Southern Florida Coastal Plain

By Steve Kambly ¹

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Ecoregion Description

 

The Southern Florida Coastal Plain ecoregion covers an area of approximately 22,407 km²  (8,651 mi²) across the lower portion of the Florida peninsula, from Lake Okeechobee southward through the Florida Keys (fig. 1).  It is comprised of “flat plains with wet soils, marshland and swamp land cover with everglades and palmetto prairie vegetation types” (U.S. Environmental Protection Agency, 2002).  The nutrient-poor environment of the ecoregion, particularly that of the Everglades, has been subject to run-off from urban and agricultural sources, which has led to changes in habitat health and diversity.  Moreover, surface water levels and sheet flow in the Everglades are very sensitive to any differences in topography due to the ecoregion’s exceedingly expansive and flat terrain.  As a result, changes of only a few centimeters in elevation may have significant impact on plant and animal communities.

The climate is generally frost-free and subtropical, consisting of a dry and a wet season.  About 1,400 mm (55 in) of rain fall annually in the ecoregion, with approximately 1,060 mm (42 in) of rainfall occurring in the wet season between June and September.  The warm dry season, from October to May, allows for year-round crop production and has been instrumental in the cultivation of winter vegetables.  Sugarcane is also widely grown and has formed the basis of the domestic sugar industry since the early 1960s (fig. 2).  The ecoregion underwent extensive land cover change between 1950 and 1970 due in large part to the implementation of water control measures, widespread use of air conditioning, mosquito control measures, improvements in transportation infrastructure, and efforts on the part of developers and government officials to promote Florida’s growth potential (Solecki, 2001) (fig. 3 and 4).

 

Contemporary Land Cover Change from 1973 to 2000

 

This ecoregion experienced 5.8 percent change during the study period, a moderate amount of land cover change in comparison to other ecoregions and, in particular, its neighbor, the Southern Coastal Plain, which had 24.9 percent change (fig. 5).  An estimated 4.4 percent of the area (986 km²) (381 mi²) converted to other land covers just once, and 1.4 percent of the ecoregion (314 km²) (121 mi²) converted more than once (table 1).  Approximately 94.2 percent of the ecoregion’s land cover remained unchanged.  The spatial distribution of change was very uneven, with high amounts occurring in urbanizing coastal areas and relatively little change inland, where the presence of reserved lands inhibits change.

Estimated change per interval varied from a high of 2.5 percent between 1973 and 1980 to a low of 1.4 percent between 1992 and 2000 (table 2).  The two intervening intervals—1980 to 1986 and 1986 to 1992—had 1.7 and 1.9 percent change, respectively.  

The estimated average annual rate of change was 0.3 percent.  The 1973 to 1980 interval showed the highest rate of change at 0.4 percent (table 2).  During this interval, the leading conversions were from wetland to agricultural land and a fire-related transfer from non-mechanically disturbed land to wetland.  The interval with the least change, 0.2 percent, was the 1992 to 2000 interval.  The leading conversions during this interval were from agricultural land to developed land and from wetland to non-mechanically disturbed land, again due to fire.

Percent change of area by land cover type indicates which land covers changed significantly between intervals and which were relatively stable (table 3). Developed lands increased in each interval, from 2.3 percent of the ecoregion in 1973 to 4.1 percent in 2000.  Agricultural land increased as well, from 17.2 percent in 1973 to 18.4 percent in 1980, but then declined in each subsequent interval, back to 17.3 percent of the ecoregion in 2000. Non-mechanically disturbed land fluctuated between zero percent and 0.6 percent during the intervals between 1973 and 1992, reflecting the natural cycle of fire and regrowth in the Everglades.  In 2000, non-mechanically disturbed land represented an estimated 0.3 percent of the ecoregion. Wetlands declined in each interval, except the third interval, and overall from 73.7 percent in 1973 to 72.2 percent in 2000, primarily as a result of expanding agricultural land and developed land covers.

Wetland to agricultural land was the most common conversion, with an estimated 348 km²  (134 mi²) converted between 1973 and 2000 (table 4).  Indeed, the highest rate of change occurred in the first interval (1973 to 1980), as 284 km² (110 mi²) of wetland covers converted to farmland.  Conversions of non-mechanically disturbed land to wetland, and wetland back to non-mechanically disturbed land were the second and fourth most common conversions, respectively.  These transitions reflect the natural role of fire and habitat renewal in wetland areas.   Agricultural land to developed land was the third most common conversion.  However, when conversions to developed land from agricultural land, forest, mechanically disturbed land, wetland, and grassland/shrubland are combined, more land—an estimated 413 km² (159 mi²)— is converted to developed land than any other cover type during the study period.  Conversions to developed land increased after 1980, as a significant amount of agricultural land that had been converted earlier from wetland became urbanized. Wetland, despite a continual decrease between 1973 and 2000, remained the dominant land cover. 

Several factors contributed to contemporary land cover change in the Southern Florida Coastal Plain. First, extensive drainage and flood control measures put into place beginning in the early 1950s by the Army Corps of Engineers ensured the continual increase of agricultural land and developed land.  In addition, an improved transportation infrastructure made the ecoregion more accessible to middle-class tourists and new residents and eased the movement of goods.  The advent of private and public pensions and health insurance enabled large numbers of retirees to settle in the ecoregion (Solecki, 2001).  Reserved lands in the form of National and State parks and wildlife refuges played a role in limiting new development, especially in wetland areas.  Reserved lands comprise about 30 percent of the ecoregion (fig. 6).  Finally, a growing awareness of environmental impacts led to measures to protect ecologically sensitive areas, including the creation of Big Cypress National Preserve in 1974 and current efforts at Everglades restoration (Carter, 1974; McCally, 1999).

 

References

 

Carter, Luther J., 1974, The Florida experience—Land and water policy in a growth state: Baltimore, Md., The Johns Hopkins University Press, 354 p.

 

 

McCally, David, 1999, The Everglades—An environmental history: Gainesville, University Press of Florida, 215 p. 

 

Solecki, W.D., 2001, South Florida—The role of global-to-local linkages in land use/land cover change in South Florida: Ecological Economics, v. 37, p. 339–356.

 

Solecki, W.D., and Walker, R.T., 2001, Transformation of the South Florida landscape, in Indian National Science Academy, Chinese Academy of Sciences, and U.S. National Academy of Sciences, Growing populations, changing landscapes—Studies from India, China, and the United States: Washington, D.C., National Academy Press, p. 237–273.

 

U.S. Environmental Protection Agency, 2002, Primary distinguishing characteristics of Level III ecoregions of the continental United States [draft]: EPA, available online at ftp://ftp.epa.gov/wed/ecoregions/us/useco_desc.doc.

 

 

Table 1.  Estimated footprint of land cover change between 1973 and 2000

 

	Overall	Number of changes
	spatial change	1	2	3	4
Percent of ecoregion	5.8%	4.4	1.2	0.2	0.0

 

 

 

Table 2.  Estimated change per interval, associated confidence intervals, and average annual rates of change

 

[The average annual rate of change compensates for the unequal lengths of the different time intervals]

 

	Period
	1973–1980	1980–1986	1986–1992	1992–2000
Total change (% of ecoregion)	2.5%	1.7%	1.9%	1.4%
Margin of error (85% confidence level)	+/–1.3%	+/–0.9%	+/–1.1%	+/–0.7%
Average annual rate of change (%/year)	0.4%	0.3%	0.3%	0.2%

 

 

 

Table3.  Estimated area for each land cover class between 1973 and 2000

 

	1973		1980		1986		1992		2000		Net change 1973–2000
Land-use/land-cover class	km²	%	km²	%	km²	%	km²	%	km²	%	km²	%
Water	616	2.7	620	2.8	636	2.8	667	3.0	705	3.1	89	0.4
Developed	516	2.3	586	2.6	671	3.0	814	3.6	922	4.1	406	1.8
Mechanically disturbed	31	0.1	19	0.1	52	0.2	36	0.2	46	0.2	15	0.1
Mining	1	0.0	3	0.0	0	0.0	3	0.0	2	0.0	0	0.0
Naturally barren	6	0.0	6	0.0	6	0.0	6	0.0	6	0.0	0	0.0
Forest	648	2.9	619	2.8	602	2.7	583	2.6	575	2.6	–73	–0.3
Grassland/Shrubland	82	0.4	77	0.3	64	0.3	79	0.4	56	0.3	–26	–0.1
Agriculture	3,859	17.2	4,124	18.4	4,085	18.2	3,943	17.6	3,871	17.3	11	0.1
Wetland	16,517	73.7	16,350	73.0	16,160	72.1	16,275	72.6	16,166	72.1	–351	–1.6
Non-mechanically disturbed	131	1	0	0	131	0.6	0	0.0	58	0.3	–73	–0.3

 

 

 

Table 4.  The leading land cover conversions in each interval

 

			Area changed	% of all
Period	From class	To class	(km2)	changes
1973–1980	Wetland	Agriculture	284	51
	Non-mechanically disturbed	Wetland	130	23
	Forest	Developed	25	4
	Mechanically disturbed	Developed	19	3
	Agriculture	Developed	17	3
	Other classes	Other classes	84	15
			559	100
1980–1986	Wetland	Non-mechanically disturbed	131	34
	Agriculture	Mechanically disturbed	37	10
	Wetland	Agriculture	37	10
	Agriculture	Developed	34	9
	Forest	Developed	18	5
	Other classes	Other classes	123	32
			380	100
1986–1992	Non-mechanically disturbed	Wetland	131	31
	Agriculture	Developed	86	20
	Agriculture	Grassland/Shrubland	31	7
	Mechanically disturbed	Developed	27	6
	Forest	Developed	22	5
	Other classes	Other classes	129	30
			426	100
1992–2000	Agriculture	Developed	60	20
	Wetland	Non-mechanically disturbed	57	19
	Wetland	Agriculture	22	7
	Wetland	Water	19	6
	Agriculture	Mechanically disturbed	18	6
	Other classes	Other classes	129	42
			305	100
Overall:
1973–2000	Wetland	Agriculture	348	21
	Non-mechanically disturbed	Wetland	261	16
	Agriculture	Developed	197	12
	Wetland	Non-mechanically disturbed	187	11
	Agriculture	Mechanically disturbed	80	5
	Other classes	Other classes	598	36
			1,671	100

 

 

 

 

Figure 1.  The Southern Florida Coastal Plain.  The randomly selected sample blocks are shown along with land use/land cover data from the 1992 National Land Cover Dataset.

 

 

 

Figure 2.  Sugarcane cultivation and processing operations dominate the Everglades Agricultural Area south of Lake Okeechobee.

 

 

 

Figure 3.  Water control and allocation infrastructure ensured the continuation of urban and agricultural growth after WWII.  This flow regulator is part of the Central and Southern Florida Flood Control Project which was authorized by Congress in 1948 and constructed by the U.S. Army Corps of Engineers.

 

 

 

Figure 4.  Demand for housing and associated development continues near coastal areas.

 

 

 

Figure 5.  The overall spatial change in all Eastern U.S. ecoregions.  Each bar chart shows the proportion of the ecoregion that experienced change on 1, 2, 3, or 4 dates.

 

 

 

Figure 6.  Established in 1947, Everglades National Park limits development, but plant and animal species within the park are greatly affected by the agricultural and urban areas beyond its borders.