Tropical rainforests represent some of the most diverse and prolific ecosystems on the planet. Thousands of varieties of plants, including diverse orchids, exist in complex webs of mutual dependency under the canopies of enormous trees. Even as many tropical ecosystems become increasingly endangered by logging, ranching and slash and burn agriculture, botanists and scientists continue to discover new species of plants within them.
One of the most interesting facts about tropical rainforest orchids is that many of them are epiphytes, meaning that they grow on trees and are not directly connected to the soil. Epiphyte seeds are brought to the trunk or branch of a tree by birds or winds, and grow there. Epiphytes are not parasitic, using the tree only for physical support. They gain the nutrients they need to survive directly from the air, rain, and any compost that is present on the surface of the tree. Approximately 70 per cent of tropical orchids are epiphytes.
Tropical rainforests exist in Central and South America, Africa, and Southeast Asia. Typical rainforest ecosystems consist of very tall trees that create an enclosing canopy, and several layers of different kinds of plants that have adapted to the filtered sunlight beneath the canopies. While epiphytes, including many orchids, grow in the middle layer, far above the ground but below the canopy, other forms of ferns, moss and ground cover grow at the base of the trees. All of these plants are fertilised, pollinated, consumed, defecated upon, and spread by a host of insects and animals that depend on them for their own survival.
The majority of orchid varieties originate in tropical rainforests. However, domestic orchids now exist all over the world, as there is a large community of orchid enthusiasts who grow them as a hobby. There are an estimated 30,000 to 40,000 varieties of orchids in the world. These fall into three main categories: the aforementioned epiphytic orchids, lithophytic orchids, which grow at the bases of trees and gain their nutrients primarily from decaying mosses, and terrestrial orchids, which grow in soil.
Rainforest ecosystems have such large trees, and store such a high percentage of their nutrients in existent biomass, that they are vulnerable to destruction by logging. When the trees are cut down and hauled away, there is very little nutrient remaining in the soil. If logging is followed by farming or grazing, the soil is quickly depleted and desertification results. Plants such as orchids require very specific ecosystems, such as intact rainforests, to survive in the wild, and are quickly depleted when those ecosystems are compromised.