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Publication #FOR290

Economic Value of Upland Invasive Plant Management in Florida State Parks1

Damian C. Adams, Anafrida N. Bwenge, Donna J. Lee, Sherry L. Larkin, and Janaki R. R. Alavalapati2


Invasive plants are a serious problem for Florida’s natural areas and a leading cause of biodiversity loss because they outcompete native plants and disrupt habitat for native animals. Florida is on the front lines of exotic plant invasions. Roughly 85% of the exotic plants entering the U.S. arrive through the Port of Miami (OTA, 1993). The high rate of new introductions is creating great concern because of the “tens rule.” According to this rule, roughly 10% of new exotic species introduced to natural areas become established, and 10% of those become invasive. In Florida, it is estimated that 1,300 exotic plant species are established and 124 (92 upland species) have been found in natural areas including state parks (FLEPPC, 2007). These species infest about 10% of Florida’s public land (roughly 1 million acres) (FDEP, 2006), and are likely to infest much more land if the introduced species and the land are not managed adequately.

While their impacts on a range of ecosystem goods and services have been documented, many of these effects have not been economically evaluated. Given the importance of tourism to the Florida economy (nature-based recreation alone is worth $7.8 billion per year [FDEP, 2001]), one of the most economically significant impacts of invasive plants is to recreation. We know that invasive plants tend to reduce the frequency and quality of recreation in natural areas, for example by limiting access to recreation sites (Adams and Lee, 2007; Adams, 2007). We also know that invasive plants are costly to manage, and public programs to control invasive plants are typically underfunded (Lee et al., 2009). Often, a dearth of economic estimates is to blame for a lackluster policy response (USGAO, 2002). In some cases, this is because the impacts are to “non-market” ecosystem goods and services—those that are not actively traded in a robust market. Previously, this was a major barrier. However, advances in non-market economic valuation methods allow us to estimate these impacts.

We conducted a survey of Florida residents to model their preferences for invasive plants and other state park attributes that influence recreation choice. We used a method that is widely accepted by economists but that has not yet been applied in the context of invasive plant management. Using our results, we infer what state park visitors would be willing to pay (via increased park entrance fees) to experience lower levels of invasive plant coverage in state parks. We coupled our willingness-to-pay estimates with Florida state park attendance data to calculate a lower bound estimate of the value of invasive plant control.


We used experimental survey questions in which respondents chose between two state parks that are assumed equal in every way except for key attributes that vary in quality or quantity. Specifically, the parks differed by several important attributes: invasive plants, entrance fees, type of facilities, and native animal and plant species. The survey was developed using a rigorous, multi-stage design and implementation method that included: (1) an initial questionnaire of 30 state park managers and recreation experts to establish relevant park attributes; (2) a questionnaire of 292 Florida residents to determine survey information needs; and (3) a questionnaire of 329 Florida residents to refine the park attributes. The final survey included background information and pictures of invasive plants; choice experiment questions (e.g., Table 1); questions about knowledge, experience and views regarding invasive plants; and demographic questions. Park attributes in our choice questions included: condition of facilities (minimal, adequate, or excellent); diversity of animal or plant species (low, medium, or high); presence of invasive species (none, few and dispersed, or numerous and dense); and entry fee (free, $10, or $10).

We recruited respondents from a balanced panel of Florida residents using the marketing firm Zoomerang. The residents’ demographic characteristics were representative of the state’s population as a whole, according to the 2000 U.S. Census. Further, we screened out those that had not engaged in nature-based recreation in the last 12 months. We collected 1,436 responses online for a response rate of 10.8% and a sampling margin of error (amount of random sampling error) equal to ± 4% (at the 95% level of confidence).

Results and Discussion

We employed an econometric model that predicted the likelihood that respondents would choose a given park based on its attributes. The estimated model was statistically significant (p<0.001), which means that the variables helped to explain park choice. Using the model parameters, we calculated estimates of willingness to pay for a change in each park attribute (Table 2).

Since our model assumes a linear relationship between WTP and attribute levels (that is, the value of improving an attribute from the low to middle level is the same as going from middle to high), we interpret our estimates as the amount the average park visitor would pay per visit to change park attributes: (1) $5.41 to reduce invasive plants coverage (e.g., from “numerous and dense” to “few and dispersed”); (2) $6.71 to increase native animal species abundance and diversity from (e.g., from low to moderate); (3) $3.73 to increase native plant species (e.g., from low to moderate); and (4) $3.72 to improve park facilities from (e.g., from minimal to adequate). Our estimates suggest that Florida residents value invasive plant management and would be willing to pay higher park entrance fees to support these efforts.

The WTP estimates are useful for policy discussions. Using our estimates and Florida state park attendance data, we estimate statewide WTP to control invasive plants in state parks. Specific data on the level of invasive plants in state parks are not available; however, we know that invasive plants are under “maintenance control” on roughly 35% of invaded state-managed acreage (DRP, 2004), which we assume means they are “few and dispersed” but would become “numerous and dense” without adequate control. Using attendance data for 128 of the 160 state parks in Florida (DRP, 2004), we determined that 115 parks are primarily considered “upland.” That is, the primary activities and features of the parks are not associated with lakes, rivers or beaches. From October 2003 through September 2004 there were 16.5 million visits to upland parks and 65% of these were by people traveling more than 50 miles (DRP, 2004). Of those who engaged in nature-based recreation in the last 12 months, the average visitation rate was 11.6 trips per person per year. Applying our WTP estimates, this equates to $62.70 per visitor per year ($5.41 per trip times 11.59 trips per year) to manage invasive plants in state parks. For 115 upland parks, this equates to $89.4 million per year ($5.41 per trip times 16,521,419 trips) for all visitors and $31.3 million ($5.41 per trip times 5,782,419 trips) for “local” residents who travel less than 50 miles (Table 3). These estimates are consistent with other studies that estimate the net benefits of invasive plant management efforts (e.g., Adams 2007). Please see Adams and Lee (2011) for a full discussion.

The estimated annual value of $89.4 million should be considered a conservative estimate of the value of managing invasive plants in Florida’s state parks for several reasons. First, we assumed that the current condition of invasive plants was “few and dispersed.” If instead the condition was “none” (no invasive plants), then we estimate that the statewide per-year WTP to control invasive plants would be $178.8 million to keep them from becoming “numerous and dense.” Second, our estimates are derived from WTP for recreation only. Other important values, such existence value (e.g., for endangered species), functional values provided by impacted areas (e.g., water quality), or cultural values for areas like the Everglades were not considered. Third, our survey focused on Florida residents who had recently engaged in nature-based recreation. It is likely that non-residents and those who infrequently visit state parks would also have high WTP to control invasive plants.


Invasive plants are a serious concern, yet funding for invasive plant management programs has been inadequate. Using survey data from 1,436 Florida residents who actively recreate in natural areas, we modeled preferences for recreation in state parks and estimated per-person and statewide willingness to pay to control invasive plants through state park entrance fees. We found that, on average, Florida residents would be willing to pay $5.41 per visit to control invasive plants. This willingness to pay is influenced by demographic variables but more strongly influenced by experience, knowledge and views regarding invasive plants. We extrapolated this value to 115 upland state parks in Florida and infer a statewide willingness to pay to control invasive plants. Local residents would be willing to pay $31.3 million per year, while all visitors would pay $89.4 million to prevent invasive plants from being “numerous and dense.” Since we only focus on recreation in state parks, these estimates are lower bounds for the total value that park visitors would be willing to pay to effectively manage invasive plants. By comparison, the state spends only about $6.3 million to control invasive plants in upland areas (FDEP, 2007). These results indicate that Florida residents would be willing to pay higher entrance fees for park management to reduce the presence of invasive species, and the state of Florida could economically justify increased expenditures of over 10 times the current level.


Adams, D. C. 2007. The economics and law of invasive species management in Florida. PhD dissertation. University of Florida, Gainesville, FL.

Adams, D. C., and D. J. Lee. 2007. Estimating the value of invasive aquatic plant control: A bioeconomic analysis of 13 public lakes in Florida. J. Ag. and Applied Econ. 39/2, 97–109.

Adams, D. C., and D. J. Lee. 2011. Public Preferences for Controlling Upland Invasive Plants in State Parks: Application of a Choice Model. Forest Policy and Economics 13, 465–472.

Division of Recreation and Parks (DRP), 2004. FY 2003/2004 Florida State Park System economic impact assessment. Tallahassee, FL.

Florida Department of Environmental Protection (FDEP), 2007. Status of the aquatic plant maintenance program 550 in Florida public waters: Annual report fiscal year 2006–2007. Tallahassee, FL.

Florida Department of Environmental Protection (FDEP), 2006. Bureau of Invasive Plant Management. Upland Invasive Exotic Plant Management Program, Annual Report, 2005–2006.

Florida Department of Environmental Protection (FDEP), 2001. Economic Benefits Study. Tallahassee, FL.

Florida Exotic Plant Pest Council (FLEPPC), 2007. List of Florida’s invasive plant species. Available at visited April 13, 2009).

Lee, D. J., D. C. Adams, and F. Rossi. 2007. Optimal management of a potential invader: The case of zebra mussels in Florida. J. Ag. and Applied Econ. 39/2, 69–81.

Lee, D. J., D. C. Adams, and C. S. Kim. 2009. Managing invasive plants on public conservation forestlands: Application of a bio-economic model. J. Forest Policy and Econ. 11, 237–243.

Office of Technology Assessment (OTA),1993. Harmful non-indigenous species in the United States. Report OTA-F-565, Washington, DC, US Government Printing Office. Available at:

U.S. General Accounting Office (USGAO), 2002. Invasive Species Clearer Focus and Greater Commitment Needed to Effectively Manage the Problems. GAO-03-1, Washington, D.C.


Table 1. 

Example choice question.

Park Attributes



Condition of facilities



Diversity of animal or plant species



Presence of invasive species


Numerous and dense

Entry fee



Which of the two parks do you prefer (check one) Park A Park B

Table 2. 

The mean willingness-to-pay estimate (WTP) and 95% confidence interval (CI) for a change in each park attribute.

Park attributes

Change in Attribute

Mean WTP

95% C.I.

Lower bound

Upper bound

Condition of facilities

Improve condition of facilities from “Minimal” to “Adequate




Diversity of plant species

Increase native plant species diversity from “Low” to “Moderate”




Diversity of animal species

Increase presence of animal species from “Low” to “Moderate”




Presence of invasive plants

Reduce invasive plant coverage from “Numerous and dense” to “Few and dispersed”




Table 3. 

Statewide willingness-to-pay (WTP) to control invasive plants in 115 Florida state parks.


Annual attendance

Annual WTP to reduce invasive plantsb

Per person



Local visitorsa



All visitors



aState resident visitors traveling fewer than 50 miles from home; assumed to be 35% of attendance.

bAssuming invasive plants are currently “few and dispersed."



This document is FOR290, one of a series of the School of Forest Resources and Conservation Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date October 2011. Visit the EDIS website at


Damian C. Adams, assistant professor, School of Forest Resources and Conservation, University of Florida; Anafrida N. Bwenge, former graduate student, Food and Resource Economics Department, University of Florida; Donna J. Lee, economist, DJL Consulting; Sherry L. Larkin, associate professor, Food and Resource Economics Department, University of Florida; and Janaki R.R. Alavalapati, professor and head, Department of Forest Resources and Environmental Conservation, Virginia Tech University; Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.