THE TROPICAL RAIN FOREST CANOPY
Tropical rain forests grow around the equator. There are no cold seasons and it rains all year round. Plenty of heat and water wash most plant nutrients out of the soils. They leak to deep soil layers where roots can not come, or are transported by rivers to the sea. The forests have plenty of light and water. Scarce nutrients are conserved by tight, biological recycling.
It takes only a few hours for most nutrients from dead plants or animals to be taken up by bacteria and other tiny organisms. Some of those are eaten, so their nutrients go to animals. Others convert nutrients and carry them to plant roots. Chains of living organisms pass nutrients on, like firemen buckets of water. This keeps rain forests healthy in such poor environments.
Tropical people get their food from such soils. Since long, they understood recycling. Tropical ways to practice agriculture were sustained during thousands of years, for example in Mexico, Indonesia or Ethiopia. Tropical rain forests produce food for no more than two or three people per square kilometre. Forests can only keep human groups alive if converted, partly into crop fields and partly into village forest gardens. Till this day, successful tropical agricultural cycles imitate the recycling and biological diversity of the original forests.
The floor and the ceiling
Forests are not eternal. All forests are born and die, also without human help. Fire, earthquakes, storms, floods or poison gas from volcanoes clear forests away. The empty places are occupied by newly born pieces of forest. The young ones grow up to resemble the old parts of the forest, but are not completely the same, just like your mother and you. However, they all have to face the same kind of environment. Roots operate in the soil, providing water and nutrients. Tree crowns rise high in the air, amidst light and oxygen.
The home of roots and the home of leaves and flowers both crawl, bristle and swarm with life. Roots live among bacteria, fungi, insects, worms and others creatures, sometimes closely associated. Associations of roots with micro-organisms absorb water and process nutrients. Most nutrients from the soil are built into such nitrogen-rich substances as vitamins, proteins and their building blocks, aminoacids. Simply said, nitrogen products travel upwards inside the wood, from the soil towards the leaves.
Leaves and flowers belong to trees, but also to other plants. Lianes attach supple, thin stems to or around tree trunks and branches, carrying leaves up high to the sun. Epiphytes grow upon tree branches and trunks. They are no parasites because they do not harm their hosts. Bromeliads, Orchids and Philodendrons are examples of epiphytes from tropical America. The staghorn fern is from Africa and some epiphytic ant plants are Asian. Figure 1 shows epiphyte communities in Trinidad, Harry Belafonte's Island in the Sun.
Together, all these plants build the roof or canopy of the rain forest. Trunks and big branches are, as it were, the beams and rafters of the roof. Smaller plants and leaves form shingles. Leaves use light energy to make sugars out of carbon dioxide from the air. The sugars travel back to the roots below through the bark. Simply said, carbon products come from the tree crown and travel downwards inside the bark, towards the roots.
Much rain causes excess sap to travel upwards from the roots. Some of this sap is sweated out from the leaves, so proteins and vitamins arrive on the outside, not inside the leaves. These feed bacteria. After the first bacterial colonists, more organisms appear in this new milieu with every rain shower. Fungi, algae and finally mosses, grow on the old Colombian rain forest leaf in Fig. 2. The leaf finally dies and falls off, carrying the hitchhikers on its back to the forest soil.
When there is much sun, the descending, syrupy sap in the bark becomes more concentrated and sugars are in excess. The roots sweat out sugars, so these are not arriving in the roots, but on the outside. The sugars feed bacteria, fungi, small worms and insects. The fungi pay back the trees by providing them with nitrogen products, vitamins for sugar, proteins for syrup.
Miss Dr. Jakoba Ruinen, in the early 1950's, was the first to describe these dynamics and the part played in them by microscopic Life as a coherent cycle. The root zone and its community of Life was much studied already and became quite well-known since. However, the processes in the treetops were much less studied. Dr. Ruinen called the interface between leaves and air the phyllosphere, and said that this was a much neglected milieu. It still is.
The floor of the forests starts being quite well-known, but not so its ceiling or canopy.
Working in the canopy
Figure 3 shows some more recent means devised for people to visit the tropical rain forest canopy. In 1946, Professor Paulian built a tower reaching the canopy in the Forêt du Banco, Abidjan, Côte d'Ivoire, West Africa. This tower was the first tool to observe and measure forest canopies. However, a tower is narrow, so only a small part of the canopy is visible. More than 20 years later, British and German researchers built walkways from tree to tree in the canopy. Today there are many, some accessible to tourists, as in Serawak, Brunei, Perú or Costa Rica.
The next contraptions were a captive hydrogen balloon with polaroid camera, built in Gabon by the Hladiks, and Vooren's ultra-light photo-plane in Taï, Côte d'Ivoire, both in the 1970's. Tree climbing with speleologist's gear was how the American botanist Scott Mori reached high forest tree crowns in French Guiana, where he sometimes spent the night. In the late '80's the French professor Francis Hallé, together with a pilot and an architect, devised a nice tool for sampling many canopies from the air. It was the canopy raft, a platform lifted up outside the forest and lowered down on the tree tops by a giant Montgolfière or hot-air balloon in the cigar-like shape of a Zeppelin, which is a motor-driven balloon.
Today, access to the canopy is not too difficult any more. Big machines are Morawetz's giant crane lifting cabins in and over the treetops, or American "canopy trams" moving along cables in and over the forest canopy in Costa Rica. The array of tools to reach and study forest canopies diversified in a few decades. Like the Oceanic bathyscaphs between 1900 and 1940, they opened a whole new world.
Reaching the forest canopy from below and entering the sunshine is like opening a trapdoor in the roof of a house. Above is another world. In tropical rain forests one abruptly arrives from the shade under the forest in the garden of our planet. The air is dry, the sun beats upon your head. In the dry season many lianes, epiphytes and trees are flowering abundantly, surrounded by clouds of insects and small birds exploiting the honey and pollinating the flowers. A concerto of animal songs and noises at dusk constitutes the sound track of this incredible spectacle. The richness of the garden is staggering, where it spreads over the green waves formed by the enormous tree crowns, alternating with deep valleys where trees have fallen.
Why work in the canopy?
The canopy is like the Garden of Eden. In Paradise one should not work, it is believed. After being banned from the Garden, Adam and Eve indeed were condemned for their sin to work and "…eat bread in the sweat of thy face." So why work in the canopy, instead of admiring it? There is no easy answer. Today's human society indeed prefers eating the forest to eating from the forest. Work is to be done, because big, rumbling machines are ready to clear the forests and transform them into stacks of skinned wood and stretches of cropping fields. Is this wrong?
No, it is not wrong, because we saw that more than two or three persons per km2 must convert and manage forest lands in order to have food, shelter and clothes. So it is not wrong to convert forests into landscapes that can support many people, as long as forests are loved and respected.
Yes, it is wrong, because we see that forests are often merely seen as a money-box for bad times or a hobby of the rich and powerful. Trees and forests are cut cheaply and roughly, with no consciousness of their unique richness and their tremendous age compared to our life-span. The greatest mass, wood, is exploited at low cost and sold for high profit, as if from a mine. This indeed is profoundly wrong, because only a fool cuts the branch on which he sits.
Canopy work is the opposite of mono-cropping or mining. There is no abundant supply of any one bulk product to be had from the canopy by mining or harvesting with big, stupid machines. On the contrary, there are many fine and expensive products to be extracted, but this has to be done selectively and delicately by small and clever tools. This option lacked realism up till a decade or so ago, because knowledge was still lacking and tools were still too crude.