Go with the flow

A  look at the Florida Everglades and biodiversity (part one)

The Florida Everglades are a “limestone plateau that is the southeastern extension of the North American continent (Brown, et al., 2006, p. 255). They are the only subtropical wetlands in North America. The Everglades are home to a diverse number of species and interdependent ecosystems. Today, due to human modification, the Florida Everglades occupies half of the original area it did a century ago (SFWMD, 2011). “Coastal prairie, pine flatwoods and hardwood hammocks have all been sacrificed in the name of progress” (Rocus & Mazzotti, 1996, p. 1).

Historically, the Everglades relied on a natural flow of water from Orlando down through the Florida Bay (see figure to the left). Originally, the water sheet flow was derived primarily from rainfall and contained little nutrients. The Everglades were considered “oligotrophic (nutrient poor)” (Brown, et al., 2006, p. 256). 

These seasonal changes allowed for a high diversity of flora and fauna, while regulating animal cycles (Brown, et al., 2006). Most of south Florida was considered uninhabitable swamp.

Increasing populations drove the efforts to drain marshlands for agricultural conversion, flood control and urban development. To accomplish those goals, the federal government developed a system of manmade canals. The natural flow of the water in the Everglades is now entirely controlled by these canals, levees and pump stations (Brown, et al., 2006).

Along with these canal systems, exotic trees were introduced to aid in the draining of the marshlands; specifically the Australian punk tree (Melaleuca quinquenervia). These trees have a very high dispersal rate and turned the marshlands into a forest (Beringer, 2011).

One obvious consequence of altering the water cycles in the Everglades is the decline in wading bird populations. “Many species are dependent on the natural water cycle to signal nesting and breeding times and to provide sufficient food supplies” (Rocus & Mazzotti, 1996, p. 2). Ninety percent of bird populations have declined in the Everglades. Wading birds play an important role in the ecological fitness of this ecosystem. They redistribute nutrients, create tree islands, and affect the demographics of fish and invertebrate populations through predation (Frederick, et al., 2008).

Stay tuned next week (part two) for a continuing look at the Florida Everglades and biodiversity loss due to changing water tables.

References:

Arrieta, Diane, 2012. Excerpt from unpublished class paper, Impact of humans on biodiversity. University of Edinburgh.

Beringer, Joe, 2004. Conserving biodiversity in South Florida. [online]: Miami University. Available at: http://jrscience.wcp.muohio.edu/filedcourse04/PapersMarineEcologyArticles/Whathav ew edoneWhattodonow.html. [18 November, 2011].

Brown, Mark T., Cohen, Mathew J., Bardi, Eliana & Ingwersen, Wesley W., 2006. Species diversity in the Florida Everglades, USA: A systems approach to calculating biodiversity. Aquatic Sciences, [online] 68, pp. 254-277. Available through: SpringerLink [12 November, 2011].

Frederick, Peter, Gawlik, Dale E., Ogden, John C., Cook, Mark. I. & Lusk Michael, 2008. The White Ibis and Wood Stork as indicators for restoration of the everglades ecosystem. Ecological Indicators, [online] 9:6, pp. s83-s95. Available through: ScienceDirect [10 November, 2011].

South Florida Water Management District (SFWMD), 2011. America’s Everglades. [online] Available at: http://my.sfwmd.gov/portal/xweb%20and%restoring/americas%20everglades [21 November, 2011].

Rocus, Denise & Mazolli, Frank J.,1996. Threats to Florida’s Biodiversity, [online]: University of Florida IFAS Extension. Available at: http://edis.ifas.edu/uw107. [8 November, 2011].

image credit: United States Geological Service. n.d. Illustration. Available at: http://sofia.usgs.gov/publications/circular/1182/index.html [22 November, 2011].