Cover Picture Credit: Jonathan Lai
A mangrove is a shrub or small tree that grows in coastal saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves occur worldwide in the tropics and subtropics, mainly between latitudes 25° N and 25° S. The total mangrove forest area of the world in 2000 was 137,800 square kilometers, spanning 118 countries and territories. Mangroves are salt-tolerant trees, also called halophytes, and are adapted to life in harsh coastal conditions. They contain a complex salt filtration system and complex root system to cope with salt-water immersion and wave action. They are adapted to the low oxygen conditions of waterlogged mud.
Mangroves can be found in over one hundred countries and territories in the tropical and subtropical regions of the world. Approximately 75% of world’s mangroves are found in just 15 countries. Asia has the largest amount (42%) of the world’s mangroves, followed by Africa (21%), Northern, Central America and the Caribbean (15%), Oceania (12%), and South America (11%). The latest remotely-sensed global synthesis estimates global mangrove forest area post-2000 as 141,333 km2.
There are important mangrove swamps in Kenya, Tanzania, the Democratic Republic of the Congo (DRC), Senegal, and Madagascar, with the latter even admixing at the coastal verge with dry deciduous forests. Nigeria has Africa’s largest mangrove concentration, spanning 36,000 km2. Oil spills and leaks have destroyed many in the last 50 years, damaging the local fishing economy and water quality. Along the coast of the Red Sea, both on the Egyptian side and in the Gulf of Aqaba, mangroves composed primarily of Avicennia marina and Rhizophora mucronata grow in about 28 stands that cover about 525 hectares. Almost all Egyptian mangrove stands are now protected.
Mangroves occur on the Pacific and Caribbean coasts of Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Panama. Mangroves can also be found in many of the Antilles including Puerto Rico, Cuba, and Hispaniola, as well as other islands in the West Indies such as the Bahamas.
Belize : the nation of Belize has the highest overall percentage of forest cover of any of the Central American countries. In terms of Belize’s mangrove cover—which assumes the form not only of mangrove ‘forest’, but also of scrubs and savannas, among others—a 2010 satellite-based study of Belize’s mangroves by the World Wildlife Fund (WWF) and the Water Center for the Humid Tropics of Latin America and the Caribbean found, in 2010, mangroves covered some 184,548 acres (74,684 hectares) or 3.4% of Belize’s territory. Brazil contains approximately 26,000 km2 of mangals, 15% of the world’s total. Ecuador has substantial remaining mangrove forests in the provinces of El Oro, Guayas, Manabi and Esmeraldas with limited forest remaining in Santa Elena.
Exploitation and conservation of the mangrove
Adequate data is only available for about half of the global area of mangroves. However, of those areas for which data has been collected, it appears that 35% of the mangroves have been destroyed. Assessments of global variation in mangrove loss indicate that national regulatory quality mediates how different drivers and pressures influence loss rates.
The United Nations Environment Programme and Hamilton (2013), estimate that shrimp farming causes approximately a quarter of the destruction of mangrove forests. Likewise, the 2010 update of the World Mangrove Atlas indicated that approximately one fifth of the world’s mangrove ecosystems have been lost since 1980, although this rapid loss rate appears to have decreased since 2000 with global losses estimated at between 0.16% and 0.39% annually between 2000 and 2012. Despite global loss rates decreasing since 2000, Southeast Asia remains an area of concern with loss rates between 3.58% and 8.08% between 2000 and 2012.
Grassroots efforts to protect mangroves from development and from citizens cutting down the mangroves for charcoal production, are becoming more popular. Solar cookers are distributed by many NGO’s as a low-cost alternative to wood and charcoal stoves. These may help in reducing the demand for charcoal.
Mangroves have been reported to be able to help buffer against tsunami, cyclones, and other storms, and as such may be considered a flagship system for ecosystem-based adaptation to the impacts of climate change. One village in Tamil Nadu was protected from tsunami destruction— the villagers in Naluvedapathy planted 80,244 saplings to get into the Guinness Book of World Records. This created a kilometer-wide belt of trees of various varieties. When the 2004 tsunami struck, much of the land around the village was flooded, but the village itself suffered minimal damage. Like seagrass, mangrove trees transport oxygen to roots of rhizomes, reduce sulphide concentrations, and alter microbial communities. Dissolved oxygen is more readily consumed in the interior of the mangrove forest. In some areas, mangrove reforestation and mangrove restoration is also underway. Red mangroves are the most common choice for cultivation, used particularly in marine aquariums in a sump to reduce nitrates and other nutrients in the water. Mangroves also appear in home aquariums, and as ornamental plants, such as in Japan, In Senegal, Haïdar El Ali has started the mangrove project, which (amongst others) focuses on reforesting several areas with mangroves.
A rainforest is an area of tall, mostly evergreen trees and a high amount of rainfall. Rainforests are Earth’s oldest living ecosystems, with some surviving in their present form for at least 70 million years. They are incredibly diverse and complex, home to more than half of the world’s plant and animal species—even though they cover just 6% of Earth’s surface. This makes rainforests astoundingly dense with flora and fauna; a 10-square-kilometer (4square-mile) patch can contain as many as 1,500 flowering plants, 750 species of trees, 400 species of birds and 150 species of butterflies.
Rainforests thrive on every continent except Antarctica. The largest rainforests on Earth surround the Amazon River in South America and the Congo River in Africa. The tropical islands of Southeast Asia and parts of Australia support dense rainforest habitats. Even the cool evergreen forests of North
America’s Pacific Northwest and Northern Europe are a type of rainforest.
Rainforest’s rich biodiversity is incredibly important to our well-being and the well-being of our planet. Rainforests help regulate our climate and provide us with everyday products.
Unsustainable industrial and agricultural development, however, has severely degraded the health of the world’s rainforests. Citizens, governments, intergovernmental organizations, and conservation groups are working together to protect these invaluable but fragile ecosystems.
Most rainforests are structured in four layers: emergent, canopy, understory, and forest floor. Each layer has unique characteristics based on differing levels of water, sunlight, and air circulation. While each layer is distinct, they exist in an interdependent system: processes and species in one layer influence those in another.
Tropical rainforests are found in Central and South America, western and central Africa, western India, Southeast Asia, the island of New Guinea, and Australia.
Sunlight strikes the tropics almost straight on, producing intense solar energy that keeps temperatures high, between 21° and 30°C. High temperatures keep the air warm and wet, with an average humidity of between 77% and 88%. Such humid air produces extreme and frequent rainfall, ranging between 2001000 centimeters per year. Tropical rainforests are so warm and moist that they produce as much as 75% of their own rain through evaporation and transpiration.
Tropical rainforests are the most biologically diverse terrestrial ecosystems in the world. The Amazon rainforest is the world’s largest tropical rainforest. It is home to around 40,000 plant species, nearly 1,300 bird species, 3,000 types of fish, 427 species of mammals, and 2.5 million different insects. Red-bellied piranhas and pink river dolphins swim its waters. Jewel-toned parrots squawk and fly through its trees. Poison dart frogs warn off predators with their bright colors. Capuchin and spider monkeys swing and scamper through the branches of the rainforest’s estimated 400 billion trees. Millions of mushrooms and other fungi decompose dead and dying plant material, recycling nutrients to the soil and organisms in the understory. The Amazon rainforest is truly an ecological kaleidoscope, full of colorful sights and sounds.
Temperate rainforests are located in the mid-latitudes, where temperatures are much milder than the tropics. Temperate rainforests are found mostly in coastal, mountainous areas. These geographic conditions help create areas of high rainfall. Temperate rainforests can be found on the coasts of the Pacific Northwest in North America, Chile, the United Kingdom, Norway, Japan, New Zealand, and southern Australia.
Benefits of Rainforests
Rainforests are critically important to the well-being of our planet. Tropical rainforests encompass approximately 1.2 billion hectares (3 billion acres) of vegetation and are sometimes described as the Earth’s thermostat.
Rainforests produce about 20% of our oxygen and store a huge amount of carbon dioxide, drastically reducing the impact of greenhouse gas emissions. Massive amounts of solar radiation are absorbed, helping regulate temperatures around the globe. Taken together, these processes help to stabilize Earth’s climate.
Rainforests also help maintain the world’s water cycle. More than 50% of precipitation striking a rainforest is returned to the atmosphere by evapotranspiration, helping regulate healthy rainfall around the planet. Rainforests also store a considerable percentage of the world’s freshwater, with the Amazon Basin alone storing one-fifth.
Rainforests provide us with many products that we use every day. Tropical woods such as teak, balsa, rosewood, and mahogany are used in flooring, doors, windows, boatbuilding, and cabinetry. Fibbers such as raffia, bamboo, kapok, and rattan are used to make furniture, baskets, insulation, and cord. Cinnamon, vanilla, nutmeg, and ginger are just a few spices of the rainforest. The ecosystem supports fruits including bananas, papayas, mangos, cocoa and coffee beans.
Rainforests also provide us with many medicinal products. According to the U.S. National Cancer Institute, 70% of plants useful in the treatment of cancer are found only in rainforests. Rainforest plants are also used in the creation of muscle relaxants, steroids, and insecticides. They are used to treat asthma, arthritis, malaria, heart disease, and pneumonia. The importance of rainforest species in public health is even more incredible considering that less than one per cent of rainforest species have been analyzed for their medicinal value.
Threats to Rainforests
Rainforests are disappearing at an alarmingly fast pace, largely due to human development over the past few centuries. Once covering 14% of land on Earth, rainforests now make up only 6%. Since 1947, the total area of tropical rainforests has probably been reduced by more than half, to about 6.2 to 7.8 million square kilometers.
Many biologists expect rainforests will lose 5-10% of their species each decade. Rampant deforestation could cause many important rainforest habitats to disappear completely within the next hundred years.
Such rapid habitat loss is due to the fact that 40 hectares of rainforest are cleared every minute for agricultural and industrial development. In the Pacific Northwest’s rainforests, logging companies cut down trees for timber while paper industries use the wood for pulp. In the Amazon rainforest, large-scale agricultural industries, such as cattle ranching, clear huge tracts of forests for arable land. In the Congo rainforest, roads and other infrastructure development have reduced habitat and cut off migration corridors for many rainforest species. Throughout both the Amazon and Congo, mining and logging operations clear-cut to build roads and dig mines. Some rainforests are threatened by massive hydroelectric power projects, where dams flood acres of land. Development is encroaching on rainforest habitats from all sides.
Economic inequalities fuel this rapid deforestation. Many rainforests are located in developing countries with economies based on natural resources. Wealthy nations drive demand for products, and economic development increases energy use. These demands encourage local governments to develop rainforest acreage at a fraction of its value. Impoverished people who live on or near these lands are also motivated to improve their lives by converting forests into subsistence farmland.
Many individuals, communities, governments, intergovernmental organizations, and conservation groups are taking innovative approaches to protect threatened rainforest habitats.
Many countries are supporting businesses and initiatives that promote the sustainable use of their rainforests. Costa Rica is a global pioneer in this field, investing in ecotourism projects that financially contribute to local economies and the forests they depend on. The country also signed an agreement with an American pharmaceutical company, Merck, which sets aside a portion of the proceeds from rainforest-derived pharmaceutical compounds to fund conservation projects.
Intergovernmental groups address rainforest conservation at a global scale. The United Nations’ REDD (Reducing Emissions from Deforestation and forest Degradation) Program, for example, offers financial incentives for reducing carbon emissions created by deforestation to 58 member countries. The Democratic Republic of the Congo used REDD funds to create an online National Forest Monitoring System that tracks and maps data on logging concessions, deforestation in protected areas, and national forestry sector measures. REDD funds were also used to investigate best practices in solving land disputes in Cambodia, which lacks proper forest zoning and boundary enforcement.
Non-profit organizations are tackling rainforest conservation through a variety of different approaches. The Rainforest Trust, for example, supports local conservation groups around the world in purchasing and managing critically important habitats. In Ecuador, the Rainforest Trust worked with the Fundación Jocotoco to acquire 495 more hectares for the Río Canandé Reserve, considered to have one of the highest concentrations of endemic and threatened species in the world. Partnering with Burung Indonesia, the Trust created 8,900-hectare reserve on Sangihe Island to protect the highest concentration of threatened bird species in Asia.
The Rainforest Alliance is a non-profit organization that helps businesses and consumers know that their products conserve rather than degrade rainforests. Products that bear the Rainforest Alliance seal contain ingredients from farms or forests that follow strict guidelines designed to support the sustainable development of rainforests and local communities. The Alliance also allows tourism businesses use of their seal after they complete an education program on efficiency and sustainability. In turn, this seal allows tourists to make ecologically smart vacation plans.
Old Growth Forest
An old-growth forest also termed primary forest, virgin forest, late seral forest or primeval forest – is a forest that has attained great age without significant disturbance and thereby exhibits unique ecological features and might be classified as a climax community. The Food and Agriculture Organization of the United Nations defines primary forests as naturally regenerated forests of native tree species where there are no clearly visible indications of human activity and the ecological processes are not significantly disturbed. More than one-third (34 percent) of the world’s forests are primary forests. Old-growth features include diverse tree-related structures that provide diverse wildlife habitat that increases the biodiversity of the forested ecosystem. Virgin forests are old-growth forests that have never been logged. The concept of diverse tree structure includes multi-layered canopies and canopy gaps, greatly varying tree heights and diameters, and diverse tree species and classes and sizes of woody debris.
The world has 1.11 billion ha of primary forest remaining. Combined, three countries – Brazil, Canada and Russia – host more than half (61 percent) of the world’s primary forest. The area of primary forest has decreased by 81 million ha since 1990, but the rate of loss more than halved in 2010–2020 compared with the previous decade. Old-growth forests tend to have large trees and standing dead trees, multi-layered canopies with gaps that result from the deaths of individual trees, and coarse woody debris on the forest floor Forest regenerated after a severe disturbance, such as wildfire, insect infestation, or harvesting, is often called second-growth or ‘regeneration’ until enough time passes for the effects of the disturbance to be no longer evident. Depending on the forest, this may take from a century to several millennia. Hardwood forests of the eastern United States can develop old-growth characteristics in 150–500 years. In British Columbia, Canada, old growth is defined as 120 to 140 years of age in the interior of the province where fire is a frequent and natural occurrence. In British Columbia’s coastal rainforests, old growth is defined as trees more than 250 years, with some trees reaching more than 1,000 years of age. In Australia, eucalypt trees rarely exceed 350 years of age due to frequent fire disturbance. Old-growth forests are often biologically diverse, and home to many rare species, threatened species, and endangered species of plants and animals, such as the northern spotted owl, marbled murrelet and fisher, making them ecologically significant. Levels of biodiversity may be higher or lower in old-growth forests compared to that in second-growth forests, depending on specific circumstances, environmental variables, and geographic variables. Logging in old-growth forests is a contentious issue in many parts of the world. Excessive logging reduces biodiversity, affecting not only the old-growth forest itself, but also indigenous species that rely upon old-growth forest habitat.
McDowell, an earth scientist at the Energy Department’s Pacific Northwest National Laboratory, said old-growth forests are essential to a stable climate because they remove carbon dioxide from the air and store it in tree trunks, roots, and soil. But such forests—those older than 140 years—have declined by 30% globally since 1900. Forests globally are becoming younger and shorter because of deforestation and climate change, reducing biological diversity and stunting forests’ ability to store atmospheric carbon, according to research published Thursday. Rising global temperatures, clear-cutting, wildfire, and climate change-driven insect infestations are leading to more trees dying and fewer trees growing old across the globe, according to the research in the journal Science. That creates an ecological imbalance that prevents the forests from storing carbon dioxide, the study found. “Trees are adapted to live in the conditions they grew up in,” said lead study author Nate McDowell. “The conditions they grew up in were historically relatively stable: Temperatures went up, but it came back down. And now it doesn’t come down anymore.”
McDowell, an earth scientist at the Energy Department’s Pacific Northwest National Laboratory, said old-growth forests are essential to a stable climate because they remove carbon dioxide from the air and store it in tree trunks, roots, and soil. Increasing levels of carbon dioxide in the air boost trees’ growth when they’re young, but they have little benefit as trees grow old. Rising temperatures also limit photosynthesis in trees, stunting their growth and possibly killing them. Increasingly severe droughts stress trees, leaving them vulnerable to infestations and disease. “We have a warmer environment now than we used to, and it’s progressively continuing to become warmer, and this is harder on trees, particularly on bigger trees,” McDowell said. Saving the mangrove forest, the rainforest and the old growth forest means saving our own lives because they are the lungs of the planet.