The Tropical Rainforest

Naomi Lichtenstein and Noah Strand 

DESCRIPTION

The tropical rainforest, with its vibrant settings and captivating life—is one of the world’s most exceptional ecosystems. Tropical rainforests exist on nearly every continent. The world’s two largest rainforests can be found adjacent to the Amazon River in South America and the Congo River in Central Africa. Together, the Amazon and Congo rainforests cover 3.5 million square miles—home to many of the rarest species on the planet. In Southeast Asia, rainforests are not known for their size; they are, however, some of the oldest on Earth—offering scientists a unique glimpse into a major stage of the planet’s evolutionary history. 

Located in close proximity to the Earth’s equator, tropical rainforests are brimming with flora and fauna; a space of 10 km² (4 mi²) alone can contain more than 1,500 species of flowering plants, 750 different trees, 400 kinds of birds, and 150 types of butterflies. Rainforest plants—rarely found elsewhere on Earth—provide food and shelter to a wide variety of living creatures, supply raw extracts used in modern medicine, and partake in gas exchanges that provide twenty percent of atmospheric oxygen. 

Tropical rainforests survive under a hot and humid climate—with temperatures ranging only slightly between 70 to 85°F (21 to 30°C). Rainforests receive at least twelve hours of sunlight a day—absorbed almost entirely by towering trees. Despite occupying only a small part of the Earth’s surface, tropical rainforests harbour an astonishing amount of biological productivity: 500 to 2,000 metric tons of leaves, wood, and other organic matter per hectare aid in soil fertility and carbon sequestration that benefit ecosystem processes worldwide. For their role in storing carbon dioxide and returning oxygen, tropical rainforests are often called ‘the planet’s lungs.’ This age-old ecosystem—whether by its unparalleled production of natural resources or its critical regulation of the climate—is deeply connected to all life on Earth.

ANIMALS FOUND IN THE TROPICAL RAINFOREST

Though they cover a mere six percent of the Earth’s surface, tropical rainforests are home to the most diverse and unique cast of animal characters on the planet—where 80 percent of all documented species can be found. Scientists say no other ecosystem has existed on Earth the longest. The Daintree rainforest in Australia is the oldest that remains today, dating back more than 180 million years—when dinosaurs still walked the Earth. Even during the prehistoric Ice Ages, when alpine glaciers and ice sheets covered much of the planet, tropical rainforests remained a steadfast sanctuary for plants and animals whose uninterrupted evolution has produced some of the most unusual and resilient species ever found—a mirror to the Earth’s ancient past. 

The living creatures native to the tropical rainforest are spread throughout its four distinct layers, from lowest to highest: the murky ground floor, the thick understory layer, the rich canopy layer, and the hostile emergent layer. The conditions of each tier varies greatly from the others, providing special insight into the animal species that inhabit them.

Ground floor: 
Unable to penetrate the fortress of trees and plants that lie overhead, sunlight is a rarity on the rainforest floor. Here, darkness is both friend and foe: for large mammal predators—such as the jaguar, puma, and leopard—the day long dimness provides an optimal setting for their careful pursuit of smaller prey that include wild boar and rodents of various sizes. The jaguar, reflected in the culture of ancient South American civilizations as a symbol of might, is perhaps the most fearsome. Its ability to climb trees and sprint at great speeds—and the most powerful bite of any big cat—place it at the top of the tropical rainforest food chain. For those predators who lack the brute strength of the jaguar, must be more creative in their search for food. 

Unlike its larger cousins, the Jaguarundi—closely related to the jaguar and puma—is only slightly bigger in size than a domesticated cat. Despite its smaller stature, this tropical rainforest hunter employs a variety of vocalized impressions to mimic ground-feeding birds, reptiles, and other creatures. With the dark as its ally, the Jaguarundi waits patiently as it draws out victims with its wide array chirps, barks, and bird-like whistles. 

The shadowy ground floor not only serves as adequate hunting ground, but shelter to millions of tiny decomposers—such as worms, termites, scorpions, caterpillars, and ants. Together, these and many other insects act as a forest-wide recycling system—breaking down dead plant litter into the vital nutrients that keep the tropical rainforest and its entire species domain alive. Remarkably, there are more than 50 million different kinds of invertebrates found in every corner of the tropical rainforest that perform an assortment of functions. One such species called the Amazonian giant centipede uses lethal venom to overpower bats, mice, and lizards much larger than itself. In the tropical rainforest, size is certainly a poor judge of strength! 

Understory:
Like the ground floor, the understory is poorly lit. Still, quite a few well-adapted plants receive just enough sunlight to survive—complete with spiraled vines and large leaves that hold much of the tropical rainforest’s closely entwined amphibian and reptile communities. This layer’s many frogs, snakes, and lizards prey on the insects that inhabit the ground floor below. Two noteworthy members of this special group are the red-eyed tree frog and the emerald tree boa constrictor. 

The red-eyed tree frog, with its striking appearance, is a frequent mascot of rainforest conservation. In fact, its bright red and green colors are used to confuse predators lucky enough to spot it—granting just enough time to make an escape. Although it is often confused with venomous poison dart frogs, the red-eyed tree frog—which does its hunting at night—uses its sticky tongue to reel in resting flies, moths, and crickets.

The emerald tree boa constrictor, found in the tropical rainforests of South America, blends in easily with its leafy surroundings. The emerald tree boa snags rodents and birds that venture too close—which can take this massive snake several months to digest.  

Canopy: 
The canopy layer gives way to the largest and perhaps most fascinating mix of species seen anywhere in the tropical rainforest. A dense roof created by thousands of trees at this level creates the dark, humid, and tranquil environment that lies below. 

The rich life found in this section of the rainforest—home to fifty percent of its total animal population—is largely due to the abundance of tree seeds, nuts, and fruits that attract species of all kinds. With so many competitors in search of food, animals in the canopy are keen to occupy their own territory. Living creatures often rely on visual displays to ward off intruders but due to extremely thick foliage, those that dwell in the rainforest canopy must use their voices instead. For this reason, this layer is known to be extremely loud at all times: from yelling primates to shrieking parrots, nearly every living creature in the canopy has its own unique call. Even if they cannot be seen, they can certainly be heard. 

There are many noisy members of the rainforest canopy, though none put up a racket like the howler monkey. When a troop of howlers is ready to send a clear message to other primates that their territory is not for trespassing, they let loose deafening cries that can be heard for up to three miles. In the case of the howler monkey, the bark seems to be far worse than the bite. 

Three-toed sloths are an easier going member of the canopy community. Their fur is an incredible subsystem of insect life: hundreds of beetles and moths at a time can be found burrowing on a hairy sloth. Should these insects decide to take off in search of food, when they return their sloth home probably won’t have gone far!  

Emergent: 
At the top of the rainforest are the ecosystem’s most resilient species, able to withstand heavy winds and rain shielded by trees in the lower layers. The trees that sprout to the top of the rainforest skyline reach heights of up to 200 feet, many of which are centuries old. Such great heights are welcoming to only a select few animals of the tropical rainforest—ruled by some of the biggest birds of prey on the planet. 

A large majority of species in the emergent layer are winged: birds, bats, and butterflies are commonly sighted at the top of rainforest. The mightiest of flyers, however, is the Harpy eagle—the largest eagle on Earth—able to dart gracefully through tree cover to snag its prey. Its enormous size allows it to take down deer and sloths, thanks in large part to talons longer than the claws of the North American grizzly bear. 

There are other animals at this level unable to fly who, when needed, take unusual measures to safely transport themselves between trees: Pygmy gliders, for example, are small rodents that use flaps between their limbs which help them ride air currents to nearby branches. 

ISSUES WITHIN THE TROPICAL RAINFOREST

As the world continues to grow in production of goods and services, the tropical rainforests, however, continue to shrink. Everyday, the rainforests are losing hundreds of animal and plant species due to rainforest deforestation alone. Some of the biggest industries that contribute to rainforest depletion are agriculture, commercial fishing, smuggling, poaching, damming, and logging. Wildlife harvests, in the Brazilian Amazon alone, 9.6 to 23.5 million mammals, birds, and reptiles are removed and taken for trafficking or products. Damming and hydroelectric projects in general are endangering rainforest waters, causing erosion from deforestation, overfishing, and poisoning from oil and chemical spills. This degradation has caused worldwide damage to the global economy, the environment, and local indigenous peoples. Factory farming,  specifically cattle pastures, occupy eighty percent of the deforested areas in the Amazon. Run-off continuously contaminates the rivers, fires used to manage fields often spread into the already desolate forests, and the overall deforestation contributes to climate change, releasing 340 million tons of carbon into the atmosphere each year. Another main issue with this is that the soil is only fertile enough to support a few crops before it needs to recover some of its nutrients. Farmers in these areas tend to clear the land to replace what has been lost, continuing the ever perpetual downward spiral, damaging the soil, and in turn the ecosystem, for the foreseeable future. Furthermore, Brazil’s Congress recently passed legislation that would soften environmental regulations that are set to protect the Amazon. This will severely contribute to the loss of biodiversity essential to all life on earth. Regardless of human impacts on rainforests worldwide, natural fires, volcanic activity, drought, and tropical storms contribute to much of the damage that has plagued the forests for years. Much of these natural disasters are also attributed to climate change effects on the planet’s systems and behavior ultimately. Estimates claim that over half of the Amazon Rainforest is at risk of burning during extreme droughts, much due to human activity exacerbating these effects. Volcanic eruptions release large amounts of carbon dioxide, burning much forest along with it. Droughts can initially weaken the canopy of the rainforest by reducing local humidity and rainfall, while scientists are concerned that global warming could worsen the droughts, leading to a greater risk of increasing extinction rates. Tropical storms like hurricanes, cyclones, and typhoons can cause extensive damage as high wind speeds can cause large swaths of land to be cleared, which can take centuries to restore naturally. 

POLICIES ADDRESSING THE ISSUES

Recent policies passed worldwide reflect the call to reduce intensive agriculture, logging, and foresting within tropical rainforest territory. Certain existing policies and programs are helping to address underlying causes, reducing debt and imports of illegal wood, and building countries’ governance capacity to help reduce deforestation themselves. The U.S., in turn could adopt specific policies that emphasize internationally recognized human rights and promote transparency and citizen participation. This could be enacted and seen through revenue management, tenure and forest zoning reforms, and national program design and implementation. Currently, the recent Waxman-Markey bill (HR 2454) includes language regarding protections and working to engage local communities. Through improving small scale irrigation systems, pushed up labor demand and wages as well as pulling labor out of a more extensive agricultural sector, reduced forest clearing by almost fifty percent in the Philippines. Additionally, increased supply from the intensive sector puts pressure on domestic agriculture prices, reducing the rent of extensive agriculture. These agricultural policies reduced emissions and even included credit programs, subsidized fertilizers and seeds, assistance in marketing, and agricultural extension programs. Internationally, the development of procurement or purchasing policies established by governments that require legality or sustainability due diligence is a growing trend. 

This may include incentives or requirements to purchase independently verified legal or sustainably certified products as well as limits in forestry services and logging permits. 

HOW TROPICAL RAINFOREST ANIMALS ARE AFFECTED

SYMBIOSIS: AN UNFORSEEN CURSE

The steady rain and consistently warm temperatures distinctive of the tropical rainforest climate provide ideal living conditions for a wide range of species. While sunlight and water are widely available to all of its living creatures, space is not. The many millions of animals that dwell in tropical rainforests must coexist with little room to spare—making their closely intertwined living and eating habits necessary for survival. The complex interplay between rainforest organisms is a special characteristic of this fascinating ecosystem: members of its four layers form relationships that mutually benefit their participants, allowing rainforest life of all kinds to make the best use of limited resources and territory. 

Symbiotic interactions among rainforest creatures vary in scale and frequency. Billions of plants and trees that blanket the entire ecosystem must be regularly pollinated by nectar-feeding bees or bats, which receive food and shelter in return. Even Capuchin monkeys take part in pollinating the rainforest: on their trips to and from the treeline, the Capuchins unknowingly spread pollen collected in their fur among various flora—including special flowers they frequently eat. 

On a micro level, ants and caterpillars near the rainforest floor also work to reciprocal advantage: caterpillars ooze a sweet chemical from their backs that ants consume as food, while the ants protect their slow-moving partner from a host of insect predators. 

Many other examples of symbiosis can be observed taking place throughout the tropical rainforest; there are more still to identify as new species await discovery by the world’s scientists. 

As human activity continues to encroach upon tropical rainforest territory, the densely packed conditions in which its species live is quickly becoming too cramped for survival. Rampant deforestation has forced many animals to now compete for food with those they would not otherwise interact. As trees continue to fall, communities of larger mammal species are pushed together. Now, overcrowded trees have pushed weaker species to the brink of extinction. 

It is the closely intertwined relationships animal species have with each other in the tropical rainforest that has proven their greatest weakness. These symbiotic partnerships are often binding: with no time to adapt, the loss of one species likely means the loss of others who rely on it. In the tropical rainforest, scientists say this phenomena is happening on a massive scale: some 137 tropical rainforest species become extinct every day. 

The destructive practices that rampage tropical rainforests are compounded by the presence of sporadic weather patterns and rising temperatures symptomatic of a changing climate—to which these ecosystems are extremely sensitive. Human-driven climate change is a growing threat of special concern for tropical rainforests—unable to withstand the type of drought and severe storms scientists predict will soon become a norm at the current pace. Barring a swift and substantial withdrawal of human activity in and around tropical rainforests, the world’s most vital ecosystem could soon disappear altogether. 

While there exist some policy initiatives in the interest of tropical rainforest species protection, too few are in place to initiate the broad change necessary to save them. Future policy to protect the invaluable wildlife found in tropical rainforests will entail clear restrictions on rainforest development: world leaders must mandate that—when it comes to cattle and lumber—this necessary ecosystem is unconditionally off limits. Only then can it be ensured that already suffering tropical rainforests can begin the decades long journey to recovery unharmed.  

WHAT CAN YOU DO?

While there is much to do on the policy front, when it comes to creating actionable change as a society, saving the Earth’s tropical rainforests starts with education. Teaching others about these vital ecosystems—and what the future could look like without them—can broaden support for rainforest protection in our community and abroad. 

At a time when tropical rainforests are at great peril, the protection of their diverse species is a priority: the wildlife trafficking business, a flagrant contributor to biodiversity loss, can and should be strictly monitored and punished. Donations and volunteer work are integral to the eradication of illegal animal trafficking. Visit the Wildlife Conservation Society or the Worldwide Fund for Nature at their website for more on ways you can help. 

We must also encourage ourselves to purchase products that place no strain on the tropical rainforest ecosystem as a whole; turning to local, small businesses is the easiest way to find legitimately sustainable goods and services—and support the economy. Additionally, we can help support and call for the implementation of government regulations on road building and infrastructure projects in the rainforests. Demanding an international coalition to protect tropical rainforests from human development is a real and meaningful effort that can help hold corporations accountable for their past and present wrongdoings. There is simply no substitute for these critically important ecosystems: ensuring their long health will take a collective effort. 

Sources: Columbus State University, Conservation International, Conserve Energy Future, Life in the Rainforest, The Living Rainforest, Mongabay, National Geographic, Nicholas Institute for Environmental Policy Solutions, Proceedings of the National Academy of Sciences of the United States of America, Rainforest Action Network, Rainforest Alliance, Rainforest Cruises, Rain-Tree Publishers, South American Vacations, Wildlife Conservation Society, Worldwide Fund for Nature