An excerpt from The Green Fuse: An Ecological Odyssey by John Harte
The following text is excerpted from Chapter Five of The Green Fuse: An Ecological Odyssey by John Harte (1993)
A peculiar dance was in progress. With a seemingly uncanny sense of timing, each performer approached and parted from first one and then another partner in endlessly varying, swaying, chiasmic rhythms. This was no ordinary production staged on a polished hardwood floor: the set was a foot-wide gap between a fallen, rotting tree trunk and the mulchy ground beneath. The dancers were scores of daddy longlegs, joined limb-to-limb to form a living web. By flexing and relaxing their legs, they created pulsating two-dimensional waves within a lacework that shimmered in the flashing specks of sunlight penetrating the verdant canopy high above.
In the tropical rain forests, pulsing conglomerations of life abound. If you sit in one spot and watch the canopy for glimpses of the brightly colored birds for which the tropics are famous, chances are you will sit for a while seeing nothing. But then, perhaps after ten mesmerizing minutes of staring at the fluttering foliage, you will suddenly first hear and then see a screaming frenzied flock of birds working their way overhead through the tall canopy. Then, in less than a minute, the flock moves on, and quiet sets in as fast as it was shattered.
Such flocking is an efficient way for birds to glean insects off the foliage and bark, because the bug that hops or flies away from one unlucky bird is likely to be snatched up by one nearby. Indeed, if the flock is large and contains a wide variety of bird species, the birds are probably going after insects as fruit-eating birds more rarely form large, mixed-species flocks.
While the frenzied screams of flocking birds and the moaning ululations of howling monkeys often comprise one’s first impressions of animal life in the rain forest, patience and mental acclimatization reveal a profusion of more hidden life forms and behaviors, which, like the dancing daddy longlegs, are ultimately more memorable. There are the trapdoor spiders, living in steep earth embankments in holes closed off from the outside world by circular flaps of dried mud hinged to open outward.
While the spiders know how to open them, their predators apparently do not. There is Albert’s lyrebird, rarely seen but sometimes heard in a few patches of rain forest in eastern Australia. A superb auditory mimic, it can reproduce anything from the laughing peals of a kookaburra to the coughs of a passing hiker. There are giant fruit-eating bats, the flying foxes, found throughout the wet tropics of Asia and Australia. They resemble big, black, broken umbrellas caught in the treetrops where they roost. There are the most hauntingly beautiful birds in the world, like the resplendent quetzal of Central America, the birds of paradise in tropical Asia, and the silktail of Fiji. You cannot help but shiver in awe when you first spot birds like these, probably after considerable searching through the thick forest growth. Other rain forest birds are not so much beautiful as bizarre, like the hornbills of Asia and Africa or the toucans of Central and South America.
The rain forest flora is no less fascinating. Shortly after enjoying the dancing web performance at La Selva, a tract of lowland rain forest set aside for biological research in Costa Rica, my wife and I sat on a riverbank, cooling our bare feet in the sluggish brown water. A kingfisher with a metallic green back and a chestnut band across the breast was doing a fine imitation of an air-to-sea missile as it repeatedly plummeted from a nearby branch. Suddenly, a sharp crack rang out, followed by a sequence of popping and swishing noises and then a thunderous crash. A giant fig had toppled, leaving a gaping sunny spot in the otherwise dense canopy.
A gap was formed, a noisy and dramatic but seemingly insignificant event in the life of a forest. In fact, tree fall in tropical forests is far from insignificant. Like presidential assassination, it is an event that alters the course of history, that shapes the future. In the gap created where the tree’s tall canopy once shaded the forest floor, numerous tree seedlings like opportunistic politicians, now have their moment in the sun. One of those seedlings is destined to outgrow the others and eventually fill in the hole in the canopy. Unlike most of the forests of the temperate and subarctic latitudes, which are dominated by a very few species of trees, the tropical rain forest is a mosaic of a huge variety of species. Any one tree is likely to be surrounded by a dozen or more different neighbors, so the seedling that ultimately wins the race to the canopy will not necessarily be the same type of tree that fell. The winner, too, perhaps a hundred years later, will fall, continuing the cycle of regrowth. This process of succession probably plays an important role in preventing a small number of tree species from becoming dominant. Gaps also help maintain the renowned diversity of animal species in the rain forest, both by maintaining tree diversity and more directly by providing temporarily open habitats in which there congregate an even greater variety of birds and other animals than is found in the dense forest.
In the wet and warm tropics, decay occurs rapidly, and so fallen trees and leaves from live trees do not last long on the forest floor. Thus, the soils in the tropics are often shallow, unlike the deep, rich soils that form in prairies, tundra, and boreal forests, where a colder climate slows the rate at which dead plant matter decays. In shallow soil, large trees cannot anchor to the ground with deep roots, so large live trees often fall rather than die and rot standing up. Many rain forest trees do, however, gain temporary respite from their horizontal fate because they are laced with giant vines, called lianas, to their neighbors or have formed finlike buttresses or multipod stilt roots above the ground. These buttresses and stilts also provide the growing tree with a means of taking up nutrients from a wider area of soil, a major advantage in the race to fill the gap first. Rapid decay, thin soils, gap formation, the race to fill gaps, roots designed to stabilize large trees and maximize nutrient uptake in thin soils – fused together, the coherence of these and other features of the rain forest are why our senses resonate with awe as we wander along the forest floor. These linked forms and fused processes are just as much a part of the biodiversity of the tropics as are the variety of species. (pp. 79-81)
To read more, Harte’s book is available for purchase on Amazon.