Sarasota County covers a land area of approximately 370,000 acres or 580 square miles. Before widespread colonization by European settlers, the County was characterized by a variety of natural vegetation communities including pine flatwoods, hardwood hammocks, scrub, prairies, fresh and saltwater marshes, mangrove forests, and seagrass beds. Although large portions of the County are still comprised of native vegetation cover, urban and agricultural development has had a significant impact on these natural systems. This has resulted in changes of both wetland and upland vegetation during the past century.
Changes in Vegetation
Between 1975 and 1986, overall vegetation cover decreased from 71% of total land cover to 47% of total land cover representing a net decrease of 33%. Significant development and land clearing took place in northern, western, and southeastern Sarasota County during this period. However, between 1986 and 1993, a 4% gain in vegetation canopy was observed, possibly due to the regrowth of vegetation that was originally cleared for development in the North Port area, as well as several developments throughout the County that had been replanted with vegetation after construction.
Between 1993 and 2002, total canopy coverage was reduced from approximately 181,077 acres to 173,907 acres which represents a net 4% loss in vegetation canopy. Based on the satellite imagery, this loss occurs in several areas throughout the County due to clearing of vegetation in the eastern and southern portions of the County for cattle grazing and other agricultural purposes along with continued residential development both west and east of I-75.
Gains in canopy were also observed throughout the County, including some of the previously cleared agricultural areas in the eastern part of the County. A total of 1,674 trees representing 68 species were inventoried during the local analysis field data collection surveys within the County. Palms (sabal, queen, Washingtonia) were the most abundant species in high density residential land uses while slash pines and sabal palms were abundant in open land areas. Live oak, Australian pine, and sabal palms were the most predominant species at recreational lands. Queen palm and live oak trees were most prevalent at medium density residential land uses. Sabal palm, slash pine, laurel and live oak trees were the most abundant species in low density residential land uses.
The average percentage of native species (by abundance) for all sites was approximately 50%. This value is similar to the 46% reported in the City of Tampa (Campbell and Landry, 1998). In addition, laurel oak which is a relatively short-lived species (~100 years) represented 10% of species found within the urban sites. In the future, these trees may represent a significant canopy loss in the urban areas as they naturally decline.
Value of Urban Forest
The combined economic benefits of the vegetation canopy within urban land uses in Sarasota County add up to approximately $8 million per year. This estimate is based on extrapolation of the average cost savings associated with air pollution controls and residential energy (air cooling) costs, for each of six urban land use types evaluated multiplied by the number of acres of each land use type which currently exists in Sarasota County.
Based on these calculations, open land provides a significant economic benefit to the County in terms of air pollution removal and is likely to provide similar benefits for stormwater runoff reduction. The economic benefits provided by this land use type are significant, because nearly 26,000 acres of this land use remains in the County. However, it should be noted that the values used to generate the cost savings values for this land use were based on only three sites, including two sites in the North Port area which are heavily canopied. These sites were originally platted and cleared for development in the 1970s (hence their designation as “open land”) but were never built out. In concert with existing land development codes and tree protection ordinances, implementation of more innovative designs to protect existing tree canopies in these areas should be considered since the greatest economic costs for air and water quality protection are represented by this land use type.
The existing vegetation canopy in medium density residential land use also provides a significant economic benefit to Sarasota County. Many older neighborhoods are becoming more heavily canopied as a result of decades of tree growth since their original development. Tree planting programs may also have a significant effect on improving air and water quality in commercial and recreational areas, however, these effects will likely take several years to be realized.
Download the entire report: Sarasota County Urban Ecosystem Analysis (March, 2004)