HAPPENINGS

On May 24, 2023, Typhoon Mawar, one of the strongest Northern Hemisphere tropical cyclones ever recorded in the month of May and the strongest globally in 2023, hit the U.S. Territory of Guam in the Western Pacific. With winds up to 145 mph, the category 4-equivalent typhoon was the strongest storm to affect the island in over two decades. After enduring 15 hours of destructive winds and torrential rain, residents found an island littered with defoliated and uprooted trees, toppled signs and damaged buildings, and flood waters that were waist-deep in low-lying areas.

The typhoon also caused extensive damage to the Antonio B. Won Pat International Airport, requiring it to close all incoming and outgoing flights. After five days of extensive repairs, on May 29, commercial flights resumed, and the first commercial post-Mawar flight arrived from Narita, Japan. After deplaning passengers at the only operational gate at the airport, the plane was ready to park, and normally, the plane would have remained overnight at the gate. But in this instance, damage to the airport made it difficult to follow normal operating procedures, and the plane was moved to the south ramp of the airport adjacent to forest land where it sat overnight.

It was here that a brown tree snake, a nocturnal and highly invasive species in Guam, likely made its way through the perimeter chain-link fence enclosing the airport. It passed what would have been a number of strategically placed snake traps which had been taken down due to the storm, and the snake found its way across the pavement and then climbed up into the aircraft wheel well.

Brown tree snakes (Boiga irregularis), or BTS for short, are not native to Guam, and they were accidentally introduced after World War II, likely through U.S. military transports. After introduction, the snake reproduced, spread, and proceeded to eat its way through the island’s indigenous and largely naïve birdlife, which evolved without snakes. Since its introduction, the species has caused the extinction of 9 of the 11 native bird species in Guam and caused millions of dollars in damage to infrastructure and the economy, including hundreds of hospitalizations from bites. Keeping the snake from spreading to other snake-free islands in the Pacific has been the core mission of the Brown Treesnake Technical Working Group and the agencies leading the BTS interdiction program. The program has been largely successful in limiting the species spread in the Pacific, and there are no known nonnative populations outside of Guam.

Severe tropical storms in the Pacific, however, can cause significant problems for island invasive species programs, affecting the ability of managers to prevent or control the spread of damaging species. Intense winds from hurricanes and typhoons can spread invasive species around, and the damage inflicted can create new opportunities for establishment. For example, after Typhoon Dolphin in 2015, researchers at the University of Guam described a worrying increase in damage to coconut palms on the island from the invasive Coconut Rhinoceros Beetle, which was discovered in Guam in 2007. This species, an invasive palm and agricultural pest, breeds in decaying vegetation, which was prolific after the storm. Researchers believe that the storm created the perfect breeding conditions for the beetle, leading to large population increases after the typhoon, which increased both the spread and impact of the beetle.

Invasive species issues, however, can also be magnified by human responses to storms and other natural disasters. For example, emergency response efforts, which can include shipments of food, clothing, and medical supplies to areas recovering from disasters, could unintentionally transport invasive species to new areas. In 2009, an invasive small Indian mongoose (Herpestes auropunctatus), was caught by the Samoa National Invasives Task Team in the vicinity of the Satitoa Wharf, Upolu Island. According to researchers who assisted with this successful capture, the animal likely hitched a ride on ships from the 2009 relief efforts after an 8.3 earthquake nearby created a tsunami that devastated the region. Invasive mongoose are found in Hawaiʻi, where they are considered a primary threat to native birds, and if this species had been established in Samoa, it could have had devastating consequences for the country’s native species and ecosystems.

In Guam, the little fire ant or LFA (Wasmannia auropunctata), an invasive species whose sting can cause painful rashes in humans and cause blindness in pets, is thought to have spread extensively throughout the island after a typhoon. Little fire ants are very small and tend to move only small distances from the parent colony to form new nests. However, this species also exhibits what has been termed ‘jump dispersal’, where a part of a colony (e.g., that contains a queen and a few workers) can be accidentally carried to a new location by people where it can establish a new colony. LFA was first detected in northern Guam in 2011, but by 2018, only 3 years after Typhoon Dolphin, it had spread extensively throughout the island. Entomologists attribute the large increase to people’s movement and consolidation of ant-infested green waste. Notably, established green waste dumping sites were concentrated near ant-free forested areas and had no buffers or treatment to limit the spread, and this allowed the little fire ants to rapidly colonize new areas.

Because of the danger of introducing invasive species after natural disasters, several groups have released guidance on the subject. The secretariat of the Convention on Biological Diversity released a Joint Statement in 2017 with the United Nations Environment Caribbean Office calling attention to the risk of invasive alien species associated with emergency relief for islands in the Caribbean. At the time, the 2017 Atlantic hurricane season was one of the costliest on record, with a surprising 17 named storms, including 10 hurricanes, 6 of which were major (category 3 or higher on the Saffir-Simpson scale). More recently, the Secretariat of the International Plant Protection Convention from the Food and Agriculture Organization of the UN adopted recommendations in 2021 on the “safe provision of food and other humanitarian aid to prevent the introduction of plant pests during an emergency situation.”

U.S. Department of Agriculture (USDA) Wildlife Services Brown Tree Snake interdiction teams are acutely aware of the potential movement of invasive species on ships and planes. At the Guam International Airport, the work of these teams includes visual inspections, perimeter control traps, and the use of canine detector dogs who are trained to smell and pinpoint the unique scents given off by brown tree snakes.

After sitting overnight for about 15 hours at a high-risk location for invasive species encounters, the passenger plane at the Guam airport was moved back to the gate. It was then inspected by a canine handler team, but the canine failed to detect a snake and no snakes were visually discovered by the handler. The plane then made a short 20-minute flight north to Saipan, the capital of the Commonwealth of the Northern Mariana Islands (CNMI), and after dropping off passengers, the CNMI Department of Wildlife BTS inspectors conducted a visual inspection of the plane as had happened on Guam, no BTS were seen. And after spending about an hour on Saipan, the plane made the short flight back to Guam.

After landing back in Guam, a mechanic conducted a routine equipment inspection of the airplane and found a female brown tree snake in the left wheel well, he reported it to the USDA interdiction team, who apprehended and removed the snake. Because Saipan has no brown tree snakes and they are also not established in Japan where the flight originated, staff concluded that the most probable origin was the Guam airport. The snake most likely accessed the aircraft when it sat overnight in an area that would normally be surrounded by traps before heading to Saipan. Luckily, the snake flew round trip to Saipan and stayed on the airplane instead of escaping into the forest, where it could have contributed to an eventual ecological catastrophe as happened in Guam.

U.S. Fish & Wildlife Staff outlined several factors in the incident report that likely contributed to the snake’s round-trip flight and many of them relate to the challenges associated with Typhoon Mawar. First, the destruction associated with severe tropical storms is known to disrupt the normal habits of wildlife, and brown tree snakes, like many wildlife species, are more active after storms. This could lead to more snakes in high-risk areas like seaports and airports. Second, storms can make it impossible to implement trapping protocols; as part of regular typhoon preparations and safety protocols, USDA deactivates BTS traps before the arrival of a storm so they are not damaged or become flying debris that can cause damage. This can make it difficult to reinitiate an interdiction program quickly after a storm passes. Finally, the airport sustained extensive damage, and as a result, standard operating procedures were not followed, and the aircraft was parked in a high-risk area that lacked snake traps and other controls, greatly increasing the likelihood of snakes or other invasive species gaining access.

The discovery of the brown tree snake on the plane was an eye-opener for invasive species managers in the Pacific and brought attention to severe storms’ impact on invasive species prevention programs. The incident report outlined several recommended actions to ensure that invasive snake prevention programs can recover quickly after typhoons. These included awareness of the increased risk of the spread of invasive species during typhoon recovery, increased vigilance for invasive species by persons involved in transportation networks, more thorough inspections during post-typhoon high-risk periods, and reinstalling traps and other control tools more quickly. Most importantly, managers discussed the need for post-typhoon procedures to follow after a storm hits and to share challenges and success stories with other Pacific Island countries and territories to help build overall regional capacity.

Another important reason for building response capacity is that climate change is expected to increase the severity of cyclones in the Pacific region. As ocean temperatures rise, the U.S. Global Change Research Program projects that cyclones will have increased wind speeds and will carry larger amounts of rainfall in the future. And more severe storms equate to the need for more emergency response efforts and the potential for greater spread and impacts of invasive species. In 2020, members from multiple state and federal departments and agencies in Hawaiʻi founded the Pacific Regional Invasive Species and Climate Change (Pacific RISCC) Management Network to address these interacting impacts. The group, which now includes members from Hawaiʻi and all the US Affiliated Pacific Islands, works to facilitate knowledge exchange, create stronger researcher-manager communities, and assess research and management needs at the nexus of climate change and invasive species in the Pacific region.

 

Hawaiʻi Conservation Conference

 

To address the need for more knowledge sharing between Pacific Island jurisdictions related to the intersection of severe tropical storms and invasive species, Pacific RISCC convened a 2-hour forum on August 1st at the 2024 Hawaiʻi Conservation Conference. This was our third forum at the conference since 2019, and each has provided an opportunity to expand the reach of the network as well as the topics that RISCC addresses. Our forum planning committee included a diverse group of emergency responders, invasive species managers, and climate adaptation experts from both Hawaiʻi and the Mariana Islands, and our session was titled: “Climate-Related Disasters in the Pacific: Sharing Lessons Learned to Increase Resilience in Hawaiʻi.” The forum goals included increasing awareness of how severe tropical storms can magnify the impacts and spread of invasive species in the Pacific, elevating the need for integrating invasive species concerns into disaster planning and response and creating climate-smart adaptation actions for increasing the resilience of communities and ecosystems in Hawaiʻi.

The forum included presentations from an expert panel with direct experience of seven different tropical cyclones in the Pacific where invasive species had significant impacts after the storm, either due to the storm itself or human responses. The case studies included storms that have impacted Hawaiʻi (Iselle), the Mariana Islands (Dolphin, Soudelor, Mangkhut, Yutu, and Mawar), and Fiji, where Cyclone Winston hit in 2016 and was the most intense tropical cyclone ever recorded in the Southern Hemisphere. After short presentations on each case study, the expert panelists described their experiences with the storm, how invasive species were affected, the greatest lessons learned, and ideas for how best to prepare for the next storm.

Finally, we divided the room of about 60 participants into three breakout groups for smaller in-depth facilitated discussions led by Pacific RISCC core team members. Groups addressed three questions, 1) What do you think should be done in Hawaiʻi to prepare for invasive species before the next big storm? 2) What should be done after a storm with respect to invasive species? And 3) What are the top invasive species of concern we need to be worried about with respect to storms? Note-takers recorded the ideas that were generated by the group, and notes were summarized and shared with everyone at the end of the session. The next steps for Pacific RISCC include digitizing and organizing the notes and sharing them with the conservation community. So far, 22 examples have been found where large tropical storms in the Pacific led to the increase or spread of invasive species, and we are using the ideas from the forum to generate a species watch list to distribute to the Pacific RISCC network.

This forum was a good first step towards elevating the issue of storms affecting invasive species, and we discovered that tremendous knowledge and experience exists among emergency responders, managers, and researchers that we can use to build Pacific Island resilience. Our challenge moving forward will be to harness this momentum to continue to build relationships and to come up with a toolbox of adaptation actions that managers can use as the climate changes for the large number of invasive species that threaten the Pacific Islands. The brown tree snake program in Guam is one great example of how invasive species managers are adapting their work in the face of severe tropical storms so that when the next big storm arrives, we will be ready.

 

EP & MJM

 

 

The Pacific RISCC is supported financially by the United States Geological Survey Pacific Islands Climate Adaptation Science Center, the U.S. Fish & Wildlife Service Science Applications, and The Pacific Research on Island Solutions for Adaptation (Pacific RISA). Pacific RISCC is also supported by many passionate volunteers who devote their time and expertise to this topic. Please visit the website to find upcoming webinars, opportunities, and to join our mailing list: Pacific Regional Invasive Species and Climate Change Management Network – Pacific Island Climate Adaptation Science Center.