Ecological Perturbations and Consequences
Besides the native species on Guam that have been negatively impacted by the introduction of the brown Treesnake, Boiga irregularis, other long-term damages in Guam remain to be thoroughly evaluated. The loss of most insectivorous birds and many lizards may leave Guam vulnerable to a variety of insect pests. In the absence of insect predators, insects arriving on Guam in ship or air traffic are potentially more likely to become established and threaten agricultural crops, public health, and the island's ecology. Examples of such problems caused by insect pests include potential outbreaks of dengue fever carried by mosquitoes, defoliation of extensive stands of the tangan tangan tree (Leucaena leucocephala) by an insect arriving from Hawaii, and a host of insects that reduce yields of fruits and vegetables grown by Guam's farmers and rural residents.
Birds and fruit bats are also important in tropical forests because they naturally disperse seeds of shrubs and trees and thereby help maintain forest diversity, contributing to recovery after typhoons and other catastrophic events. Whether some trees particularly dependent on seed dispersal by birds or fruit bats will decline in abundance or disappear is unknown, but the distribution of at least one introduced plant has changed as a result of the disappearance of birds that previously dispersed its seeds. Birds and bats are also potentially important as pollinators of some forest plants.
Many Pacific Island ecosystems have much in common with Guam's environment and are directly linked to Guam through commerce. The threat of snakes arriving and colonizing these islands is demonstrated time and again as individual snakes reach islands such as Wake Island, Kwajalein, Oahu, Diego Garcia, Saipan, Tinian, Okinawa, Rota, Pohnpei, Cocos Island, and Texas. The introduction and establishment of brown Treesnake populations on other oceanic islands would likely have consequences similar to those on Guam. This is particularly relevant to islands that support unique species, have less complex power supply systems, and whose economies are largely based on tourism. For example, establishment of the snake on Oahu could have a major effect on tourism. Accidental transport of brown Treesnakes to subtropical areas of the continental United States may result in unwanted colonizations that impact the dependability of electrical supplies, tourism, agricultural production, and native species already at risk due to other factors. Brown Treesnakes also pose a threat to the poultry and agriculture industries in Hawaii and portions of the mainland United States. Continuing feature stories on brown Treesnake problems in major newspapers and network television programs demonstrate the growing concern in the United States regarding the potential introduction and spread of this snake.