Tourists Are Loving Hawaii’s Coral Reefs To Death

Millions of tourists visit Hawaii every year, but tragically, these tourists are damaging and destroying the very coral reefs they come to experience, which are already at high risk of global collapse

Tourists on Hanauma Bay, Oahu, Hawaii. (Credit: Rick Zhuang / CC BY-NC-ND 2.0)

Rick Zhuang via a Creative Commons license

Millions of tourists visit Hawaii every year, but tragically, these tourists are damaging and destroying these islands’ natural environment, particularly its coral reefs, according to a recent study.

A team of scientists led by Princeton University, in collaboration with Arizona State University (ASU), examined the local impacts of tourists on live coral cover. The scientists were limited in their investigations by the COVID lockdown, so they had to devise a different way to document where visitors were located. To do this, they searched out geotagged Instagram photographs from tourists visiting the Hawaiian reefs and found more than 250,000 images posted on the site between 2018 to 2021.

“They take pictures of the beaches, and they post on social media”, said Bing Lin, a PhD candidate in science, technology and environmental policy at Princeton University’s School of Public and International Affairs and lead author of the study. “Instagram is by far the main platform through which social media presence is documented, and so I came up with the idea of using Instagram to get a sense of a large-scale representation of where people are distributed in Hawaii.”

After collecting the Instagram tourist images, they then used Artificial Intelligence to analyze and compare them to aerial mapping images of Hawaii’s coral reefs that had a 2 meter (6.5 feet) resolution depth, or a 16 meter (52.5 feet) resolution depth provided by ASU scientists.

ASU researchers used high-resolution airborne mapping and a machine learning procedure to map the ... [+] Hawaiian sea floor. This image shows the ASU Global Airborne Observatory in action. (Image courtesy of ASU.)

Image courtesy of ASU

“We took the world’s first live coral maps and combined them with the power of social media and data analytics to derive wholly new information on the interaction between people and reefs”, said study co-author, Greg Asner, director of the ASU Center for Global Discovery and Conservation Science in the Julie Ann Wrigley Global Futures Laboratory.

“The results were astonishing to see at such a large geographic scale and yet also corroborative at the local scales in which some communities have voiced significant concern about coral reef tourism”, Professor Asner added.

Not surprisingly, Mr Lin and his collaborators found that sites with more live coral cover that were accessible to tourists were visited more often (Figure 1). Also not surprisingly, they found that the most popular tourist sites were more degraded compared to less popular sites.

“We were able to find that coral reefs not only played a really significant role in attracting tourism, but also that the tourism subsequently seemed to suppress live coral coverage at the sites in which tourism was most concentrated”, Mr Lin reported.

F I G U R E 1 | The relative distributions and drivers of on-reef and overall coastal visitation ... [+] across the main Hawaiian Islands. Top panels: relative coastal visitation intensities across the main Hawaiian islands, with the three most visited sites for overall and on-reef tourism labelled. Bottom panels: relative contributions of the most important variables associated with on-reef and overall coastal visitation based on random forest regression models, and their corresponding partial dependence plots. Error bars depict 95% CI of 100 bootstrap samples in the variable importance plots. Dotted lines depict partial dependencies, shaded regions depict 95% CI of 100 bootstrap samples, and blue lines depict LOESS smooth curves in the partial dependence plots. (doi:10.1038/s41893-022-01021-4)

doi:10.1038/s41893-022-01021-4

The data also showed that most visitors either stayed close to shore or remained on the beaches, whilst a smaller (but not insignificant) number of tourists went snorkelling or took scuba diving excursions that brought them into indirect and direct contact with more distant reefs. These interactions were obvious from the condition of the corals — the farther that the corals were from shore (and from the hoards of people), the better their health.

According to Mr Lin and his collaborators’ findings, the most degraded reefs on the island of Oahu were Waikīkī Beach, Waimea Bay, Lanikai Beach and Shark’s Cove. The Big Island also had several sites with heavily degraded reefs. These reefs are directly impacted by on-reef visitations and physical damages caused by recreating tourists, such as sitting or walking on corals or physically breaking them, Mr Lin told me in email. Damages and degradation to more distant reefs mostly come from diver contact, when divers either intentionally or accidentally come into contact with corals.

Coral reefs are also indirectly impacted by local infrastructure development (especially hotels) and by the elevated levels of pollution created by the presence of so many people. One of the most common forms of localized pollution comes from the nearly universal use of sunscreens designed to prevent sunburn and skin cancer caused by strong ultraviolet (UV) sunlight radiation (ref & ref). Sunscreens rinse off into water when people go swimming or wading, and can also enter waterways through wastewater, particularly from bathing or showering. The active ingredients in sunscreens that reduce the amount of UV radiation on the skin have been detected in the water, sediment, and animal tissues in aquatic environments, but scientists are still intensively investigating what the consequences of these chemical pollutants might be.

High-rise hotels on the beach in Hawaii. (Credit: Jess Loiterton / CC BY)

Jess Loiterton via a Creative Commons license

“Local stressors to the world’s reefs are often overshadowed by the large, looming threat of global climate change and subsequent coral bleaching”, Mr Lin pointed out. “However, our research underscores the importance of localized stressors in also contributing to coral decline.”

In addition to drawing millions of visitors every year, creating millions of local jobs and generating billions of dollars in tourism revenues, coral reefs are important ecosystems that are vital to protecting coastlines by mitigating storm waves as well as providing a home to a number of economically valuable marine fisheries and safeguarding an astonishing variety of marine biodiversity.

Various fish including bigscale soldierfish / 'ū'ū (Myripristis berndti), Moorish idols / kihikihi ... [+] (Zanclus cornutus), and a masked angelfish (Genicanthus personatus) swim in a small outcropping of coral on a reef in Papahānaumokuākea Marine National Monument. (Credit: Andrew Gray / NOAA / CC BY-NC 2.0)

Andrew Gray / NOAA via a Creative Commons license

For these reasons, establishing strong local reef-protecting policies and coral restoration efforts could become common practices, especially at popular tourist sites in Hawaii and elsewhere. We already know that reef visitation is higher when the reef is healthy, the water is clean and the site is easily accessible. Thus, promoting stronger coastal management practices can simultaneously benefit both coastal ecology and conservation as well as enhance the revenues generated from tourism.

“Coastal tourism is a multibillion-dollar industry and will increasingly feature in the future use of marine resources”, Mr Lin told me in email. “It is only through an adequate understanding of tourism’s large-scale impacts on reef ecosystems that we can appropriately pinpoint pathways to make it more sustainable.”

Bing Lin, Yiwen Zeng, Gregory P. Asner and David S. Wilcove (2023). Coral reefs and coastal tourism in Hawaii, Nature Sustainability | doi:10.1038/s41893-022-01021-4

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