Samoa Guide, 23. Banyan trees

In contrast, both kinds of aoa are very important for wildlife. In fact, a good case can be made that they are the most important tree species for the fruit-eating birds and bats of Samoa. There are two reasons why they are so important. First, they produce enormous amounts of fruit. When one of the huge banyans has crop of fruit, its spreading crown has room for a whole army of hungry fruit-eaters. In a single tree, I have seen three lupe (Pacific Pigeons), eight manutagi (Purple-capped Fruit-Doves), four manuma (Many-colored Fruit-Doves), a dozen fuia (Samoan Starling), scattered iao (Wattled Honeyeaters) and miti vao (Polynesian Starlings) -- all at the same time. No other Samoan trees provide such a feast. The second reason why banyans are so important is that they fruit at all times of year. Most kinds of large forest trees have a definite fruiting season: for example, asi tends to fruit from
April to July, but some banyans have ripe fruit every month of the year. Between 10-30% of banyan trees have ripe fruit in any given month. This means that a fruit-eater can always find banyan fruit, even if all other fruits were out of season.

In the complex world of the Samoan rainforest, each of our native plants and wildlife contributes a unique and essential part. Just as the beauty of a hymn would be less without the harmonies of different voices, so the beauty of the Samoan forests would be less if any of our plants or animals were lost. And yet, as in a choir, there are a few natural “voices” that sing out above the rest. These are the plants and animals most important for the harmony of Samoa's natural world. Foremost among these are the aoa, or banyan trees.

One Samoan bird has come to depend on the reliable banyan. This is the manuma, or Many-colored Fruit-Dove, one of the rarest birds on Tutuila. In two years of observation, I have recorded manuma eating fruit on 99 occasions. In 98 of these 99 times, the manuma were eating banyan fruit (the one exception was berries of the soga bush). One probable reason why the manuma is so rare today is the loss of many banyan trees, particularly in the Tafuna Plain. If this bird is to survive here, it is essential that banyan trees be protected, and, if possible, increased in number.

The seedling first anchors itself by sending roots into the little pocket of decaying leaves or moss where it has sprouted, then it wraps more and more roots around the tree that supports it, called the “host” tree. Soon the banyan's roots are spreading down the trunk, and finally they reach all the way to the ground. By then the fate of the host tree is sealed. It is literally buried beneath the growing banyan -- strangled to death. Eventually the body of the host tree decays away, leaving no trace behind, except sometimes a long hollow extending up inside the middle of the full-grown banyan. Because banyans will start life on almost any type of host tree, they kill very few of any particular kind, and so are no threat to other plant species. Still, they're rather...fascinating, don't you think?

In Samoa, we have two different kinds of native banyan trees, both called aoa. One kind (Ficus prolixa) becomes a huge tree, with an enormous spreading trunk that seems to be a twisted net of many smaller trunks. This kind of banyan has green fruit. The stronghold of this kind of banyan in American Samoa was the Tafuna Plain, where hundreds of the huge trees used to grow. Today, only a small fraction remain. Most have been cut down to make room for the uncontrolled development in this part of Tutuila. Fortunately, a few magnificent trees still survive. The other kind of aoa (Ficus obliqua) is usually much smaller and does not have such a spreading form. Its trunk usually looks more “normal”, though it may have a hollow inside. This type of banyan seems to favor cliffs and steep slopes, although it can also be found on flat land. It doesn't always start life as a strangler, but sometimes grows up by itself. The easiest way to recognize this kind of aoa is its fruit, which is orange or red when ripe.

There is also an introduced kind of banyan tree in Samoa, the pulu. This tree, originally from Asia, is usually planted along the coast in villages; a large one grows next to the public market in Fagatogo. Pulu trees differ from aoa trees by their much larger leaves and larger, fuzzy red fruit. Although pulu are handsome trees that are useful for stabilizing our coasts, their fruits are not favored by wildlife, and so they do not play an important role in Samoa's natural symphony.

Banyans are fascinating plants. Now, a lot of people don't think of plants as “fascinating”. After all, they just sit there, right? Well, not banyans. Although banyans give life to countless animals by feeding them with their fruit, all banyans start out as killers -- stranglers, to be exact. Another name for the banyan is “strangler fig”.

The aoa is a member of the fig family. They earn the other part of their name by their strange way of growing. Most plants, of course, sprout from seeds that have fallen to the ground, and grow up toward the sun. Banyans usually do the opposite: they sprout from seeds that have been left by birds high in a tree, and grow down toward the ground.

In addition to their important role in feeding wildlife, aoa trees also provide homes for many animals. Lulu (Barn Owls) frequently sleep and nest in the hollow trunks. Tava'e (tropicbirds) find large nesting shelters, and fuia (Samoan Starlings) and ti'otala (White-collared Kingfisher) find protected nest holes. From its open, sheltered base to its spreading, fruit-laden crown, a banyan tree is a haven for wildlife.

Sadly, banyans today are under threat in American Samoa. Many were severely damaged by cyclones in 1990-91. Many others have been cut down, and more are threatened by continued development, particularly in the Tafuna Plain. Some of the most magnificent banyans that still stand have been make into gigantic trash barrels, their hollow trunks filled with mounds of used diapers and rusting cans. This garbage is sometimes burned, which can kill the banyan even if that is not intended.

What can you do? Give banyans the respect and protection they deserve. If your family is lucky enough to have an aoa on your land, please take care of it. Don't cut it, burn it , or use it as a garbage dump. If you notice a young banyan getting started, help it along by clearing away vines. If you know someone who has a banyan on their land, talk to them about its importance for wildlife. The banyan is a living testimony to the bounty and riches of Samoan nature, and is a lifeline for our wildlife.