Lord Howe Island subtropical forests

• Category: Forest Biomes
• Geographic Location: South Pacific Ocean
• Summary: Situated on this remote volcanic island, these forests have protected status, but introduced species threaten the endemic ones.

Lord Howe Island is located in the South Pacific Ocean, some 435 miles (700 kilometers) east of Australia and 840 miles (1,350 kilometers) northwest of New Zealand. Approximately six miles (ten kilometers) long, the crescent-shaped island is a remnant of a volcano that formed about seven million years ago. During this time, the volcano eroded to create Lord Howe Island; a series of islets of the Admiralty Group; and Ball’s Pyramid, an islet separated from Lord Howe Island by approximately thirteen miles (twenty-one kilometers) of water. There are two prominent peaks on the southern portion of the island: Mount Gover and Mount Lidgbird, with elevations of 2,870 feet (875 meters) and 2,550 feet (777 meters), respectively.

The climate is subtropical, with mean annual rainfall of just under 68 inches (173 centimeters). The average annual high temperature is 72 Fahrenheit (22 Celsius); the average annual low temperature is 63 Fahrenheit (17 Celsius). The warm temperatures and steady rainfall throughout the year create an optimal environment to support the lush rainforest that covers the vast majority of the island, along with some areas of scrub, grassland, and clearings in the lowlands and on the cliffs.

Biota

In 1982, 75 percent of the island was declared a Natural World Heritage Site, and the biological and cultural heritage was entrusted to the Lord Howe Island Board, which is responsible for eradicating the invasive goats from the island and for significantly decreasing the population of feral pigs. Efforts to control other introduced species, such as rats and plants, are ongoing. The removal of some feral animals has resulted in the recovery of the forest understory.

Due to the geographic isolation of the island, Lord Howe Island and its marine surrounds are home to a unique assemblage of birds, insects, plants, and marine animals, all of which reflect a high degree of endemism (species found nowhere else). Because the vast majority of Lord Howe Island’s fauna and flora evolved in isolation, it is an impressive example of biodiversity. Of the 239 native species of vascular plants, 113 are endemic species, several of which are considered rare, endangered, or vulnerable, and many of which have very restricted ranges. Chionochloa conspicua, for example, is known from a single clump located on Mount Lidgbird.

The forests here, mainly rainforest, can be assessed as either lowland, submontane, or montane. The lowland swaths are characterized by mixed evergreen fruit trees, laurels, fringetrees, tea trees, broadleaf types, palms, and the palm-like shrubs known as pandans, or ketakis. Laurels and palms are the hallmarks of the submontane. Ferns, mosses, and epiphytes abound in the understory of both these zones. The montane zone hosts cloud forests, so called because they are nearly continuously subject to very high moisture. Dominant here are fragrant flowering shrubs from the family Winteraceae and the heavily-fruited, but stunted trees of family Eriaceae.

There are 202 bird species that have been identified on the island, and 129 native and introduced bird species breed regularly here. Nine of the original fifteen native land bird species are extinct, including seven endemic species. There are four extant endemic land birds, including two species and two subspecies: the abundant Lord Howe white-eye (Zosterops lateralis tephropleurus), Lord Howe Island woodhen (Hypotaenidia sylvestris), Lord Howe Island golden whistler (Pachycephala pectoralis contempta), and Lord Howe Island currawong (Strepera graculina crissalis). The woodhen was reduced to twenty-five individuals in the 1970s, but due to an aggressive management program, the population was well over 200 by the 1980s. Their population remained stable and increased slightly through the late 2010s, reaching nearly 900 birds. However, an overpopulation of rodents caused a sharp decline in their population in the early twenty-first century, and the Lord Howe Island woodhen was again classified as endangered in early 2022.

Seabirds also use the island extensively. Lord Howe Island is one of the few known breeding grounds of the Providence petrel (Pterodroma solandri), located in the cloud forests of the island. Approximately half the world’s population of the flesh-footed shearwater (Ardenna carneipes) breeds on the island, and the island has the greatest concentration of red-tailed tropicbirds (Phaethon rubricauda). Twelve additional species of seabirds have been documented breeding on the island.

The large forest bat (Eptesicus sagittula) is the only native mammal. As a result of introduced predators, there are only two identified native reptiles—a skink (Oligosoma lichenigerum) and a gecko (Christinus guentheri)—both of which are classified as vulnerable. Many endemic invertebrates inhabit these subtropical forests, including snails, flies, earthworms, and spiders. Of more than 100 spiders described on the island, up to 50 percent are thought to be endemic. This island is the only place in Australia without poisonous spiders.

Human Impact

Due to the island’s geographic isolation, the island was not settled until the early nineteenth century, and has never been heavily populated. Consequently, it is unlike most other Pacific islands in that it has not been dramatically altered by people, and most of the island is still forested. It is estimated that only 10 percent of the island has been cleared for human use, and an additional 20 percent of the native vegetation has been disturbed by the introduction of animals, including cattle, goats, feral sheep, feral pigs, and rats.

In the late 1800s, trade began from the island in the form of the Kentia palm, endemic to the island. This palm, one of four endemic here, became very popular in Britain, Europe, and the United States by the early 1900s, and is one of the most popular decorative palms in the world. The sale of seeds and seedlings remains today, along with tourism, the only form of outside income for the small population of the island. In 2024, the population of Lord Howe Island was around 380 permanent residents, with a limit of 400 tourists at any given time.

Although most of Lord Howe Island is protected, continued management is necessary to prevent the introduction of invasive species. Historically, introduced predators have devastated the endemic fauna, and introduced plants have displaced native species. In 2019, the country launched the Rodent Eradication Project to eliminate the rats and mice that were introduced in 1918 and 1850. The project used 22,000 bait stations and 40 tonnes of poison distributed using helicopters. Over thirty threatened species of plants and animals recovered in the following year. The long-term recovery of the island’s many threatened species will be successful only through the continued control and management of these exotic species.

A more immediate threat to the ecosystems is climate change. Due to the island's small size, any change in rising sea levels translates into a potentially heavy loss of land mass. The southernmost coral reef on earth has seen bleaching due to warming ocean temperatures in the twenty-first century, with the most severe bleaching seen in 2019 nearer the coast in shallow waters. Low cloud cover is essential to the moisture and humidity of the island’s ecosystem, but increasing sea temperatures continue to raise these clouds. As the clouds lift and provide less insulation, the sun increasingly dries habitats that are typically moist and increases average daily temperatures. Rainfall has also been decreasing as a result of climate change.

Bibliography

Cox, Lisa. "Lord Howe Island Coral Bleaching 'Most Severe We've Ever Seen', Scientists Say." The Guardian, 31 Mar. 2019, www.theguardian.com/australia-news/2019/apr/01/lord-howe-island-coral-bleaching-most-severe-weve-ever-seen-scientists-say. Accessed 24 Dec. 2024.

Davey, A. Plan of Management: Lord Howe Island Permanent Park Preserve. New South Wales National Parks and Wildlife Service, 1986.

Department of Environment and Climate Change. Lord Howe Island: Biodiversity Management Plan. Australian Government, 2007.

"Lord Howe Island Group." World Heritage Outlook, worldheritageoutlook.iucn.org/explore-sites/wdpaid/5001. Accessed 24 Dec. 2024.

McDougall, Ian, et al. “Origin and Evolution of Lord Howe Island, Southwest Pacific Ocean.” Journal of the Geological Society of Australia, vol. 28, no. 1-2, 1981, pp. 155–76, doi:10.1080/00167618108729154. Accessed 24 Dec. 2024.

Recher, Harry F., and Stephen S. Clark. “A Biological Survey of Lord Howe Island with Recommendations for the Conservation of the Island’s Wildlife.” Biological Conservation, vol. 6, no. 4, 1974, pp. 263–73, doi:10.1016/0006-3207(74)90005-6. Accessed 24 Dec. 2024.

Reid, Sarah. "What Does It Take to Protect Paradise? Ask Australia’s Lord Howe Island." Adventure, 3 Dec. 2021, adventure.com/australia-lord-howe-island-conservation. Accessed 24 Dec. 2024.

Siossian, Emma, and Cameron Marshall. "Cloud Forest Thrives on World Heritage-Listed Lord Howe Island After Pest Eradication." ABC, 7 Mar. 2021, www.abc.net.au/news/2021-03-08/cloud-forest-of-lord-howe-island-thrives-since-rat-removal/13216880. Accessed 24 Dec. 2024.