A Place Out of Tropical: Tropical Rainforests and the Perils They Face - information on tropical forests, deforestation, and biodiversity
By Rhett Butler
BACKGROUND INFORMATION ON RAINFORESTS
Rainforests are forest ecosystems characterized by high levels of rainfall, an enclosed canopy and high species diversity. While tropical rainforests are the best-known type of rainforest and the focus of this section of the web site, rainforests are actually found widely around the world, including temperate regions in Canada, the United States, and the former Soviet Union.
Tropical forests presently cover about 2.4 billion hectares or about 16 percent of Earth's land surface.
The world's largest rainforest is the Amazon rainforest
Brazil has the largest extent of rainforest cover
Rainforests also exist outside the tropics, including temperate North America, South America, Australia, and Russia.
An estimated 50 percent of terrestrial biodiversity is found in rainforests
Rainforests are thought to store at least 250 billion tons of carbon
Deforestation and degradation of tropical forests account for roughly 10 percent of global greenhouse emissions from human activities
Tropical rainforests typically occur in the equatorial zone between the Tropic of Cancer and Tropic of Capricorn, latitudes that have warm temperatures and relatively constant year-round sunlight. Tropical rainforests merge into other types of forest depending on the altitude, latitude, and various soil, flooding, and climate conditions. These forest types form a mosaic of vegetation types which contribute to the incredible diversity of the tropics.
The bulk of the world's tropical rainforest occurs in the Amazon Basin in South America. The Congo Basin and Southeast Asia, respectively, have the second and third largest areas of tropical rainforest. Rainforests also exist on some the Caribbean islands, in Central America, in India, on scattered islands in the South Pacific, in Madagascar, in West and East Africa outside the Congo Basin, in Central America and Mexico, and in parts of South America outside the Amazon. Brazil has the largest extent of rainforest of any country on Earth.
Global forest cover
Rainforests provide important ecological services, including storing hundreds of billions of tons of carbon, buffering against flood and drought, stabilizing soils, influencing rainfall patterns, and providing a home to wildlife and indigenous people. Rainforests are also the source of many useful products upon which local communities depend.
While rainforests are critically important to humanity, they are rapidly being destroyed by human activities. The biggest cause of deforestation is conversion of forest land for agriculture. In the past subsistence agriculture was the primary driver of rainforest conversion, but today industrial agriculture — especially monoculture and livestock production — is the dominant driver of rainforest loss worldwide. Logging is the biggest cause of forest degradation and usually proceeds deforestation for agriculture.
Organization of this site
The rainforest section of Mongabay is divided into ten "chapters" (the original text for the site was a book, but has since been adapted for the web), with add-on content in the form of special focal sections (e.g. The Amazon, the Congo, REDD, etc), appendices, and other resources.
There is also a version of the site geared toward younger readers at kids.mongabay.com
ABOUT RAINFORESTS (SUMMARY)
Chapter 1: Rainforest distribution and characteristics
Each rainforest is unique, but there are certain features common to all tropical rainforests.
The global distribution of tropical rainforests can be broken up into four biogeographical realms based roughly on four forested continental regions: the Afrotropical, the Australiasian, the Indomalayan/Asian, and the Neotropical. Just over half the world's rainforests lie in the Neotropical realm, roughly a quarter are in Africa, and a fifth in Asia.
- Location: rainforests lie in the tropics.
- Rainfall: rainforests receive at least 80 inches (200 cm) of rain per year.
- Canopy: rainforests have a canopy, which is the layer of branches and leaves formed by closely spaced rainforest trees some 30 meters (100 feet) off the ground. A large proportion of the plants and animals in the rainforest live in the canopy.
- Biodiversity: rainforests have extraordinarily highs level of biological diversity or “biodiversity”. Scientists estimate that about half of Earth's terrestrial species live in rainforests.
- Ecosystem services: rainforests provide a critical ecosystem services at local, regional, and global scales, including producing oxygen (tropical forests are responsible for 25-30 percent of the world's oxygen turnover) and storing carbon (tropical forests store an estimated 229-247 billion tons of carbon) through photosynthesis; influencing precipitation patterns and weather; moderating flood and drought cycles; and facilitating nutrient cycling; among others.
Dozens of countries have tropical forests. The countries with the largest areas of tropical forest are (in order):
Other countries that have large areas of rainforest include Bolivia, Cameroon, Central African Republic, Ecuador, Gabon, Guyana, India, Laos, Malaysia, Mexico, Myanmar, Papua New Guinea, Republic of Congo, Suriname, and Venezuela.
- Democratic Republic of Congo
Chapter 2: Rainforest structure
Rainforests are characterized by a unique vegetative structure consisting of several vertical layers including the overstory, canopy, understory, shrub layer, and ground level. The canopy refers to the dense ceiling of leaves and tree branches formed by closely spaced forest trees. The upper canopy is 100-130 feet above the forest floor, penetrated by scattered emergent trees, 130 feet or higher, that make up the level known as the overstory. Below the canopy ceiling are multiple leaf and branch levels known collectively as the understory. The lowest part of the understory, 5-20 feet (1.5-6 meters) above the floor, is known as the shrub layer, made up of shrubby plants and tree saplings.
Chapter 3: Rainforest biodiversity
Tropical rainforests support the greatest diversity of living organisms on Earth. Although they cover less than 2 percent of Earth’s surface, rainforests house more than 50 percent of the plants and animals on the planet.
There are several reasons why rainforests are so diverse. Some important factors are:
While species everywhere are known for utilizing symbiotic relationships with other species to survive, the biological phenomenon is particularly abundant in rainforests.
- Climate: because rainforests are located in tropical regions, they receive a lot of sunlight. The sunlight is converted to energy by plants through the process of photosynthesis. Since there is a lot of sunlight, there is a lot of energy in the rainforest. This energy is stored in plant vegetation, which is eaten by animals. The abundance of energy supports an abundance of plant and animal species.
- Canopy: the canopy structure of the rainforest provides an abundance of places for plants to grow and animals to live. The canopy offers sources of food, shelter, and hiding places, providing for interaction between different species. For example, there are plants in the canopy called bromeliads that store water in their leaves. Frogs and other animals use these pockets of water for hunting and laying their eggs.
- Competition: while there is lots of energy in the rainforest system, life is not easy for most species that inhabit the biome. In fact, the rainforest is an intensively competitive place, with species developing incredible strategies and innovations to survive, encouraging specialization.
Chapter 4: The rainforest canopy
In the rainforest most plant and animal life is not found on the forest floor, but in the leafy world known as the canopy. The canopy, which may be over 100 feet (30 m) above the ground, is made up of the overlapping branches and leaves of rainforest trees. Scientists estimate that more than half of life in the rainforest is found in the trees, making this the richest habitat for plant and animal life.
The conditions of the canopy are markedly different from the conditions of the forest floor. During the day, the canopy is drier and hotter than other parts of the forest, and the plants and animals that live there have adapted accordingly. For example, because the amount of leaves in the canopy can make it difficult to see more than a few feet, many canopy animals rely on loud calls or lyrical songs for communication. Gaps between trees mean that some canopy animals fly, glide, or jump to move about in the treetops. Meanwhile plants have evolved water-retention mechanisms like waxy leaves.
Scientists have long been interested in studying the canopy, but the height of trees made research difficult until recently. Today the canopy is commonly accessed using climbing gear, rope bridges, ladders, and towers. Researchers are even using model airplanes outfitted with special sensors — conservation drones — to study the canopy.
Chapter 5: The rainforest floor
The rainforest floor is often dark and humid due to constant shade from the leaves of canopy trees. The canopy not only blocks out sunlight, but dampens wind and rain, and limits shrub growth.
Despite its constant shade, the ground floor of the rainforest is the site for important interactions and complex relationships. The forest floor is one of the principal sites of decomposition, a process paramount for the continuance of the forest as a whole. It provides support for trees responsible for the formation of the canopy and is also home to some of the rainforest's best-known species, including gorillas, tigers, tapirs, and elephants, among others.
Chapter 6: Rainforest waters
Tropical rainforests support some of the largest rivers in the world, like the Amazon, Mekong, Negro, Orinoco, and Congo. These mega-rivers are fed by countless smaller tributaries, streams, and creeks. For example, the Amazon alone has some 1,100 tributaries, 17 of which are over 1,000 miles long. Although large tropical rivers are fairly uniform in appearance and water composition, their tributaries vary greatly.
Rainforest waters are home to a wealth of wildlife that is nearly as diverse as the biota on land. For example, more than 5,600 species of fish have been identified in the Amazon Basin alone.
But like rainforests, tropical ecosystems are also threatened. Dams, deforestation, channelization and dredging, pollution, mining, and overfishing are chief dangers.
Chapter 7: Rainforest people
Tropical rainforests have long been home to tribal peoples who rely on their surroundings for food, shelter, and medicines. Today very few forest people live in traditional ways; most have been displaced by outside settlers, have been forced to give up their lifestyles by governments, or have chosen to adopt outside customs.
Of the remaining forest people, the Amazon supports the largest number of indigenous people living in traditional ways, although these people, too, have been impacted by the modern world. Nonetheless, indigenous peoples' knowledge of medicinal plants remains unmatched and they have a great understanding of the ecology of the Amazon rainforest.
In Africa there are native forest dwellers sometimes known as pygmies. The tallest of these people, also called the Mbuti, rarely exceed 5 feet in height. Their small size enables them to move about the forest more efficiently than taller people.
There are few forest peoples in Asia living in fully traditional ways. The last nomadic people in Borneo are thought to have settled in the late 2000's. New Guinea and the Andaman Islands are generally viewed as the last frontiers for forest people in Asia and the Pacific.
Chapter 8: Deforestation
Every year an area of rainforest the size of New Jersey is cut down and destroyed, mostly the result of human activities. We are cutting down rainforests for many reasons, including:
wood for both timber and making fires;
agriculture for both small and large farms;
land for poor farmers who don’t have anywhere else to live;
grazing land for cattle (the single biggest driver of deforestation in the Amazon);
plantations, including wood-pulp for making paper, oil palm for making palm oil, and rubber;
road construction; and
extraction of minerals and energy.
In recent decades there has been an important shift in deforestation trends. Today export-driven industries are driving a bigger share of deforestation than ever before, marking a shift from previous decades, when most tropical deforestation was the product of poor farmers trying to put food on the table for their families. There are important implications from this change. While companies have a greater capacity to chop down forests than small farmers, they are more sensitive to pressure from environmentalists. Thus in recent years, it has become easier—and more ethical—for green groups to go after corporations than after poor farmers.
Rainforests are also threatened by climate change, which is contributing to droughts in parts of the Amazon and Southeast Asia. Drought causes die-offs of trees and dries out leaf litter, increasing the risk of forest fires, which are often set by land developers, ranchers, plantation owners, and loggers.
Chapter 9: Rainforest importance
While rainforests may seem like a distant concern, they are critically important for our well-being. Rainforests are often called the lungs of the planet for their role in absorbing carbon dioxide, a greenhouse gas, and producing oxygen, upon which all animals depend for survival. Rainforests also stabilize climate, house incredible amounts of plants and wildlife, and produce nourishing rainfall all around the planet.
Chapter 10: Rainforest conservation
- Help stabilize the world’s climate: Rainforests help stabilize the world’s climate by absorbing carbon dioxide from the atmosphere. Scientists have shown that excess carbon dioxide in the atmosphere from human activities is contributing to climate change. Therefore, living rainforests have an important role in mitigating climate change, but when rainforests are chopped down and burned, the carbon stored in their wood and leaves is released into the atmosphere, contributing to climate change.
- Provide a home to many plants and animals: Rainforests are home to a large number of the world’s plant and animals species, including many endangered species. As forests are cut down, many species are doomed to extinction.
- Help maintain the water cycle: The role of rainforests in the water cycle is to add water to the atmosphere through the process of transpiration (in which plants release water from their leaves during photosynthesis). This moisture contributes to the formation of rain clouds, which release the water back onto the rainforest. In the Amazon, 50-80 percent of moisture remains in the ecosystem’s water cycle. When forests are cut down, less moisture goes into the atmosphere and rainfall declines, sometimes leading to drought. Rainforests also have a role in global weather patterns. For example researchers have shown that forests in South America affect rainfall in the United States, while forests in Southeast Asia influence rain patterns in southeastern Europe and China. Distant rainforests are therefore important to farmers everywhere.
- Protect against flood, drought, and erosion: Rainforests have been compared to natural sponges, moderating flood and drought cycles by slowing run-off and contributing moisture to the local atmosphere. Rainforests are also important in reducing soil erosion by anchoring the ground with their roots. When trees are cut down there is no longer anything to protect the ground, and soils are quickly washed away with rain. On steep hillsides, loss of forest can trigger landslides.
- Are a source for medicines and foods and support forest-dependent people: People have long used forests as a source of food, wood, medicine, and recreation. When forests are lost, they can no longer provide these resources. Instead people must find other places to get these goods and services. They also must find ways to pay for the things they once got for free from the forest.
Rainforests are disappearing very quickly. The good news is there are a lot of people who want to save rainforests. The bad news is that saving rainforests will be a challenge as it means humanity will need to shift away from business-as-usual practices by developing new policies and economic measures to creative incentives for preserving forests as healthy and productive ecosystems.
Over the past decade there has been considerable progress on several conservation fronts. Policymakers and companies are increasingly valuing rainforests for the services they afford, setting aside large blocks of forests in protected areas and setting up new financial mechanisms that compensate communities, state and local governments, and countries for conserving forests. Meanwhile, forest-dependent people are gaining more management control over the forests they have long stewarded. Large international companies are finally establishing policies that exclude materials sourced via deforestation. People are abandoning rural areas, leading to forest recovery in some planes.
But the battle is far from over. Growing population and consumption means that rainforests will continue to face intense pressures. At the same time, climate change threatens to dramatically alter temperatures and precipitation patterns, potentially pushing some forests toward critical tipping points.
Thus the future of the world's rainforests in very much in our hands. The actions we take in the next 20 years will determine whether rainforests, as we currently know them, are around to sustain and nourish future generations of people and wildlife.
Just how useful is forest restoration? New study seeks to find out
(03/27/2015) Across the world, scientists estimate there are about two billion hectares of degraded forestland. In Indonesia alone, 25 million hectares of former logging concessions currently have no management, according to research. A study recently published in mongabay.com’s open access journal Tropical Conservation Science suggests this may represent an important opportunity for biodiversity conservation through restoration.
APRIL violates sustainability policy by clearing peat forest after Jan cut-off
(03/26/2015) New data shows Asia Pacific Resources International Holdings Limited (APRIL) is continuing to destroy rainforests on deep peat despite a high profile pledge to clean up its operations. Today Greenomics-Indonesia released an analysis of two NASA Landsat images confirming that APRIL's subsidiary PT Riau Andalan Pulp Paper (RAPP) has cleared significant tracts of peat forest on Pulau Pedang island off Sumatra's coast since January 2015.
Mexico’s club mosses at risk of extinction
(03/26/2015) All nine species of the club moss genus Phlegmariurus found in the state of Veracruz in eastern Mexico are at risk of extinction, according to a new study published in the journal Tropical Conservation Science. One of these species, P. orizabae, has not been recorded in the wild since 1854.
Destruction of elephant, tiger, and orangutan habitat doubles
(03/25/2015) The rate of forest loss in Indonesia's Leuser Ecosystem — the only place on Earth where rhinos, orangutans, tigers, and elephants live in the same habitat — has more than doubled due to logging, encroachment, and conversion to industrial plantations, warn conservationists. In a statement issued Tuesday, the Sumatran Orangutan Society reported that 80,316 hectares of forest were lost between 2008 and 2013, a sharp increase from the 30,830 hectares cleared between 2002 and 2008.
Photos: expedition to Amazon’s white sands may have found new primate
(03/24/2015) Most people think of the Amazon rainforest as one massive, homogenous ecosystem—a giant castle of green. However, within the Amazon rainforest lie a myriad of distinct ecosystems, sporting unique characteristics and harboring endemic species. One of the rarer ecosystems in the Amazon is the white sands forest.
Reforestation programs may help reduce illegal logging in Indonesian Borneo
(03/24/2015) Can the act of planting a tree change one’s attitude towards forests and conservation? Erica Pohnan, Hotlin Ompusunggu, and Campbell Webb, from the conservation NGO Alam Sehat Lestari (ASRI), set out to answer this question by evaluating the effectiveness of reforestation programs in and around Gunung Palung National Park in West Kalimantan, Indonesia.
'How about that extension?' activists ask as forest exploitation moratorium deadline nears
(03/24/2015) Less than two months before the expiration of an Indonesian forest exploitation moratorium set up under an agreement with Norway, activists called on Environment and Forestry Minister Siti Nurbaya Bakar to extend the prohibition, as she promised to do after taking office last year.
World's fragmented forests are deteriorating
(03/24/2015) The world's forests are fragmented and deteriorating, states a new paper published in Science Advances. After analyzing satellite imagery and compiling data from long-term fragmentation studies, the authors conclude that 70 percent of remaining forest land exists within 1 km of an edge, which negatively impacts their fauna, flora, and ecosystem services.
Seeing the trees but not the forest (commentary)
(03/20/2015) Understanding forest dynamics is necessary for the sound management of forests, for both production and conservation. This includes an understanding of the extent of forest area, information about what the forest contains and how the forest resource is managed. Forest monitoring provides this information.
Study finds roads in Southeast Asia may be devastating forests, wildlife
(03/20/2015) Habitat loss and illegal hunting are leading drivers behind mammal population decline and extinction in the tropical forests of Southeast Asia. But what's driving these drivers? Road infrastructure, according to research. Researchers conducted the first-ever comprehensive study examining the impacts of road infrastructure on mammal populations in Southeast Asia; their findings were recently published in PLOS One.
DRC mulls changing Virunga's boundaries for oil
(03/19/2015) Last Friday, the government of the Democratic Republic of Congo (DRC) announced it was considering changing the boundaries of Virunga National Park to accommodate oil exploitation. Africa's oldest park, Virunga is home to around a quarter of the world's mountain gorillas as well as thousands of other species, many of them threatened with extinction.
Who's funding palm oil?
(03/19/2015) Palm oil may be the single most important crop that you never heard of. A vegetable fat that resembles reddish butter at room temperature, palm oil is derived from the fruit of the oil palm tree. Both nutritious and highly versatile, palm oil is now an important component of products ranging from biofuels and food to soaps and cosmetics. Estimates indicate that as much as 50 percent of the products used by the average Western consumer every day contain palm oil or its derivatives.
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By Rhett A. Butler
An overview of tropical rainforests for kids, based on mongabay.com's popular web site for children (kids.mongabay.com). Rainforests describes tropical rainforests, why they are important, and what is happening to them.
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