INTRODUCTION AND HISTORY

Hurricane Andrew, a Category 5 storm, crossed the 

southern Florida peninsula on the morning of August 

24, 1992 (Fig. 1). Following the storm, the National 

Park Service conducted an environmental damage 

assessment to gauge the storm’s impacts on the 

natural resources of south Florida Park Service holdings (Pimm et al., 1994). Although hurricanes have 

impacted Park Service lands such as the Everglades in 

the past (Houston and Powell, 2003), no systematic, 

permanent sampling scheme has been established to 

monitor long-term recovery (or lack thereof) following 

disturbance.

In October 1992, vegetation monitoring plots were 

established in heavily damaged areas of mangrove 

forest on the southwest coast of the Everlgades, 

along the Lostmans and Broad Rivers (Smith et al., 

1994, see Fig. 2). As the permanent plot network 

was being established, funding was awarded for 

Development of a Long-term Sampling Network to Monitor Restoration Success in the 

Southwest Coastal Everglades: Vegetation, Hydrology, and Sediments

Figure 1. What is left of a mangrove forest that was 

crossed by the eye wall of Hurricane Andrew. The photo 

was taken in Biscayne National Park in September 1992, 

three weeks after the storm.

U.S. Department of the Interior

U.S. Geological Survey

the South Florida Global Climate Change project 

(SOFL-GCC). This led to the establishment of a network of hydrological monitoring stations (Anderson 

and Smith, 2004). Finally, sediment elevation tables 

(SETs) were installed at many locations. SETs provide the means to measure very small changes (2 

mm) in the sediment surface elevation accurately over 

time (Cahoon et al., 2002). We also set up marker 

horizons to measure accretion of sediment at each 

site (Smith and Cahoon, 2003). Sampling sites were 

located along three transects extending from upstream 

freshwater wetlands to downstream saltwater wetlands 

along the Shark, Lostmans and Chatham Rivers in 

Everglades National Park (Fig. 2). 

USGS Fact Sheet FS–2004-3015

Figure 2. Location of sampling sites in Everglades 

National Park. RED dots = surface and groundwater 

stage and conductivity; YELLOW dots = surface and 

groundwater stage and conductivity, permanent vegetation plots, and sediment elevation sampling; light 

GREEN dots = sediment porewater piezometers and 

permanent vegetation plots; light BLUE dots = permanent vegetation plots; large TAN dot = location of 

the mangrove marsh ecotone boardwalk, with surface 

and groundwater wells, sediment porewater piezometers, and permanent vegetation plots.
While we were developing our sampling network for 

basic scientic research needs, concern mounted over 

the health of the Greater Everglades Ecosystem and 

in particular over the inuence of decreased freshwater ows (Smith et al., 1989). Ecosystem restoration 

planning was begun, resulting in the multi-agency, 

$8 billion Comprehensive Everglades Restoration Plan 

(CERP). Our co-located sampling networks (Fig. 3) 

allow us to track the interaction of hydrology, sediment, and vegetation over time, and will provide the 

opportunity to monitor the progress of the Everglades 

restoration and to gauge its success. Our earlier 

research questions have been modied over time to 

place a major emphasis on CERP needs, while still 

recognizing the importance of other processes, including disturbance and sea-level rise.

Our research addresses processes relevant to the following restoration and related questions:

* How will increasing freshwater ow affect 

wetland primary production?

* Will increasing freshwater inow alter nutrient 

availability?

* Does recovery following disturbance in mangroves depend on freshwater inow?

Figure 3. Oblique aerial photograph of a representative 

study site layout with vegetation plots, hydrology station, 

and sediment elevation tables (SETs). The greenish color is 

mangrove forest and the grayish color is black needle-rush 

marsh. Estuarine fauna is also sampled at this site.

* Will the position of vegetation ecotones change 

in response to upstream water management?

* What will be the inuence of global climate 

change, such as sea-level rise, on the Everglades restoration?

* Will processes of wetlands soil formation be 

altered by sea-level rise and changed freshwater inow?

ILLUSTRATIVE RESULTS

The trajectory of vegetation change, growth, mortality, 

and recruitment has been highly variable among plots. 

Indeed, most plots have followed unique patterns. 

The only overall pattern was the increase in stem density observed in all plots (Fig. 4). The species that 

dominated recruitment varied, sometimes being Rhizophora mangle (red mangrove), often Laguncularia 

racemosa (white mangrove), but never Avicennia germinans (black mangrove). The rate of stem-density 

increase has varied among plots by over two orders of 

magnitude. Individuals are continuing to recruit into 

the population at many sites.

Mortality is occurring at all sites. Sources of tree mortality include continuing demise from damage initially 

caused by Hurricane Andrew, trees being killed by falling debris, lightning, wind-throw during winter cold 

fronts, freeze, re, and several less intense tropical 

cyclones since Andrew such as Hurricanes Georges, 

Harvey, Irene, and Mitch. Trees in the smaller-size 

classes are beginning to perish due to suppression 

(that is, being overtopped and heavily shaded by larger 

neighbors, see Fig. 4). 

Observed patterns of growth by trees that survived 

Andrew or that recruited into the plots are hard to 

explain. Productivity cannot be explained simply by 

sediment-porewater nutrient concentrations, which are 

highly variable. Salinity and hydrologic parameters 

seem most promising to explain patterns of biomass 

increase following the catastrophic disturbance from 

Hurricane Andrew.

In addition to inuencing mangrove forest structure, 

the severe disturbance from Hurricane Andrew has 

affected the stability and elevation of the sediment 
Figure 5. Surface-water hydrology (red) and sediment-elevation dynamics at two river-mouth locations in Everglades 

National Park. The black lines show sediment surface 

elevation over time (solid with error bars, ± 1 SE) and the 

linear trend in elevation (dashed). The green lines show 

sediment elevation minus accretion (solid with error bars) 

and the linear trend (dashed).

Figure 4. Results from three surveys at the Lostmans 

Ranger Station plot are shown. The X and Y axes 

are arbitrary, with 0,0 representing the center of the 10m 

radius plot. The vertical axis shows stem diameter at 

breast height, in cm. The top gure depicts the plot as 

it appeared prior to Hurricane Andrew (based on a “reconstruction” from the initial sampling in October 1992). 

The middle panel shows the situation in January 1995. 

Recruitment is well underway and consists of an even 

mix of Rhizophora and Laguncularia. The bottom gure 

shows the status in October 2002, 10 years after the hurricane. Rhizophora now dominates the pool of recruits.

Mouth of the Shark River

-60

-50

-40

-30

-20

-10

0

10

20

Sediment Elevation

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Stage

1998 1999 2000 2001 2002 2003

surface. In the lower Lostmans River, an area highly 

impacted by the storm, sediment elevation has been 

decreasing for at least ve years (Fig. 5). The forests 

at the mouth of the Shark River, an area not impacted 

by Hurricane Andrew, are remaining at constant elevation (Fig. 5). Visual inspection of the data indicates 

that surface-water dynamics do not seem to be related 

to sediment-elevation changes.

Sampling of these vegetation plots, hydrology stations, 

and sediment elevation tables will continue in order 

to monitor the effect of increasing freshwater inow 

that will occur as a major component of the Everglades 

restoration. We will also use the data currently available to develop performance measures that can be used 

by CERP.

Mouth of the Lostmans River

-8

-4

0

4

8

12

16

20

Sediment Elevation

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

Stage

1998 1999 2000 2001 2002 2003

Avicennia

Rhizophora

Laguncularia

Pre-Hurricane Andrew

January 1995

October 2002

Avicennia

Rhizophora

Laguncularia

Avicennia

Rhizophora

Laguncularia
LITERATURE CITED

Anderson, G.H., and Smith, T.J., III, 2004, Data from

the mangrove hydrology sampling network for the

Lower Shark River, Everglades National Park: Water

years 1995 - 2002. U.S. Geological Survey Open-File

Report 02-457.

Cahoon, D.R., Lynch, J.C., Hensel, P., Boumans, R.,

Perez, B.C., Segura, B., and Day, J.W. Jr., 2002, A

device for high precision measurement of wetland

sediment elevation; I. Recent improvements to the

sedimentation-erosion-table. Journal of Sedimentary

Research, 72 (5): p. 730-733.

Houston, S.H., and Powell M.D., 2003, Surface wind

fields for Florida Bay hurricanes. Journal of Coastal

Research, 19: p. 503-513.

Pimm, S., Davis, G., Loope, L., Roman, C., Smith, T.J.

III, and Tilmant J., 1994, Hurricane Andrew. BioScience, 44: p. 224-229.

Smith, T.J., III, and Cahoon D.R., 2003, Wetland

sediment surface elevation in the Florida Everglades:

response to surface water stage variation. Proceedings,

5th International Symposium on Coastal Engineering

and Science of Coastal Sediment Processes. East

Meets West Productions, Corpus Cristi, TX.

CD-ROM.

Smith, T.J., III, Hudson, J.H., Robblee, M.B., Powell,

G.V.N., and Isdale, P.J., 1989, Freshwater flow from

the Everglades to Florida Bay: A historical reconstruction based on fluorescent banding in the coral Solenastrea bournoni. Bulletin of Marine Science, 44: p.

274-282.

Smith, T.J., III, Robblee, M.B., Wanless, H.R., and

Doyle T.W., 1994, Mangroves, hurricanes and lightning strikes. BioScience, 44: p. 256-262.

ACKNOWLEDGMENTS

Funding for this work was provided by the USGSBRD Global Climate Change Program, the USGS Priority Ecosystems Studies Program, and the Critical

Ecosystems Studies Initiative administered by Everglades National Park.

For more Information Contact:

Thomas J. Smith III.

U.S. Geological Survey

600 Fourth Street South, St. Petersburg, FL. 33701

Phone: 727-803-8747 x 3130 Fax: 727-803-2030

Email: Tom_J_Smith@usgs.gov