Interim Review of the Florida Keys Carrying Capacity Study (2001)

For years policy makers at local and state levels have been workingto achieve a balance between economic development, quality of life,and environmental protection in the Florida Keys. After a lengthyprocess of public debate and legal proceedings, Florida AdministrationCommission Rule 28.20.100 was issued in 1996, requiring the preparationof a “carrying capacity analysis...designed to determine the abilityof the Florida Keys ecosystem, and the various segments thereof,to withstand all impacts of additional land development activities.” That ruling led to the initiation of the Florida Keys Carrying CapacityStudy and its companion Carrying Capacity Analysis Model, which aresponsored by the U.S. Army Corps of Engineers (the Corps) and theFlorida Department of Community Affairs and are being carried outby the contractor URS (formerly Dames and Moore). The Corps and theFlorida Department of Community Affairs, in turn, requested thatthe National Academy of Sciences/National Research Council establisha committee to provide an authoritative, independent technical reviewof this ambitious effort.

The charge to this committee was as follows:

“[R]eview and evaluate the scientific methods, principles, and datathat form the basis for the Florida Keys Carrying Capacity Studyand the accompanying Carrying Capacity Analysis Model being developedby the State of Florida. The committee will assess the ability ofthe Keys Study to fulfill its stated goal of ‘determining the abilityof the Florida Keys ecosystem to withstand all impacts of additionalland development activities,' and the extent to which the conclusionswere reached based on a sound scientific process.

Specifically the committee will review and comment on the following:

• the overall design assumptions

• the data used

• the requirements, responses, limiting factors, and thresholds forstudy categories selected

• the determination of how land development activities will affectstudy categories

• the adequacy and reliability of the study as a basis for local andstate land management and planning decisions.”

The Keys Study is moving forward on a strict and very rapid schedule.Pending its outcome, strict limits have been placed on further developmentin the Keys through a rate-of-growth ordinance. These limits anda strong public desire to move beyond the impasse toward a long-termsolution provide strong motivations to move forward as quickly aspossible without sacrificing the credibility of the end product.

To provide rapid feedback to the project managers the National ResearchCouncil agreed to provide this interim report. The report is basedlargely on presentations made by the contractor at a two-day workshopheld in Key Largo, Florida, January 9-10, 2001 (referred to in thisreport as the January workshop), where the contractor described progressto date in designing the

CCAM. The committee will prepare a second, more detailed report whenthe contractor presents a complete, working version of the CCAM,scheduled for June 2001.

The Keys Study is an innovative endeavor, and the committee is unanimousin its appreciation of the ambitious vision it represents. The committeemembers are also very aware that our understanding of the detailsof the study is limited by our recent and relatively brief exposureto it. The committee also remains mindful that the study is a workin progress. Although various enhancements and mid-course correctionsmay already have been made by the time this report is received, thecommittee nevertheless believes that an independent assessment ofprogress to date will remain useful to the project's sponsors andprogram managers. In some cases the observations and recommendationsin this report echo those made publicly by participants at the Januaryworkshop. In all cases the comments contained in this report reflecta consensus of this committee, based on intensive discussions throughoutthe workshop and the following day and in subsequent correspondence.

Before addressing the specifics of project management and the technicalcontent of the CCAM, it is worth examining the Keys Study's broaderphilosophy and objectives. Although the following discussion focuseson the use of particular terms (such as “carrying capacity,” “thresholds,” and “model”), the committee believesthat the inconsistent use of these terms reflects underlying conceptualchallenges in the Keys Study, and the conflicting perspectives andneeds of different end-users.

The term “carrying capacity” is not easy to define. The glossary in the scope of work for theKeys Study defines “carrying capacity” as “maximum population impacts an area can sustainover time with a given level of technology and societal preferences.” This definition is rooted in the concepts of regional planning (Godschalk,Parker, and Knoche, 1974) and implies that there are defined thresholdsgiven certain assumptions. Under this view, carrying capacity islimited by a set of maximum impacts that can be tolerated—a questioninvolving human preferences about the quality of the environmentand nature of communities. These impacts can also be modified ifsuitable technologies exist and are purchased. Such an approach willbe most useful to the Florida Department of Community Affairs andother planning entities that have been directed by Florida ExecutiveOrder 96-108 to “adhere to and implement the findings of a carryingcapacity analysis as it relates to and affects the rate of growthand permit allocation in Monroe County.”

The scope of work also clearly states that “[t]he carrying capacity analysis shall consider aesthetic, socio-economic(including sustainable tourism), quality of life and community characterissues, including the concentration of population, the amount ofopen space, diversity of habitats, and species richness.” These factorsare important for residents and local leaders who care deeply aboutthe impacts of alternative land development scenarios on the localeconomy, community character, and the environment.

On the other hand, the scope of work elsewhere explains that “[a] broad approach was chosen where elements of human society wouldbe included as explicit variables in the modeling yet the value of protecting non-human species and the ecologicalsystem would establish the fundamental basis of the study” [emphasis added] and that the Keys Study will “determine the level of land development . . . that can be supportedby a healthy, balanced, functioning

ecosystem in the Florida Keys.” These goals reflect an attempt to apply the theoretical notion ofecological carrying capacity to assess relative environmental impacts.

Unfortunately there simply are no objective, scientific criteriafor determining “a healthy, balanced, functioning ecosystem . . .” Natural systems rarely exhibit quantifiable “thresholds” for species success and ecosystem functioning. In other words, thereare no clear limits that separate healthy and non-healthy conditions.Whereas the habitat requirements for a few threatened and endangeredspecies are reasonably well known, this is not the case for mostcomponents of the Keys ecosystem. Most evidence suggests that plantsand animals respond to change in extremely complex ways, sometimesgradually and reversibly, sometimes with sudden non-linearities.For similar reasons, the terms “indicator species” and “keystone species” do not have clear meanings, as discussedin Section 6 of this report.

Furthermore, both ecosystems and human communities are dynamic systems.The ability of an ecosystem to sustain viable populations shiftsover time, in response to natural and human factors that vary overthe short-term (e.g., annual and decadal disturbances and cycles)and the long-term (e.g., climate change). Community preferences alsoshift over time, as do technological alternatives for mitigatingthe impacts of human development. Thus, the notion of carrying capacityas the basis for determining limits for development depends on valuejudgments made by stakeholders about the desired state of the naturaland built environments and will always be a moving target that mustbe regularly reassessed.

The use of the word “model” is itself problematic. Although the concept of a carrying capacityanalysis model for the Florida Keys human and natural ecosystemsis appealing, the construction of a precise, mechanistic model thatsimulates all human and natural systems and their interactions, assuggested by the scope of work, is simply not possible within thecurrent limits of funding, time, and basic knowledge. More realisticis the more modest goal of producing a useful planning tool thatcan be combined with other public policy efforts to help “determinethe level of land development activities that will avoid (or at leastminimize) further irreversible and/or adverse impacts to the FloridaKeys ecosystem.” De-emphasizing the goal of creating a full, numericalsimulation model will also make it easier to incorporate less tangible,but critical, factors that affect the quality of life.

As a first step, the Keys Study should downplay the concept of producinga precise, numerical “model” and focus instead on the production of a semi-quantitative“impact assessment tool” that can be used to help illustrate the consequences of variousdevelopment scenarios on the environmental and social systems inthe Keys. In keeping with this view, this report refers to the CCAMas an assessment tool, offering suggestions as to how the tool canbe refined and focused in keeping with available knowledge and resources.The actual terminology to be used in the draft CCAM should be carefullyconsidered by the design team.

Although the Keys Study must, of course, stay within the intent andspirit of the legal order that set it in motion, the sponsors andcontractor will ultimately have to decide and agree on what can bemeaningfully achieved. The contractor, the Corps, the Florida Departmentof Community Affairs, Monroe county managers, and other interestedparties should acknowledge the existence of conceptual ambiguitiesand differing user needs, and continue to discuss realistic expectationsfor the Keys Study's products, particularly the CCAM. Continued useof inconsistent definitions or reliance on an unrealistic pictureof nature will make it difficult to achieve a common understandingof the goals for this vast and complex undertaking.