Tropical rainforests, in general, receive between 50 to 250 inches of rainfall each year. Hawaii’s Mount Waialeale is in a class by itself. It's the world's wettest rainforest, averaging 450 inches (that’s more than 37 feet of water) each year.
Most tropical rainforests lie along the equator in the "tropics"—between the Tropic of Capricorn and Tropic of Cancer—where sunlight strikes the Earth at roughly a 90-degree angle for a full 12 hours a day. This consistent and direct dource of energy maximizes photosynthesis, resulting in an unusual abundance and variety of plant life.
Because of heavy rains, the soil found in most tropical rainforests is shallow and very poor in nutrients. Nutrients are mainly found in a layer of decomposing leaf litter—also called a root mat—which is quickly broken down by various species of decomposers (insects, bacteria, and fungi). Shallow-rooted plants take up these nutrients before rainfall can wash them away.
The practice of cutting or burning down trees to clear land for agricultural purposes is short-sighted as the productive nutrients are held in the mass of a tree’s roots rather than in the soil itself.
Half of the Earth’s biodiversity resides in our rainforests, and yet these biomes are among the most threatened on our planet. Scientists have documented that more than 50 million acres of rainforest—an area the size of England, Scotland, and Wales—are destroyed or seriously degraded each year. Consequently, fragile ecosystems are destroyed and the planet loses untold numbers of yet-to-be-catalogued species.
To get an idea of what’s at stake, Academy scientists, led by Dr. Brian Fisher, curator and chairman of the Academy’s department of entomology, began traveling to Madagascar in 2002 to document the island’s arthropods. (Arthropods are animals with jointed legs and exoskeletons such as ants, insects, spiders, butterflies, and crustaceans.)
During that expedition, Fisher helped establish the Bibikely Biodiversity Center in Tsimbazaza National Park. There, scientists from both Madagascar’s Malagasy Academy of Science and the California Academy of Sciences work together to catalog the country’s rich biodiversity and, at the same time, to develop conservation priorities that will help ensure the survival of plants and animals found nowhere else on Earth.