Look Out Below! Impacts of Recreational Divers on Coral Reefs

This is the second instalment of a series of environmentally-themed pieces submitted by doctoral researchers at the University of Michigan. This collaboration between the University of Michigan and University of Edinburgh began when a professor at the University of Michigan forwarded a link to the IANS blog, along with the opportunity to connect with its editors, to PhD students in Michigan's School of Natural Resources and Environment. After an initial meeting over Skype, two of Michigan's doctoral students were lucky enough to jet over to Edinburgh and participate in a lovely weekend workshop with IANS' staff. From there, the collaboration was born!

By Joseph R. Krieger (Contributor)

Ecotourism has been defined as “responsible travel to fragile, pristine, and usually protected areas that strive to be low impact and small scale” [1]. Its purpose is to “educate the traveler, provide funds for ecological conservation, directly benefit the economic development and political empowerment of local communities, and foster respect for different cultures and for human rights” [1]. Ecotourism typically focuses on volunteering and environmental responsibility, centering on travel to destinations where flora and fauna are the primary attractions. A main goal of ecotourism is to offer tourists a look into the impact of human beings on the environment, and to inspire a greater understanding and respect for natural habitats. Therefore, in addition to evaluation of natural environments, an integral part of ecotourism is the promotion of recycling, energy efficiency, water conservation, and creation of economic opportunities for local communities. For these reasons, ecotourism often appeals to environmental and social responsibility organizations.

Ecotourism has been promoted especially on coral reefs which are among the most beautiful and ecologically diverse ecosystems in the world. They occur predominately in tropical and subtropical coastal waters, providing a complex and unique environment for millions of organisms. Coral reefs are also a vital economic and commercial resource that have been over utilized and undermanaged in many countries. Due to their locations at appealing sites with tropical allure, coral reef ecosystems attract millions of visitors annually, contributing to their rapid decline. It has been estimated that as much as 5% of worldwide live coral cover has already been lost [2] and that some areas have lost as much as 80% live coral cover as a consequence of both natural and anthropogenic influences. If current human impacts are left unchecked, coral reef ecosystems are in danger of global collapse.

Within the diversity of activities that range from conventional tourism to ecotourism, there has been much disagreement as to the levels of biodiversity preservation and environmental impact that can be included in ecotourism. For this reason, environmentalists, special interest groups, and governments define ecotourism differently. Nature tourism, low impact tourism, green tourism, bio-tourism, ecologically responsible tourism, and others terms have been used in the literature and in marketing, although they are not necessary synonymous with ecotourism. Environmental organizations have insisted that ecotourism should be conservation supporting, sustainably managed, nature-based, and environmentally educated while the tourist industry and many governments focus primarily on the product aspect, treating ecotourism as any sort of tourism based in nature. 

Although ecotourism is one of the fastest-growing sectors of the tourism industry, growing annually by 10-15% worldwide [3], many ecotourism projects fail to meet self proclaimed standards of integrity. While ecotourists claim to be educationally motivated and environmentally concerned, they rarely understand the ecological consequences of their visits and how their day-to-day activities impact the environment.

Coral reefs experience periodic stresses from many natural factors including storms that cause coral fragmentation and abrasion. River and land sediment run-off also cause stress to reef ecosystems by reducing water clarity and the amount of light available to the photosynthetic algae that are symbiotic in coral tissues. Increased sedimentation on the coral reef surface can lead to reduced rates of feeding and recruitment by corals. Naturally occurring coral diseases including black band disease and white pox have also been responsible for killing corals, especially in the Caribbean Sea. Various coral-eating fishes such as parrot fish (Sparisoma) bite off chunks of coral, not only causing damage by predation and but also physically contacting reefs, causing corals to fracture. One of the most widely-publicized examples of biological stress to coral reefs is predation by the crown-of-thorns sea star, Acanthaster planci. This sea star feeds on the tiny coral polyps which comprise reefs, and has had a tremendous impact on areas of the Great Barrier Reef. As coral systems are able to withstand such a barrage of natural stressors, it is possible to assume that introducing “eco-friendly” managed businesses and tourist activities would result in relatively inconsequential negative impacts. Unfortunately this is not typically the case.

Coastal development has had severe negative impacts on coral reef ecosystems. Human population increases near coral reefs cause pollutants to enter local water systems. Increased river-runoff that contains chemicals (nitrogen and phosphorous from fertilizer) and sediment (from exposed soils) have resulted in increases in coral bleaching events. These processes, and other, have let to 87% of the corals in inshore areas of the Great Barrier Reef becoming bleached to at least some extent, compared to 28% in offshore areas [4]. Increases in river-runoff pollutants also parallel increases in algal biomass along coastal areas. Some macroalgae compete for the hard substrate that new corals need to colonize [5]. These algae out-compete colonizing corals, thus limiting the reef’s ability to grow and recover from damage.

Of all the ways previously discussed in which human’s physically impact and interact with reefs, recreational SCUBA diving is the most direct. Because of this, regulation of diver behavior on reefs is of the utmost importance. Although SCUBA diving is promoted as a true “ecotourist” activity, recreational divers are known to cause extensive negative impacts on coral reef ecosystems. Divers in the Red Sea were observed to contact live coral substrate as many as 25 times during a 45 minute dive [6]. While this number may seem small by itself, when this contact rate is multiplied with the 250,000-300,000 divers that visit this reef area in a single year, the resulting contact rate per reef area is staggering. While each contact between diver and coral does not necessarily lead to the death of the coral, it contributes to an overall deterioration in coral health.

The majority (as much as 80%) of diver-coral contacts are unintentional [7]. Such contacts typically arise from the inexperience of the diver and/ or a lack of understanding that their actions can cause harm to corals. Addressing this issue is the responsibility of the local governments and dive agencies or businesses that establish the facilities and programs whereby divers are able to visit these reefs.

Efforts by coral reef managers to reduce diver-coral contact have produced mixed results. The most common form of contact prevention is short briefings that are given by dive shop personnel in an effort to raise reef awareness. These briefings were designed to teach proper reef etiquette to divers and to help reduce unintentional contacts. However, not all management facilities administer these briefings and of those that do, many vary in length and detail and have varying effects on diver behavior. To date, the greatest deterrent to diver damage appears to be direct intervention by underwater dive guides, which has been observed to reduce diver-coral contact rates from 11.6 to 2.4 contacts per 40-min dive in some systems (Barker and Roberts 2004).

However, a review of studies examining the impacts of divers on corals worldwide, including in the Great Barrier Reef in Australia [8,9], the northern Red Sea [5,10] and the Mesoamerican Reef in the Caribbean Sea [11], suggest that in the current age of rapidly increasing issues in biological conservation, there is expanding public pressure to reduce activities that clearly harm the environment. The market for products harvested by sustainable means has never been greater [12]. This has created momentum for environmental movements such as REEF (Reef Environmental Education Foundation, www.reef.org) to push for more sustainable diving practices. Increased diver demand for conservation-orientated diving operations is expected to encourage more dive shops to incorporate conservation principles into their existing operational procedures, creating a positive feedback loop that enhances both the knowledge and implementation of coral reef conservation.

An additional incentive for improved management practices emphasizes the importance of dive-based recreational tourism on local economies. The natural diversity (fishes, marine mammals) and aesthetic appearance (reef coral condition) of local reef dive sites represent important natural resources for the recreational diving industry. Several studies have demonstrated that dive quality and natural experience, in terms of the quality and quantity of marine life, are important factors that divers consider when selecting recreational diving sites [13,14,15]. While some studies have proposed that divers merely seek destinations with warm clear waters [10], others have found that divers care about the quality of the reefs they visit16, and are willing to pay more to visit healthier looking reefs [17,18].

These new trends in consumer – resource relationships have led to improved natural systems in locations such as Kenya, Alaska, and Yellowstone National Park [19]. As coral reef resources continue to be degraded by changes in global climate conditions, it can be hoped that mitigation of direct- diver impacts worldwide will lead to parallel improvements in these natural systems which may help to offset some of these devastating effects.


Joe is a PhD candidate at SNRE whose research focuses on both fisheries management practices and species-environmental connectivity in aquatic ecosystems. His dissertation examines early-life stage traits and behavior of lake sturgeon in the Great Lakes Basin, and looks to identify impediments to restoration and successful management of this threatened species. Joe has a bachelors in biology from Central Michigan University and a master’s in marine biology from Auburn University. 

[1] Honey, M. 1999. Ecotourism and Sustainable Development. Who owns paradise? 2nd Edition, Washington D.C. Island Press. p. 33.

[2] Wilkinson, C., 2004. Status of Coral Reefs of the World: 2004. Australian Institute of Marine Science.

[3] Weaver , D. B., and Lawton, L. J. 2007. Twenty years on: The state of contemporary ecotourism research. Tourism Management 28, 1168-1179.

[4] Berkelmans, R. and Oliver, J.K. 1999. Large-scale bleaching of corals on the Great Barrier Reef. Coral Reefs 18, 55-60.

[5] Chadwick, N.E., and Morrow, K M. 2011. Competition Among Sessile Organisms on Coral Reefs. Pp. 347-371. In: Dubinsky, Z., and Stambler, N. (eds.). Coral Reefs: An Ecosystem in Transition. Springer, New York.

[6] Zakai, D., Chadwick- Furman, N. E., 2002. Impacts of intensive recreational diving on reef corals at Eilat, northern Red Sea. Biological Conservation 105, 179-187.

[7] Barker, N. H. L., Roberts, C. M., 2004. Scuba diver behaviour and the management of diving impacts on coral reefs. Biological Conservation 120, 481-489.

[8] Rouphael, A.B., Inglis, G.J., 1997. Impacts of Recreational SCUBA diving at sites with different reef topographies. Biological Conservation82, 329-336.

[9] Harriott, V. J., Davis, D., and Banks, S. A. 1997. Recreational diving and its impact in marine protected areas in Eastern Australia. Ambio 26, 173-179.

[10] Hawkins, J.P., Roberts, C.M., 1993. Effects of recreational SCUBA diving on coral reefs: trampling on reef-flat communities. Journal of Applied Ecology 20, 25-30.

[11] Gibson, J., McField, M., and Wells, S. 1998. Coral reef management in Belize: an approach through integrated coastal zone management. Ocean & Coastal Management 39,        229-244.

[12] Vermeir, I., Verbeke, W., 2006. Sustainable food consumption: Exploring the consumer “Attitude-Behavioral Intention” gap. Journal of Agricultural and Environmental Ethics 19, 169-194.

[13] Dixon, J. A., Sherman, P. B., 1991. Economics of Protected Areas: A New Look at Benefits and Costs. Earthscan, London.

[14] Kenchington, R. A., 1993. Tourism in coastal and marine environments – a recreational perspective. Ocean and Coastal Management 19, 1-16.

[15] Pendleton, L. H., 1994. Environmental quality and recreational demand in a Caribbean coral reef. Coastal Management 22, 399-404.

[16] Medio, D., Ormond, R. F. G., and Pearson, M. 1997. Effect of briefings on rates of damage to corals by SCUBA divers. Biological Conservation 79, 91-95.

[17] Schuhmann, P., Casey, J., Oxenford, H. A., 2008. The value of coral quality to SCUBA divers in Barbados. Proceedings of the Eleventh International Coral Reef Symposium, Ft. Lauderdale, FL.

[18] Wielgus, J., Chadwick-Furman, N. E., Dubinsky, Z., Schechter, M., Zeitouni, N. 2002. Dose-response modeling of recreationally important coral-reef attributes: a review and potential application to the economic valuation of damage. Coral Reefs 21, 253-259.

19. Eagles, P. F., and McCool, S. F. 2002. Tourism in national parks and protected areas: Planning and management. CABI.