Introduction

Across the invisible equatorial line spans a green ring of vegetation at the apex of Earth’s biodiversity. Receiving the most direct sun rays of any latitude year-round, over the course of hundreds of millions of years, the modern day tropical rainforests emerged. On this section of the globe, water evaporates towards the sky just as fast as it falls to the ground. In this veritable hot-house, a complex system of plants and animals developed to maximize every bit of space to harness the ultimate power of the sun. By comparing temperature between the forested areas of the equator to non-forested areas that receive these intense solar rays, it becomes obvious that this green ring around the equator is a cooling pack that prevents this zone from overheating. This is due to the high amount of water stored, shade and evaporative cloud cover creation. These forests are a massive reserve of fresh water and are absolutely necessary for processing carbon dioxide and maintaining the temperatures of the region and our planet. And of course, no true rainforest would be complete without heavy amounts of rain which falls at least more than half the year, if not almost year-round. 

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Biodiversity

With more plant and animal species than anywhere else, tropical rainforests are the most biodiverse ecosystems on Earth. Covering only 12% of the planet’s land surface, the rainforest contains about 50% of the Earth’s biodiversity. There is very little seasonal change in the average rainforest. Within 10 degrees north and south of the equator, life here receives equal amounts of sunlight year-round. Being warm, wet and humid, while receiving the most direct solar rays, creates the perfect environment for plants to continuously grow, evolve and thrive. 

 

 

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Forest Floor

In a classic mature tropical rainforest, only 2% of sunlight reaches the forest the floor. Here plants have evolved to grow with less light (one of the reasons why tropical rainforest plants have become the most popular indoor house plants worldwide). However for some of the plants, creeper vines and especially many tree species, the ultimate goal is to climb towards the light. 

Contrary to popular descriptions, the forest floor of a rainforest is not clear of vegetation or easy to walk through. In some areas plant numbers are more dense than others and if one is to walk off trail, it is still advised to bring a machete (and clearly mark your trail because it is easy to get lost). Walking about one can observe a variety of ferns and other small herbaceous plants dotting the ground, from shrubs to bushes, stilt palms, small trees and saplings that will eventually become large trees. Wide fanned-out buttress tree roots are another common feature. These wide roots are necessary to stabilize these large, often epiphyte covered trees, because roots in this area do not anchor deep into the soil, therefore they need to cover more surface area. Primarily in areas absent of large trees and along riverbanks is where the floor of the forest is most densely packed, with groves of medium sized plants dominating the area to maximize light. 

 

The forest floor is also covered in decaying plant and animal matter. And subsequently patches of fungi, visible and hidden just beneath the surface, work hard to decompose this material back into nutrients for growing plants. Worms, beetles, termites, millipedes and other insects, as well as micro organisms are also found on the forest floor taking part in the decomposition process. Unlike temperate forests, in a lowland rainforest the top layer of soil and decaying matter is surprisingly thin. This is because high humidity and warm temperatures provides the most ideal conditions for rapid decay. However as elevation increases, due to cooler temperatures, organic material breaks down slower and the top soil gradually increases in thickness. Large four legged mammals also roam the forest floor, juxtaposed with small lizards and frogs.

 

 

 

 

 

 

 

Understory Layer

Occupying the space between the canopy and the forest floor, the understory layer consists of shade-tolerant shrubs, herbs, small trees, and large woody vines. Within this zone, broad leaf, epiphytic vines can also be found along the trunks of large trees, utilizing the space to receive more light than they would on the forest floor. The understory is home to an abundance of small birds, snakes and a variety of other animals across the spectrum. 

 

 

 

 

 

 

 

 

Canopy layer

To fully understand rainforest ecology, one must understand the world of the canopy; the section of the forest containing nearly 50% of the forest’s species. As we follow thick woody lianas and broad leaf epiphytic vines up the trunk of the tree we begin to encounter branches holding more epiphytes. Throughout nearly all rainforests of the world, ferns, orchids, moss and bromeliads (in Central & South America) can be found to varying degrees in the canopy as larger birds, tree frogs, reptiles and small to medium size mammals  roam about. 

 

 

 

 

 

 

Emergent Layer

Rising above the canopy, is the emergent layer. Trees that endured the elements which achieved the highest levels growth. Randomly scattered throughout the forest, these trees can be home to eagles, large bats, parrots and some monkey species. Among the tree species that can achieve emergent status are Ceibas, Dipteryx, and cuipos among others. In the dynamic ecosystem of the rainforest, these trees can drastically alter the forest floor. Upon falling over from lightning or old age, these trees will knock down many other trees in their path creating gaps in the forest. This allows light to penetrate the forest floor and new plants species to colonize the area. 

 

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Soils

Generally the soils of lowland rainforest are nutrient-deficient, hard-packed clay which experience significant leaching (the loss of nutrients due to significant rain). Among these clay soils there are two types: ultisols and oxisols. Ultisols are characterized as weathered, acidic red clay soils deficient in key nutrients such as calcium and potassium. Oxisols are acidic, usually less reddish in color, nutrient deficient soils, which happen to be well-drained compared to ultisols. In some areas the soil may even be a sandy base. And generally speaking, the organic top soil in these areas is usually very thin, in some areas less than an inch thick, due to the fact that organic material breaks down most rapidly in this hot humid climate. 

 

However not all are made of the 2 clay substrates. In places with a history of volcanic activity or locations accumulating sediment runoff at the base of mountain ranges, the soil tends to be more nutrient rich. As the forest goes higher in elevation, the soils tend to be more mineral rich due to the geological profile of the mountains. In addition the top soil of high elevation cloud forests are much thicker due to the cooler temperatures which break down the dense decaying plant matter at a much slower pace. As a result of the dense decaying matter, the humus / peat soil in a cloud forest slowly accumulates over hundreds, if not thousands of years.

 

 

 

 

Fungi

In and above this soil substrate lies one of the key ingredients of the forest and principle decomposers that turn dead and living organic materiel into nutrients for plants: fungi. Just like the veins in an anatomical human body diagram, the mycelium web of fungal threads thoroughly engulf almost every corner of the forest floor and even the trunks of living trees. They are essentially the veins of the forest.  The mycelium is particularly important for the growth of trees, because these connective tissues existing on the outside and inside of roots that exchange water and nutrients as well as being one of the conduits for chemical communication between the standing trees and other plants in the forest. When one sees mushrooms rise out of the ground and rotting logs, they are merely the fruiting bodies of the mycelium. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Biodynamic role of Climate & Fresh Water Management

Rainforests play a significant role in attracting and holding large amounts of water and ultimately generating rain. In fact, with regards to the larger rainforests like the Amazon, 50% of the rain which falls in the forest comes from the forest, which is known as a closed loop cycle. From the rivers to the plants to the rain, water is in constant circulation in rainforests. In this cycle water in the ground moves through the roots of plants and fungal mycelium to circulate through the plants and trees and ultimately perspire from the ground, plants and trees to form low hanging clouds which move along the lower atmosphere above the forest and evenuatually fall back down into the forest as rain, mist or early morning dew. This happens to varying degrees 365 days a year. However the more torrential rains happen when this evaporation from the forest joins larger global weather patterns driven by the jetstreams. These jet streams are partially controlled by the sun and the shifting temperature zones of the ocean, and the water evaporating from these areas.

 

 However there is a newer theory proposed, called the ‘biotic pump’, which states that forests attract rain from the ocean by creating low pressure zones that create a vacuum sucking warmer air from the ocean. It is a known fact that there is more water vapor in the air of a large forested area than there is in the open ocean. This is because in a forest, especially a dense rainforest with its incredible amount of leaves, there is more surface area for water to evaporate from. One might assume at a warmer latitude with direct sunlight hitting a large body of water more evaporation, thus rain is occurs. However this is not the case. In the Amazon & Congo rainforests there is 2-3 times as much percipition than there is in the Atlantic ocean at the same latitude. So to summarize the biotic pump, as water evaporates from the forest it changes from gas to liquid condensing into clouds. As clouds form, the air pressure drops, causing more vapor to rise causing an upward air current that also pulls air horizontally closer to the ground from outside the forest like a vacuum, including the air from the ocean. The ocean air containing water vapor combines with clouds above the forest making stronger storms increasing the total amount of rainfall. Therefore forests create a massive constant air current which attracts moisture from hundreds of miles away, which not only pulls moisture to the forests, but the surrounding areas adjacent to the forest. 

 

Ultimately rainforests, which attract water also hold large amounts of water in the plants and trees. These forests which have the densest vegetation effectively become living bio-reservoirs of water. Of the fresh water on Earth, twice as much water can be found in the plants than in rivers and lakes. In other words, the Amazon forest contains twice as much water as the rivers, lakes and swamps within it. These plants, with their complex root systems and dense organic matter also act filtration for sediment runoff, and toxic chemicals in our atmosphere. So as the water runs into rivers, lakes and reservoirs which end up as our drinking water it is also cleaner thanks to the forest.

 

 

Photosynthesis & Climate

Lastly forests are famously known for the fact that they produce oxygen. Through the process of photosynthesis light, carbon dioxide, water and nutrients produce sugars for the plant to live and as a byproduct of this process oxygen is release. It is know that carbon dioxide is a natural and essential part of our atmosphere: its food for the plants and keeps our Earth warm. However humans are generating record amounts of carbon dioxide through the burning of fossils and deforestation, which is causing the Earth to warm beyond sustainable levels, affecting climate and unbalancing the Earths life systems. This is why rainforests are so important, because they have the highest levels of plants they also produce the highest levels oxygen. As plants grow through the process of photosynthesis, they are essentially converting this massive amount of carbon into accumulated organic matter, thus storing the carbon (all living things on Earth are carbon based life forms). This is another reason to keep forest standing and intact, because if forests are chopped down and burned, they are releasing massive amounts of carbon back into the atmosphere, which took thousands if not millions of years to accumulate through the steady expansion of the forest. If massive rainforests are burned to the ground, they are no longer producing oxygen, balancing carbon levels, holding water and attracting new cooling life-giving rain clouds. This massive release of stored carbon is further warming the atomosphere. Standing healthy, sizeable rainforests are essential for life on Earth and the future survival of humans. 

 

 

 

 

 

 

 

Rainforest Zones:

 

Neotropics

The tropical jungles of Central and South America, which includes the Amazon, the largest tropical rainforest in the world. Containing the most biodiverse selection of epiphetic plants in trees, the rainforests of the Americas are a dazzling sight to behold. This includes bromeliads, orchids, anthuriums, cacti, ferns, tabacon, philodendron, monstera, and many other plants. These forests also have the highest biodiversity of birds. Not known for the largest mammals in the jungle, neither the smallest, these forests have a number of interesting creatures including tapir, anteater, sloths, jaguars, ocelots, kinkajous, tayras, peccaries, armadillos, opossums, raccoons, coatis, deers, foxes, agoutis, capybaras and many others depending on the area. With regards to the primates, many of the monkeys are distinct from the primates of Africa and Asia, due to their prehensile tail which allows them to grab and hang on to tree branches. Reptile and amphibian diversity is also high, with the most notable being the colorful poison frog. And in the sky these forests are known for their hummingbirds, tanagers, macaws, toucans and harpy eagles to name a few. 

 

 

Africa

Known by many as the jungles with the largest mammals in the world, the Congo, is also happens to be the youngest major rainforest. The Congo is also the second largest rainforest in the world. Generally speaking the rainforests here have a similar make up to rainforest around the world, but tend to have less biodiversity of epiphytic plants in the canopy. They also are known for their larger clearings in the forest known as bais. Often initially created by the movements of elephants, bais are a place where mammals and birds come to drink water and socialize. Often in these bais one will find elephants, water buffalo, hippopotamus, antelopes, gorillas, chimpanzees, monkeys, wild boars, parrots, hyenas and the occasional leopard. Deeper into the forest, one will find the more elusive mammals like the okapi, servile or the pangolin. In the canopy Grey parrots, turacos, sun birds and hornbills can be found. 

 

South East Asia

Considered to be the oldest rainforest on Earth, the rainforests of Asia contain a high biodiversity of epiphytes. Half the forests in this region lie on the mainland of Asia (extending from India/Sri Lanka to Vietnam), while the other half are spread out amongst the Islands of Indonesia (the area of Indonesia & Malaysia geographically referred to as Sundaland) and the Philippines. These forest are rich in mammal diversity with some notable species being tigers, clouded leopards, rhinos (a critically endangered population in Sumatra remaining), orangutans, gibbons, elephants, tapirs, pangolins, slow loris, tarsiers, deer, water buffalo, and wild boars. In canopies of Asia the greatest variety and the largest of the hornbills can be found along with parrots, and sunbirds among many others. The rainforests of South East Asia are by far the most biodiverse rainforests in the Eastern Hemisphere. 

 

Madagascar

For its size, the most endemically distinct island, and of course known by many as the home of the lemurs. Found along the East coast, the Madagascar rainforest sits at the base of the coastal mountains. These mountains prevent the moist tropical winds of the Indian Ocean from dispersing across the island, instead concentrating this moisture on the lowland forests. Here an astounding 82% of the plants are endemic, only found in these forests. Like most tropical rainforests, these forests also contain primates; lemurs. With 5 distinct families on the island and 15 species in the jungle, their elongated nose and sense of smell are just a few of the things that set them apart from other primates. But lemurs are unique here. Nearly all of the mammals in these forests are endemic. Perhaps the second most notable mammal is the Fossa, the apex predator of the island. A partially arborial mid-size predator in the Eupleridae family resembling a cross between a cat and civet. Madagascar is also known for having the highest diversity of chameleon lizards

 

Papua New Guinea / Australia

While the flora of the forests of New Guinea and Queensland Australia, are very similar to that of Asia, the fauna, in particular the mammals, all of which are marsupial. Marsupials are animals that carry their young in a pouch on their belly. This includes possums, cuscus and tree kangaroos among others. New Guinea is also the 3rd largest rainforest in the world, which also includes the most orchid species in the Eastern Hemisphere. This zone, especially New Guinea, is known for their birds-of-paradise. From the family of birds known as Paradisaeidae, these colorful, uniquely feathered birds are known for their elaborate mating rituals.  

 

 

Universal to all Jungles

And of course, there are characteristics that all tropical rainforests around the world share. Just to name a few: ferns, palms, strangler fig trees, liana vines, creeping broadleaf vines, orchids, moss, epiphytes (though some contain more than others), cup fungi, bamboo and species of trees with wide buttress trunks. With regards to fauna, all tropical rainforests contain parrots, large lizards & snakes and crocodiles (or something similar). They also contain a significantly higher biodiversity of insects than in temperate zones. And lastly but certainly not least, tropical rainforests, due to their high density of vegetation hold exceptional amounts of water which keeps the area cooler and positively affects the weather. 

 

Temperate Rainforests

Occuring in the temperate zones, either farther north or farther south in the 2 hemispheres, temperate rainforest are often comprised of a mix of pine and broadleaf trees. Like other rainforests, these all contain ferns, orchids and moss and some even contain bamboo. However, most, except for the ones in Asia, do not contain primates. Furthermore while generally being more diverse than their neighboring ecosystems, they have significantly less biodiversity with flora and fauna than tropical rainforests. Among the most notable temperate rainforests the North American Pacific Northwest, the Valdivian temperate rainforests in South America, New Zealand, southeastern Australia, Atlantic rainforests of Ireland, southern Norway, southern Japan, Bulgaria, Turkey, Georgia, Tawain, southern China and northern Iran. Many of the rainforest also receive snow in the winter. 

 

 

Conservation Challenges of the Tropics

Rainforests face many conservation challenges with the greatest threat being expanding agriculture. Rainforests with their reliable precipitation and agreeable climate sought after by many. In lowlands among the biggest threats are palm oil, pineapple, soy and cattle. With regards to growing crops in the lowlands, insect density is high and the soils are usually poor and nutrient deficient which leads many producers to dump exorbitant amounts of fertilizer and pesticides on their crops. In the higher cloud forest regions the threat is even greater due to the fact the soils are usually nutrient rich and the cool mild climate allows people to grow a wider variety of crops. This of course makes the land more sought after for development. Among the main crops in these regions are coffee, tea, avocados, and infestations of invasive non-native eucalyptus. 

 

When complex forests which balance out the soil are replaced with large scale commercial farming monocultures, the soil is no longer able to self-sustain and often rapidly deteriorates. Monocultures which are large plantations of a single crop reduce insect biodiversity as well as bird biodiversity and so on, decimating biodiverse animal populations. This is why forested buffer zones and green belts are essential in large scale farming, especially in tropical zones. 

 

In addition to large scale, multi-national funded agriculture, small-scale slash and burn farming is an issue that fragments the forest. With regards to slash and burn, small to medium size plots are clear by cutting the foilage than during the drier part of the year, the land is burned to resettle the nutrients. However in this method, there is usually little to no mulching of organic matter. This is often in favor of lighting the land on fire multiple times which produces less nutrients with each successive burn until the land becomes nutrient deficient and unsuitable for cultivation, thus pushing farmers to slash and burn new sections of the forest, turning the land to swiss cheese. This practice has been historically implemented by many indigenous cultures with little to no overall negative impact on the land. However as populations grow, causing forests to shrink and subsistence farming communities expand, this is pushing many areas to the brink, with many wild animals being the first to permanently disappear. 

 

But the forest faces more threats then the rapid, wreckless expansion of agriculture and it's outdated practices. Over-hunting and the sale of bushmeat from the forest, can also be done to excess, causing various species to go extinct causing an imbalance in the food chain. Among the other threats are the demand for commercial logging, as well as illegal selective logging. Mining, oil prospecting, the construction damns and roads. Poaching of exotic animals for the pet trade is also another significant impact.  Various mammals, especially monkeys, parrots, toucans, frogs and snakes are all among the animals being poached. Also some animals like the pangolin are also under threat for poaching due to the demand for the scales in Chinese traditional medicine. Rare plants are also being poached, especially orchids and aroids. 

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Rainforests are also home to indigenous people that have lived there for thousands of years. When rainforests are cut down and replaced, it not only threatens their culture, their right to life, but also their very existence. 

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From it's incredible beauty, to respect for life, to maintaining a healthy existence here on Earth, we have a reason to protect and properly maintain these ecological jewels known as rainforests. Our future depends on it!