The University of Hawai‘i collaborated with Stanford University, Stockholm Resilience Center, National Oceanic and Atmospheric Administration (NOAA), and other institutions to map the impact of human activities and natural events in slowing reef recovery after severe coral bleaching in the main Hawaiian Islands. The study accumulated 10-years worth of data to show an assessment of reef health and its implications.
What are coral reefs and why do they matter?
According to NOAA, coral reefs are colossal constructions made of limestones deposited by coral polyps. Covering only 0.1 percent of the sea floor, coral reefs protects an amalgam of 4,000 species of fish, 700 species of coral, and thousands of other plants and animals. Also, approximately 25% of all marine life relies on them. However, coral reefs face an increasing array of threats, including pollution, unsustainable fishing practices, and global climate change all driven by human activities.
Dr. Sarah Allen, Director of the First-Year Writing and Mentoring Programs and an Associate Professor in the English Department at the University of Hawaiʻi at Mānoa, who is currently teaching Rhetoric and Environmental Justice said, “I don’t think the importance of the coral reefs—
to Hawai’i, to the world—can be overstated. Half a billion people rely on reefs for food.”
What is coral bleaching and why should we care?
The Ocean Agency defines coral bleaching as the discoloration of corals and turn white. This phenomenon happens when the corals become stressed due to the rising water temperature and excessive exposure to sunlight. Allen stated that “looking at expansive images of bleached and dead coral, the devastation is heart-breaking and alarming.”
The first global bleaching event happened in 1998 when am expansive underwater heatwave exterminated 16% of the corals across the globe. The second global bleaching occurred in 2010 and according to NOAA, the third global bleaching event has been ongoing for three years since October 2015 and has already become the longest event recorded. As a result of coral bleaching, the livelihoods of 500 million people and income worth over $30 billion are at stake.
“We’re seeing bleaching on a global scale. Worse, this isn’t about the diminishment and death of a single species; the death of coral means the death of the many species who rely on the reefs for food,” added Allen.
What are tipping points and why do they matter?
According to the Pacific Islands Ocean Observing System (PacIOOS), tipping points are caused by human pressures and environmental conditions that change an ecosystem that may be difficult or impossible to reverse. One of the goals of the collaborative study is to further provide the need to research and raise awareness to scientist and policymakers around the world.
The study of coral reefs in Hawai‘i and why is it important?
The team of Ocean Tipping Points examined reef tipping points in the main Hawaiian Islands having diverse reefs structure, appearance, and sensitivities. According to PacIOOS, this variety means that resilient reefs do not all look similar, and the level of stressors that trigger “tipping” will differ among the reefs. The team stressed that once a tipping point has been crossed, reef recovery can be costly and lengthy. In Kāne‘ohe Bay and Maunalua Bay on O‘āhu there are huge and ongoing efforts to protect the reefs from hostile algae. The study’s analyses will hopefully help determine commendable levels of strategies to avoid or reverse these tipping points. The PLOS One’s journal mentions that coral reefs have been declining in Hawai‘i due to the intense human pressure from recreational over the past 100 years.
Anthropogenic drivers for reef deterioration
Residents of Hawai‘i deeply rely on fisheries for economic, social, and cultural services. According to PacIOOS, overfishing causes the degradation of marine ecosystem and long-term economic loss. Allen listed, “I remember the first time I saw images of fish farms—it was like the first time I saw a feedlot.” Commercial catch of reef fishes is reported to the State of Hawai‘i Department of Aquatic Resources (DAR) based on large reporting blocks, however, according to NOAA Marine Recreational Information Program (MRIP), non-commercial nearshore catch for each island is 10 times greater than the reported commercial catch. The results show that the island of O‘āhu constitutes the greatest number of both commercial and non-commercial reef fish catch among the main Hawaiian Islands.
According to the United States Environmental Protection Agency (EPA), Hawai‘i has the highest number of onsite waste disposal system per capita in the United States, many of which are close to the Hawaiian coastline. These disposal system, then, expunge excess nutrients and pollutants into groundwater that goes directly into the ocean. The study stresses that excess nutrients triggers macroalgal blooms that kill corals.
Coastal habitats are under pressure from anthropogenic activities. Humans have altered or removed landscape features that benefit the population of Hawai‘i. These modifications like seawalls, piers, breakwaters leave bare and tilled soil vulnerable to erosion that adds to the excess nutrients that can affect reef health. According to the findings from the PLOS One journal, the largest area of continuous modification were on O‘āhu from Waikīkī to Pearl Harbor, and Kāne‘ohe Bay.
Natural drivers for reef deterioration
Sea surface temperature, according to PacIOOS, influences primary production, species migration patterns, and coral health. The rise of seawater temperature can result in harmful effects on the marine ecosystem such as coral bleaching. According to the PLOS One journal, windward coastlines tend to have cooler ocean temperature compared to leeward coastlines.
Chlorophyll-a, per the PLOS One journal, is a widely used representation for phytoplankton biomass and an essential source of energy in the marine ecosystem. High levels often indicate poor water quality, however, elevated chlorophyll-a concentrations are not necessarily a bad thing for it means more energy. Even though this is the case, high concentration of chlorophyll-a indicates a constant rise of sea surface temperature. The study suggests that the northwest shorelines of Kaua‘i, O‘āhu, and Maui and the south shore of Moloka‘i are infested with chlorophyll-a.
What do we do?
“Ideally, our creativity will mean more and more people working together to save, to bring back, the coral reefs. The key is going to be not only raising awareness but bringing industry to the effort,” exclaimed Allen.
This collaborative study hopes to allow for future analysis and understanding of the coral reefs. Also, the findings provide a scientific basis for improved policy and management actions at the state level through engagement with Hawai‘i DAR. The study, per PacIOOS, finds that these anthropogenic stressors diminished both economic and sociocultural benefits of nearshore reefs in Hawai‘i.
“I know that there have been a number of approaches to restoring coral reefs, e.g., coral gardening and transplanting coral, but if we want to put a stop to the devastation, then we’ll have to address the cause—anthropogenic climate change. And, that means people working together in a global effort to make change, particularly with regards to industry and consumerism,” pleaded Allen.