Can The Everglades Be Restored To Its Original, Pre-European Condition?

The Everglades Restoration Plan, while a very important and beneficial environmental project,  intends to “restore the magnificent River of Grass [the Everglades]“. As they also write

Marjory Stoneman Douglas wrote about the problems of the Everglades in 1947, describing a ecosystem that was beautiful yet already clearly suffering…..The Comprehensive Everglades Restoration Plan will capture freshwater destined for sea – the Everglades’ lifeblood – and direct it back to the ecosystem to revitalize it. It will improve water supplies for people and farms, too. The nation’s largest such project, it will cost $7.8 billion and take more than 20 years to develop.”

Having visited  Everglades National Park many times, it is a worthy goal to seek this. However, unfortunately, as we and others have shown, the weather (and thus the hydrology and ecology) of the Everglades are affected by what occurs throughout central and southern Florida. The amount of freshwater today (from rain), unfortunately, is significantly less then it was prior to European disturbance. 

Recently, I was asked to summarize what we have found in our studies of Florida. This information is given below.

Three dimensional modeling of south Florida began with the paper

Pielke, R.A., 1974: A three-dimensional numerical model of the sea breezes over south Florida. Mon. Wea. Rev., 102, 115-139. http://www.climatesci.org/publications/pdf/R-2.pdf

This study found that a spatial grid increment of 11 km was needed in order to accurately represent the sea breeze convergence patterns which form on many days over this region, and that focus thunderstorm activity over the peninsula. The curvature of the coastline, Lake Okeechobee, as well as wetlands exerts a major influence on these convergence zones. An example of this relationship is shown in Figure 1.

Figure 1:  Vertical velocity prediction 9.5 hours after simulated sunrise and composite radar map for equivalent times for June 29, 1971.

This study built on the pioneering research on sea breezes of Estoque (1962 : The sea breeze as a function of prevailing synoptic situation. J. Atmos. Sci., 19, 244-250).

A number of research papers followed that further elucidated the role of the surface in south Florida in affecting the region’s weather. These include:

Observationally related papers include

The specific paper

Marshall, C.H. Jr., R.A. Pielke Sr., L.T. Steyaert, and D.A. Willard, 2004: The impact of anthropogenic land-cover change on the Florida peninsula sea breezes and warm season sensible weather. Mon. Wea. Rev., 132, 28-52.

provides a demonstration of the major role that landscape change has had on south Florida. The change in landscape is illustrated in Figure 2 from http://www.climatesci.org/publications/pdf/R-272.pdf].

 
Figure 2.  USGS land-cover data for (left) pre-1900 natural land cover and (right) 1993 land use.

This study had the following major conclusions:

  1. The region has become about 10-15% drier on average in July and August as a result of the conversion of the natural landscape. A major reason is the loss of wetlands which, in the past, provided significant water vapor input to sea breeze generated thunderstorms.
  2. The region has higher daytime temperatures and lower nighttime temperatures [of several degrees Celsius in places] as a result of the landscape change.
  3. There are local exceptions to #1 and #2 such as slightly cooler temperatures along the coast due to an invigorated sea breeze (since it is warmer inland during the day), as well as small regions of enhanced rainfall associated with the patterning of the landscape  which produce local areas of increased low level wind convergence.

An important implication from this study is that attempts to mitigate changes to the south Florida hydrology and ecology as part of the Everglades Restoration Project cannot result in the return to the climate regime that existed prior to the large scale landscape disturbances of the 20th century. While the Everglades Restoration Plan should be pursued, there should be no illusion that the hydrology and ecology can be restored to what it was originally when first settled.

 

 

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