Limited functional redundancy in high diversity systems: resilience and ecosystem function on coral reefs

Abstract Biodiversity is frequently associated with functional redundancy. Indo‐Pacific coral reefs incorporate some of the most diverse ecosystems on the globe with over 3000 species of fishes recorded from the region. Despite this diversity, we document changes in ecosystem function on coral reefs at regional biogeographical scales as a result of overfishing of just one species, the giant humphead parrotfish (Bolbometopon muricatum). Each parrotfish ingests over 5 tonnes of structural reef carbonates per year, almost half being living corals. On relatively unexploited oceanic reefs, total ingestion rates per m² balance estimated rates of reef growth. However, human activity and ecosystem disruption are strongly correlated, regardless of local fish biodiversity. The results emphasize the need to consider the functional role of species when formulating management strategies and the potential weakness of the link between biodiversity and ecosystem resilience.     

Human activity selectively impacts the ecosystem roles of parrotfishes on coral reefs

Around the globe, coral reefs and other marine ecosystems are increasingly overfished. Conventionally, studies of fishing impacts have focused on the population size and dynamics of targeted stocks rather than the broader ecosystem-wide effects of harvesting. Using parrotfishes as an example, we show how coral reef fish populations respond to escalating fishing pressure across the Indian and Pacific Oceans. Based on these fish abundance data, we infer the potential impact on four key functional roles performed by parrotfishes. Rates of bioerosion and coral predation are highly sensitive to human activity, whereas grazing and sediment removal are resilient to fishing. Our results offer new insights into the vulnerability and resilience of coral reefs to the ever-growing human footprint. The depletion of fishes causes differential decline of key ecosystem functions, radically changing the dynamics of coral reefs and setting the stage for future ecological surprises.     

White-band disease and the changing face of Caribbean coral reefs

In recent decades, the cover of fleshy macroalgae has increased and coral cover has decreased on most Caribbean reefs. Coral mortality precipitated this transition, and the accumulation of macroalgal biomass has been enhanced by decreased herbivory and increased nutrient input. Populations of Acropora palmata (elkhorn coral) and A. cervicornis (staghorn coral), two of the most important framework-building species, have died throughout the Caribbean, substantially reducing coral cover and providing substratum for algal growth. Hurricanes have devastated local populations of Acropora spp. over the past 20–25 years, but white-band disease, a putative bacterial syndrome specific to the genus Acropora, has been a more significant source of mortality over large areas of the Caribbean region.Paleontological data suggest that the regional Acropora kill is without precedent in the late Holocene. In Belize, A. cervicornis was the primary ecological and geological constituent of reefs in the central shelf lagoon until the mid-1980s. After constructing reef framework for thousands of years, A. cervicornis was virtually eliminated from the area over a ten-year period. Evidence from other parts of the Caribbean supports the hypothesis of continuous Holocene accumulation and recent mass mortality of Acropora spp. Prospects are poor for the rapid recovery of A. cervicornis, because its reproductive strategy emphasizes asexual fragmentation at the expense of dispersive sexual reproduction. A. palmata also relies on fragmentation, but this species has a higher rate of sexual recruitment than A. cervicornis. If the Acropora spp. do not recover, macroalgae will continue to dominate Caribbean reefs, accompanied by increased abundances of brooding corals, particularly Agaricia spp. and Porites spp. The outbreak of white-band disease has been coincident with increased human activity, and the possibility of a causal connection should be further investigated.     

The threat to coral reefs from more intense cyclones under climate change

Ocean warming under climate change threatens coral reefs directly, through fatal heat stress to corals and indirectly, by boosting the energy of cyclones that cause coral destruction and loss of associated organisms. Although cyclone frequency is unlikely to rise, cyclone intensity is predicted to increase globally, causing more frequent occurrences of the most destructive cyclones with potentially severe consequences for coral reef ecosystems. While increasing heat stress is considered a pervasive risk to coral reefs, quantitative estimates of threats from cyclone intensification are lacking due to limited data on cyclone impacts to inform projections. Here, using extensive data from Australia's Great Barrier Reef (GBR), we show that increases in cyclone intensity predicted for this century are sufficient to greatly accelerate coral reef degradation. Coral losses on the outer GBR were small, localized and offset by gains on undisturbed reefs for more than a decade, despite numerous cyclones and periods of record heat stress, until three unusually intense cyclones over 5 years drove coral cover to record lows over >1500 km. Ecological damage was particularly severe in the central‐southern region where 68% of coral cover was destroyed over >1000 km, forcing record declines in the species richness and abundance of associated fish communities, with many local extirpations. Four years later, recovery of average coral cover was relatively slow and there were further declines in fish species richness and abundance. Slow recovery of community diversity appears likely from such a degraded starting point. Highly unusual characteristics of two of the cyclones, aside from high intensity, inflated the extent of severe ecological damage that would more typically have occurred over 100s of km. Modelling published predictions of future cyclone activity, the likelihood of more intense cyclones within time frames of coral recovery by mid‐century poses a global threat to coral reefs and dependent societies.     

珊瑚礁区的生物多样性及其生态功能

珊瑚礁区生物多样性程度可以与陆地热带雨林相提并论,目前关于珊瑚礁物种多样性及其空间分布特征方面研究进展迅速,是生物多样性研究的重要基地。作为一种生态资源,珊瑚礁还具有重要的生态功能,近年来由于全球气候逐渐变暖、人类活动影响不断加剧,导致其生物多样性缩减、生态功能严重退化。珊瑚礁生态系统多样性、遗传多样性已成为珊瑚礁研究热点,珊瑚礁生态环境效应和保护管理方面的研究也越来越受到重视。我国珊瑚礁主要分布在广阔的南海海域和海南岛、台湾岛、香港和广东广西沿岸,礁区生物种类繁多,多样性程度较高,以往研究主要涉及地质、地貌、生物、环境等方面,现今和今后一段时间里迫切需要加强生物多样性和生态功能研究,以确保更有效地保护和管理珊瑚礁。     

Anticipative management for coral reef ecosystem services in the 21st century

Under projections of global climate change and other stressors, significant changes in the ecology, structure and function of coral reefs are predicted. Current management strategies tend to look to the past to set goals, focusing on halting declines and restoring baseline conditions. Here, we explore a complementary approach to decision making that is based on the anticipation of future changes in ecosystem state, function and services. Reviewing the existing literature and utilizing a scenario planning approach, we explore how the structure of coral reef communities might change in the future in response to global climate change and overfishing. We incorporate uncertainties in our predictions by considering heterogeneity in reef types in relation to structural complexity and primary productivity. We examine 14 ecosystem services provided by reefs, and rate their sensitivity to a range of future scenarios and management options. Our predictions suggest that the efficacy of management is highly dependent on biophysical characteristics and reef state. Reserves are currently widely used and are predicted to remain effective for reefs with high structural complexity. However, when complexity is lost, maximizing service provision requires a broader portfolio of management approaches, including the provision of artificial complexity, coral restoration, fish aggregation devices and herbivore management. Increased use of such management tools will require capacity building and technique refinement and we therefore conclude that diversification of our management toolbox should be considered urgently to prepare for the challenges of managing reefs into the 21st century.     

Ecological persistence interrupted in Caribbean coral reefs

The recent mass mortality of Caribbean reef corals dramatically altered reef community structure and begs the question of the past stability and persistence of coral assemblages before human disturbance began. We report within habitat stability in coral community composition in the Pleistocene fossil record of Barbados for at least 95 000 years despite marked variability in global sea level and climate. Results were consistent for surveys of both common and rare taxa. Comparison of Pleistocene and modern community structure shows that Recent human impacts have changed coral community structure in ways not observed in the preceding 220 000 years.     

珊瑚礁生态修复研究进展

珊瑚礁生态系统有着很高的生物多样性和重要的生态功能。20世纪80年代以后全球范围内珊瑚礁的大面积退化引起了人们广泛的关注。简述了世界珊瑚礁资源现状,破坏原因,生态修复方法以及我国的珊瑚礁资源现状和修复策略等。国际上通用的生态修复策略主要是根据珊瑚的两种繁殖方式进行的,此外再配合人为的适度干扰,增加珊瑚的成活率。方法主要有：珊瑚移植、Gardening、人工渔礁、底质稳固、幼体附着等以及对相关利益者的宣传,海岸带的保护等。我国珊瑚礁退化严重,但是由于缺乏相关的科技资料报道和技术支持,缺乏系统的研究,使得珊瑚礁的生态修复成绩甚微,今后应在该领域开展更多的工作。     

An analysis of fish‐habitat associations on disturbed coral reefs: chaetodontid fishes in New Caledonia

A concordance analysis was used to study the simultaneous influence of several environmental data sets on chaetodontid (butterflyfish) distributions. This multivariate and multitable method enabled the correlation of three types of benthic characteristics (mineral substratum, coverage of structural species and large echinoderms) with butterflyfish abundances in two bays of the urban centre of Nouméa (New Caledonia). The first concordance axis was related to a gradient in the coverage of branching corals. This disturbance gradient compared damaged reef areas dominated by long‐spined sea urchins to areas with an extensive coverage of branching corals. The abundance of corallivorous chaetodontids was related to this gradient, supporting the view of corals as a food and shelter source for these fishes. The second concordance axis was interpreted as a gradient of heterogeneity in the coverage of benthic life‐forms. The abundance of omnivorous chaetodontids was related to this gradient. Thus, the concordance axes defined two key components of habitat structure that were related to the entire fish community structure.     

Structure of Caribbean coral reef communities across a large gradient of fish biomass

The collapse of Caribbean coral reefs has been attributed in part to historic overfishing, but whether fish assemblages can recover and how such recovery might affect the benthic reef community has not been tested across appropriate scales. We surveyed the biomass of reef communities across a range in fish abundance from 14 to 593 g m⁻², a gradient exceeding that of any previously reported for coral reefs. Increased fish biomass was correlated with an increased proportion of apex predators, which were abundant only inside large marine reserves. Increased herbivorous fish biomass was correlated with a decrease in fleshy algal biomass but corals have not yet recovered.     

Co-occurrence of herbivorous fish functional groups correlates with enhanced coral reef benthic state

Aim

Biodiversity loss is impacting essential ecosystem functions and services across the globe. Recently, our interest in the benefits of biodiversity for ecosystem function has shifted focus from measurements of species richness to functional diversity and composition. However, the additional importance of other community characteristics, such as species evenness and co-occurrence, for diversity-driven ecosystem function is less known. We used herbivorous coral reef fish as a model system to investigate how co-occurrence of different functional groups, rather than purely functional diversity, within an assemblage might affect the coral reef benthic state.

Location

Western Atlantic.

Time period

2007–2017.

Major taxa studied

Herbivorous reef fish.

Methods

We analysed benthic and fish assemblage data from 601 sites across 12 countries in the western Atlantic. Using diversity–interaction models, we investigated how the composition and relative abundances of reef fish functional groups were correlated with benthic cover and estimates of coral calcification rates. We used statistical interactions to explore the importance of co-occurrence of herbivorous fish functional groups for the coral reef benthic state.

Results

We found that co-occurrence of herbivorous fish functional groups, in addition to functional diversity, was correlated with reduced algal cover and increased coral accretion. Moreover, pairwise statistical interactions between functional groups were significantly correlated with an improvement in the coral reef benthic state.

Main conclusions

Our results support the idea that functional group co-occurrence, in addition to functional diversity, within herbivorous fish offers additional benefits to the coral reef benthic state. We identify farming damselfish and excavating parrotfish as potential key determinants of the coral reef benthic state and highlight that co-occurrence of cropping and scraping herbivores might promote coral accretion. Our findings support the argument that protecting herbivore abundance without regard to the species and functional groups present is not enough to preserve coral reef health and that fine-scale community composition must be considered.     

Flattening of Caribbean coral reefs: region-wide declines in architectural complexity

Coral reefs are rich in biodiversity, in large part because their highly complex architecture provides shelter and resources for a wide range of organisms. Recent rapid declines in hard coral cover have occurred across the Caribbean region, but the concomitant consequences for reef architecture have not been quantified on a large scale to date. We provide, to our knowledge, the first region-wide analysis of changes in reef architectural complexity, using nearly 500 surveys across 200 reefs, between 1969 and 2008. The architectural complexity of Caribbean reefs has declined nonlinearly with the near disappearance of the most complex reefs over the last 40 years. The flattening of Caribbean reefs was apparent by the early 1980s, followed by a period of stasis between 1985 and 1998 and then a resumption of the decline in complexity to the present. Rates of loss are similar on shallow (<6 m), mid-water (6–20 m) and deep (>20 m) reefs and are consistent across all five subregions. The temporal pattern of declining architecture coincides with key events in recent Caribbean ecological history: the loss of structurally complex Acropora corals, the mass mortality of the grazing urchin Diadema antillarum and the 1998 El Nino Southern Oscillation-induced worldwide coral bleaching event. The consistently low estimates of current architectural complexity suggest regional-scale degradation and homogenization of reef structure. The widespread loss of architectural complexity is likely to have serious consequences for reef biodiversity, ecosystem functioning and associated environmental services.     

Island biogeography of Caribbean coral reef fish

Aim The goal of our study was to test fundamental predictions of biogeographical theories in tropical reef fish assemblages, in particular relationships between fish species richness and island area, isolation and oceanographic variables (temperature and productivity) in the insular Caribbean. These analyses complement an analogous and more voluminous body of work from the tropical Indo‐Pacific. The Caribbean is more limited in area with smaller inter‐island distances than the Indo‐Pacific, providing a unique context to consider fundamental processes likely to affect richness patterns of reef fish. Location Caribbean Sea. Methods We compiled a set of data describing reef‐associated fish assemblages from 24 island nations across the Caribbean Sea, representing a wide range of isolation and varying in land area from 53 to 110,860 km². Regression‐based analyses compared the univariate and combined effects of island‐specific physical predictors on fish species richness. Results We found that diversity of reef‐associated fishes increases strongly with increasing island area and with decreasing isolation. Richness also increases with increasing nearshore productivity. Analyses of various subsets of the entire data set reveal the robustness of the richness data and biogeographical patterns. Main conclusions Within the relatively small and densely packed Caribbean basin, fish species richness fits the classical species–area relationship. Richness also was related negatively to isolation, suggesting direct effects of dispersal limitation in community assembly. Because oceanic productivity was correlated with isolation, however, the related effects of system‐wide productivity on richness cannot be disentangled. These results highlight fundamental mechanisms that underlie spatial patterns of biodiversity among Caribbean coral reefs, and which are probably also are functioning in the more widespread and heterogeneous reefs of the Indo‐Pacific.     

西沙珊瑚礁生态系统完整性评价与动态仿真模拟研究

以中国西沙珊瑚礁生态监控区为例,从生态系统完整性视角出发,结合珊瑚礁功能群组与环境变化的多重反馈效应,运用系统动力学方法构建了西沙珊瑚礁生态系统动态诊断模型,并通过基础情景和典型干扰情景（捕捞活动、陆源沉积、长棘海星（Acanthaster planci）暴发）的模拟过程,分析该生态监控区2010-2050年生态系统完整性的发展趋势及演变机理。结果显示：（1）系统动力学与生态系统完整性评价方法的整合,为珊瑚礁生态系统完整性的定量研究提供了一种可行性的方法;（2）珊瑚礁生态系统各效应指数中累积效应的变化最为明显,2010-2050年指数最大增长17.2,年均增长率约为1.2%,综合完整性指数在波动变化中稳步上升,珊瑚礁受损程度由中受损向中、低受损转变;（3）不同状态的珊瑚礁生态系统完整性,在其演化的不同阶段各有差异性,并且这种差异通常随时间推移才逐渐放大;（4）无论何种情景下,珊瑚礁生态系统都具有一定的恢复能力,尤其处于系统演化的释放重组阶段（2035-2040年）,生态系统的不稳定将创造了一定的可恢复性。研究结果对于分析西沙珊瑚礁生态系统的整体演化过程提供了理论借鉴,也为我国后续的珊瑚礁生态系统适应性修复理论模式研究提供了重要的基础。     

Macroalgae exhibit diverse responses to human disturbances on coral reefs

Scientists and managers rely on indicator taxa such as coral and macroalgal cover to evaluate the effects of human disturbance on coral reefs, often assuming a universally positive relationship between local human disturbance and macroalgae. Despite evidence that macroalgae respond to local stressors in diverse ways, there have been few efforts to evaluate relationships between specific macroalgae taxa and local human-driven disturbance. Using genus-level monitoring data from 1205 sites in the Indian and Pacific Oceans, we assess whether macroalgae percent cover correlates with local human disturbance while accounting for factors that could obscure or confound relationships. Assessing macroalgae at genus level revealed that no genera were positively correlated with all human disturbance metrics. Instead, we found relationships between the division or genera of algae and specific human disturbances that were not detectable when pooling taxa into a single functional category, which is common to many analyses. The convention to use percent cover of macroalgae as an indication of local human disturbance therefore likely obscures signatures of local anthropogenic threats to reefs. Our limited understanding of relationships between human disturbance, macroalgae taxa, and their responses to human disturbances impedes the ability to diagnose and respond appropriately to these threats.     

Black reefs: iron-induced phase shifts on coral reefs

The Line Islands are calcium carbonate coral reef platforms located in iron-poor regions of the central Pacific. Natural terrestrial run-off of iron is non-existent and aerial deposition is extremely low. However, a number of ship groundings have occurred on these atolls. The reefs surrounding the shipwreck debris are characterized by high benthic cover of turf algae, macroalgae, cyanobacterial mats and corallimorphs, as well as particulate-laden, cloudy water. These sites also have very low coral and crustose coralline algal cover and are call black reefs because of the dark-colored benthic community and reduced clarity of the overlying water column. Here we use a combination of benthic surveys, chemistry, metagenomics and microcosms to investigate if and how shipwrecks initiate and maintain black reefs. Comparative surveys show that the live coral cover was reduced from 40 to 60% to <10% on black reefs on Millennium, Tabuaeran and Kingman. These three sites are relatively large (>0.75 km²). The phase shift occurs rapidly; the Kingman black reef formed within 3 years of the ship grounding. Iron concentrations in algae tissue from the Millennium black reef site were six times higher than in algae collected from reference sites. Metagenomic sequencing of the Millennium Atoll black reef-associated microbial community was enriched in iron-associated virulence genes and known pathogens. Microcosm experiments showed that corals were killed by black reef rubble through microbial activity. Together these results demonstrate that shipwrecks and their associated iron pose significant threats to coral reefs in iron-limited regions.     

南海主要珊瑚礁水域的鱼类物种多样性研究

根据2004年5–7月和2005年3–4月采用深水三重刺网在南海的羚羊礁、华光礁、银砾滩、东岛、滨湄滩、排洪滩、本固暗沙、比微暗沙、武勇暗沙、海鸠暗沙、双子群礁、中业群礁、鲎藤礁、美济礁、仁爱礁、仙宾礁、南方浅滩、棕滩、大渊滩、永署礁、南薰礁、牛轭礁、道明群礁等23座主要珊瑚礁过渡性水域进行的2个航次专业调查资料, 分析了南海主要珊瑚礁水域的鱼类种类组成和群落特征。结果表明, 在珊瑚礁水域软骨鱼类以真鲨目和鲼目的种类数占优势, 硬骨鱼类以鲈形目和鲀形目的种类数占优势。相对重要指数(IRI)大于500的鱼类定为优势种, 西沙群岛有5种, 分别为迈氏条尾魟(Taeniura meyeni)、长吻裸颊鲷(Lethrinus miniatus)、胡椒鲷(Plectorhinchus pictus)、黄斑胡椒鲷(P. flavomaculatus)和灰六鳃鲨(Hexanchus griseus); 中沙群岛有6种, 分别为黄斑胡椒鲷、迈氏条尾魟、圆燕鱼(Platax orbicularis)、密斑刺鲀(Dioson hystrix)、红裸颊鲷(Lethrinus rubrioperculatus)和胡椒鲷; 南沙群岛有3种, 分别为黑梢真鲨(Carcharhinus limbatus)、灰三齿鲨(Triaenodon obesus)和星点鲹(Caranx stellatus)。针对南海珊瑚礁水域鱼类个体大小悬殊的特点, 本文分别以个体数和生物量为基础计算该水域的Margalef丰富度指数、Shannon-Wiener多样性指数、Simpson多样性指数和Pielou均匀度指数。物种组成的区域差异分析结果表明, 各珊瑚礁水域的鱼类物种无论与南海北部陆架海域还是与南沙西南陆架区相比都有明显的差异, 而属于相同生境类型水域的鱼类物种相似性较高。     

Population structure and connectivity of the mountainous star coral,Orbicella faveolata,throughout the wider Caribbean region

As coral reefs continue to decline worldwide, it becomes ever more necessary to understand the connectivity between coral populations to develop efficient management strategies facilitating survival and adaptation of coral reefs in the future. Orbicella faveolata is one of the most important reef‐building corals in the Caribbean and has recently experienced severe population reductions. Here, we utilize a panel of nine microsatellite loci to evaluate the genetic structure of O. faveolata and to infer connectivity across ten sites spanning the wider Caribbean region. Populations are generally well‐mixed throughout the basin (F_ST = 0.038), although notable patterns of substructure arise at local and regional scales. Eastern and western populations appear segregated with a genetic break around the Mona Passage in the north, as has been shown previously in other species; however, we find evidence for significant connectivity between Curaçao and Mexico, suggesting that the southern margin of this barrier is permeable to dispersal. Our results also identify a strong genetic break within the Mesoamerican Barrier Reef System associated with complex oceanographic patterns that promote larval retention in southern Belize. Additionally, the diverse genetic signature at Flower Garden Banks suggests its possible function as a downstream genetic sink. The findings reported here are relevant to the ongoing conservation efforts for this important and threatened species, and contribute to the growing understanding of large‐scale coral reef connectivity throughout the wider Caribbean.     

珊瑚礁生态系统病毒研究进展

病毒对珊瑚礁生态系统中的生物进化、生物地球化学循环、珊瑚疾病等方面具有重要的生态影响。随着珊瑚礁的全球性退化,病毒在珊瑚礁生态系统中的功能与危害日益显现。综述了珊瑚礁生态系统中病毒的研究现状与进展,包括：（1）珊瑚礁病毒的多样性与分布特征（水体、宿主、核心病毒组）;（2）珊瑚礁病毒的生态功能（感染方式、促进生物进化、生物地球化学循环）;（3）珊瑚礁病毒对全球气候变化的响应（热压力、珊瑚疾病）。总体而言,珊瑚礁生态系统具有极高的病毒多样性,所发现的60个科占已知所有病毒科数量的58%。珊瑚的核心病毒组主要由双链DNA病毒、单链DNA病毒、单链逆转录病毒所组成,珊瑚黏液层对病毒具有富集作用。"Piggyback-the-Winner"（依附-胜利）是病毒在珊瑚礁中主要的生物动力学模式,其可通过水平基因迁移的方式促进礁区生物进化。病毒可通过裂解细菌与浮游藻类的途径参与珊瑚礁的生物地球化学循环,尤其是碳循环与氮循环过程。此外,病毒还具有介导珊瑚热白化与直接引发珊瑚疾病的能力,这会影响珊瑚礁生态系统应对气候变化的适应性与恢复力。基于国际上的研究进展综述,结合南海珊瑚礁生态现状提出以下研究方向,以期促进我国珊瑚礁病毒学的发展：（1）开展南海珊瑚礁中病毒多样性的识别及其时-空分布特征研究;（2）探索病毒对南海珊瑚热白化、珊瑚疾病的介导作用及其与气候变化的关系;（3）揭示病毒对南海珊瑚礁生物地球化学循环的贡献。     

Global change and coral reefs: impacts on reefs, economies and human cultures

Coral reefs have reconstituted themselves after previous large sea-level variations, and climate changes. For the past 6000 years of unusually stable sea-level, reefs have grown without serious interruptions. During recent decades, however, new stresses threaten localized devastation of many reefs. A new period of global climate change is occurring, stimulated by anthropogenic increases in greenhouse gases. Coral reefs will cope well with predicted sea-level rises of 4.5 cm per decade, but reef islands will not. Higher sea levels will provide corals with greater room for growth across reef flats, but there are no foreseeable mechanisms for reef island growth to keep pace with sea-level rise, therefore many low islands may ultimately become uninhabitable. Climate change will introduce localized variations in weather patterns, but changes to individual reefs cannot be predicted. Reefs on average should cope well with regional climate change, as they have coped with similar previous fluctuations. Air temperature increases of 0.2–0.3 °C/decade will induce slower increases in sea-surface temperatures, which may cause localized, or regional increases in coral bleaching. Changes in rainfall will impact on reefs near land masses. Likewise, increased storms and variations in El Nino Southern Oscillation (ENSO) may stress some reefs, but not others. The greatest impact of climate change will be a synergistic enhancement of direct anthropogenic stresses (excessive sediment and pollution from the land; over-fishing, especially via destructive methods; mining of coral rock and sand; and engineering modifications), which currently cause most damage to coral reefs. Many of the world's reefs have been degraded and more will be damaged as anthropogenic impacts increase under the ‘demophoric’ increases in population (demos) and economic (phoric) activity. This biotic and habitat loss will result in severe economic and social losses. Reefs, however, have considerable recovery powers and losses can be minimized by effective management of direct human impacts and reducing indirect threats of global climate change.