Shifting baseline syndrome among coral reef scientists

The paper tests the shifting baseline syndrome (SBS) among Florida Keys coral reef experts. SBS posits that scientists adopt the environmental conditions at the start of their careers as the baseline for assessing change. The study asks whether Florida Keys reef scientists use early-career reef conditions as their baselines and whether age, experience, or professional affiliation affect perceived baselines. It aims to (1) determine consensus years-before-present (YBP) and coral cover baselines for the Florida Keys bank reef at ~10 m depth; (2) identify what information sources inform experts’ baselines; and (3) assess generational differences in direct experience of Acropora-dominated reefs. Understanding potential SBS among experts is important for setting coherent restoration and management targets in a system with extensive historical decline and limited historical data.

The concept of SBS was introduced by Pauly (1995) and has been widely cited and discussed in conservation literature (e.g., Sheppard 1995; Dayton et al. 1998; Jackson et al. 2001; Saenz-Arroyo et al. 2005; Pinnegar and Engelhard 2008; Knowlton and Jackson 2008; Soga and Gaston 2018). Papworth et al. (2009) described two SBS types—intergenerational knowledge loss and personal amnesia. Some scholars argue SBS assumptions can conflict with ecology (Campbell et al., 2009), and Eddy et al. (2018) attempted to estimate a global coral baseline via expert and non-expert surveys, though without site specificity. For the Florida Keys, extensive background documents accelerating coral reef decline and management context exist: the Florida Keys National Marine Sanctuary (designated 1990) oversees diverse habitats but faces compounding stressors including water quality degradation, storms, Diadema die-off, warming, and nutrient enrichment (Lapointe et al. 2004; Lessios et al. 1984; Hoegh-Guldberg 1999). Historical scientific work documents higher past coral cover and zonation (Goreau 1959; Dustan 1977; Dustan and Halas 1987; Porter and Meier 1992), with CREMP showing significant declines since 1996 and macroalgae and octocoral increases. Meta-analyses suggest basin-wide declines in the Caribbean (Gardner et al. 2003). This literature frames debates over appropriate coral baselines and the roles of local versus global drivers.

Study site and focus: Florida Keys reef tract, specifically the bank reef and buttress zone at ~10 m depth, to ensure habitat specificity when eliciting baselines. Study population: Florida Keys reef experts across federal, state, local government, universities, NGOs, and private sector. Sampling and recruitment: Snowball sampling initiated via the Coral listserv; eight initial respondents (“seed”) and referrals yielded 94 additional contacts; 45 responded (47.9% response rate). Including the test interview and seeds, N=54 interviews were conducted January–May 2016. Data collection: One-on-one telephone interviews using open-ended questions (Appendix I) covering three aims: (1) YBP and coral cover baselines and their relationship to age, years of experience, and number of Florida Keys dives; (2) sources informing baselines; (3) whether respondents had witnessed an Acropora-dominated reef in the Florida Keys. Responses were recorded manually and entered into a spreadsheet. For ranges (e.g., “the 1970s” or “30–35%”), midpoints were used (e.g., 1975; 32.5%). Measures and covariates: Age; years of Florida Keys experience; number of Florida Keys research dives. Employment type categorized as government vs. nongovernment and by sector (university, NGO, private). Analysis: Pearson correlation coefficients assessed relationships between YBP baseline and age, years of experience, and number of dives; likewise for coral cover baseline. One extreme outlier YBP response (6000 YBP) was excluded from correlation analyses to satisfy test assumptions; remaining YBP responses ranged 12–126. Descriptive statistics (means, percentages) summarized sources of baseline information and Acropora experience. Ethical considerations: Interviews reported in aggregate, identities confidential per George Mason University human subjects policy. Interview characteristics: Total interview time 37.6 hours; average respondent age 56; average reported dives ~2453 (one missing). Employment distribution: government (27), NGOs (7), private (7), universities (18).

• Consensus baselines: Across ages, experience levels, dive counts, and affiliations, respondents converged on approximately 44 years before present (YBP) as the temporal baseline (mean 44; corresponding to 1972) and about 33% stony coral cover for the Florida Keys bank reef at ~10 m depth. - Years-before-present (YBP): Excluding one outlier (6000 YBP), mean YBP across groups was 44–48. No significant correlations between YBP baseline and age (r = −0.074, p = 0.607, n = 51), years of experience (r = 0.098, p = 0.493, n = 51), or number of dives (r = 0.085, p = 0.559, n = 50). Similar means for respondents <60 and ≥60 years (both 44 YBP), government (45 YBP) vs. nongovernment (44 YBP), <20 vs. >20 years’ experience (44 YBP for both), and <1500 (41 YBP) vs. >1500 dives (48 YBP). - Coral cover percentage: Mean baseline cover across all respondents was 33% (range 4%–67%). Group means were tightly clustered: younger than 60 (34%), 60+ (33%), government (34%), nongovernment (33%), <20 years’ experience (30%), >20 years (36%), <1500 dives (32%), >1500 dives (34%). No significant correlations between cover baseline and age (r = 0.052, p = 0.72, n = 50) or number of dives (r = 0.024, p = 0.87, n = 49). A positive trend with years of experience did not reach p < 0.05 (r = 0.256, p = 0.072, n = 50). - Generational experience of Acropora-dominated reefs: 70% of experts under age 40 reported never witnessing an Acropora-dominated reef in the Florida Keys, whereas 96% of experts over age 60 reported that they had. Despite this experiential disparity, baselines did not differ by age. - Information sources informing baselines: Only 17% reported relying on personal observations; most cited recent quantitative ecological data (e.g., Diadema die-off, documented declines) as primary inputs. Historical data were infrequently cited (13%). - Sample and participation: 54 experts interviewed; total testimony 37.6 hours; response rate 47.9%; 96% of interviewees were professional scientists; average age 56; mean ~2453 Florida Keys dives.

The findings do not support the presence of shifting baseline syndrome among Florida Keys reef experts. Despite strong generational differences in direct experience with Acropora-dominated reefs, experts of different ages, experience levels, and affiliations converged on similar temporal (≈44 YBP, 1972) and coral cover (≈33%) baselines. This suggests that expertise, education, and access to peer-reviewed and monitoring data can mitigate SBS by anchoring expectations in quantitative evidence rather than solely in personal experience. The lack of correlation between baselines and age, years of experience, or dive counts indicates that experiential exposure alone does not drive baseline selection among experts. Instead, respondents primarily referenced recent quantitative ecological data and well-known events (e.g., Diadema die-off) when forming baselines, with relatively little reliance on historical or anecdotal sources. This consensus has practical relevance: unified baselines can facilitate coherent restoration targets and management strategies across agencies, NGOs, academia, and private stakeholders within the Florida Keys. The results also raise questions about the role and uptake of historical ecological data in coral reef management; although advocated in the literature, such data were seldom cited by respondents, suggesting a need for better integration and translation of historical insights into operational management frameworks.

This study provides empirical evidence that Florida Keys reef experts are not exhibiting shifting baseline syndrome with respect to temporal and coral cover baselines for the bank reef at ~10 m depth. There is strong cross-sector consensus around baselines of ~44 years before present (1972) and ~33% stony coral cover, largely informed by quantitative ecological datasets rather than personal or historical anecdotal observations. These agreed-upon baselines can inform unified restoration goals and policy within the Florida Keys National Marine Sanctuary and related programs. Future research should (1) develop methodologies to integrate historical and social data with modern monitoring to refine baseline setting; (2) explore how knowledge exchange and outreach can increase the actionable use of historical ecology in management; (3) test for SBS and consensus in other reef regions and habitats with clearly defined site, zone, and depth parameters; and (4) assess how consensus baselines translate into restoration outcomes over time.

The study relies on snowball sampling, which can introduce network and selection biases despite sample “saturation.” The sample size is modest (N=54) and limited to Florida Keys–experienced experts, which may constrain generalizability beyond the specified site, habitat, and depth (bank reef, buttress zone at ~10 m). Responses are self-reported via telephone interviews and include subjective judgments of baselines; one extreme outlier was excluded to meet statistical assumptions. Historical data scarcity in the region limits triangulation. Not all survey questions from the broader dissertation are analyzed here, and underlying interview data are not publicly available due to confidentiality, which limits external verification and reanalysis.