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The Crisis of Invasive Species in Guam

Updated: Mar 11, 2021

By Mana Ravenel

Sitting in the heart of the western North Pacific Ocean is the tropical paradise of Guam. The island is home to a pleasantly warm climate: white sand beaches with clear waters and rich cultural heritage.

With such desirable traits, it comes as no surprise that the island is a hotspot for travelers. In 2018 alone, Guam welcomed over 1.52 million tourists. In the last twenty years, Guam’s tourism industry has experienced rapid growth, however, the island has a long-running history of visitors, going back hundreds of years.

Following its European discovery in 1521, Guam has been visited relentlessly by other nations, most significantly Spain and the United States of America. With the constant traveling to and from Guam by these nations, not only did the island experience exposure to new and different ideas, technologies, and beliefs, but they also experienced exposure to new species. Species such as the brown tree snakes and coconut rhinoceros beetles were introduced to the island, an introduction that would prove detrimental to Guam’s native species.

In the ’40s, Guam began to experience a devastating decline in its bird populations. Forests were growing quieter without these creatures' chirpings, and it wasn’t until 1987 that US ecologist Julie Savidge provided evidence that the brown tree snake is at fault for this. Before the existence of brown tree snakes on Guam, the island had twelve native bird species. Today, ten of these species are extinct whilst the remaining two are critically endangered. The loss of these birds has significantly impacted and altered the ecosystem; with so few birds, the spreading of seeds is incredibly difficult, resulting in the falling of both the delicate ecosystem and diversity of Guam’s forests.

Guam’s trees—specifically the coconut palms and the cycas Micronesia—also face a more direct threat, the coconut rhinoceros beetles. Since their first sighting in 2007, these beetles have caused great destruction to the island’s coconut trees. Adult beetles bore into the palms’ crowns to feed on sap, essentially causing tree mortality once they destroy the growing tip. The effects these invasive species have on Guam’s trees are not only devastating, but they are extremely noticeable as well. Many of the island’s trees do not look like the thick, healthy palms one may picture. Rather, they have little to no top leaves, have diamond-shaped patterns in their leaves, and have holes in their trunks, looking visibly damaged and sickly.

According to the Global Invasive Species Database, Guam is infested with 129 documented invasive organisms. In addition to the brown tree snake and coconut rhinoceros beetle, organisms such as the little fire ants, Asian cycad scale, banana bunchy top virus, and the giant African snail are incredibly detrimental to Guam’s ecosystems, posing threats to native species. Invasive species are known to compete with natives for resources. Invasive plants, essentially, “colonize” native forests, dominating Guam’s forestry and killing native plants.

The threatening and decimating of native species and reduction of biodiversity are drastic consequences that come with the presence of invasive species, especially on an ecosystem as delicate as Guam’s. If the crisis of invasive species is not dealt with, Guam’s native flora and animals will only continue to decimate, forever changing the island’s diverse ecosystem.

Combating these non-native organisms is difficult, but not impossible. Small ways to help control and limit the spread of invasives includes not moving plants, potted plains, soils, or green trimmings from infested areas. Doing so would only aid the transportation of the invasives. Though the eradication of invasives such as the brown tree snakes is rather difficult, that of pests such as the Manokwari flatworm can be done by using hot water. The best way to help in the fight against the invasives is by reporting it to the Department of Agriculture Biosecurity Division either by calling directly at 671-475PEST (7378), emailing, or filing a report at the Biosecurity Division’s website.

Written by writer Mana Ravenel

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