Mack, R.N., Simberloff, D., Lonsdale, W.M., Evans, H., Clout, M., and Bazazz, F.A. 2000. Biotic invasions: causes, epidemiology, global consequences, and control. Ecological Applications 10:689-710.
Link: http://www.jstor.org.ezproxy.tru.ca/stable/pdfplus/2641039.pdf?acceptTC=true
Hickey, V. 2010. The quagga mussel crisis at Lake Mead National Recreational Area, Nevada (U.S.A.). Conservation Biology 24:931-937.
Many parks are typically established with competing mandates that involve serving people as well as conserving nature. The rivalry of these mandates can become the culprit of many problems. Humans directly benefit from conservation efforts though it seems that anthropogenic activity typically results in obstruction of conservation efforts and as a result natural ecosystem flow and ecological service to humans is negatively impacted. With this said, it is easy to see that these competing mandates can be incompatible and uncomplimentary to one another and detrimental effects subsequently arise. An example of a park that was established on the basis of these mandates is Lake Mead National Recreational Area in Southwestern United States.
Lake Mead Park is a reservoir originally established as land set aside after the construction of Hoover Dam in 1936. In 1953, Lake Mohave was also created as a reservoir from another hydroelectric station and together these lakes were assigned as preserved land and a recreational area in 1964 (Hickey, 2010). The purpose of the park was to provide water recreation opportunities for present and future generations in a manner that will preserve the scenic, historic, scientific, and other important features of the area. This purpose seems to convey that ecological services to humans is of first priority, but with this said future recreation depends on softening the impacts of human activities to conservation nature as much as possible. Therefore natural conservation is of second if not of equal importance to ecological services. Lake Mead Park is a prime example of serious problem arising from competing mandates. As a result of adhering to the parks purpose and implemented orders, Lake Mead Park managers failed in regards to the containment, management, prevention, and treatment of non-native invasive species. In other words, the invasive quagga mussel (Dreissena rostriformis bugensis) epidemic was not dealt with sufficiently when efforts to meet both public and conservationist’s needs were not enough to prevent the problem.
The quagga mussel is a subspecies of freshwater mussel that is 1 of the 7 Dreissena species. It is native to the Dneiper river drainage of Ukraine and it was thought to be first introduced to the United States in Lake St. Clair (near Detroit, Michigan) in 1988 (Hickey, 2010). Because basic scientific information of Dreissena is incomplete and there is a lack of existing data on environmentally safe and effective control, four options were discussed in order to deal with the mussel outbreak. These options included doing nothing, closing off the park to vessels, prevention of vessels traveling to different parts of Lake Mead, and educating and enforcing regulations. The option of doing nothing was out of the question as it did not comply with its mandate to preserve the ecosystem in its natural state. Closing off the parks to vessels also violated the human recreation mandate. Preventing the travel of vessels to different parts of Lake Mead, and therefore slowing colonization, did not make sense when the turbulent water from Hoover Dam’s intake pipes did not prevent the colonization of adult mussels and veligers (mollusk larva) downstream. Furthermore, this prevention of vessel travel is likely very difficult despite financing due to the open-accessibility and large size of the park and its numerous launching sites which would require numerous law-enforcement agents. However, to some degree this option was followed via park zoning (restricting recreational activity and other land uses to particular locations within the park, leaving other areas undisturbed). It was decided that the last option, to educate public and enforce regulations, would be the major effective mode of treatment without violating park mandates.
There was a huge amount of support and funding available to the education and law-enforcement program as many urban and agricultural communities, as well as several migratory birds and propagating, endangered fish species, depend on the Lakes for freshwater. Furthermore, the Park’s water feeds into hydroelectric stations, is supplied to many industries, and is the sole source of drinking water to some 55 million residents and tourists. The education and regulation enforcement project involved inspection, decontamination (cleaning, draining, and drying of vessels), and monitoring of traveling vessels from different parts of the lake. In addition, the team produced signs in high human activity areas of the park explaining the ecological effects of the invasive species and associated boat operation and maintenance costs (Hickey, 2010).
The detrimental effects of the over abundance of quagga mussels can clog water intake structures, remove phytoplankton (which zooplankton depend on and in turn higher trophic levels), increase water clarity (which results in increased light penetration to aquatic plants and alters the composition of dominant species), raise the acidity of water as their pseudofeces decompose, and increase the exposure of their predators to increased amounts of organic pollutants within the mussel’s tissues (Hickey, 2010).
Despite the parks efforts to prevent the outbreak of Dreissena rostriformis bugensis via its early detection program and its sufficiently funded education and law-enforcement project, quagga mussels now thrive in Lake Mead Park and the lake continues to be responsible for some degree of the mussel spread. The park is now experiencing large financial and conservational losses involving decreased human recreational satisfaction, damage to vessels and water treatment plants, and alteration of natural fauna and flora. Notably, the Park’s zoning technique (which was established to form a compromise between conservation and human use) seemed to have magnified the issue by creating an efficient pathway for invasion. With restricted access to several parts of the park, humans were concentrated and forced to use similar pathways to enter and exit the park. These pathways as a result repeatedly imported and exported invasive species that which exploited the natural resources of that area. In turn the exploited areas act as an effective reservoir to help spread the thriving mussel to several different areas. Zones aren’t a great idea, and at the very least they could be used as a buffer zone between disturbed and undisturbed areas. It is within these zones that extensive effort must be put towards prevention.
There is documentation that suggests where conservation efforts, in such an example of Lake Mead Park, could have been successful in detecting and preventing invasion. For instance, during contamination for vessels traveling from one part of the lake to another, it is not the efficacy of the tools themselves that are responsible for controlling the abundance of an invasive species but rather the commitment and diligence of park managers. Furthermore, parks in general need to execute ecosystem wide strategies and long term goals rather than employing quick fixes and focusing on one species (Mack, 2000). This mind/goal set will conserve funds by directing money towards prevention rather than the more expensive alternative of post-entry control (Mack, 2000). The attributes that indicate whether or not a species will become invasive are inconclusive as species are so different from one another. In addition to this statement, it is also difficult to determine where and when a species will become invasive especially when most introductions do not result in invasiveness due to unfavorable environments and temporal variations (Mack, 2000). Overall, careful management towards prevention of invasiveness is crucial in avoiding sever global consequences.
Words:1190
No comments:
Post a Comment