I’ve been thinking about tangan-tangan lately. Mostly because I started hiking again, and whacking my way through stands of tangan-tangan brings it to the forefront of my mind. Sure is a lot of it on Guam and Saipan. I always knew it was introduced to foliate the islands after WWII, but that was about it. Turns out it is a species called Leucaena leucocephala, also known as the white lead tree, cow tamarind, and koa haole in Hawaii. It is a legume, like string beans or peas. As the LegumeWeb site says: “The principal unifying feature of the family is the fruit, a pod, technically known as a Legume. The Legume is modified in many ways to facilitate dispersal by animals, wind and water.”
Huh. Apparently it can be used as fodder for cattle, the seeds can be popped like popcorn, and of course it makes a convenient source of firewood. The stuff is technically a weed, and it grows like mad here on Guam. We have entire forests of the stuff; basically anywhere there is limestone soils, tangan-tangan grows profusely, crowding out other, native species. It is a shrubby, small tree, branches usually one to two inches thick, with seed pods on the topmost branches. It tends to get about 15-20 feet high, forming nearly impenetrable thickets. It grows rapidly, especially in disturbed areas, which is probably why it is so successful here. Typhoons tend to disrupt the jungle canopy and tangan-tangan takes full advantage of the light and space afforded by these openings.
Tangan-tangan is considered one of the top 100 worst invasive species according to the Global Invasive Species Database. Take a look at that list, it seems like Guam is a textbook study case for invasive species. Compared to some of the nefarious creatures on that list, tangan-tangan seems innocuous. Then again, are any of these species ‘nefarious?’ They don’t have the capacity for evil, they are simply exploiting the environment in a fantastically successful way. Most of them are doing so at the expense of indigenous species however, and most of them are spread by the activities of mankind. So if anybody is to blame, it’s us.