Importance of coral reefs to Guam

Figure 1: A photo of Tumon Bay and its hotels. Photo credit: Mari Deinhart.

Coral reefs are important to Guam for many reasons, but the primary reason is the protection of the island. Reefs help to protect the beaches that draw in local residents and tourists. They are a natural coastline protection against storm surges, coastal erosion, and high waves, especially during tsunamis, tropical storms, and typhoons. Coral reefs form a barrier that buffers coastal areas from severe weather events, protecting human lives, economic activities, and coastal properties.

During large storms, coral reefs can reduce the height of the waves by about half; without reefs, wave heights could be between four and 12 meters, but with reefs, wave height can be decreased to heights between two and six meters. Waves from typhoons can cause a lot of damage to homes and structures along Guam’s coastlines, such as hotels and businesses (Figure 1). But coral reefs help diminish wave energy, up to 90 percent during low tides, making them smaller and slower which can save up to $8 million yearly in damage costs.

Coral reefs are also important to Guam because they supply the fish that many people need, both culturally and for sustenance. Fishing has assisted CHamoru as well as immigrant cultures in maintaining a connection to the sea and its resources, by keeping maritime qualities of their traditional culture alive.

Fishing is culturally important to Guam because the fish are often caught for cultural events such as weddings, funerals, neighborhood parties, village fiestas, and church events. A survey showed that 65 percent of fishermen fish for enjoyment and because fishing emphasizes their cultural identity. More than half of fishermen surveyed said they fish for both sustenance and cultural reasons. Coral reefs also provide fish for sustenance; 18 percent of people fish to provide food for their family. Coral reefs provide a lot to Guam by supporting fishing for cultural and sustenance purposes.

Tourism on Guam

Tourism is important to the island of Guam. It is one of the largest industries on the island, representing over 50 percent of Guam’s economy, and bringing in over $1.5 billion to the economy annually (Guam Visitors Bureau, 2017). One out of three jobs on Guam is directly linked with the tourism industry. In 2016 alone, there were over 1.5 million visitors on Guam for both business and recreation. Many tourists come to Guam specifically for the beaches, coral reefs, and the outdoor activities available.

Around 28 percent of tourist revenue comes from coral reefs and other marine-based activities and depends on a healthy marine ecosystem. Tourist exit surveys show that 37 percent of visitors come to Guam for the “Sea, sun and sand,” five percent for scuba diving, and 15 percent for other water sports. Besides SCUBA diving, these other marine-based activities include snorkeling, kayaking, jet skiing, charter fishing, and wind surfing.

Direct impacts of tourism on coral reefs

Figure 2: Young snorkeler kicking corals with fin. Photo credit: David Burdick, Guam Reef Life.

Tourism can have large impacts on the health of coral reefs around the world. Coral reefs are impacted by tourists in both direct and indirect ways, and many of the direct impacts to corals are related to snorkelers and scuba divers. These direct impacts are often caused by fin strikes on corals, grabbing, kneeling, walking and standing on corals, and equipment striking corals (Figure 2).

Every year, approximately 300,000 dives are recorded in Guam; two-thirds of the dives being logged by tourists. On average, 10,000 people are diver-certified yearly, with half of the certifications being for entry-level divers. Beginner divers and snorkelers often cause most of the damage due to their inexperience and lack of education and awareness.

Beginning and inexperienced divers will follow the lead of their guide; however, many guides instruct divers to touch corals, often for pictures (Figure 3). Camera users can also cause higher amounts of damage because they kneel or hold on to corals while trying to take a picture. These occurrences often lead to coral breakage, physical injury, and death. In addition, injured corals are more susceptible to diseases.

Figure 3: A dive instructor teaching his students to touch and hold onto a coral colony. Photo credit: David Burdick, Guam Reef Life.

Tourists walking on seagrass beds can damage the seagrass beds and can affect coral reefs. Scuba divers and snorkelers often walk on seagrass beds to get out to the dive sites. This tends to uproot and break seagrass blades and may have long-term impacts such as a decrease in fish abundance and diversity. Many fish species use seagrass beds as nurseries for their larva, but with the damage done to seagrass beds, these fish species loose that protection for their young which can lead to a decrease in fish abundance and diversity.

Indirect impact of tourism on coral reefs

Tourism can also have indirect impacts on coral reefs. These indirect impacts can range from kicking up sediment, to feeding fish, to using toxic sunscreens. When sediment is kicked up it settles onto corals and leads to decreases in coral growth and reproduction, by forcing the corals to divert energy to the removal of sediment. Sediment can also block light from corals, smother live coral, and prevent larvae from settling onto hard substrates. These can lead to changes in the community structure of the coral reef.

Figure 4: Tourists feeding fish. Photo credit: David Burdick, Guam Reef Life.

Another indirect impact comes from fish feeding (Figure 4), which attracts fish for tourists to see. Fish are often fed foods that are not a part of their normal diets. This causes fish to stop doing their jobs on the reefs. An example would be parrotfish that eat algae; if they are being fed, they are less likely to scrape algae of corals, which can lead to algal overgrowth. This can have a negative impact on the coral reef ecosystem because algal overgrowth prevents new coral larvae from settling and changes the composition of the ecosystem. Fish feeding can also disrupt normal distribution of fish, or even cause them to exhibit abnormal aggression. The fish may come to expect food from humans and may display aggressive behavior when not fed.

Another indirect impact to coral reefs comes from sunscreens. Sunscreen washes off during water activities and the chemical from these sunscreens has led to sunscreen pollution in nearly 10 percent of coral reefs globally. Sunscreens have negatively impacted corals in a variety of ways such as increasing risk of viral infections, killing coral larvae, and worsening coral bleaching. A higher concentration of tourists in one location can increase the impacts seen by sunscreen pollution.

What can be done?

There are a variety of ways to help minimize the impacts of tourism on coral reefs. One way is to include the tourism industry in the development of sustainable coral reef management. This causes the industry to have a bigger investment in managing a resource it depends on. There can also be fees for snorkeling and scuba diving that go directly to the management and protection of coral reefs. The easiest way to help lessen tourism impacts on coral reefs is to increase snorkeler and diver education. This can be done by dive shops by giving a short information session to divers before they go into the water. Dive guides can also lead by example and even intervene underwater if they see divers or snorkelers damaging the corals or feeding fish.

How can you help?

You can also help to minimize your impact on coral reefs. You can wear reef-safe sunscreens or even limit the use of sunscreens by wearing more sun-protective clothing. It can also help to minimize damage if you become more aware of where you are walking and what you may be walking on when in the water. If you careful to walk through areas where there is no seagrass or coral, then that greatly reduces coral damage. Another way to reduce damage is by practicing your diving and snorkeling skills as much as possible, since beginner and inexperienced divers often cause the most damage. This makes you less likely to strike or damage corals. One final way to minimize our impacts is to just learn more about the things we want to see. Tourism can have negative impacts on coral reefs, but with good management and willingness of people to help, then the impacts can be lessened or even negated.

For more information on store-bought reef or homemade reef safe sunscreens, follow the links below.

Reef safe sunscreen brands

Homemade reef safe sunscreens

About the author

Kelsie Ebeling-Whited was a master’s student with the University of Guam Marine Laboratory. She graduated in 2020. Her thesis was “Mating Success of the Six-Bar Wrasse (Thalassoma Hardwicke, Labridae) Utilizing Two Mating Strategies.”

Editor’s note

This author was a beginning graduate student in 2018 taking a course in scientific writing at the University of Guam. This article was assigned to provide the student with practice in communicating science to non-scientists. The student chose the topic  which is related either to their thesis project or work experience. The instructor in the course is Dr. Laurie Raymundo, a UOG Marine Laboratory faculty member.

For further reading

Allen, Stewart D., and Paul Bartram. Guam as a fishing community. Administrative Report H-08-01. Honolulu: Pacific Islands Fisheries Science Center, 2008.

Barker, Nola H.L., and Callum M. Roberts. “Scuba diver behavior and the management of diving impacts on coral reefs.” Biological Conservation 120, no. 4 (2004): 481-489.

Diaz-Pulido, Guillermo, Laurence J. McCook, Sophie Dove, Ray Berkelmans, George Roff, David. I. Kline, Scarla Weeks, Richard D. Evans, David H. Williamson, and Ove Hoegh-Guldberg. “Doom and boom on a resilient reef: Climate change, algal overgrowth, and coral recovery.” PLOS One 4, no. 4 (2009): 1-9.

Burdick, David. “Diver/snorkeler impacts.” Guam Reef Life, 2017.

Guam Visitors Bureau. Guam Tourism Strategic Plan 2020. Tumon: Guam Visitors Bureau, 2014.

Hannak, Judith S., Sarah Kompatscher, Michael Stachowitsch, and Jürgen Herler. “Snorkeling and Trampling in Shallow-water Fringing Reefs: Risk Assessment and Proposed Management Strategy.” Journal of Environmental Management 92, no. 10 (2011): 2723-2733.

Lamb, Joleah B., James D. True, Srisakul Piromvaragorn, and Bette L. Willis. “Scuba diving damage and intensity of tourist activities increases coral disease prevalence.” Biological Conservation 178, (2014): 88-96.

McCoshum, Shaun M., Alicia M. Schlarb, and Kristen A. Baum. “Direct and indirect effects of sunscreen exposure for reef biota.” Hydrobiologia 776, (2016): 139-146.

Pascal, Nicolas, Michel Allenbach, Angelique Brathwaite, Lauretta Burke, Guillaume Le Port, and Eric Clua. “Economic valuation of coral reef ecosystem service of coastal protection: A pragmatic approach.” Ecosystem Services 21, A (2016): 72-80.

Porter, Val, Trina Leberer, Mike Gawel, Jay Gutierrez, David Burdick, Victor Torres, and Evangeline Lujan. Status of the Coral Reef Ecosystems of Guam. Technical Report No. 113. Mangilao: Marine Laboratory, University of Guam, 2005.

van Beukering, Pieter, Wolfgang Haider, Margo Longland, Herman Cesar, Joel Sablan, Sonia Shjegstad, Ben Beardmore, Yi Liu, and Grace Omega Garces. The Economic Value of Guam’s Coral Reefs. Technical Report No. 116. Mangilao: Marine Laboratory, University of Guam, 2007.

Williamson, Jane E., Evan E. Byrnes, Jennalee A. Clark, David M. Connolly, Sabine E. Schiller, Jessica A. Thompson, Louise Tosetto, Julieta C. Martinelli, and Vincent Raoult. “Ecological impacts and management implications of reef walking on a tropical reef flat community.” Marine Pollution Bulletin 114, no. 2 (2017): 742-750.

Wilson, Scott P., and Krista M. Verlis. “The ugly face of tourism: Marine debris pollution linked to visitation in the southern Great Barrier Reef, Australia.” Marine Pollution Bulletin 117, no. 1-2 (2017): 239-246.