The CREW Land & Water Trust is a private, non-profit conservation organization dedicated to the preservation and stewardship of the water resources and natural communities in and around the Corkscrew Regional Ecosystem Watershed (CREW).

CREW is the largest intact watershed in Southwest Florida, straddling Lee and Collier Counties.

What does this unique watershed do for Southwest Florida?

Recharges the groundwater for our drinking water supply

Offers a beautiful space for public recreation

We carry out our mission statement by coordinating the land acquisition, land management, and public use of this 60,000-acre watershed in partnership with the South Florida Water Management District, which owns a significant amount of CREW and manages that land – including the CREW trail systems, and the Florida Fish & Wildlife Conservation Commission , which monitors wildlife and hunting and provides law enforcement. Other partners include Conservation Collier  and Lee County's Conservation 20/20 .

South Florida Water Management District

Corkscrew Regional Ecosystem Watershed

On your way here from the trailhead, you passed through a region of Pine Flatwoods, a relatively flat ecosystem dominated by southern slash pines and sabal palms (Sabal palmetto) with an undergrowth of saw palmetto (Serenoa repens), gallberry (Ilex glabra), wax myrtle (Myrica cerifera) and mixed grasses. Pine Flatwoods are often found dotted with small, circular marshes like the one in front of you. From the air, they can sometimes look like old bomb craters, but in fact, they’re actually “depression marshes,” sometimes called “flatwoods marshes” or “seasonal ponds.”  

These marshes tend to form in sandy soils when water erosion causes the underlying limestone to slowly dissolve, allowing the overlying surface to collapse into dimple-like depressions. They become inundated during the wet season as the water table becomes sufficiently saturated and water runoff from higher elevation collects here. Once the marsh in front of you becomes full, excess water will flow out over the edges opposite us and spread across the land into a much larger marsh further to the south.

You might notice how slash pine and saw palmetto tend to ring the higher and drier outer edges of this marsh. As your attention shifts closer towards the center, you’ll see different types of vegetation become more prominent. Although depression marshes are usually rather shallow (often < 1 meter), they tend be shallowest around the outer edges and deepest in the middle. As a result, there may be concentric bands or zones with slightly different hydroperiods and thus different kinds of vegetation. The center, which, usually gets inundated first and holds water longest is where you’ll likely find saw grass (Cladium mariscus), pickerelweed (Pontederia cordata) and duck potato (Sagittaria lancifolia), while further out from the center maidencane (Panicum hemitomon) and St. John’s-wort (Hypericum perforatum) may be more prominent. 

Depression marshes like this one are important breeding habitats for amphibians like frogs and newts because here they’re isolated from larger species of fish that prey on eggs and tadpoles. Nevertheless, these marshes are also important feeding grounds for wading birds like egrets and herons. When the dry season approaches, these marshes get more and more shallow until the only water remaining are small pools teeming with amphibians, crayfish, mollusks, and insects, providing a veritable buffet for many bird species, as well as reptiles like the banded water snake (Nerodia fasciata).  

Without periodic fires and seasonal inundation, this marsh would inevitably shift away from largely herbaceous vegetation and become increasingly dominated by woody shrubs and trees like coastal plain willow (Salix caroliniana), common buttonbush (Cephalanthus occidentalis), groundsel tree (Baccharis halimifolia), and wax myrtle (Myrica cerifera). These changes would negatively impact the habitats of many interdependent species. New species would eventually move in while those who had depended on this marsh for breeding and feeding would be forced to move on to wetter habitats.  

Your photo contributions will help land managers, scientists and students better understand the hydroperiods of this marsh and the diversity of flora and fauna found here.  

NOTE: CREW’s boardwalks and the observation platform on which you’re standing were constructed from ipê (Tabebuia serratifolia) wood, also known by the trade name Pao Lope.  It is extremely hard, rot resistant, and fire resistant, enabling it to withstand the harsh climate of south Florida. Further, it is not chemically treated, protecting the water resources of the watershed from toxins that could leach out of chemically treated lumber. 

Important concepts: A “hydroperiod” refers to the length of time each year that a wetland has standing water.  

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CREW Marsh Trails Depression Marsh

As you look out into to this part of the 5,000-acre sawgrass marsh, it might be difficult to imagine that until relatively recently the area directly in front of this point had been almost entirely overcome by the encroachment of coastal plain willow (Salix caroliniana). Although this woody shrub is native to the southeastern United States, Mexico and parts of Central America and the Caribbean, it can under the right conditions displace the dominant herbaceous vegetation of marshes like this one. When the hydrology or fire intervals of the marsh are altered, coastal plain willow can take over, crowding out the sawgrass, sedges and grasses and slowly transforming herbaceous marshes into swamps dominated almost entirely by willow shrubs.  

Over the last several years, the South Florida Water Management District (SFWMD) and Florida Fish and Wildlife Conservation Commission (FWC) have worked diligently to restore the marsh ecosystem by removing encroaching willow. Two years ago, the area in front of you was overgrown with coastal plain willow, but from 2021-2022 more than 26 acres of these woody shrubs were removed by mechanical shredding. Restoration of this marsh is important not just for the functioning of the watershed, but also because it ensures critical habitats for frogs, snails, crayfish, and fish, and for the multitude of bird species that prey upon them.  

As you look out over the marsh, consider what it may have looked like before and what it may look like again in a few years should climate change and human development around CREW’s margins continue to create conditions for coastal plain willow to begin encroaching yet again.  

Your photo contributions will help land managers, scientists and students better understand the hydroperiods of this marsh and the diversity of flora and fauna found here, and track how quickly Carolina willow returns to this area of the marsh.  

NOTE: CREW’s boardwalks and the observation platform on which you’re standing were constructed from ipe (Tabebuia serratifolia) wood, also known by the trade name Pao Lope.  It is extremely hard, rot resistant, and fire resistant, enabling it to withstand the harsh climate of south Florida. Further, because this wood doesn’t need to be chemically treated, it’s a better alternative for protecting the water resources of the watershed than chemically treated lumber, which can leech toxins into the surrounding environment.    

CREW Marsh Trails Boardwalk

The dominant vegetation in marshes are grasses and sedges, but swamps, which are forested wetlands, are defined by their trees, such as bald cypress (Taxodium distichum), red maple (Acer rubrum), pond apple (Annona glabra), and pop ash (Fraxinus caroliniana), which you see here on both sides of the boardwalk.  

This is a particular kind of swamp called a slough (pronounced “slew”), a broad, shallow, and slow-moving river. This area might appear mostly dry during months when rain is scarce, but during the wet season, water levels in this slough might be as much as a meter deep. Although the water in this slough may appear still, almost stagnant, it’s moving, even if very slowly - sometimes just a mere hundred meters per day as it transports large amounts of water into the large seasonal marsh southeast of where you’re standing. When the slough is carrying water, it provides habitats for an abundance of fish species and aquatic invertebrates, providing a buffet for larger mammals and reptiles that prey on them.  

The pop ash (Fraxinus caroliniana) is the dominant tree in this particular slough and gives it its name. This native species is found in the wet soils of swamps and floodplains throughout the southeastern United States. Individual trees can grow to more than 30 feet (>9 meters) in height and are often found with multiple crooked or canted trunks. During the wet season water flows slowly between the spreading bases of pop ash trees, which are wider at the bottom, giving them greater stability in the soft shifting soils and flowing swamp waters. Pop ash trees are also deciduous; that is, they lose their leaves in the dry season when the life-giving waters of the slough dry up. Depending on the time of year you visit, you may find an open canopy with an unobstructed view of the sky, or you may find a closed canopy with an abundance of shade.  

You may also notice an abundance of different kinds of epiphytes attached to the trunks and limbs of trees around you. Epiphytes (or “air plants”), including the ferns and bromeliads , use their roots to cling to the bark of trees. These plants aren’t parasitic; rather, they’re simply using the real estate available on these trees to access moisture and nutrients by absorbing them directly from their environment using tiny hairs on their roots and leaves. Epiphytes are particularly fond of the humid air that accumulates in this slough when the canopy is at its most dense from May to October. 

Among the many epiphytic plants you are likely to see here in the Pop Ash Slough are resurrection ferns (Pleopeltis polypodioides), which you’ll often find growing on the tops of tree branches.  During dry spells, these ferns curl up, turn brown, and appear dead, but with a little rain, they unfurl their fronds and once again turn bright green. It’s an adaptation that allows them to survive our dry season. Unlike ferns growing in soil, resurrection ferns cannot tap into groundwater; instead, they rely on rainwater than runs down tree branches or humidity in the air. 

You’ll probably also see wild splotches of color on the trees and on boardwalk itself. These are lichen, a composite of fungi and either algae or bacteria. In this special relationship, the fungus, which is unable to produce its own food and cannot survive on its own, provides a surface for its alga/bacteria partner to reside. It’s a partnership that provides the latter real estate higher up in the air where it has better access to sunlight and water it needs for photosynthesis. In turn, the fungi feed themselves from the sugars produced by its food-producing partners. You’ll probably notice lichens come in all shapes and sizes; some are flat, others appear leafy, and some like tiny shrubs. They also come in riot of colors, including black, brown, white, gray, silver, yellow, green, red, and orange. How many can you see here? 

Your photo contributions will help land managers, scientists and students better understand the hydroperiods of this slough and the diversity of flora and fauna found here. 

NOTE: CREW’s boardwalks and the observation platform on which you’re standing were constructed from ipe (Tabebuia serratifolia) wood, also known by the trade name Pao Lope.  It is extremely hard, rot resistant, and fire resistant, enabling it to withstand the harsh climate of south Florida. Further, because this wood doesn’t need to be chemically treated, it’s a better alternative for protecting the water resources of the watershed than chemically treated lumber, which can leech toxins into the surrounding environment.  

CREW Marsh Trails Pop Ash Slough 

From this tower you can look out over the 5,000-acre sawgrass marsh that is the headwaters of the Imperial River. To the left is Immokalee, straight ahead is Audubon’s Corkscrew Swamp Sanctuary and Naples, and to the right is Bonita Springs. To the far right are Estero and the campus of Florida Gulf Coast University. This relatively large marsh collects runoff until it overflows, spilling excess water as sheet flow that will eventually meander further south towards the western Everglades and southwest towards Estero Bay.  

This marsh provides several “ecosystem services” to our communities. These services are direct or indirect benefits we freely derive from healthy, intact and functioning ecosystems. We may not always be aware of how much we depend on these ecosystem services, but they are nevertheless vital to the wellbeing of our communities.  

First, marshes like this one store lots and lots of water during the wet season. This is an important contribution towards flood protection for surrounding communities. On average, Southwest Florida receives 54 inches of rain per year, much of it falling from May to October. Some storms can drop several inches of rain in a matter of hours and marshes like this one provide places where vast amounts of water can accumulate. During Hurricane Irma in 2017, the lower deck just below you became entirely submerged with water backing up over the trails that brought you here.  

Imagine if this marsh was filled in and paved over for housing or retail development. Where would all the water that typically ends up here go during and after storms? Without wetlands like this one to store runoff, much of that water would quickly flow south and southwest into the canals and rivers that pass through the neighborhoods of Bonita Springs, North Naples, Golden Gate, and Ave Maria. These communities would then face an increased risk of flooding if those waterways received more water than they could hold.   

Second, wetlands act as nature’s kidneys. Vegetation and the soils through and over which surface and groundwater moves help clean debris, pollutants, and excess nutrients from water, purifying it along the way. This natural filtration helps ensure that water flowing into CREW from adjacent roadways and from agricultural, industrial, retail, and residential areas is cleaned before it flows further to the south and southwest. Without the filtration these wetlands provide, immense quantities of contaminated water and sediments could eventually end up negatively impacting the fragile ecosystems of Estero Bay, the Western Everglades, and the Ten Thousand Islands.  

Third, wetlands like these also help recharge our groundwater aquifers. CREW lands sit atop Florida’s multi-layered aquifer system. These aquifers, including those right below us, are made up of layers of sand and porous limestone that can hold vast amounts of fresh groundwater in nooks and crevices of various sizes. Some of the water that collects in wetlands like those around you will eventually percolate down through the soil, filling up those underground reservoirs far beneath our feet. When we need water, we drill down into those aquifers and pump fresh groundwater back to the surface. In fact, this ground water is the primary source for most of SWFL’s household and agricultural water needs, but if we pull too much out of these aquifers without allowing them to recharge, they can become brackish from saltwater intrusion or simply run out. The more rain that falls on roads and parking lots or that is quickly diverted away from wetlands like these via ditches and canals, the less water there will be to recharge those aquifers.  

Your photo contributions will help land managers, scientists and students better understand the hydroperiods of this marsh and the flora and fauna found here.  

Corkscrew Regional Ecosystem Watershed

Florida

4 chronologs managed by Corkscrew Regional Ecosystem Watershed

CREW Marsh Trails Depression Marsh

CREW Marsh Trails Boardwalk

CREW Marsh Trails Pop Ash Slough

CREW Marsh Trails Observation Tower

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