rather because of “overlapping jurisdictional boundaries” (Weller 103). There is also the issue of preferential conservation in that certain types of wetland are just easier to save than others. Large basin wetlands are easy to buy and save, whereas tiny bogs scattered around the land are hard to rope into a conservation area that might protect them. To compound this problem, not only are certain types of wetlands easier to save, but some are found in locations more prone to development (Dahl 2000).
In the simplest sense, of course, any wetland saved is better than none, and the rate of destruction in the United States has definitely declined in the recent past. The rate of loss in the 1990s has been estimated at less than 60,000 acres annually, compared to 290,000 acres annually in the 70s and over 450,000 through the 50s and 60s (Dahl 2000). Still, the fact remains that a “No Net-Loss” policy has not been realized.
Various plans to acquire land for preservation and to enhance existing land is a positive influence on the status of wetlands; however, more regulatory measures are needed to entirely curtail the influence of development on wetlands. The Food Security Act has had a major impact on agricultural draining of wetlands, and the Clean Water Act has unquestionably played a major role in greatly reducing the destruction of wetlands for development purposes. For the most part, however, ducks have been the major benefactors of legally enacted conservation programs, with other species tending not to garner so much benefit (“North American”; Scheider and Pence 1992). Granted, a high proportion of other birds can benefit from policy driven by science focused on ducks, but the needs of certain species prevent that number from being 100 percent.
When set in the context of stopover sites for migrating birds, fragmentation of wetlands is another important concern. Whereas outright destruction of wetlands is relatively easy to prevent by enacting of laws, fragmentation is a much more imprecise threat that is more difficult to identify and stop.
One negative effect associated with wetland fragmentation-aside from the obvious impact of habitat loss-is something called the edge effect. While there is still debate on how much impact this effect has (and, in some cases, whether or not it even exists), it is generally noted that predation rates on young birds is greatest within a certain distance from the edge of a particular ecosystem (Paton 1994). What this means, then, is that with increasing fragmentation of wetland habitat we would expect to see decreasing nest success, further endangering already stressed populations of migratory birds (Rosenberg and Noon 1997). Moreover, fragmentation isolates populations from one another, which leads to decreased viability and survival rates (Rosenberg and Noon 1997).
Fragmentation does not require an obvious separation in order to have a negative effect on migratory birds, however, and can be achieved by invasions of alien species, small habitat modifications such as creating hiking trails, and other seemingly unobtrusive things (Finch and Yong 2000).
The SWANCC decision has the potential to threaten already-threatened and fragmented wetland landscapes by removing from federal protection those wetlands that may have been substantially isolated through development. Federal policy has not completely ignored this issue, however. In western states the Bureau of Land Management has adopted policies that try to minimize the impact of grazing on fragmentation (a major cause in the region) of forested wetland landscapes (Temple 1998). Additionally, conservation areas purchased through federal measures such as the Migratory Bird Conservation Fund and the North American Wetlands Conservation Act are typically driven to set aside large parcels of land, both for logistical and scientific reasons of maintaining habitat. Such measures obviously protect against future fragmentation of the acquired land but do not protect generally against fragmentation nationwide.
Another not-so-obvious problem facing migratory birds is urbanization. While urbanization directly threatens wetlands through development, it also indirectly threatens species that use wetlands by altering wildlife communities. The most profound example of this is the effect cities can have of “enhancing” predator communities, which then have a negative effect on bird population and the survival of young. Generally, urban areas introduce new predators (i.e., cats and dogs), “subsidize” predators that can subsist on human garbage, and cause an increase in the numbers of smaller predators by eliminating larger predators (Marzluff et al. 1998). Migratory bird populations-and bird populations in general-are more negatively affected by the actions of smaller predators than they are of larger predators, since smaller predators tend to be the more voracious nest predators (Marzluff et al. 1998; Block and Finch 1997).
Urbanization can also threaten wetlands by taxing local aquifers, thereby lowering water tables (Marzluff et al. 1998). Additionally, species diversity can be influenced by the presence of urban (and suburban) areas, which tend to select for certain species and promote unnaturally high densities of species that are well-adapted to the city, altering competition and reducing biodiversity (Marzluff et al. 1998; Block and Finch 1997).
In some ways, the effects of urbanization are indirectly addressed by the fact that mitigation done for wetlands destroyed in an urban area is often conducted in a suburban or rural setting, depending on the individual circumstances. This is especially the case for mitigation banks, which, owing to practicality, also tend to replace urban wetland with rural or suburban wetland. Such actions also have the influence of altering the position of wetlands in the landscape, however, which can have negative effects on migratory birds.
While legal actions over the years have managed to greatly reduce the rate of wetland destruction, that rate has not yet reached zero and will most likely not reach it for quite a while. Nonetheless, achievements so far are laudable. Fragmentation and urbanization have yet to be significantly addressed as problems by legislation, however, with fragmentation being protected against in specific instances (e.g., sanctuaries, refuges) but not in general, and with urbanization not really addressed at all. Generally there has been little effort to address anything other than the most direct impacts of urbanization on wetlands.
* * *
In summary, it seems that while great strides have been made in protecting wetlands, there are still some important blind spots that need to be addressed. The threats to wetlands serving as breeding habitat, particularly in the case of waterfowl that are perceived as economically valuable, seem to be addressed much better than those threats to wetlands that serve as stopover habitat. As with virtually any environmental issue, there is a certain degree of uncertainty and overlap, but for the most part it seems that legislation having a significant interest in stopover habitat has yet to be introduced. Likewise, the more concrete problem of wetland loss has been addressed quite well, relatively speaking, whereas the other, less easily quantifiable problems of fragmentation and urbanization have yet to be addressed.
Bibliography
Block, William M.; Finch, Deborah M., technical editors. 1997. Songbird ecology in southwestern ponderosa pine forests: a literature review. Gen.Tech.Rep.RM-GTR-292. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. 152 p. <http://www.ncal.verio.com/~nsn/effects.html>
Dahl, Thomas E. 1990. Wetlands losses in the United States 1780’s to 1980’s. U.S. Department of the Interior, Fish and Wildlife Service, Washington, D.C. Jamestown, ND: Northern Prairie Wildlife Research Center Home Page. <http://www.npwrc.usgs.gov/resource/othrdata/wetloss/wetloss.htm>
Dahl, T.E. 2000. Status and trends of wetlands in the conterminous United States 1986 to 1997. U.S. Department of the Interior, Fish and Wildlife Service, Washington, D.C. 82 pp.
Emergency Wetlands Resources Act of 1986. U.S. Department of the Interior, Fish and Wildlife Service. <http://laws.fws.gov/lawsdigest/emwet.html>
Finch, Deborah, and Wang Yong. “Landbird migration in riparian habitats of the middle Rio Grande: A Case Study.” Studies in Avian Biology. No 20: 88-98. 2000
Food Security Act Of 1985. US Army Corps of Engineers, Directorate of Civil Works, Planning, and Policy. <http://www.usace.army.mil/inet/functions/cw/cecwa2/envdref2/pages/fsao1985.htm>
A Guide to the Laws and Treaties of the United States for Protecting Migratory Birds. U.S. Department of the Interior, Fish and Wildlife Service. <http://migratorybirds.fws.gov/intrnltr/treatlaw.html>
Hulsey, Brett, et al. “Permitting Disaster in America.” Sierra Club. March 20, 2000. <http://www.sierraclub.org/wetlands/reports/flooding/>
Keating, David M. “The Changing Wetland Legal Landscape: Solid Waste Agency of Northern Cook County vs. U.S. Army Corps of Engineers.” Appraisal Journal 69 (2001): 283-286.
Lipske, M. “How Much Is Enough?” National Wildlife 28 (1990): 18-23.
Marzluff, John, et al. “Urban Environments: Influences On Avifauna And Challenges For The Avian Conservationist.” Avian Conservation. Island Press: Washington, D.C., 1998
Migratory Bird Conservation Account. U.S. Department of the Interior, Fish and Wildlife Service. <http://budget.fws.gov/greenbook/1700MBCA.pdf>
Migratory Bird Conservation Act. U.S. Department of the Interior, Fish and Wildlife Service. <http://laws.fws.gov/lawsdigest/migbird.html>
Migratory Bird Hunting and Conservation Stamp Act. U.S. Department of the Interior, Fish and Wildlife Service. <http://laws.fws.gov/lawsdigest/mighunt.html>
Naugle, David, et al. “A Landscape Approach to Conserving Wetland Bird Habitat in the Prairie Pothole Region of Eastern South Dakota.” Wetlands 21 (2001): 1-17.
National Wetlands Priority Conservation Plan. U.S. Fish and Wildlife Service, 1989
North American Wetlands Conservation Act Progress Report 1998-1999. U.S. Fish and Wildlife Service, 2000.
Paton, Peter. “The Edge Effect on Avian Nest Success: How Strong Is the Evidence?” Conservation Biology 8 (1994): 17-26.
Plissner, Jonathan H.; Haig, Susan M. “Postbreeding movements of american avocets and implications for wetland connectivity in the western great basin.” Auk 117 (2000): 290-299.
Rosenberg, Daniel K. and Barry Noon. “Biological Corridors: Form, Function, and Efficacy.” Bioscience 47 (1997): 677-678.
Scheider, Kathryn, and Diane Pence. Migratory Nongame Birds of Management Concern in the Northeast. U.S. Department of the Interior, Fish and Wildlife Service, 1992.
Section 404. Legal Information Institute, U.S. Code. <http://www4.law.cornell.edu/uscode/unframed/33/404.html>
Solid Waste Agency Of Northern Cook Cty. v.Army Corps Of Engineers (99-1178). Legal Information Institute, Supreme Court Collection. <http://supct.law.cornell.edu/supct/html/99-1178.ZS.html>
“Supreme Court Guts Clean Water Act Protection of ‘Isolated’ Wetlands Used by Migratory Birds.”‘ Ecology Law Quarterly 28 (2001): 543-546.
Temple, Stanley A. “Easing the Travails of Migratory Birds.” Environment 40 (1998): 6-14.
Voluntary Habitat Restoration with Private Landowners. U.S. Department of the Interior, Fish and Wildlife Service. <http://partners.fws.gov/TechAsis/techasis.html>
Weller, Milton W. Wetland Birds: Habitat Resources and Conservation Implications. Cambridge University Press: New York, 1999.
Wetlands Loan Act. U.S. Department of the Interior, Fish and Wildlife Service. <http://laws.fws.gov/lawsdigest/wetloan.html>