Guam’s snake infestation provides grim warning for Hawaii
Researchers have found the brown tree snake's harmful reach has extended from birds to Guam's forests.
New research in Guam soberly reveals how the introduction of a single non-native organism can throw an entire ecosystem off kilter. The information emphasizes why guarding against non-native plants and animals is a serious matter for an isolated state that relies on its environment for the health of its economy and the well-being of its human inhabitants.
Most Hawaii residents are well aware of the threat the brown tree snake presents to the islands' native birds, but the research on Guam shows the damage ranges beyond winged species to the forests where they were fundamental components of the ecosystem.
The snake, accidentally introduced from the Admiralty Islands after World War II, has killed off 10 native forest bird species on Guam. Of each of the remaining two, fewer than 200 individuals survive.
With few natural predators, the snakes number in the hundreds of thousands, with estimates of 3,000 per square mile. Though they have been known to harm small children and domesticated animals, effects on humans have been viewed as tolerable -- power outages when snakes climb utility poles and the absence of bird sound and songs.
However, University of Washington biologists have found that the disappearance of birds is damaging Guam's forests. Though a small part of a forest environment, birds played a key role for 60 percent to 70 percent of native trees, eating and spreading seeds through their droppings. Also, when seeds pass through their digestive systems, an outer coating is removed, speeding germination.
Researchers discovered that without birds, seeds on Guam generally did not spread beyond the canopy of parent trees and had coatings intact. In comparison, seed dispersal was much wider on nearby islands and seedlings spread two to three times farther away.
Seeds that take root near parent trees are less likely to thrive and grow into healthy trees. Scientists anticipate that without birds, forests on Guam will diminish to isolated stands, further reducing the environment needed to sustain a diversity of wildlife.
Guam has given up trying to eradicate the snakes and is focused on preventing them from hitching rides on ships and planes to other locations. Hawaii remains vulnerable to the snakes due to increased military traffic and inconsistent funding for cargo inspection and deterrence.
There have been several brown tree snake sightings in the islands, but so far none have been positively identified in the wild. It might just be a matter of time because Hawaii seems like a sieve when it comes to keeping out non-native and invasive species.
Stinging nettle caterpillars, coqui frogs and gall wasps have slipped through porous borders. Countless plants like tibouchina and miconia, thought to be harmless imports for gardens, and exotic lizards like Jackson chameleons, brought in as pets, have come to occupy Hawaii.
The cost to control destructive species has been measured in money, but the consequences should be counted in loss of forests that serve as watersheds and prevent runoff that damages the ocean, marine life and the environment that lures tourists to Hawaii.