September 11, 2002
is the driver of life and nowhere is this more obvious than in the
warm subtropical climate of Florida. The peninsula's landscape has literally
emerged from the sea and its existing vegetation and sandy soils are now
sculpted by the twin products of wildfire and water. Famed for its climate
the state has, since the end of the Civil War, attracted more and more
visitors and residents alike because of the balmy breezes, moist air and
apparently endless miles of fresh and salt water shoreline. Our famed fisheries,
nearly 700 miles of sand beaches and waterlogged forests all play a critical
role in forming the biological wealth and ambient charm of the state. The
climate we have always banked on as a natural attribute for the state,
however, is now changing. The changes prove to be so fast and of such a
great magnitude that the role water has played in this state's sustenance
will also change. Water comes from a never ending cycle of evaporation,
condensation, rain, and runoff or recharge depending on where the water
moves. We are all spectators to this continuous transformation upon which
is a large range of uncertainty about what future scenarios predict for
rainfall, or precipitation in Florida, due to increasing average global
temperatures. The historical patterns of rainfall across the state serve
only as a retrospective within which to frame a very uncertain future.
The past is not a predictive measure of what will or will not occur as
the planet warms in response to excessive overloading of carbon waste vapors
in the air. Climate --as the year to year persistence of weather patterns
over time at a particular place-- is an asset in Florida. The future is
in doubt with regards to a predictable and reliable climate, particularly
in respect to rainfall patterns which account for much of our water.
How much doubt can we tolerate in a growing state? Florida's increasing population varies in density from 16,000 to 3,000 people per square mile in populated areas. This is a serious question. Since six degrees of latitude separate the northern state boundary from the Florida Keys, natural variability when added to differing densities of population complicate the uncertainty with respect to future water supplies. For example, rainfall provides surface and underground water across the state in a very uneven pattern. This is because rainfall averages range from between highs of 60-69 inches annually to lows of 40 to 49 inches annually. Central Florida and the Keys receive relatively lower average rainfalls and the panhandle and southeastern coasts capture higher rainfall levels. However, the patterns between Pensacola and Miami are quite different. From Escambia to Port St. Joe rainfall is more evenly delivered in winter and summer months, whereas a summer peak and winter drought is most pronounced in the Everglades region. South central Florida has --on average-- less annual rainfall than does north central.
Three types of climate patterns occur across Florida distinguishing northern from central and southern regions. Orange, Seminole and Lake counties lie on that northern and central climatic boundary. Together with Polk and Brevard these counties lie at the hydrological apex of the state's surface water flows. By that we mean that from this part of the central Florida ridge of sand and clay, water moves to the south, the north and the west, besides seeping down into the underground caverns that riddle the peninsula. Population, rainfall patterns and surface and underground movement of moisture all complicate water availability in a regime of growing climate uncertainty.
Historically vast areas of aquifer recharge vegetation, forests and swamps have been collecting areas for rainfall. Like the Everglades, Paines Prairie, or the Green Swamp these reservoirs are to us what mountain snows and elevated watershed forests are to northern and western states. The amount of water we have available is in rough proportion to the catchment area or basin over which the water flows. The Floridan aquifer, existing beneath most of the northern and central reaches of the peninsula, has always been an additional deep reservoir to meet water needs. Like any basin, you can't withdraw more from a holding area than is deposited by rainfall and runoff into the basin.
Take for example the St., Johns Marsh. This is a huge collecting area of low lying wetlands in Indian River, Brevard, Osceola and Orange Counties that acts as the source for the state's longest river. Without the extensive seasonal and permanently flooded prairies, there would be no net transfer of water from south central to northeastern Florida.
Clearly as climate change affects rainfall, two considerations must be added to the uncertainty and variability of rain patterns of across Florida. Despite the disagreement of some models showing more rain and others revealing more drought for Florida, rainfall intensity is likely to increase. That means more and heavier precipitation is likely to occur than we have been accustomed to in the last century. With rainfall intensity rising runoff increases. Anything that causes the quick runoff of water, such as paved streets, parking lots and other impervious surfaces, will add to the increased runoff, or the measure of water from rainfall moving across the surface of the landscape.
The other impact of climate uncertainty is the abrupt character of changes in temperature. The amount of carbon dioxide and its equivalent vapor gas wastes in the atmosphere is building at a rate greater than biological or chemical systems can assimilate. The rate of change in temperature is also at a greater pace than vegetation, especially slower growing species can adjust to. Grasses, for example are more responsive to temperature stress than are trees. Whole forest communities may change their species mixture, or be replaced by more tolerant species, faster than we have been accustomed to finding across the state. In areas where sea level is rising, such as Waccasassa Bay we have already seen evidence of fresh water tolerant Sabal Palms (the state tree) being replaced by salt tolerant marsh grass. There is evidence in Florida Bay of salt tolerant mangroves replacing fresh water tolerant saw grass which is retreating over a 3.3 kilometer wide boundary line since 1940.
The World Wildlife Fund asserts that "extreme rain events.... changes hydrology through altered runoff patterns, but also increases the frequency of summer droughts." Aside from the growing uncertainty due to rapid population migration, land use changes and agricultural losses "Warming and precipitation changes will have major consequences for vegetation in Florida, and changes in sea surface temperatures pose a major threat to coral reefs and other marine systems," concludes the same World Wildlife Fund study.
What this means for the future is that neither climate nor water are the
sort of amenities we can take for granted any longer. Any prudent, conservative
approach to the current and growing future climate uncertainties would
err on the side of extreme caution. In times of drought, habits we instilled
in times of ample rainfall can payoff more handsomely than waiting until
we run out of the water that simultaneously drives our economy and environment.
Densely populated cities are already pressing against very limited water
supplies. While people require adequate water for good nutrition, health
and hygiene we must realize that wildlife, fisheries and vegetation are
also forms of investment in high quality water that are essential to meet
these needs. Florida has vast areas of sand hills and impenetrable swamps,
like Colorado has the Rocky Mountains for reasons of topography that serve
to make ample water available for springs, vegetation, fish, shellfish,
manatees and wildlife, not to mention viable settlements.
Climate change, or the growing climate uncertainty we are facing will erode our shorelines, force salt water into the tiny lenses of freshwater under the ground and may even encourage us to be more cautiously efficient. Conservation becomes more and not less important in this uncertain age, but active protection of water quality and public health become of preeminent importance now because our margin for error is becoming intolerably slim. Sixteen million people using hundreds of gallons of water per day can't possibly tolerate the level of mistakes we have lived with in water policies since the 1930s. This undervalued and under priced resource is soon becoming among the most important sources for our healthy and secure future.
Joseph V. Siry
Florida Climate Alliance
Ocklawaha River Restoration Coordinator
Florida Defenders of the Environment