Ecology of Big Cypress National Preserve
Ecology of Big Cypress National Preserve
The first national preserve to be established, Big Cypress National Preserve is located in South Florida. Larger than the state of Rhode Island, it contains a wide range of plants and animals found nowhere else. The Preserve was created to protect these unique organisms and the flow of freshwater as it comes from the Kissimmee River down to the Everglades. Widely known for its continuous cypress swamps, this Preserve features five distinct ecosystems. With these ecosystems being dependent on their elevation, some are continuously covered by water while others only experience minor flooding. The time each ecosystem spends underwater is known as its hydroperiod. Varying hydroperiods result in a difference of dominate vegetation and animal communities. With a tropical climate and frequent rains, this region experiences a wet season (May – October) and a dry season (November – April) which drastically alters the availability of water, leading floods and fires to be crucial events that dictates life in the Preserve. Originally selected to become the grounds for a major airport, Big Cypress is a now region of high biodiversity. However, the preserve’s endangered animals and plants face uncertainty due to oil extraction and invasive species.
Five Major Ecosystems
Cypress Swamps are the largest type of ecosystem throughout the park and contain plant communities dominated by cypress trees. The two species of pond cypress and bald cypress are the most flood-tolerant of all the trees in Florida. The biggest of these trees were logged in the early 1900s, so all that remains is second growth. Bald Cypress towers over other trees, such as Red Maple and Sweet Bay. Growing in flooded depressions of the swamp, these forests are called cypress strands. A peculiar feature of cypress trees are knobby protrusions that extend from the tree’s roots. These features vary in size and height, and their direct function is still not fully understood. These trees provide habitat to a variety of other life; in their branches, birds like warblers and flycatchers sing sweet songs in order to find mates. With a hydroperiod of 200 to 300 days, aquatic life is dominant. Killifish and mosquitofish are adapted to withstand fluctuations in water level and quality. While the adults perish in the dry season, their eggs survive buried in the mud until the swamp is flooded again. Another feature of the swamp is the donut shape of cypress forest, referred to as cypress domes. In the middle of these domes the water is deep to support trees and is surrounded by wetland plants. The closer a cypress tree is to the middle of the dome, the taller it is, while trees on the outlying perimeter are smaller. In these cypress domes River Otters and Wood Storks gracefully move through the water and are completely dependent upon the swamp. The most famous inhabitant of cypress swamps are their prehistoric predators, American Alligators. Silently swimming between the knees of cypress trees, they are an apex predator of the ecosystem that keeps animal populations in balance. A distinct feature of the swamp is alligator holes, excavated depressions in the swamp’s muck and mud. They retain water and act as a form of ecosystem engineering, since these organisms modify their habitat in order to suit their needs. During the dry season many species gather in either alligator holes or the middle of cypress domes where they can seek refuge in the remaining water.
Found only at the highest elevations in the park, Hardwood Hammocks have a short hydroperiod of a few weeks. A rich number of plants ranging from cabbage palms, gumbo limbo, and pigeon plum contribute to a condensed canopy. This densely vegetated ecosystem resembles a tropical forest with lichens, ferns, and epiphytes growing upon the trees. Many of the plants in Hardwood Hammocks are of West Indian origin, meaning that they also grow on islands in the Caribbean. Birds brought their seeds over to Florida thousands of years ago and these plants thrived due to the sub-tropical climate. Many migratory species of birds such as kingbirds and warblers use these hammocks as refuge. Large mammals including the Florida Panther and Black Bear often seek shelter in the relatively dry understory of Hardwood Hammocks during the wet season. Within the Preserve, these hardwood hammocks appear as islands among the flooded swamps and prairies. These islands are tear-drop shaped due to the movement of water from north to south.
Characterized by their frequent exposure to fire, Pinelands are located in the south-east corner of Big Cypress National Preserve. Found at higher elevations on top of hard limestone, the hydroperiod for this ecosystem lasts anywhere from 20-60 days a year. The common occurrence of fires helps to keep Pinelands as a relatively open area and devoid of grasses and trees. The dominant type of vegetation is the Slash Pine, which is very resistant to fire. Slash pine has adapted its needles in order to withstand fire and heat helps to open up its pinecones to release their seeds. After a fire burns through the ecosystem, these seeds are often the only remaining source of food for birds and rodents which then go to disperse the seeds to new regions. The mature pine trees harbor a multitude of insects, which red-cockaded woodpeckers peck through the bark to consume. This endangered species excavates holes within the thick trunks of long-leaf and slash pines high up in the canopy. The understory is mostly composed of saw palmetto. Along its leaves are sharp teeth that ward away animals from eating its fruit. Colorful snakes and gopher tortoises traverse the rough savanna-like terrain in search of food. With the exclusion of fire for more than two decades, hardwood trees have invaded this ecosystem causing it to slowly transition into a tropical hardwood hammock. Called forest succession, this process is occurring in regions of the Preserve where controlled fires are no longer initiated.
Wet Prairies are defined by their long-standing shallow water and herbaceous vegetation. With a hydroperiod range of 3 to 7 months, they are found in low lying areas and in-between other ecosystems. Since this ecosystem is inundated for such a long time, it supports a diverse range of plants and animals. Mostly devoid of trees, prominent plants include pickerel weed, sawgrass, and water lily. Periodic fires help to eliminate the presence of woody plants that would otherwise outcompete the prairie grasses. Many wading birds use this ecosystem to raise their young and forage in the shallow water for fish. However, they must be careful, as American Alligators hide submerged waiting for prey to cross their path. Small marsh rabbits swim between the area’s vegetation looking to forage on leaves and fruit.
Alongside the preserve's southwest boundary, Estuaries are a dynamic ecosystem where the conditions are always varying. This unique type of ecosystem is formed when freshwater from the swamp mixes with saltwater from the Gulf of Mexico. This mixture of water is called brackish and contains a large amount of nutrients. Dense mangrove forest covers the shoreline, while beds of seagrass carpet the shallow productive water. On the coast, these mangroves help to prevent coastal erosion by stabilizing sediments with their roots and acting as a buffer during hurricanes. Additionally, the roots of the Red Mangrove provide protection for young fish to live before they are big enough to venture out into the ocean. A major portion of Florida’s fish that are fished commercially and recreationally are dependent upon mangrove communities in their juvenile years. Upon the branches of the mangroves are massive populations of breeding birds. Called rookeries, they are composed of many different bird species including Brown Pelicans, Roseate Spoonbills, and Herons. During low tide, the water recedes to reveal mudflats that are home to many different types of crabs and worms. This diverse array of birds descends from their perches to forage. With special shaped beaks, they probe through the mud for buried organisms. This buffet for birds makes estuaries an essential habitat, as they not only provide food but nesting grounds and shelter as well. Charismatic animals such as the West Indian Manatee are abundant in this ecosystem. Feasting on the sea grass meadows that grow in the nutrient-rich waters of the estuary, these gentle giants seek refuge in the warm shallows. The estuary also serves as a nursery for manatees since it is protected from the rough waves of Florida’s coastline. Manatees can often be distinguished from one another by scars on their backs from collisions with boats. Once endangered, efforts have been undertaken to preserve sea grass meadows and reduce boat speed in manatee habitat in order to protect these aquatic mammals.
Fauna
Encompassing over 725,00 acres of wetlands, many different species of animals call Big Cypress home. On the branches and trunks of trees are colorful Florida Tree Snails. Reaching a length of two to three inches, their shells can be many different colors. Due to their vibrant shell colors, these snails used to be at risk from collectors. Now it has been made illegal to take these snails away from their habitat. As herbivores, they eat fungus and algae on trees. Inhabiting the hardwood hammocks of the Preserve, these snails are more active after sunset due to a higher humidity, making them nocturnal.
Deep within the swamps of Big Cypress National Preserve lurks the elusive Florida Panther. Once plentiful when Florida was still a new frontier, as the peninsula has become more developed, less than 150 panthers remain in the wild. The state animal of Florida, the Florida Panther is an endangered species whose range is restricted to South Florida. They are a subspecies of Mountain Lions that have become adapted to Florida’s environments. Covered in tan fur, they can grow to become six to seven feet in length. These solitary big cats weave through the different habitats of the Preserve to find prey. With a single adult requiring 200 square miles of territory, they often are forced to venture into farmland to find food. Because their population is so small, panthers face the issue of low genetic diversity. In addition, habitat destruction, over-hunting of prey, and car crashes are major threats. Conservation efforts are underway to increase their available habitat and educate the public on the issues they face. To counteract the issues caused by a low population, scientists have brought in panthers from Texas to boost the available number of mates.
Flora
Within Big Cypress are many different types of plants, with some of the most prominent being epiphytes. These are plants which grow upon the bark of other plants by attaching their roots around them. Growing high up in the canopy, they compete to have the best access to sunlight. With none of their roots reaching the ground, they must obtain nutrients and water in non-conventional ways. The stems and roots of epiphytes are often adapted to collect and store water when it rains. They are an important part of Florida ecosystems as they provide shelter and food for many small animals like frogs. The three main groups of epiphytes - otherwise known as “air plants” - are bromeliads, ferns and orchids. They usually grow upon the sturdy trunks of cypress, pond apple, and deep within the dense hammocks and forest of swamps. Big Cypress National Preserve has some of the highest concentrations of epiphytes ranging from Spanish Moss to Resurrection Fern. The most famous of all epiphytes in Florida is the endangered Ghost Orchid, which has less than 1500 individuals left growing in the wild. Within the green and gray hues of cypress domes, the Ghost Orchid stands out with its white petals. These ornate orchids have a fleeting blooming period of only a handful of weeks every few years and depend upon a single moth species for pollination. Only the Sphinx Moth has a probiscis (tongue) long enough to reach the pollen and nectar hidden between its intricate petals. This delicate flower is becoming increasingly rare as poachers often remove them from their habitats for collection.
Over twenty percent of Big Cypress National Preserve is composed of wet prairies. The ground throughout this ecosystem is covered by a thick mat of yellow-gray material that is mushy to the touch. Called periphyton, it is a whole assemblage of organism that include algae, fungi, microbes and bacteria. This complex community is the foundation of wet prairies. It acts as a primary producer conducting photosynthesis, converting light from the sun into energy so that it can grow. Many other organisms like fish and apple snails eat the periphyton, which in turn are eaten by predators. This unassuming soggy mat serves as the basis for the food web of wet prairies. In addition to being a source of food, the photosynthesis of periphyton creates oxygen as a byproduct. The oxygen helps to support the life the reside in its surrounding water. Within the layers of periphyton live snails, crayfish, and other small invertebrates that use it as a refuge when the prairie dries out. As periphyton accumulates over time, it creates a type of soil called marl which is found throughout South Florida. Periphyton also serves as an indicator of ecosystem health. Changes in the environment such as altered water levels or nutrient pollution can be easily detected by observing how the periphyton is doing. Without periphyton, the ecosystem of wet prairies would not be as diverse or productive as it is today.
Preserve in Peril
Surviving the logging of its old growth forests and development attempts, Big Cypress National Preserve has overcome many obstacles. Yet the ecosystems of the Preserve are still threatened by humans. The water in Big Cypress National Preserve originates from the headwaters of the Kissimmee River and Lake Okeechobee. After the water is filtered by the environments of the Preserve, it makes its way south towards Everglades National Park and Florida Bay. This movement of water from north to south is called sheet flow. As Florida has become more developed over the past century, large expanses of dams and canals have been built to exert control over flooding. While these efforts have protected farmlands and suburbs from the destruction of floods, they have also restricted the flow of freshwater from moving towards the south. Instead, the water is directed into canals which either bring it to sugarcane farms or to be emptied out into the ocean. Additionally, sugarcane farms cause phosphorus pollution leading to poor water quality in Big Cypress. Too much phosphorus changes the plant communities from open water areas to dense vegetation, affecting the areas where water birds can forage. Excess phosphorus in the water makes it hard for fish to survive and contributes to the loss of periphyton, which are the basis of the food web. The different ecosystems of Big Cypress require a constant flow of freshwater to remain productive and healthy. With shorter hydroperiods, ecosystems like Wet Prairies would not be as productive and able to host a diverse number of birds and fish, while cypress trees need standing water so that they can grow strong and support their associated communities. Currently, plans are being made to restore the flow of water to its original path. Such disruptions to the ecosystems of Big Cypress allow for invasive species to gain a foothold within the Preserve. Organisms such as Australian Pine and feral hogs from halfway across the world have been introduced to the state of Florida. Invasive species do well in Florida due to its sub-tropical climate and lack of natural predators. Throughout the Preserve and most of South Florida, Burmese Python are an invasive species wreaking havoc. Originally from Asia, these snakes have greatly impacted the health of the region’s ecosystems. Research efforts by the USGS show that pythons have contributed to the decline of small mammals and water birds within South Florida.