Tim R Mcclanahan

• PhD, Environmental Engineering
• Senior Conservation Zoologist at Wildlife Conservation Society

Trophic cascades caused by a reduction in predators of sea urchins have been reported in Indian Ocean and Caribbean coral reefs. Previous studies have been constrained by their site-specific nature and limited spatial replication, which has produced site and species-specific understanding that can potentially preclude larger community-organization...

Ongoing declines in the structure and function of the world's coral reefs require novel approaches to sustain these ecosystems and the millions of people who depend on them. A presently unexplored approach that draws on theory and practice in human health and rural development is to systematically identify and learn from the 'outliers'-places where...

We examined the associations between geography, biodiversity, national spending on conservation, governance and cultural traits. Cultural traits and social metrics of modernization correlate positively with national spending on conservation. Further, we show the global distribution of this spending culture is poorly aligned with the distribution of...

Fish biomass is a primary driver of coral reef ecosystem services and has high sensitivity to human disturbances, particularly fishing. Estimates of fish biomass, their spatial distribution, and recovery potential are important for evaluating reef status and crucial for setting management targets. Here we modeled fish biomass estimates across all r...

Ecological baselines are disappearing and it is uncertain how marine reserves, here called fisheries closures, simulate pristine communities. We tested the influence of fisheries closure age, size and compliance on recovery of community biomass and life-history metrics towards a baseline. We used census data from 324 coral reefs, including 41 prote...

Models of the future of coral reefs are potentially sensitive to theoretical assumptions, variable selectivity, interactions, and scales. A number of these aspects were evaluated using boosted regression tree models of numbers of coral taxa trained on ~1000 field surveys and 35 spatially complete influential environmental proxies at moderate scales...

The ability to strengthen governance institutions and fisheries restrictions and laws is needed to improve conservation and management of common‐pool resources. We evaluated the potential for stimulating change with modest interventions by studying fishing village households before and after a 27‐month intervention period in a high‐priority coral r...

Reducing resource depletion and promoting ecosystem‐based management are considered key climate change adaptation policies. Therefore, the resource status of an identified climate refugia in a semi‐enclosed bay on the Kenya–Tanzania border was evaluated for sustainability. Both fisheries stock and catch assessment methods found low production and e...

Both the ecological and social dimensions of fisheries are being affected by climate change. As a result, policymakers, managers, scientists and fishing communities are seeking guidance on how to holistically build resilience to climate change. Numerous studies have highlighted key attributes of resilience in fisheries, yet concrete examples that e...

Aim Strong social‐ecological trade‐offs between resource extraction and protection have created challenges for large, protected area management in natural resource‐dependent countries. Therefore, local governments and community conservation activities are becoming common and information about low environmental exposure and high biodiversity can pro...

Identifying locations of refugia from the thermal stresses of climate change for coral reefs and better managing them is one of the key recommendations for climate change adaptation. We review and summarize approximately 30 years of applied research focused on identifying climate refugia to prioritize the conservation actions for coral reefs under...

In a changing climate, there is an imperative to build coupled social-ecological systems-including fisheries-that can withstand or adapt to climate stressors. Although resilience theory identifies system attributes that supposedly confer resilience , these attributes have rarely been clearly defined, mechanistically explained, nor tested and applie...

Marine reserves are known to impact the biomass, biodiversity, and functions of coral reef fish communities, but the effect of protective management on fish traits is less explored. We used a time-series modelling approach to simultaneously evaluate the abundance, biomass, and traits of eight fish families over a chronosequence spanning 44 years of...

Current models of the future of coral reefs rely on threshold (TM) and multivariate environmental variability models (VM) that vary in how they account for spatial and temporal environmental heterogeneity. Here, a VM based on General Additive Model (GAM) methods evaluated the empirical relationships between coral cover (n = 905 sites pooled to 318...

Current best‐practice policy recommendations for managing fish stocks are achieved by a mixture of maintaining modest fishing mortality (restricting effort, times and gear), marine reserve networks and not subsidizing unprofitable fisheries. A seldom evaluated question is how effective these proposed approaches are for maintaining all fish stocks a...

Mauritius is reported to have the highest marine species endemism in the Western Indian Ocean faunal Province but the status of these species has not been evaluated. To address this knowledge gap, 119 reef sites were sampled to evaluate populations of 16 species of rare and endemic reef fish and corals using scuba‐based surveys conducted by citizen...

The long-term consequences of managing overfished fisheries through either gear restrictions or closures are among the many dilemmas facing small-scale fisheries managers. To evaluate long-term outcomes, fishing effort and catch were measured from 1995 to 2019 in two districts in Kenya, one that established a marine reserve in 1991 and another that...

Which management actions work best to prevent or halt overfishing and to rebuild depleted populations? A comprehensive evaluation of multiple, co-occurring management actions on the sustainability status of marine populations has been lacking. Here, we compiled detailed management histories for 288 assessed fisheries from around the world (accounti...

The effectiveness and outcomes of management are expected to improve when people are informed, engaged and influential in governance and management procedures. The social‐ecological and demographic contexts should, however, influence an individual's perceptions and willingness to engage and access appreciable benefits from management. To evaluate h...

Knowing the responses of high-latitude corals to thermal impacts will be critical to predicting the possibility for range expansion of reefs provoked by climate change. We, therefore, tested how oceanographic and island geography variation and subsequent interactions between chronic and acute environmental stresses would influence the temperate cor...

Coral reef communities exposed to rapid temperature rises and frequent thermal anomalies were evaluated for taxonomic turnover via presence/absence information over a 27-year period experiencing large changes in the dominant taxa. Temporal turnover of the taxa within sites was consistently high (~ 40%) due to both inter-annual episodic and directio...

Temperature variability, habitat, coral communities, and fishing intensity are important factors influencing coral responses to climate change. Consequently, chronic and acute sea-surface temperatures (SSTs) and their interactions with habitat and fishing were studied along the East African coast (~ 400 km) by evaluating changes over a ~ 25-year pe...

• Reef fish biomass is increasingly recognized as a key indicator of fishery and biodiversity status linked to ecosystem integrity on coral reefs, and yet the evaluation of appropriate baselines for biomass, and what drives variation in potential baselines, is sparse. • Variability in reef fishable biomass was assessed to test for the existence of...

Caribbean reefs have experienced unprecedented changes in the past four decades. Of great concern is the perceived widespread shift from coral to macroalgal dominance and the question of whether it represents a new, stable equilibrium for coral-reef communities. The primary causes of the shift—grazing pressure (top-down), nutrient loading (bottom-u...

Conservation and management policies rely on the perceived status of marine ecosystems, which are influenced by proxies and estimation methods. These include the number of protected areas, the percent coverage of nearshore areas, frequency or area relative to other ecosystems, and a diverse set of possible but often poorly evaluated impacts. Based...

Complex histories of chronic and acute sea surface temperature (SST) stresses are expected to trigger taxon- and location-specific responses that will ultimately lead to novel coral communities. The 2016 El Niño-Southern Oscillation provided an opportunity to examine largescale and recent environmental histories on emerging patterns in 226 coral co...

Aim Predictions for the future of coral reefs are largely based on thermal exposure and poorly account for potential geographic variation in biological sensitivity to thermal stress. Without accounting for complex sensitivity responses, simple climate exposure models and associated predictions may lead to poor estimates of future coral survival and...

Herbivory is a key process that controls the abundance and accumulation of algal turf on tropical coral reefs. The capacity of reefs to prevent algal accumulation hinges on the balance between algal production and consumption (i.e., grazing). In this study, we quantify algal turf biomass accumulation and grazing using experimental substrata and her...

The role of a marine reserve and fisheries regulations in restoring fish populations on reefs disturbed by climate impacts was evaluated. Eight patch reefs, divided equally between no-fishing and fished zones in the remote Glover’s Reef atoll lagoon, were studied for 22 yr: 13 yr before and 9 yr after a ban on parrotfish capture. Findings indicate...

Climate change is expected to reinforce undesirable social and ecological feedbacks between ecosystem degradation and poverty. This is particularly true for resource-dependent communities in the developing world such as coral reef fishing communities who will have to adapt to those new environmental conditions and novel ecosystems. It is therefore...

Common-pool resources are challenged by a number of factors including broadly acceptable resource extraction restrictions and effective implementation of proposed restrictions. Consequently, we evaluated fisher's perceptions of effectiveness of their governance institutions and benefits of restrictions in 16 East African marine fishing communities....

A complex landscape for reef management Coral reefs are among the most biodiverse systems in the ocean, and they provide both food and ecological services. They are also highly threatened by climate change and human pressure. Cinner et al. looked at how best to maximize three key components of reef use and health: fish biomass, parrotfish grazing,...

Fishing sustainably is a fundamental problem in tropical regions where diverse fisheries and scarce fisheries information challenges efforts to make reliable estimates and associated policies. To improve evaluations and decisions, we compared the predictions of six surplus production models calibrated using various permutations of fisheries‐depende...

The health of coastal human communities and marine ecosystems are at risk from a host of anthropogenic stressors, in particular, climate change. Because ecological health and human well-being are inextricably connected, effective and positive responses to current risks require multidisciplinary solutions. Yet, the complexity of coupled social–ecolo...

Marine fish stocks are an important part of the world food system and are particularly important for many of the poorest people of the world. Most existing analyses suggest overfishing is increasing, and there is widespread concern that fish stocks are decreasing throughout most of the world. We assembled trends in abundance and harvest rate of sto...

Unsustainable fishing is a major driver of change in marine ecosystems. The ways that fishing gears target fishes with different ecological functions are unclear, particularly in complex multispecies fisheries. Here, we examine whether artisanal fishing gears selectively target fishes with unique combinations of ecological traits (diet, body size,...

A R T I C L E I N F O Keywords: commons fisheries management coral reefs transdisciplinary social-ecological systems monitoring and evaluation sustainability A B S T R A C T Multi-scale social-ecological systems (SES) approaches to conservation and commons management are needed to address the complex challenges of the Anthropocene. Although SES app...

Under extreme heat stress, corals expel their symbiotic algae and colour (that is, ‘bleaching’), which often leads to widespread mortality. Predicting the large-scale environmental conditions that reinforce or mitigate coral bleaching remains unresolved and limits strategic conservation actions1,2. Here we assessed coral bleaching at 226 sites and...

The outcomes of subsidizing natural and fishing capital were studied in nearshore coral reef fisheries initiated by the devolution of governance and management from national to county governments. One county promoted a net subsidy program of preferred mesh sizes with a distinct purchase and distribution date, while the other supported the ongoing m...

Without drastic efforts to reduce carbon emissions and mitigate globalized stressors, tropical coral reefs are in jeopardy. Strategic conservation and management requires identification of the environmental and socioeconomic factors driving the persistence of scleractinian coral assemblages—the foundation species of coral reef ecosystems. Here, we...

Without drastic efforts to reduce carbon emissions and mitigate globalized stressors, tropical coral reefs are in jeopardy. Strategic conservation and management requires identification of the environmental and socioeconomic factors driving the persistence of scleractinian coral assemblages—the foundation species of coral reef ecosystems. Here, we...

This presentation presents an evaluation of a net subsidy program in southern Kenya where the fisheries was studied for 3 years before and after the subsidy. The "control" in this BACI design was a county with more closures.

A presentation given at a mini-session at the Western Indian Ocean Marine Science Association (WIOMSA), July 2, 2019, Mauritius. The paper summarizes the governance issues around MPAs and restrictions as relevant to climate refugia in East Africa.

Caribbean reefs have experienced unprecedented changes in the past four decades. Of great concern is the perceived widespread shift from coral to macroalgal dominance and the question of whether it represents a new, stable equilibrium for coral-reef communities. The primary causes of the shift -- grazing pressure (top-down), nutrient loading (botto...

Complex social-ecological interactions underpin many environmental problems. To help capture this complexity, we advance an interdisciplinary network modeling framework to identify important relationships between people and nature that can influence environmental conditions. Drawing on comprehensive social and ecological data from five coral reef f...

The slide show was presented at Stanford Center for Ocean Solutions. https://oceansolutions.stanford.edu/news-stories/april-17-wildlife-conservation-societys-tim-mcclanahan-discusses-democratizing

Threats from climate change and other human pressures have led to widespread concern for the future of Australia’s Great Barrier Reef (GBR). Resilience of GBR reefs will be determined by their ability to resist disturbances and to recover from coral loss, generating intense interest in management actions that can moderate these processes. Here we q...

Baselines and benchmarks (B&Bs) are needed to evaluate the ecological status and fisheries potential of coral reefs. B&Bs may depend on habitat features and energetic limitations that constrain biomass within the natural variability of the environment and fish behaviors. To evaluate if broad B&Bs exist, we compiled data on the biomass of fishes in...

Identifying the species that are at risk of local extinction in highly diverse ecosystems is a big challenge for conservation science. Assessments of species status are costly and difficult to implement in developing countries with diverse ecosystems due to a lack of species-specific surveys, species-specific data, and other resources. Numerous tec...

Common‐pool governance principles are becoming increasingly important tools for natural resource management with communities and comanagement arrangements. Effectiveness of these principles depends on variability in agreements, trust, and adherence to institutional norms. We evaluated heterogeneity in governance principles by asking 449 people in 3...

Resilience underpins the sustainability of both ecological and social systems. Extensive loss of reef corals following recent mass bleaching events have challenged the notion that support of system resilience is a viable reef management strategy. While resilience-based management (RBM) cannot prevent the damaging effects of major disturbances, such...

Broad-scale overharvesting of fish is one of the major drivers of marine biodiversity loss and poverty, particularly in countries with high dependence on coral reefs. Given the heterogeneity of fishing effort and management success, and the scarcity of management resources, it is necessary to identify broad-scale locations for promoting successful...

ABSTRACT The productivity and diversity of coral reefs is being threatened by a number of human disturbances that could be better understood and managed with appropriate indicators. Here, I evaluated 9 biomass-weighted fish life history trait metrics and 4 categories of biomass (total, fishable, target, and non-target) using a large single-observer...

A number of people asked me to post my presentation at the 2018 IMCC conference in Kuching, Malaysia for a special session on Justice in Marine Conservation. Here is the abstract: Justice, fairness, and economic trade-offs are related concepts that are critical for considering and developing effective management in fisheries. Critical to how these...

The consequences of coral bleaching for reef corals, growth, productivity, and biodiversity are reviewed. Coral taxa are differentially affected by temperature stresses, and the complexities of their life histories make gross generalizations about impacts difficult. Some impacts, such as lost cover, reproduction, and recruitment, are highly visible...

Significance Marine reserves that prohibit fishing are a critical tool for sustaining coral reef ecosystems, yet it remains unclear how human impacts in surrounding areas affect the capacity of marine reserves to deliver key conservation benefits. Our global study found that only marine reserves in areas of low human impact consistently sustained t...

The original version of the Article was missing an acknowledgement of a funding source. The authors acknowledge that A. Safaie and K.Davis were supported by National Science Foundation Award No. 1436254 and G. Pawlak was supported by Award No. 1436522. This omission has now been corrected in the PDF and HTML versions of the Article.

A holistic basis for achieving ecosystem‐based management is needed to counter the continuing degradation of coral reefs. The high variation in recovery rates of fish, corresponding to fisheries yields, and the ecological complexity of coral reefs have challenged efforts to estimate fisheries sustainability. Yet, estimating stable yields can be det...

Coral bleaching is the detrimental expulsion of algal symbionts from their cnidarian hosts, and predominantly occurs when corals are exposed to thermal stress. The incidence and severity of bleaching is often spatially heterogeneous within reef-scales (<1 km), and is therefore not predictable using conventional remote sensing products. Here, we sys...

Aim Large‐scale variation in species richness results from multiple environmental controls. We proposed to identify the main factors that influence species richness of reef corals to provide insight into natural forces and their implications for future climate impacts. Location Indian Ocean. Methods We applied quantile regression (QR) to predict...

The status of fisheries requires establishing and evaluating benchmarks derived from unfished ecosystems. Habitats, environmental conditions, properties of the fish communities, and management systems could potentially influence the variability surrounding benchmarks. Consequently, eighteen variables including habitat, number of species, life histo...

Aim To describe, model and assess the relative importance of environmental and climatic factors likely influencing the regional distribution of coral cover and assemblages with contrasting life histories and susceptibilities to bleaching. Location We compiled the first comprehensive empirical dataset for coral communities in the south‐eastern Indi...

The economic and socio-political interactions between countries can have major impacts on transboundary conservation decisions and outcomes. Here, we examined for 14 Western Indian Ocean (WIO) continental and island nations the extent of their marine coral reef species, fisheries and marine protected areas (MPAs), in the context of their geopolitic...

Microbioerosion rates and microbioeroder community structure were studied in four Kenyan protected coral-reef lagoons using shell fragments of Tridacna giant clams to determine their response to the influence of terrestrial run-off. Fourteen different microbioeroder traces from seven cyanobacteria, three green algae and four fungi species were iden...

Conflicts over the imposition of restrictions in common-pool resources management institutions are expected to arise from variations in human values, perceptions of justice, and the disparate demographic scales of benefits and costs. We hypothesized and tested a series of propositions about how the demographic scale and context of common restrictio...

Elucidating factors that influence natural resources and diversity can assist managing species and their ecological functions. Key management options include protecting unique locations or implementing restrictions that more broadly protect ecological attributes and their services. To evaluate these 2 options, we examined 23 fish families in 152 un...

Government-managed marine protected areas (MPAs) can restore small fish stocks, but have been heavily criticized for excluding resource users and creating conflicts. A promising but less studied alternative are community-managed MPAs, where resource users are more involved in MPA design, implementation and enforcement. Here we evaluated effects of...

Data used for univariate analyses. (XLSX)

Comparison of MPA effects based on A) time series within MPAs and B) site-for-time surveys between MPAs. Relative increase in mean total fish biomass based on time series analysis within large government MPAs (data from McClanahan and Graham 2005) and site-for-time survey (this study) show similar results and suggest that time since closure is an i...

Relationships between fish size and market value. Linear relationships between fish size (standard length, cm) and market value (price in Kenyan shilling, Ksh/kg) for five value groups. (DOCX)

Data used for multivariate analyses. (XLSX)

List of fish taxa found during the study in the six study areas in Kenya. (DOCX)

Reducing the capture of small fish, discarded fish, and bycatch is a primary concern of fisheries managers who propose to maintain high yields, species diversity, and ecosystem functions. Modified fishing gear is one of the primary ways to reduce by-catch and capture of small fish. The outcomes of gear modification may depend on competition among f...

Introduction: The state of natural resources is greatly influenced by market access. Consequently, resource trader’s incentives, decisions, and willingness to comply with management can influence efforts to achieve sustainability. Trader’s impacts will depend on their economic niches, which are influenced by cultural norms, skill, social relationsh...

Raw data and code

Supporting information

A priority for modern conservation is finding and managing regions with environmental and biodiversity portfolio characteristics that will promote adaptation and the persistence of species during times of rapid climate change. The latitudinal edges of high-diversity biomes are likely to provide a mixture of environmental gradients and biological di...

The 1998 and 2016 thermal anomalies were among the 2 most severe global-scale anomalies in recent history, with broad-scale impacts on reef condition. In 2 Kenyan fully protected national park reef lagoons, the water flow, light, and temperature exposure severity of these 2 events was grossly similar at 7.3 cm s⁻¹, ~50 Einsteins m⁻² d⁻¹ and ~85 deg...