A Journey Through Lower Green Swamp Nature Preserve

The Hillsborough County Department of Conservation and Environmental Lands Management (CELM) is hosting a series of field trips for the Florida Nature and Birding Festival in October. In anticipation of the October 20th trip to our largest ELAPP property, Lower Green Swamp Nature Preserve, I was lucky enough to get a tour from CELM Environmental Lands Management Specialist, Rebecca Winch. So, come along with us for a virtual walk of this 12,809-acre property and its history.

The bridge over the Itchepackesassa Creek.

After passing Lower Green's management office, the first feature on the central trail is a sturdy bridge crossing Itchepackesassa Creek. This was shortly after Hurricane Debby came through, and I was curious if there had been any concerns about the structure, as several ELAPP properties had seen flooding. Rebecca had this to say:

"After the storm, the water got almost up to the supports underneath the bridge, but not quite. We checked for signs of erosion on either side. This bridge was actually designed to allow logging equipment to cross to thin these trees out. So, it's an extremely robust bridge."

A hawk perches on a bowing pine tree. The area beyond the bridge is flatwoods, with wide open canopies; the undergrowth is composed largely of low palmetto, native grasses, and forbs. Photo by Rebecca Winch.

The mention of logging equipment in a nature preserve might seem contradictory, but it's a key part of Lower Green Swamp's transformation story. Rebecca explains:

"[Before it was a nature preserve] more than a million trees were planted in the southern part of the preserve. They weren't thinned or really managed in any way. So, everything you see around you, which is now open pine flatwoods, was a dark forest. I mean, it was packed."

Packed it was. Photographs from the time show dense stands of trees, with a thick understory of invasive Caesarweed. This near-monoculture offered little in terms of biodiversity or suitable wildlife habitat.

The contrast between the open canopy of the present and the dense, shaded forest of the pine plantation in this historic photograph is extraordinary. 

The transition to a nature preserve necessitated a dramatic shift in management approach. Rebecca continues:

"When we took over the running of Lower Green Swamp and turned it into a nature preserve, these trees needed to be thinned out in order to create the pine flatwoods that we're looking at now. We used logging as a way to do that. We also took out diseased trees and those that weren't the right ecotype for the area. We've been replanting longleaf and southern slash ever since."

Staff had discovered that the seed stock for this pine plantation was "of poor quality for this area." This is a common mistake when selecting plants for use in Florida. We share many species with the rest of the southeastern United States, but populations in Florida often have genotypic adaptations to the subtropical environment.

Goldenrod blooming vigorously. Photo by Rebecca Winch. 

The northern ecotypes of slash pine initially planted proved ill-suited to the local conditions, making them susceptible to pitch canker disease. This vulnerability, combined with overcrowding, led to severe pine beetle infestations. It was not a total loss; many of the existing trees were preserved, but new plantings are carefully selected to be compliant with Environmental Lands Management practices.

Rebecca says succinctly, "It's a common issue that you'll see in these conservation lands. There are too many trees. People think green is good and trees are good, but that's not always the case."

The thinning of trees and the practice of prescribed fire also help reduce the severity of dangerous wildfires. Learn more about the practice and Lower Green wildland fire crew leader, Mike Jones in this article! Photo by Rebecca Winch.

It may seem contradictory at first, but once you're in the open flatwoods and seasonal wetlands of Lower Green Nature Preserve, and you see the diversity of blooming plants, insects, and wildlife that these restored areas support, the benefits of this environmental lands management become clear.

The bridge over the Itchepackesassa Creek doesn't just mark the historic beginning of this pine plantation, but literally straddles a massive change Americans brought to the area in the late 19th century. Three-quarters of a mile down the trail, Rebecca stops us at a small pavilion.

Rebecca indicates across one of the many freshwater marshes in Lower Green Swamp. Photo by James Robe.

"This is the way that we normally come for birdwatching. This marsh is a fantastic place for seeing wading birds; we've had sandhill cranes nesting out in the middle of the marsh. See all the dead oaks along the edges? This was all drained to create more cow pasture; we've been doing hydrological restoration in this preserve ever since we took over to rehydrate these wetlands."

This restoration work aims to reverse the effects of "ditching," a practice that greatly increased during Florida's early statehood in the mid-19th century. Huge volumes of land previously held by the Seminole Nation, Spanish, and assorted allies were surveyed, parceled, and distributed to American citizens under the condition that they 'improve' the land. Settlers often drained wetlands to create arable land or pastures. While this practice allowed for agricultural expansion, it came at a significant ecological cost.

Wetlands support a myriad of wildlife which we enjoy. An Eastern Black Swallowtail butterfly (Papilio polyxenes) nectars at a carolina redroot (Lachnanthes caroliana). This butterfly relies exclusively on several wetland plants to reproduce, such as, water dropwort (Tiedemannia filiformis) and spotted water hemlock (Cicuta maculata). Photo by James Robe.

Ditching involves digging channels to divert water from wetlands into streams or rivers, lowering the water table and drying out formerly wet areas. This process dramatically alters the natural hydrology and ecology, often resulting in the loss of critical wetland habitats and the species that depend on them.

An 1849 survey by Arthur M. Randolph, commissioned by the Surveyor General's office in St. Augustine, provides valuable insights into the area's original hydrology. When overlaid on modern satellite imagery, this historical document reveals changes in the landscape.

Today, the Itchepackesassa Creek flows north from the southeast of Section 35, westward under the bridge, and then northwest towards Blackwater Creek and the Hillsborough River.

In the original surveys, we see that the distinct westward section under the bridge is absent from the records; rather, the waters of Itchepackesassa Creek pool in two wetlands, labeled A and B with yellow pins. Likely in an effort to drain those wetlands and stabilize soils for the road which can be seen terminating near wetland B, a deep ditch was dug between wetland A and wetland B. This ditch is now traversed by the bridge Rebecca and I crossed earlier.

An American Green Tree Frog (Hyla cinerea) does best in wet prairies, cypress swamps, and other hydric habitats. Photo by Rebecca Winch. 

CELM's hydrological restoration efforts aim to recreate the natural water flow patterns that existed before human intervention. Rebecca elaborates on their approach:

"[CELM] is looking at the water levels historically in these wetlands, and they're blocking ditches at the exact right height to rehydrate the wetlands to their historic levels. These ditch blocks are put at a height that when this wetland gets this full, the water goes over into the next wetland in the series. They're basically at the height of the land in between the wetlands that was there before they ditched."

The restoration of wetlands at Lower Green Swamp Preserve offers numerous ecological and environmental benefits. By rehydrating these areas to their historic levels, the preserve is recreating crucial habitats for a diverse array of flora and fauna. Wading birds like herons, egrets, and the sandhill cranes Rebecca mentioned find ideal nesting and foraging grounds in these restored wetlands.

Lower Green Swamp's watershed is essential to preserving water quality in Blackwater Creek and the Hillsborough River. Photo by James Robe.

Beyond supporting wildlife, restored wetlands provide important ecosystem services. They act as natural water filters, improving water quality by trapping sediments and absorbing excess nutrients and pollutants. This filtration process helps protect downstream water bodies, including the Hillsborough River, from contamination. Wetlands also play a crucial role in flood control, acting like sponges to absorb excess water during heavy rains and slowly releasing it during drier periods. This function is particularly valuable in Florida's climate, where intense rainfall events are common.

Lands are often nominated for inclusion in the ELAPP program due to the ecosystem services they provide. Lower Green Swamp Preserve is also home to a groundbreaking carbon banking project - the first of its kind on county land in the state of Florida. This carbon bank takes the concept of ecosystem services a step further, generating revenue that directly supports CELM's conservation efforts.

Blazing Stars (Liatris spp) blooming in Lower Green Swamp. If you choose to integrate this plant into your garden at home, ensure you select the correct species and ecotype for Florida. Photo by Rebecca Winch.

The carbon bank project encompasses 5,242 acres, which is about 40% of the total preserve. It includes areas of the old pine plantation, cypress domes, and riparian zones. The project type is classified as "Improved Forest Management" and is registered with the American Carbon Registry for the voluntary carbon offset market.

The project is rigorously monitored. The Climate Trust reviews the site every two years, and an independent third-party review is conducted every three years. This ensures the carbon sequestration claims are accurate and verifiable.

The results have been impressive. Initially estimated to generate 162,000 Emission Reduction Tons (ERTs), the project has produced 218,527 ERTs. This translates to removing a total of 314,424 tons of CO2 over 20 years - equivalent to taking 87,387 passenger vehicles off the road and generating approximately $1.5 million in revenue from environmental services. This money will be reinvested into Environmental Lands Management, supporting further conservation efforts.

Photo by Rebecca Winch.

Beyond its financial benefits, the carbon bank adds another layer of protection to the preserve with a 40-year commitment, helps outline Best Management Practices for sustainable forests, and serves as a model for assessing other preserves for potential carbon offset projects.

For those inspired to get a tour of Lower Green themselves, an exciting opportunity is coming up soon. As part of the Hiking Spree, a guided hike is scheduled for Saturday, March 22nd  at 6am. Led by environmental specialists Rebecca Winch, the trip is an ideal chance for nature lovers to see what Lower Green Swamp Nature Preserve has to offer. Register here. 

Photo by Rebecca Winch.