Mangrove Restoration in the Indian River Lagoon

Executive Summary

Mangrove forests form an important part of the Florida coastal ecosystem. The Indian River Lagoon is an important global resource, as it is the only place in North America where tropical waters meet temperate waters. Mangrove forests protect coastal areas in the event of storm surges. Rising ocean waters are expected to increase the number and intensity of coastal storms in Florida (WWF, 2005). In addition to the ecological benefits, the Indian River Lagoon is important to the economy of the surrounding lagoon counties.

Currently, the mangrove forests in the Indian River Lagoon are disappearing at rates ranging from 44% to over 80% of their 1940s and 1950s levels, as determined by aerial photographs (Department of Environmental Protection, n.d.). These findings make restoration and preservation of Indian River mangrove forests a priority. Storms destroy mangrove forests, as do other natural events. However, humans also have a significant impact on the destruction of mangrove forests.

The Indian River Lagoon is a federally protected estuary and home to numerous threatened and endangered species. Legislation is already in place to help prevent further human destruction of the lagoon and its valuable resources. Several replanting programs are already underway with varying degrees of success, but efforts thus far are not enough to offset the rate of destruction. In addition, many plantings suffer heavy losses as young saplings fail to thrive.

The purpose of this project is to oversee a major replanting effort in an area that has suffered enormous economic losses due to mangrove deforestation. The area chosen is the City of Fort Pierce in St. Lucie County. This county receives approximately $5 million dollars a year from industries based on lagoon resources. Fishing activities from the lagoon outpace other agricultural activities, and the lagoon brings in approximately $3 million dollars from recreation and tourism (Nocera, 1998).

Introduction and Background

Replanting efforts in St. Lucie County will cost approximately $2 billion dollars, but this investment is expected to be recovered through new industry and agricultural activities within ten years of the replanting effort. The reason for the extended recovery period is that new plantings are not expected to provide an effective habitat for at least five years. Once established, it will take approximately four additional years to recover the investment. This project will be the first in a broader effort to restore the Indian River Lagoon and the important natural resources it offers to surrounding communities and the world.

Lagoons represent fragile ecosystems that are highly susceptible to environmental change. They are rich with a diverse abundance of plant and wildlife that are important to coastal regions. The Indian River Lagoon is a restricted-type lagoon, which is highly dependent on wind patterns for circulation and mixing. This type of lagoon tends to demonstrate a net transport of water toward the sea, and wind patterns result in surface currents and a downwind accumulation of water (Hill, 2001). Lagoons such as this are well-mixed and typically demonstrate a homogeneous salinity in the vertical column (Hill, 2001).

The tide plays a role in water transport within the Indian River Lagoon, although wind remains the most significant factor influencing the lagoon's characteristics (Hill, 2001). Global climate change is expected to increase the number of storms and hurricanes over time, and Florida is one of the key areas expected to be heavily influenced by these changes. The mangrove forests of the Indian River Lagoon are considered to be species of special concern in Florida. As storms and hurricanes increase, it is feared that the mangrove fringe habitat of the region will suffer, placing many other species in danger. This research examines the problems associated with mangrove fringe ecosystem loss in the Indian River Lagoon and explores solutions to help prevent further environmental damage in the face of climate change.

Loss of the mangrove forests could precipitate a global-level extinction of species. Mangrove trees represent highly specialized species adapted to survive in environmental conditions that would be detrimental to most other organisms. Mangrove fringe forests provide nutrition to a wide variety of organisms that would otherwise be unable to tolerate such conditions (Hill, 2001). They are an important part of the coastal ecosystem, and their loss would trigger a cascade effect on many other species. Loss of the mangrove fringe forests could potentially affect as many as 400 species, including fish, reptiles, mammals, and birds (Hill, 2001). Birds and fish constitute a majority of the species found in the coastal lagoon. Barnacles, sponges, mollusks, segmented worms, insects, crabs, and shrimp are only a few examples of the species that utilize mangrove roots as habitat. In addition, mangroves have proven beneficial in slowing tsunamis by breaking up wave energy in Asian coastal communities (WWF, 2005).

Florida's mangroves are highly susceptible to fluctuations in temperature, tidal levels, salinity, and soil conditions (Department of Environmental Protection, n.d.). It is estimated that Florida has approximately 469,000 acres of mangrove forests. Environmental damage can affect mangrove populations significantly, as can human activity, including polluted runoff from urban areas and agriculture (Department of Environmental Protection, n.d.). By comparing aerial photographs from the 1940s and 1950s with current photographs of the same areas, it is possible to quantify mangrove forest loss and the rate of destruction. For instance, over the past 100 years the Tampa Bay area has lost over 44% of its coastal wetland acreage, while the Indian River has lost 86% of the mangrove areas available as fisheries since the 1940s (Department of Environmental Protection, n.d.). Currently, there are approximately 8,000 acres of mangroves within the Indian River Lagoon area, of which only 1,900 are still available for use as fisheries (Department of Environmental Protection, n.d.).

The Indian River Lagoon is unique — the only environment of its kind in North America. It is the only place where tropical ocean waters meet temperate-zone waters, creating an ecosystem that supports one of the most biologically diverse habitats in the world. Due to this uniqueness, the Indian River Lagoon has been designated an estuary of national significance by the EPA (Nocera, 1998). The lagoon is home to 36 animal species currently listed as threatened or endangered, making it a critical area for conservation efforts.

Not only is the Indian River Lagoon an important environmental resource, it is also a significant source of income for lagoon counties. These counties benefit from recreation and tourism, manufacturing, agriculture, and commercial fishing. Lagoon counties receive an estimated $3 billion per year from the combined income of these activities (Nocera, 1998). Approximately 80,000 acres of lagoon generate nearly $12,500 per acre per year, with $10,000 in fish revenue per acre per year (Nocera, 1998). Loss of mangrove habitat therefore translates directly into devastating economic losses for the local economy.

Climate Change and Lagoon Restoration Approaches

The mangrove forests of the Indian River Lagoon are an important global treasure from both an environmental and an economic standpoint. This research explores the feasibility of a mangrove restoration project that will help expand the existing mangrove stands to historical levels where possible.

Coastal storms cause immediate and severe damage to mangrove forest areas. As the frequency and intensity of these storms increases, they are expected to compound the destruction already underway due to human practices. It is difficult to quantify potential storm losses precisely, as storm projections remain speculative. However, further loss of Indian River Lagoon mangrove forests will have a devastating environmental and economic impact regardless of the cause. Therefore, efforts must be undertaken to restore what has already been lost and to preserve what remains.

The goal of any restoration project is ideally to return an area to the pristine condition that existed before habitat destruction occurred. However, this is an unrealistic goal in many cases, as the soil, salinity, companion species, and other ecosystem components may have been irrevocably altered. A more realistic approach is to restore the area to its natural function (Lewis & Streever, 2000). This will be the approach taken in this study. The goal will be to restore the mangrove forests to their natural function, rather than focusing exclusively on reintroducing original species. The emphasis will be on establishing species with the greatest chance of survival under current conditions and those that will serve functions similar to the species that were lost.

Two general approaches are used in mangrove restoration. The first focuses on replanting mangroves to replenish those that were lost. The second concentrates on identifying the causes of loss and preventing further habitat destruction, supporting natural recovery of the ecosystem once the sources of harm have been eliminated (Lewis & Streever, 2000). Both approaches have merit for different reasons. Natural recovery takes between 15 and 30 years, and only if the sources of destruction can be adequately controlled (Lewis & Streever, 2000). Replanting may also be difficult if the area has been so altered that it can no longer support certain mangrove species; however, the diversity of mangrove species means it may be possible to find one suited to the new environmental conditions.

Manmade habitat destruction can be controlled to a degree — for instance, through limits on pollution from runoff and manufacturing waste. However, destruction caused by increasing storm damage cannot be controlled. Such damage could significantly hinder slow natural recovery processes. It is therefore proposed that supplemental replanting be undertaken alongside programs to eliminate further human-caused destruction. This two-pronged approach will promote rapid stand recovery while preventing additional losses to newly established and existing mangrove trees.

Several mangrove repopulation projects have already begun with varying degrees of success. Local laws now prohibit the dumping of wastes and other forms of pollution into the Indian River Lagoon in compliance with the 1987 Estuaries and Clean Water Act (EPA, 2008). An aggressive public awareness program has been underway since the late 1980s, helping people and businesses understand the income potential and ecological value of the Indian River Lagoon. However, these efforts are not sufficient on their own, making a greater concentration on replanting efforts necessary.

Conclusion

The importance of achieving success in restoring the mangrove forests along the Indian River is significant, particularly when one considers the protection from storm surges that mangroves provide. The cost of the project is modest and can be recouped over time through increased industry and resource use from the lagoon. That economic return, however, pales in comparison to the life-safety and property-protection value of a healthy mangrove buffer against the intensifying storms expected in the future. The costs of not embarking on this project cannot be estimated.