Secretariat of the Pacific Regional Environment Programme

PEIN Country Profile and Virtual Environment Library

Guam

Excerpts from Wikipedia

Geography

Guam lies between 13.2°N and 13.7°N and between 144.6°E and 145.0°E, and has an area of 209 square miles (541 km2), making it the 32nd largest island of the United States. It is the southernmost island in the Mariana island chain and is the largest island in Micronesia. This island chain was created by the colliding Pacific and Philippine tectonic plates. The Mariana Trench, a deep subduction zone, lies beside the island chain to the east. Challenger Deep, the deepest surveyed point in the Oceans, is southwest of Guam at 35,797 feet (10,911 m) deep. The highest point in Guam is Mount Lamlam, which is 1,332 feet (406 m). The island of Guam is 30 miles (48 km) long and 4 mi (6 km) to 12 mi (19 km) wide. The island experiences occasional earthquakes due to its location on the western edge of the Pacific Plate and near the Philippine Plate. In recent years, earthquakes with epicenters near Guam have had magnitudes ranging from 5.0 to 8.7. Unlike the Anatahan volcano in the Northern Mariana Islands, Guam is not volcanically active.[6] However, due to its proximity to Anatahan, vog does occasionally affect Guam.[7]

The northern part of the island is a forested coralline limestone plateau while the south contains volcanic peaks covered in forest and grassland. A coral reef surrounds most of the island, except in areas where bays exist that provide access to small rivers and streams that run down from the hills into the Pacific Ocean and Philippine Sea.[8] The island's population is most dense in the northern and central regions.[5]

Climate

The climate is characterized as tropical marine. The weather is generally hot and very humid with little seasonal temperature variation. The mean high temperature is 86 °F (30 °C) and mean low is 76 °F (24 °C) with an average annual rainfall of 96 inches (2,180 mm). The dry season runs from December through June. The remaining months constitute the rainy season. The months of January and February are considered the coolest months of the year with night time temperatures in the mid to low 70's and generally lower humidity levels. The highest risk of typhoons is during October and November. They can occur, however, year-round.

An average of three tropical storms and one typhoon pass within 180 nautical miles (210 mi; 330 km) of Guam each year. The most intense typhoon to pass over Guam recently was Super Typhoon Pongsona, with sustained winds of 125 miles per hour, which slammed Guam on December 8, 2002, leaving massive destruction.

Since Super Typhoon Pamela in 1976 wooden structures have been largely replaced by concrete structures.[9][10] During the 1980s wooden utility poles began to be replaced by typhoon-resistant concrete and steel poles. After the local Government enforced stricter construction codes, many home and business owners built their structures out of reinforced concrete with installed typhoon shutters.

Ecological issues

Guam exemplifies the effects of bioinvasion.

The brown tree snake

Thought to be a stowaway on a U.S. military transport near the end of World War II, the brown tree snake (Boiga irregularis) came to Guam and killed virtually all of the native bird population on an island that has no native species of snake; this snake has no natural predators on the island. While slightly venomous, the brown tree snake is relatively harmless to human beings. Although some studies have suggested a high density of the brown tree snake, residents rarely see these nocturnal snakes. Prodigious climbers, the snakes cause frequent blackouts by shorting across lines and transformers. The Guam Customs & Quarantine Agency is training detector dogs to seek out Brown Tree Snakes throughout inland Guam in an effort to further mitigate and reduce their escalating population. [15][16]

Coconut Rhinoceros Beetle

An infestation of the coconut rhinoceros beetle (CRB), Oryctes rhinoceros, was detected on Guam on September 12, 2007. CRB is not known to occur in the United States except in American Samoa. Delimiting surveys performed September 13-25, 2007 indicated that the infestation was limited to Tumon Bay and Faifai Beach, an area of approximately 900 acres (3.6 km2). Guam Department of Agriculture (GDA) placed quarantine on all properties within the Tumon area on October 5 and later expanded the quarantine to about 2,500 acres (10 km2) on October 25; approximately 0.5 miles (800 m) radius in all directions from all known locations of CRB infestation. CRB is native to Southern Asia and distributed throughout Asia and the Western Pacific including Sri Lanka, Upolu, Western Samoa, American Samoa, Palau Islands, New Britain, West Irian, New Ireland, Pak Island and Manus Island (New Guinea), Fiji, Cocos (Keeling) Islands, Mauritius, and Reunion.

Adults are the injurious stage of the insect. They are generally night-time fliers and when they alight on a host, they chew down into the folded, emerging fronds of coconut palms to feed on sap. V-shaped cuts in the fronds and holes through the midrib are visible when the leaves grow out and unfold. If the growing tip is injured, the palm may be killed or severe loss of leaf tissue may cause decreased nut set. Feeding wounds may also serve as an infection pathway for pathogens or other pests. The effects of adult boring may be more severe on younger palms where spears are narrower. Mortality of young palms has already been observed on Guam. Oviposition and larval development typically occurs in decaying coconut logs or stumps.

Control measures have been developed for CRB and the current strategy on Guam is to implement an integrated eradication program using pheromone-baited, attractive traps to capture adults, various methods to eliminate infested and susceptible host material, and pesticides to kill larvae and adults. Pesticides may also be applied to uninfested trees as a preventive treatment. USDA-APHIS has completed an Environmental Assessment for the coconut rhinoceros beetle eradication program on Guam (EA Number: GU-08-1, http://www.guaminsects.net/uogces/kbwiki/images/d/dc/CRB_EA.pdf). The eradication program is a cooperative effort between USDA (APHIS and Forest Service), GDA and the University of Guam (UOG). This document follows the Forest Service Pest Risk Assessment (Kliejunas et al. 2001)format and is intended to provide information regarding the current status of CRB on Guam, its potential to spread to uninfested locales, and the consequences of establishment. The high, moderate or low risk values are based on available biological information and the subjective judgment of the authors.

Other invasive species

From the seventeenth through nineteenth centuries, the Spanish introduced pigs, dogs, chickens, the Philippine deer (Cervus mariannus), black francolins, and water buffalo. Water buffalo, known as carabao locally, have cultural significance. Herds of these animals obstruct military base operations and harm native ecosystems. After birth control and adoption efforts were ineffective, the U.S. military began euthanizing the herds in 2002 leading to organized protests from island residents.[17]

Other introduced species include cane toads imported in 1937, the giant African snail (an agricultural pest introduced during WWII by Japanese occupation troops) and more recently frog species which could threaten crops in addition to providing additional food for the brown tree snake population. Reports of loud chirping frogs native to the Caribbean and known as coquí, that may have arrived from Hawaii, have led to fears that the noise could threaten Guam's tourism.[18]

Introduced feral pigs and deer, over-hunting, and habitat loss from human development are also major factors in the decline and loss of Guam's native plants and animals.

Threats to indigenous plants

Invading animal species are not the only threat to Guam's native flora. Tinangaja, a virus affecting coconut palms, was first observed on the island in 1917 when copra production was still a major part of Guam's economy. Though coconut plantations no longer exist on the island, the dead and infected trees that have resulted from the epidemic are seen throughout the forests of Guam.[19] Also during the past century, the dense forests of northern Guam have been largely replaced by thick tangan tangan brush (Leucaena-native to the Americas). Much of Guam's foliage was lost during World War II. In 1947, the U.S. military introduced tangan tangan by seeding the island from the air to prevent erosion. In southern Guam, non-native grass species also dominate much of the landscape.

Wildfires

Wildfires plague the forested ("boonie" or "jungle") areas of Guam every dry season despite the island's humid climate. Most fires are man-caused with 80 percent resulting from arson.[20] Poachers often start fires to attract deer to the new growth. Invasive grass species that rely on fire as part of their natural life cycle grow in many regularly burned areas. Grasslands and "barrens" have replaced previously forested areas leading to greater soil erosion. During the rainy season sediment is carried by the heavy rains into the Fena Lake Reservoir and Ugum River leading to water quality problems for southern Guam. Eroded silt also destroys the marine life in reefs around the island. Soil stabilization efforts by volunteers and forestry workers to plant trees have had little success in preserving natural habitats.[21]

Aquatic preserves

As a vacation spot for scuba divers, efforts have been made to protect Guam's coral reef habitats from pollution, eroded silt, and overfishing that have led to decreased fish populations. In recent years the Department of Agriculture, Division of Aquatic and Wildlife Resources has established several new marine preserves where fish populations are monitored by biologists.[22] Prior to adopting U.S. Environmental Protection Agency? standards, portions of Tumon bay were dredged by the hotel chains in order to provide a better experience for hotel guests.[23][24] Tumon Bay has since been made into a preserve. A federal Guam National Wildlife Refuge in northern Guam protects the decimated sea turtle population in addition to a small colony of Mariana fruit bats.[25]