Having studied one small rainforest community for over twenty years,I would have to say that rainforest ecology cannot yet be explained beyond the most basic essentials. We still have so much to learn about rainforest ecosystems and they are being cut down at such a rate that it is possible that we will never fully understand what we have thrown away for the sake of short term profits.
Rainforests occur in the vast tropical and subtropical regions of the world’s terrestrial environment. Land makes up only a quarter of the surface of the Earth. Of that, the regions between the Tropics of Capricorn and Cancer must produce most of the world’s diversity since they contain not only the majority of the world’s rainforests but also the most productive ecosystems in the oceans, the coral reefs. Even the task of naming all the species in the rainforest is woefully unaccomplished. Most of the insect and other invertebrate species being wiped out valley by valley worldwide were never named before they disappeared.
Currently it is estimated that hundreds of species are becoming extinct each day or week, depending on the estimator. We are causing one of the Earth’s Major Extinction Events, the first individual species that can claim such an ‘honor’. All the earlier great Extinction Events were caused by cosmic forces or earthly turmoils, but with the invention of bulldozers and chainsaws, mankind learned how to raze whole forests and turn them into wood products and pastures and in the process wipe out perhaps millions of species. We are doing it as I write and later, when this is read article by someone, it will probably still be happening. This rainforest destruction process impacts on the whole question fo how to explain Rainforest Ecology, as this title demands.
The ecology of a rainforest is exceedlingly complex. It is hard enough to unravel the food web in a simple ecosystem much less to begin to understand the relationships between the thousands of plants and animals that can exist in even a small area of rainforest. The rainforests of Costa Rica, luckily partly protected, contain more bird species than all of North America, with its great variety of ecosystems from tundra and taiga to coniferous and deciduous temperate forests to mountain and desert communities. This has to indicate an even greater number of plant and invertebrate species to support that great bird diversity along with the other species of mammals, reptiles and amphibians.
Even Charles Darwin was overwhelmed by the rainforest when he landed in South America on the voyage of the Beagle. As a collector for taxonomy, he could have spent the whole three years of the journey in one corner of the Brazilian rainforest and not made a dent on the variety that was there. It was too mind-bogglingly complex to work out mechanisms for how it had all come to be. Darwin needed the relatively simple ecosystems of the Galapagos Islands for that. Yet his theory of change by natural selection is visible all around in a rainforest. Not limited by cold winters, trees have adapted to breed and flower at any time of the year. Every new flower becomes a target for insects which change to meet the needs and requirements of their new food sources. Isolation comes in every valley and new species evolve rapidly to fill new niches. Along with genetics and geology, the amazing diversity of life forms in a rainforest shows evolution in action.
Plants and animals, producers, consumers and decomposers: a rainforest harbours multitudes of species at each of these trophic levels. They grow, breed and die. Some flourich, others become extinct and still more evolve to take their place. There is no way in under two thousand words to explain rainforest ecology. If you get a chance, experience it instead. Visit what remains of the coastal rainforests in Brazil and Australia or journey to the edge of the Amazon or to Costa Rica or Southeast Asia or Africa and stand on the edge and try to understand it. You won’t succeed but you will get a much better understanding of it than I can convey in words.
Rainforest used to be called jungle and described as a ‘green hell’. This is because it is not the natural habitat of most of the human species. A few tribes like the Pygmies and some of the South American Indians could cope in that environment. As diverse as it is, it is still very hard to both find enough to eat and to survive the hazards, which include dangerous predators, dissease-carrying insects and poisonous plants. It is also way harder to navigate in than a grassland. The vegetation is too thick to penetrate easily and the trees so tall you cannot see to find your way. It was not called a green hell for nothing. Only its destruction allows it to be penetrated, but then there is nothing left to understand, except pathetic dead bodies in museum collections.
We must find other ways of building our civilization than on the bodies of rainforest creatures. I fear that we won’t value it until it is almost lost. Then we will have to replant from the island refuges that are left. The result will not be the same. At first, being regrowth forests, the diversity will be low. We can only return that which did not become extinct, cloning notwithstanding. And then it will probably take millions of years for the diversity to return. But I believe it will, one way or another. Life has survived at least six major extinction events. It will survive ours. Whether we do also is another matter.
