Historical Lessons

The story of invasive species on Guam spans centuries. By examining how non‑native organisms arrived and spread, we can identify missteps to avoid and strategies that have proven effective. This timeline and discussion summarise key events and lessons learned.

Timeline of Major Introductions

Time Period	Event	Lessons Learned
1600s–1700s	Introduction of livestock such as Philippine deer, pigs and water buffalo for food and transport.	Domestic animals readily become feral without predators; early settlers lacked controls. Populations still impact forests today.
Late 1940s	Brown tree snake arrives in military cargo after WWII and spreads undetected.	Unintentional stowaways can have catastrophic ecological consequences. Rapid response protocols were not in place, allowing snakes to establish and eradicate most native birds.
2003	Asian cycad scale detected on Guam.	Delay in detection allowed the insect to spread and kill over 90 percent of cycads. Highlights importance of plant quarantine and public reporting.
2007	Coconut rhinoceros beetle (CRB‑G biotype) first found near Tumon Bay.	Lack of early eradication enabled CRB to spread; resistant biotype undermines traditional biocontrol. Sanitation and continuous surveillance are critical.
2011	Little fire ant identified at a landfill site.	Containment measures prevented island‑wide spread so far, demonstrating the value of public education, rapid baiting and quarantine of green waste.

What Went Wrong?

Many early introductions occurred before people understood how vulnerable island ecosystems can be. Guam lacked quarantine laws and enforcement capacity for much of its history, and by the time authorities realised the scale of the problem, some species were already established. The brown tree snake went undetected for decades, causing bird extinctions and costly power outages. Similarly, the coconut rhinoceros beetle and cycad scale spread before eradication could be attempted.

Eradication attempts have sometimes failed because they lacked long‑term funding or community support. For example, CRB control programmes were halted when funding expired, allowing populations to rebound. On the other hand, public involvement has been key to containing little fire ants—citizen reports and coordinated baiting have prevented a more serious infestation.

Lessons for the Future

Invest in prevention: Strong biosecurity at ports and airports can stop new invaders before they arrive. Inspection of cargo, vehicles and nursery plants is far cheaper than after‑the‑fact control.
Rapid response: When a new invasive species is detected, quick action—including delimiting surveys and eradication attempts—dramatically increases the chance of success.
Continuous funding: Control programmes must be sustained until the target is eliminated or at least suppressed. Short‑term funding leads to a boom‑and‑bust cycle of pest resurgence.
Community engagement: Residents, farmers and students play a vital role. Reporting unusual sightings, following sanitation guidelines and participating in clean‑ups make a difference.