Forest is a type of Habitat or Biome which has high density of Trees. The FAO (Food and Agriculture Organization) defines Forest as a land with Tree crown cover (or equivalent stocking level) of more than 10% and area of more than 0.5 hectare. The Forest is in fact a complex ecosystem with distinct interrelationships of non living organisms (the plants, animals, micro-organisms) and the non-living, inorganic or abiotic part (soil, climate, water, organic debris, rocks) of an environment. Forests can develop wherever there is an average temperature greater than about 10° C in the warmest month and an annual rainfall in excess of about 200 mm annually. Forests houses over two-thirds of known terrestrial Species of the World. There are various type of Forests of which the Tropical Rainforests are located at latitudes of 10° north and south of the Equator and the latitudes between 53°N and 67°N have Boreal Forests. Over 30% of the Earth's surface is covered with Forests in modern times where as once they covered 50% of total surface of the World. This has happened mainly because of Deforestation caused by Human need for wood, food, housing etc.

• Types of Forests and their Classification
  
  • UNEP-WCMC Classification
  • WWF Classification

• Forest Distribution
• General Characteristics of Forests
• Origin of Forests
• Benefits of Forests

                        Forest Types and Classification

Forests have been classified in different ways. They have been classified according to the Biomes in which they exist, combined with leaf longevity of the dominant Species i.e. whether they are evergreen or deciduous. Another Classification is classified whether the Forests are composed predominantly of Broad-Leaf Trees, Coniferous (needle-leaved) Trees, or Mixed.

1. UNEP-WCMC Classification

United Nations Environment Programme - World Conservation Monitoring Centre divides the World's Forest into 26 major types, which reflect climatic zones as well as the principal types of Trees. These 26 Forest categories are used to enable the translation of Forest types from national and regional classification systems to a harmonised global one.

Temperate and Boreal Forest Types

1.  Evergreen Needleleaf Forest - Natural Forest with > 30% canopy cover, in which the canopy is predominantly (> 75%) Needleleaf and Evergreen.

2.  Deciduous Needleleaf Forest - Natural Forests with > 30% canopy cover, in which the canopy is predominantly (> 75%) Needleleaf and Deciduous.

3.  Mixed Broadleaf / Needleleaf Forest - Natural Forest with > 30% canopy cover, in which the canopy is composed of a more or less even mixture of Needleleaf and Broadleaf crowns (between 50:50% and 25:75%).

4.  Broad Leaf Evergreen Forest - Natural Forests with > 30% canopy cover, the canopy being > 75% evergreen and Broadleaf.

5.  Deciduous Broadleaf Forest - Natural Forests with > 30% canopy cover, in which > 75% of the canopy is deciduous and Broadleaves predominate (> 75% of canopy cover).

6.  Freshwater Swamp Forest - Natural Forests with > 30% canopy cover, composed of Trees with any mixture of leaf type and seasonality, but in which the predominant environmental characteristic is a waterlogged soil.

7.  Sclerophyllous Dry Forest - Natural Forest with > 30% canopy cover, in which the canopy is mainly composed of sclerophyllous Broadleaves and is > 75% evergreen.

8.  Disturbed Natural Forest - Any Forest type above that has in its interior significant areas of disturbance by people, including clearing, felling for wood extraction, anthropogenic fires, road construction, etc.

9.  Sparse Trees and Parkland - Natural Forests in which the Tree canopy cover is between 10-30%, such as in the steppe regions of the world. Trees of any type (e.g., needleleaf, broadleaf, palms).

10.  Exotic Species Plantation - Intensively managed Forests with > 30% canopy cover, which have been planted by people with Species not naturally occurring in that country.

11.  Native Species Plantation - Intensively managed Forests with > 30% canopy cover, which have been planted by people with Species that occur naturally in that country.

Tropical Forest Types

12.  Lowland Evergreen Broadleaf Rain Forest - Natural Forests with > 30% canopy cover, below 1200m altitude that display little or no seasonality, the canopy being >75% evergreen Broadleaf.

13.   Lower Montane Forest - Natural Forests with > 30% canopy cover, between 1200-1800m altitude, with any seasonality regime and leaf type mixture.

14.  Upper Montane Forest - Natural Forests with > 30% canopy cover, above 1800m altitude, with any seasonality regime and leaf type mixture.

15.  Freshwater Swamp Forest - Natural Forests with > 30% canopy cover, below 1200m altitude, composed of Trees with any mixture of leaf type and seasonality, but in which the predominant environmental characteristic is a waterlogged soil.

16.  Semi-evergreen Moist Broadleaf Forest - Natural Forests with > 30% canopy cover, below 1200m altitude in which between 50-75% of the canopy is evergreen, > 75% are Broadleaves, and the Trees display seasonality of flowering and fruiting.

17.  Mixed Broadleaf/Needleleaf Forest - Natural Forests with > 30% canopy cover, below 1200m altitude, in which the canopy is composed of a more or less even mixture of Needleleaf and Broadleaf crowns (between 50:50% and 25:75%).

18.  Needleleaf Forest - Natural Forest with > 30% canopy cover, below 1200m altitude, in which the canopy is predominantly (> 75%) Needleleaf.

19.  Mangroves - Natural Forests with > 30% canopy cover, composed of Species of mangrove Tree, generally along coasts in or near brackish or salt water.

20.  Disturbed Natural Forest - Any Forest type above that has in its interior significant areas of disturbance by people, including clearing, felling for wood extraction, anthropogenic fires, road construction, etc.

21.  Deciduous/Semi-Deciduous Broadleaf Forest - Natural Forests with > 30% canopy cover, below 1200m altitude in which between 50-100% of the canopy is Deciduous and Broadleaves predominate (> 75% of canopy cover).

22. Sclerophyllous Dry Forest - Natural Forests with > 30% canopy cover, below 1200m altitude, in which the canopy is mainly composed of sclerophyllous Broadleaves and is > 75% evergreen.

23.  Thorn Forest - Natural Forests with > 30% canopy cover, below 1200m altitude, in which the canopy is mainly composed of deciduous Trees with thorns and succulent phanerophytes with thorns may be frequent.

24.  Sparse Trees and Parkland - Natural Forests in which the Tree canopy cover is between 10-30%, such as in the savannah regions of the world. Trees of any type (e.g., Needleleaf, Broadleaf, Palms).

25.  Exotic Species Plantation - Intensively managed Forests with > 30% canopy cover, which have been planted by people with Species not naturally occurring in that country.

26.  Native Species Plantation - Intensively managed Forests with > 30% canopy cover, which have been planted by people with Species that occur naturally in that country.

These 26 major types can be reclassified into 6 broader categories:

i)  Temperate Needleleaf - Temperate Needleleaf Forests cover a larger area of the world than any other Forest types. They mostly occupy the higher latitude regions of the northern hemisphere, as well as high altitude zones and some warm temperate areas, especially on nutrient-poor or otherwise unfavourable soils. These Forests are composed entirely, or nearly so, of coniferous Species (Coniferophyta). In the Northern Hemisphere pines Pinus, spruces Picea, larches Larix, silver firs Abies, Douglas firs Pseudotsuga and hemlocks Tsuga, make up the canopy, but other taxa are also important. In the southern hemisphere most coniferous Trees, members of the Araucariaceae and Podocarpaceae, occur in mixtures with Broadleaf Species that are classed as Broadleaf and Mixed Forests.

ii)  Temperate Broadleaf and Mixed - Temperate Broadleaf and mixed Forests, which include a substantial component of Trees in the Anthophyta, cover over 6.5 million km2 of the Earth's surface. They are generally characteristic of the warmer temperate latitudes, but extend to cool temperate ones, particularly in the southern hemisphere. They include such Forest types as the mixed deciduous Forests of the USA and their counterparts in China and Japan, the Broadleaf evergreen rain Forests of Japan, Chile and Tasmania, the sclerophyllous Forests of Australia, the Mediterranean and California, and the southern beech Nothofagus Forests of Chile and New Zealand.

iii)  Tropical Moist - Tropical moist Forests cover more than 11 million km2 of the humid tropics and include many different Forest types. The best known and most extensive are the Lowland Evergreen Broadleaf Rainforests, which make up over half this area and include, for example: the seasonally inundated varzea and igapó forests and the terra firme Forests of the Amazon Basin; the Peat Forests and moist dipterocarp Forests of Southeast Asia; and the high Forests of the Congo Basin. The Forests of tropical mountains are also included in this broad category, generally divided into upper and lower montane formations on the basis of their physiognomy, which varies with altitude. The montane Forests include cloud Forest, those Forests at middle to high altitude, which derive a significant part of their water budget from cloud, and support a rich abundance of Vascular and Non-Vascular Epiphytes. Mangrove Forests also fall within this broad category, as do most of the Tropical Coniferous Forests of Central America.

iv)  Tropical Dry - Tropical dry Forests are characteristic of areas in the tropics affected by seasonal drought. Such seasonal climates characterise much of the tropics, but less than 4 million km2 of tropical dry Forests remain. The seasonality of rainfall is usually reflected in the deciduousness of the Forest canopy, with most Trees being leafless for several months of the year. However, under some conditions, e.g. less fertile soils or less predictable drought regimes, the proportion of evergreen Species increases and the Forests are characterised as "sclerophyllous". Thorn Forest, a dense Forest of low stature with a high frequency of thorny or spiny Species, is found where drought is prolonged, and especially where grazing animals are plentiful. On very poor soils, and especially where fire is a recurrent phenomenon, Woody Savannas develop.

v)  Sparse Trees and Parkland - Sparse Trees and parkland are Forests with open canopies of 10-30% crown cover. They occur principally in areas of transition from Forested to non-Forested landscapes. The two major zones in which these ecosystems occur are in the boreal region and in the seasonally dry tropics. At high latitudes, north of the main zone of boreal Forest or Taiga, growing conditions are not adequate to maintain a continuous closed Forest cover, so Tree cover is both sparse and discontinuous. This vegetation is variously called open Taiga, open lichen woodland, and Forest tundra. It is Species-poor, has high bryophyte cover and is frequently affected by fire.

vi)  Forest Plantations - Forest plantations, generally intended for the production of timber and pulpwood increase the total area of Forest worldwide. In 1999 FAO has estimated that total plantation area in developed countries is about 600,000 km2 and in developing countries it is about 550,000 km2. Commonly mono-specific and/or composed of introduced Tree Species, these ecosystems are not generally important as habitat for native biodiversity. However, they can be managed in ways that enhance their biodiversity protection functions and they are important providers of ecosystem services such as maintaining nutrient capital, protecting watersheds and soil structure as well as storing carbon. They may also play an important role in alleviating pressure on natural Forests for timber and fuel-wood production.

2. WWF (World Wide Fund for Nature) Classification

The type of Forest depends mainly on location - that is, distance from equator and altitude - and climate.

Basic Classification

• Tropical Forest - These type of Forests are characterised by their location neat the equator. They have year-round high temperatures and abundant rainfall which makes them a dense and lush with vegetation. They are vital storehouses of biodiversity on the planet.

• Sub-tropical Forests - These are found to the south and north of the Tropical Forests. The Trees here are adapted to resist the summer drought.

• Mediterranean Forests - These Forests are found to the south of the temperate regions around the coasts of the Mediterranean, California, Chile and Western Australia. The growing season is short and almost all Trees are evergreen, but mixed hardwood and softwood.

• Temperate Forests - These Forest are found in eastern North America, north-eastern Asia, and western and eastern Europe. Temperate Forests are a mix of Deciduous and Coniferous Evergreen Trees. Usually, the Broad-Leaved Hardwood Trees shed leaves annually. There are well-defined seasons with a distinct winter and sufficient rainfall.

• Coniferous Forests - Coniferous Forests are found in the cold, windy regions around the poles. There are both Hard-woods and Conifers found in this region. The Conifers are evergreen and structurally adapted to withstand the long drought-like conditions of the long winters, whereas the Hard-Woods are Deciduous.

• Montane Forests - These Forests receive most of their precipitation from the mist or fog that comes up from the lowlands and as such are also known as cloud Forests. Some of these Montane Woodlands and Grasslands are found in high-elevation tropical, subtropical and temperate zones. Plants and animals in these Forests are adapted to withstanding the cold, wet conditions and intense sunlight. Trees are mainly Conifers.

Detailed Classification

1.  Tropical and Subtropical Moist Broadleaf Forest - These types of Forests are generally found in large, discontinuous patches centred on the equatorial belt and between the Tropics of Cancer and Capricorn. These Forests are found around the world, particularly in the Indo-Malayan Archipelagos, the Amazon Basin, and the African Congo. In general, biodiversity is highest in the Forest canopy which can be divided into five layers: overstory canopy with emergent crowns, a medium layer of canopy, lower canopy, shrub level, and finally understory.

• These Forests are characterized by low variability in annual temperature and high levels of rainfall (>200 centimetre annually).

• Forest composition is dominated by semi-evergreen and evergreen deciduous Tree Species. These Trees number in thousands and contribute to the highest levels of Species diversity in any terrestrial major Habitat type.

• A perpetually warm, wet climate promotes more explosive plant growth than in any other environment on Earth. A Tree here may grow over 75 feet in height in just 5 years.

• The canopy is home to many of the Forest's animals, including Apes, Monkeys, Hornbills, Toucans, and the Harpy Eagle. Below the canopy, a lower understory hosts to Snakes and Big Cats. The Forest floor, relatively clear of undergrowth due to the thick canopy above, is prowled by other Animals such as Gorillas and Deer.

Some of the Ecoregions of Tropical and Subtropical Moist Broadleaf Forest

1. Seychelles and Mascarenes Moist Forests in Islands to the north and east of Madagascar, off the east coast of Africa.
2. East African Coastal Forests in Kenya, Somalia, Tanzania.
3. Albertine Rift Montane Forests in Burundi, Democratic Republic of Congo, Rwanda, Tanzania, Uganda.
4. Sulawesi Moist Forests in Sulawesi, a large island to the south-east of Borneo, in Indonesia.
5. New Guinea Montane Forests in The island of New Guinea, north of Australia.
6. Queensland Tropical Forests in Northeastern Australia.
7. Lord Howe-Norfolk Islands Forests in Islands off the east coast of Australia in the Tasman Sea.
8. South-western Ghats Moist Forests in Western coast of India.
9. Northern Indochina Subtropical Moist Forests in Southern China, northern Laos, Myanmar, Thailand, and Vietnam.
10. Taiwan Montane Forests in Taiwan, a large island off the eastern coast of China.
11. Peninsular Malaysian Lowland and Mountain Forests in Malaysia, Singapore, Thailand.
12. Nansei Shoto Archipelago Forests between southern Japan and Taiwan.
13. Eastern Deccan Plateau Moist Forests in India.
14. Cardamom Mountains Moist Forests in Cambodia and Thailand.
15. Talamancan and Isthmian Pacific Forests in Costa Rica and western Panama.
16. Central Andean Yungas in Argentina, Bolivia, and Peru.
17. Atlantic Forests in Argentina, Brazil, Paraguay.
18. South Pacific Islands Forests in American Samoa, Cook Islands, Fiji, French Polynesia, Niue, Samoa, Tonga, Wallis and Futuna Islands.

2.  Tropical and Subtropical Dry Broadleaf Forest - These are found in southern Mexico, south-eastern Africa, the Lesser Sundas, central India, Indochina, Madagascar, New Caledonia, eastern Bolivia and central Brazil, the Caribbean, valleys of the northern Andes, and along the coasts of Ecuador and Peru.

• These Forest are are warm year-round, and may receive several hundred centimetres or rain per year but they also experience long dry seasons which last several months and vary with geographic location.

• Deciduous Trees predominate these Forests, and during the drought a leafless period occurs, which varies with Species type.

• The newly bare Trees open up the canopy layer, enabling sunlight to reach ground level and facilitate the growth of thick underbrush.

• Tropical Dry Forests are home to a wide variety of wildlife including monkeys, large cats, parrots, various rodents, and ground dwelling birds. Many of these Species are adapted to the prevalent environment.

Some of the Ecoregions of Tropical and Subtropical Dry Broadleaf Forest

1. Madagascar Dry Forests in Western coast of Madagascar.
2. Nusu Tenggara Dry Forests in South-east Asia: Indonesia.
3. New Caledonia Dry Forests in New Caledonia, a large island north-east of Australia.
4. Indochina Dry Forests in Cambodia, Laos, Thailand, Vietnam.
5. Chhota-Nagpur Dry Forests in Eastern India.
6. Mexican Dry Forest in Guatemala and Mexico.
7. Tumbesian-Andean Valleys Dry Forests in Colombia, Ecuador, and Peru.
8. Chiquitano Dry Forest in Bolivia and Brazil.
9. Atlantic Dry Forests in North-eastern Brazil.
10. Hawaii's Dry Forests in Hawaiian Islands.

3.  Tropical and Sup-Tropical Coniferous Forest - These are found predominantly in North and Central America, these tropical regions experience low levels of precipitation and moderate variability in temperature.

• Tropical and Subtropical Coniferous Forests are characterized by diverse Species of conifers, whose needles are adapted to deal with the variable climatic conditions.

• These biomes feature a thick, closed canopy which blocks light to the floor and allows little underbrush. As a result, the ground is often covered with fungi and ferns. Shrubs and small Trees compose a diverse understory.

Some of the Ecoregions of Tropical and Suptropical Coniferous Forest

1. Sierra Madre Oriental and Occidental Pine-Oak Forests in Southwestern United States and Central Mexico.
2. Greater Antillean Pine Forests in Cuba, Dominican Republic, Haiti, and Greater Antilles Islands.
3. Mesoamerican Pine-Oak Forests in Mexico, Guatemala, Nicaragua, Honduras, El Salvador.

4.  Temperate Broadleaf and Mixed Forest - These are found in central China, eastern North America, Caucasus, the Himalayas, southern Europe, and the Russian Far East.

• Forests here experience a wide range of variability in temperature and precipitation.

• In regions where rainfall is broadly distributed throughout the year, Deciduous Trees mix with Species of evergreens. Species such as Oak (Quercus spp.), Beech (Fagus spp.), Birch (Betupa spp.) and Maple (Acer spp.) fill up the landscape of these Forests.

• Structurally, these Forests are characterized by 4 layers: a canopy composed of mature full-sized dominant Species and a slightly lower layer of mature Trees, a shrub layer, and understory layer of Grasses and other Herbaceous Plants.

• Most biodiversity in these Forests is concentrated much closer to the Forest floor.

Some of the Ecoregions of Temperate Broadleaf and Mixed Forest

1. Eastern Australia Temperate Forests in South-eastern Australia.
2. Tasmanian Temperate Rain Forests in Tasmania - an island off South-eastern Australia.
3. New Zealand Temperate Forests in Southern island of New Zealand
4. Eastern Himalayan Broadleaf and Conifer Forests in Bhutan, China, India, Myanmar, Nepal.
5. Western Himalayan Temperate Forests in in India, Nepal, Pakistan.
6. Appalachian and Mixed Mesophytic Forests in Eastern United States.
7. Russian Far East Temperate Forests in South-eastern Pacific coast of Russia.

5.  Temperate Coniferous Forest - Temperate Coniferous Forest are found predominantly in areas with warm summers and cool winters, and vary enormously in their kinds of plant life. These include the Pacific Northwest, the Validivian Forests of South-western South America, the Rainforests of New Zealand and Tasmania, the North-eastern Atlantic (small, isolated pockets in Ireland, Scotland, and Iceland), south-western Japan, and those of the eastern Black Sea .In some, Needleleaf Trees dominate, while others are home primarily to Broadleaf Evergreen Trees or a mix of both Tree types.

• These are common in the coastal areas of regions that have mild winters and heavy rainfall, or inland in drier climates or Montane areas.

• Many Species of Trees inhabit these Forests including Pine, Cedar, Fir, and Redwood which are huge Trees, especially the Redwood.

• The understory (vegetation which grows under the tall Trees) also contains a wide variety of Herbaceous and Shrub Species.

• Structurally, these Forests are rather simple, consisting of 2 layers generally: an overstory and understory. However, some Forests may support a layer of shrubs. Pine Forests support an Herbaceous ground layer that may be dominated by grasses and forbs that lend themselves to ecologically important wildfires. In contrast, the moist conditions found in temperate rain Forests favour the dominance by ferns and some forbs.

Some of the Ecoregions of Temperate Coniferous Forest

1. Pacific Temperate Rainforests in West Coast of United States and Canada.
2. Klamath-Siskiyou Coniferous Forests in California and Oregon.
3. Sierra Nevada Coniferous Forests in Western United States.
4. South-eastern Coniferous and Broadleaf Forests in South-eastern United States.
5. Valdivian Temperate Rainforests / Juan Fernandez Islands in Argentina, Chile.
6. European-Mediterranean Montane Mixed Forests in South-eastern Europe.
7. Caucasus-Anatolian-Hyrcanian Temperate Forests in Armenia, Azerbaijan, Bulgaria, Georgia, Iran, Russia, Turkey, Ukraine.
8. Altai-Sayan Montane Forests in China, Kazakhstan, Mongolia, Russia.
9. Hengduan Shan Coniferous Forests in China.

6.  Boreal Forests / Taiga - These Forests are found in inland Canada, Alaska, Sweden, Finland, inland Norway, much of Russia (especially Siberia), as well as parts of the extreme northern continental United States (northern Minnesota, Michigan's Upper Peninsula, northern Wisconsin, Up-state New York, Vermont, New Hampshire, and Maine), northern Kazakhstan, northern Mongolia, and northern Japan  (Hokkaido).

• There are two major types of Taiga. i) The Southern Part is the Closed Canopy Forest, consisting of many closely-spaced Trees with mossy ground cover. In clearings in the Forest, shrubs and wild flowers are common, such as the Fireweed. The other type is the ii) Lichen Woodland or Sparse Taiga, with Trees that are farther-spaced and lichen ground cover; the latter is common in the northernmost Taiga.

• The Taiga or Boreal Forest has a subarctic continental climate with very large temperature range between seasons, but the long and cold winter is the dominant feature. The short summer (24-hr average 10°C or more) lasts 1–3 months and always less than 4 months. The winters last 5 – 7 months, with average temperatures below freezing. Temperatures vary from -54°C to 30°C (-65°F to 86°F) throughout the whole year.

• The Taiga experiences relatively low precipitation throughout the year (generally 200–750 mm annually, 1,000 mm in some areas), primarily as rain during the summer months, but also as fog and snow. As evaporation  is also low for most of the year, precipitation exceeds evaporation, and is sufficient to sustain the dense vegetation growth. Snow may remain on the ground for as long as nine months in the northernmost extensions of the Taiga ecozone.

• The Forests of the Taiga are largely coniferous, dominated by Larch, Spruce, Fir, and Pine.

• The Taiga is home to a number of various Mammals, such as Moose, Reindeer, American Black Bear, Grizzly Bear and Wolverine.

Distribution

Forests are found in all regions of the World which are capable of sustaining Tree growth, at altitudes up to the Tree line, except where natural fire frequency or other disturbance is too high or hostile environment like Antarctica.

General Characteristics of Forests

• Domination of Trees - Forests are mostly dominated by large Plants like Trees. Some Trees especially in Rainforests gain a lot of height to get more sunlight. Most of other Plants face tough competition from large Plants as these tend to receive most of the nutrition from the environment. Some Plants have evolved to become Creeper and Climbers to combat this competition. They climb over Trees to reach the sunlight as well.

• Forest Canopy - Forest Canopy refers to the cover of  Tall Forests. This top portion of a community of Trees or Plant Crowns serves as the interface between the atmosphere and the land. The Canopy is also the upper habitat for other biological organisms in a Forest ecosystem. The structure of Forest Canopy varies from  Forest to Forest because because of the availability of nutrients, Tree arrangement and differences in biological Species. The Forest Canopy is an Ecosystem in itself as it supports a variety of life which is not found in the Forest itself.

• Availability of good amount of Water - Most of the Forests receive sufficient rains to support the organisms which depend on it. It is only in dry season that these may face shortage of water. This rain water forms ponds and streams which supports further life forms like Plant and Animals.

• Great Biodiversity - Forests are one of the major Habitats which support a great biodiversity of life than any other Habitat. This is attributed to the easy availability of food and shelter. Scientists estimate that more than half of all the world's plant and animal Species live in tropical Rainforests. A part of this diversity are the local tribal people who depend on the Forest for almost all their needs.

• Forest Floor - The Forest Floor is composed of fallen leaves, stems, twigs, branches and bark on the surface of the soil. A Forest floor also contains organic and inorganic substances. The Forest Floor is inhabited by various living organisms, such as the fungi, bacteria and other microorganisms as it is rich in nutrients and mineral contents. The Forest Floor has a significant role in the transfer of nutrients in the life cycle of the Forest ecosystem. The leaves that fall on the Forest Floor keep on piling up. These leaves decompose over a period of time and provide essential nutrients which promote the growth of Trees.

• Variation in Soil Fertility - The soil of Temperate Forests is fertile because Trees' leaves drop to the ground every fall. This litter contributes to the layers of organic material found in Forest soil. The old leaves become a source of food for bacteria and fungi. These organisms facilitate the breaking down of the leaves and other organic material. Decomposition enriches the Forest soil as it provides more nutrients to the living Trees and plants in the Forest ecosystem. However, the soil in tropical rain Forests has poor quality because of the torrential rains. The constant rain erodes and dissolves soil nutrients before the Trees can benefit from them.

• Complex Ecosystems - Forests are among the most complex ecosystems in the World. Conifer Forests have the simplest structure: a Tree layer rising to about 98 feet (30 m), a shrub layer that is spotty or even absent, and a ground layer covered with lichens, mosses, and liverworts. Deciduous Forests are more complex; the Tree canopy is divided into an upper and lower story, while Rain Forest canopies are divided into at least three strata. The Forest floor in both of these Forests consists of a layer of organic matter overlying mineral soil. The humus layer of tropical soils is affected by the high levels of heat and humidity, which quickly decompose whatever organic matter exists. Fungi on the soil surface play an important role in the availability and distribution of nutrients, particularly in the northern coniferous Forests. Some Species of fungi live in partnership with the Tree roots, while others are parasitically destructive.

Origin of Forests

During the Silurian Period (420 million years ago) ancient Plants and Arthropods began to occupy the land. Over the millions of years that followed, these land colonizers developed and adapted to their new Habitat. The first Forests were dominated by Giant Horsetails, Club Mosses, and Ferns that stood up to 40 feet tall. Life on Earth continued to evolve, and in the late Paleozoic, Gymnosperms appeared. By the Triassic Period (245-208 mya), Gymnosperms dominated the Earth's Forests. In the Cretaceous Period (144-65m mya), the first Flowering Plants (angiosperms) appeared. They evolved together with Insects, Birds and Mammals and radiated rapidly, dominating the landscape by the end of the Period. The landscape changed again during the Pleistocene Ice Ages — the surface of the planet that had been dominated by tropical Forests for millions of years changed, and Temperate Forests spread in the Northern Hemisphere.

Importance of Forests

• Forests are commonly referred to as Lungs of the Earth. It is primarily because of the presence of a variety of Plants which due to their high density produce massive amount of Oxygen which enables other organisms to breathe. According to one estimate 1 acre of Forest provides over 6 tons of oxygen per year.

• Forests provide home to diverse Animal and Plant Species which not only provide biodiversity on the Earth but each Species has an important role in the ecosystem.

• About 1/4 of all the medicines that is produced, originates from Rainforest Plants. For example Curare (toxic plant) comes from a tropical vine, and is used as an anaesthetic and to relax muscles during surgery. Similarly Quinine is derived from the 'Cinchona Tree' which is used to treat Malaria.

• Forests provide timber which is used for building houses, furniture etc.

• Forests are the most  important component of Earth's Ecosystem as it prevents soil erosion, maintains water cycle, check global warming etc. Without all these roles performed by Forests, the Earth would be uninhabitable.

• Wildlife tourism generates lots of capital which in turn increases the revenue of the government.

• Forests still harbour various Species of living organisms which are still being discovered. Each Animal, Insect and Plant contains its individual genetic material that has been evolving for thousands of years. Protecting the Forests not only preserves a process of life that started billions of years ago but it also gives us missing clues to various riddled aspects of life itself.