A Global Assessment of Human Eäects on Coral Reefs
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Marine Pollution Bulletin Vol. 38, No. 5, pp. 345±355, 1999 Ó 1999 Elsevier Science Ltd. All rights reserved Printed in Great Britain PII: S0025-326X(99)00002-8 0025-326X/99 $ ± see front matter A Global Assessment of Human Eects on Coral Reefs G. HODGSON Institute for Environment and Sustainable Development, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, People's Republic of China Coral reefs have been used by humans as recreation areas awareness among coral reef scientists about the need for and as a source of food and other products for thousands a global assessment of coral reef health. Participants of years. The eects of humans on coral reefs are not well concluded that, ``The data base for evaluating the con- understood, especially on a regional or global scale. A dition of the worldÕs reefs is quite inadequate.'' The special survey protocol called ``Reef Check'' was designed reasons: too few coral reef scientists who spend too little to be used by volunteer recreational divers, trained and led time on reefs, and who use dozens of dierent methods by marine scientists, and based on the use of high value, to study diverse research topics ± many unrelated to reef easily identi®ed indicator organisms. During a period of health. There are few cases of long-term studies of the 2.5 months, a global survey of over 300 reefs in 31 same reef, and the use of one method to study many countries and territories indicates that few reefs remain reefs is rare. The Colloquium participants concluded unaected by man, even very remote sites. Over®shing has that, ``There is an urgent need to provide a compre- reduced ®sh and invertebrate indicator organisms to low hensive assessment of reefs ...'' A new approach was levels at most reefs, including those within marine pro- needed that would provide a sucient ``snapshot'' of tected areas. The ratio of live to dead coral cover was information about an individual reef to judge its status, higher in the Red Sea than in other regions, indicating that and would allow each reef to be compared with others in reef corals are in the best condition there. In future years, the region and around the world on an annual basis. by increasing the number of reefs and the frequency of Many traditional studies of reefs have been designed surveys, the Reef Check program could provide a valuable with a relatively narrow focus on either ®sh or hard method to detect broad-brush changes on a local, regional coral ecology, and have not captured sucient infor- and global scale, as well as increasing public support for mation about a broad suite of reef organisms to allow an coral reef conservation. Ó 1999 Elsevier Science Ltd. All interpretation of reef health. ``Coral reef health'' is a rights reserved general concept that refers to a balance in the ecosystem that may be shifted by e.g., disease or human activities. Keywords: reefs; ®sheries; marine ecology; global survey; The present survey attempts to de®ne objective measures human eects; conservation. of reef health based on the numbers of indicator or- ganisms and other parameters aected by human ac- For thousands of years, humans have gathered and tivities. ®shed for coral reef organisms for use as curios, jewelry, and food. More recently, exploitation of reefs has in- Methods creased as novel medicinal compounds have been ex- tracted and as reef-related tourism has expanded. In 1996, I designed a protocol to rapidly carry out the According to media reports, anecdotal accounts from ®rst global survey of coral reefs. The draft protocols scuba divers and published work of marine scientists were posted on the NOAA coral listserver in late 1996 from diverse locations around the world, increasing and criticism was invited. Following revision of the populations of humans have been damaging coral reefs protocols, a global survey program called ``Reef Check'' at an unprecedented rate (Luchavez and Alcala, 1988; was advertised on the listserver, and about 40 pages of Wilkinson et al., 1993; Munro and Munro, 1994; Grigg detailed instructions were placed on a website and Birkeland, 1997). Despite the ecological and eco- (www.ust.hk/webrc/ReefCheck/reef.html) along with nomic importance of coral reefs, we have a poor un- an invitation to form survey teams. The basic concept derstanding of how this ecosystem responds to human was to create an international network of national, re- activities, particularly on a regional or global scale. gional and local coordinators who would be responsible The 1993 Colloquium on Global Aspects of Coral for all aspects of the surveys in their chosen area. All Reefs: Health, Hazards and History held at the Uni- surveys would be conducted using one set of methods versity of Miami was a critical turning point in raising during a period of 2.5 months and the data submitted to 345 Marine Pollution Bulletin the coordinating oce at the Hong Kong University of TABLE 1 Science and Technology. Reef check indicator organisms for over®shing (OF), dynamite ®shing (DF), cyanide ®shing (CF), aquarium ®sh ®shing (AF), pollution (PL) and curio collection (CR). Reef health indicators The framework for the survey methods was modeled Organism Indicator for after existing methods, such as (English et al., 1997). A OF DF CF AF PL CR major dierence, however, was that 25 worldwide and regional ``health indicators'' were initially chosen to World Lobster x provide information about the eects of human activi- Grouper (>30 cm) x x x ties such as cyanide ®shing, aquarium ®sh collection and Fleshy algae x harvesting of invertebrates. Primary criteria for selecting Hard coral x x Dead coral x x ``indicators'' were: (1) ease of ®eld identi®cation, (2) Sponge x high information content regarding reef health with re- Butter¯y ®sh x spect to anthropogenic eects such as pollution or direct Sweetlips ± Haemulidae x x x x harvest, and (3) a broad geographic distribution. For Indo-paci®c only several indicators, higher taxonomic categories such as Barrimundi cod x x x (Cromileptes altivelis) families were used, rather than species, to ensure accu- Humphead wrasse x x x rate identi®cation by non-specialists. Species were used (Cheilinus undulatus) only when they could be positively identi®ed due to a Bumphead parrot®sh x x x (Bolbometopon muricatum) distinctive shape and color. Edible indicators also gen- Giant clams x x erally have a high market value. For example, spiny (Tridacna spp.) lobster of the family Palinuridae, and the grouper family Trochus shells x (Trochus niloticus) Serranidae were chosen to be two of the eight worldwide Edible holothurians x indicators. For the purpose of selecting regional indi- (4 species) cators, the worldÕs oceans were divided into the Indo- Crown of thorns star®sh ? Õ (Acanthaster planci) paci®c, Red Sea and Caribbean regions. Due to Hawaii s Triton shell x unique ®sh fauna, several dierent indicators were (Charonia tritonis) needed, therefore Indo-paci®c regional analyses for ®sh Caribbean only Nassau Grouper x do not include Hawaiian data. An example of an Indo- (Epinephalus striatus) paci®c regional indicator is the distinctive humphead Snapper ± Lutjanidae x wrasse Cheilinus undulatus, a cyanide ®shing indicator. Parrot®sh (>20 cm) x Barracuda (>1 m) x This species is the preferred ®sh in restaurants in Hong Queen conch x x Kong and southern China where they sell for US$100 (Strombus gigas) per kg. To supply this market, diving ®shermen Helmet conch x x throughout the region use sodium cyanide to stun and (Cassis madagascariensus) capture live humpheads, the bigger the better (Johannes and Riepen, 1995). The full list of coral reef health in- dicators used in the survey is found in Table 1. questions about the biophysical aspects of each reef, as well as socioeconomic descriptors of human activities in Site selection the area, and space for anecdotal and historical back- Site selection was based on the goal of testing the null ground information. The reef sampling design was based hypothesis that reefs still exist that are not aected sig- on surveys of two depth contours, 3 and 10 m. At each ni®cantly by human activities. Teams were instructed to depth, one or more survey lines (transects) were placed survey outer slopes on exposed reefs that were consid- along the reef contour to obtain a total length of 100 m. ered to be the ÔbestÕ sites in their area ± those believed to The ®sh survey was carried out ®rst. Fish indicator taxa be least aected by human activities and having the were recorded along four 20 m long, 5 m wide belt highest percentage of the seabed covered by living hard transects (separated by 5 m gaps) for a survey area of 2 coral and the highest populations of indicator ®sh and 400 m at each depth (3 and 10 m). After the transects other invertebrates. Thus the surveys were intentionally were deployed, the ®sh survey was delayed for 15 min to biased towards reefs in relatively good condition. De- allow the ®sh to recover from any disturbance by divers. tailed questions about the type of reef were included so Fish were recorded within the belt transect for a period that post-processing could take such dierences into of 3 min at 5 m intervals. In some locations, coral reef account. was only found at one of the two depths ± so only one contour was surveyed. For some ®sh, size limits (see Survey protocol Table 1) were used to limit the work such that a team of The protocol included collection of four types of data: four divers could complete one survey per day, and to a site description; a ®sh survey, an invertebrate survey focus data collection on the ®sh sizes targeted by ®sh- and a substrate survey.