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Guam’s fadang tree continues to decline, but other close relatives are good garden plants for island

HAGÅTÑA (The Guam Daily Post) — These alien insects are so tiny that 10,000 of them can fit on your fingernail. Yet their appetite is so ravenous that they can kill a large tree in about one year.

They invaded Guam in 2003 and targeted Guam’s fadang trees as their favorite tree for feeding. At that time, fadang was the most abundant tree on Guam, so the supply of food must have seemed like an all-you-can-eat buffet.

Fast forward to today, and the tree population has been so decimated by the invasive insect that fadang has been added to the United States Endangered Species Act. There may be no other example worldwide where an insect invasion caused the most abundant local tree to rapidly become threatened with extinction.

Click to enlarge
Benjamin Deloso, left, chats with a cycad leaf vendor in Pampanga province, north of Manila, the Philippines. Uses of cycad products around the world will be discussed during a Dec. 2 workshop at UOG.
Paris Marler inspects leaves of a cycad tree in Thailand for insect damage. Marler will discuss her research of insects that feed on cycad leaves in Guam, the Philippines, and Thailand during a Dec. 2 workshop at UOG.
Benjamin Deloso discusses use of cycad plants in UOG’s cycad garden. The cycad in the foreground is from Mexico, the large cycad in the background is from Australia, and the containerized cycad that Deloso holds is from Florida. Plants will be available for purchase at an upcoming UOG workshop.  Contributed photos

Fadang and some other plants use floating seeds to travel from island to island. We do not know the exact year that fadang immigrated to Guam, but we do know that it has been living on Guam at least 5,000 years longer than humans. This is one of many reasons that the human activity that caused the recent pest invasion causes such dismay, as the ecosystem services that fadang has provided to Guam’s environments throughout the millennia are now on the brink of being lost.

Just how can an insect so small kill a 15-foot-tall tree so rapidly? Does the insect attack any other Guam trees? Are there appropriate alternate plant species that can be planted in Guam’s yards to replace the dying fadang trees? These and many other relevant questions have been answered by sustained research that has been conducted at the University of Guam during the past 15 years.

Fadang is a cycad

Guam’s fadang tree is called “Cycas micronesica” by scientists. The species is native to Palau, Yap, Guam, and Rota. Fadang differs from all other native trees in that it produces cones instead of flowers, similar to pine trees. It is the only native tree that produces seeds without fruits, rather than bearing seeds inside of fruits. This uniqueness is one of the many issues that have scientists alarmed at the demise of the unique tree’s population.

Fadang belongs to a group of plants called cycads. These plants have a direct connection to the Jurassic era, living alongside dinosaurs and perhaps being eaten by them. They were common at that time and have survived all extinction events throughout the eons. Today there are about 350 species of cycads worldwide. They are the planet’s most threatened plant group.

The threats to Guam’s cycad are unique in relation to the global situation. The major threats to other cycad species are wild collection of plants and destruction of habitat. Some species are so rare that collectors will do almost anything to get their hands on a plant. This has pushed some cycad species to the brink of extinction. But the major threats to Guam’s cycad are restricted to damage by invasive insects. According to University of Guam scientists, this positions Guam at the vanguard of cycad research as other areas of the world will become more damaged by invasive species in the future. The local results from fadang research will be available to inform conservation efforts when alien insects begin to threaten other cycad species.

Other cycad species

Fadang is one of only two cycad species that are native to the United States. The other species is from Florida, where Native Americans historically utilized the plant as a source of flour for culinary purposes. Similarly, the Chamorro residents of Guam and Rota historically used fadang seeds as a source of flour.

The University of Guam has been evaluating how well this Florida cycad species and many other species perform in Guam’s soils and climate. The results have revealed that most cycad species perform well under local conditions, and Guam’s residents who desire to have a cycad in their home garden have many species from which to choose. The University of Guam has a new cycad garden that showcases the global diversity among the many cycad species. The garden will be used in a workshop scheduled for December 2 to answer the many relevant questions about the demise of fadang, what has been done to stave off extinction, and what the near future holds for this important Guam tree.

“The research conducted at the University has generated more scientific publications on Guam’s cycad species in the past decade than any other cycad species,” said Lee Yudin, director of UOG’s Agricultural Experiment Station. “We are gratified to be able to communicate what has been learned at next week’s workshop.

Deloso is research associate with the College of Natural and Applied Sciences, University of Guam. Marler is research associate with the Center for Sustainability, Palawan, the Philippines.