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  • There are two major types of natural forests, based on their age and structure:

  • Old – growth forest : Is an uncut or regenerated primary forest that has not been seriously distributed by human activities or natural disasters for several hundred years or more.

  • Second-growth forest: Is a stand of trees resulting from secondary ecological succession. These forests develop after the trees in an area have been removed by human activities such as clear-cutting for timber or cropland or by natural forces such as fire, hurricanes or volcanic eruption.


Through photosynthesis, forests help stabilize the earths temperature and slow projected climate change as a part of the global carbon cycle.



  • Support energy flow and chemical cycling

  • Reduce soil erosion

  • Absorb and replace water

  • Purify water and air

  • Influence local and regional climate

  • Store atmospheric carbon


  • Fuel wood

  • Lumber

  • Pulp to make paper

  • Mining

  • Livestock grazing

  • Recreation

  • Jobs


  • Selection cutting is cutting of certain trees in an area.

  • Clearcut system Clear cutting is cutting every tree in a certain area.

  • Strip cutting  is cutting portions (strips) of trees in succession.


  • There are two types of fires that can affect forest ecosystems.

  • SURFACE FIRE : Usually burn only undergrowth and leaf litter on the forest floor. They may kill seedlings and small trees, but they spare most mature trees and allow most wild animals to escape.

  • CROWN FIRE : Is an extremely hot fire that leaps from treetop to treetop, burning whole trees. This usually occurs in forests that have not experienced surface fires for several decades, a situation that allows dead wood, leaves and other flammable ground litter to accumulate.


DEFORESTATION: Is the temporary or permanent removal of large expanses of forest for agriculture, settlements, or other uses.

Surveys by the World Resources Institute (WRI) indicate that over the past 8,000 years, human activities have reduced the earth’s original forest cover by about 46%, with most of this loss occurring in the last 60 years.



  • Decreased soil fertility from erosion.

  • Runoff of eroded soil into aquatic systems

  • Premature extinction of species with specialized niches

  • Loss of habitat for native species and migratory species such as birds and butterflies

  • Regional climate change from extensive clearing

  • Release of CO2 into atmosphere

  • Acceleration of flooding

Harmful environmental effects of deforestation.



Major Causes of the Destruction and Degradation of tropical Forests

  • Basic Causes

  • Not valuing ecological services

  • Crop and timber exports

  • Poverty

  • Population growth

  • Secondary Causes

  • Roads

  • Fires

  • Settler farming

  • Cash crops

  • Cattle ranching

  • Logging

  • Tree plantations

A 2005 study by forest scientists found that widespread fires in the Amazon basin are changing weather patterns by raising temperature and reducing rainfall.

This is converting large deforested areas of tropical forests to tropical grassland (savanna) , if the current burning and deforestation continues, 20-30% of the amazon will turn into a savanna in the next 50 years. And most of it will become a savanna by 2080.

Philippines and the African country of Nigeria on the other hand are experiencing settler farming, cash crops and logging, which have made them lost most of their once-abundant tropical hardwood forest.

HOW SHOULD WE MANAGE AND SUSTAIN FORESTS? fires in the Amazon basin are changing weather patterns by raising temperature and reducing rainfall.

We can sustain forests by emphasizing the economic value of their ecological services, removing government subsidies that hasten their destruction, protecting old-growth forests, harvesting trees no faster than they are replenished, and planting trees.


Sustainable Forestry

  • Identify and protect forest areas high in biodiversity

  • Rely more on selective cutting and strip cutting

  • No clear-cutting on steep slopes

  • Sharply reduce road building into uncut forest areas

  • Leave most standing dead trees and fallen timber for wildlife habitat and nutrient cycling

  • Plant tree plantations primarily on deforest and degraded land

  • Certify timber grown by sustainable methods

  • Include ecological services of forests in estimating their economic value

WE CAN IMPROVE THE MANAGEMENT OF FOREST FIRES fires in the Amazon basin are changing weather patterns by raising temperature and reducing rainfall.

In the USA, the Smokey Bear educational campaign undertaken by the Forest Service and the National Advertising Council has prevented countless forest fires.Ecologists warn that trying to prevent all forest fires may increase the likelihood of destructive crown fires by allowing accumulation of highly flammable under-brush and smaller trees in some forests.

Ecologist and forest fire experts have proposed several strategies for reducing fire-related harm to forests and people.

1ST APPROACH: Is to set small, contained surface fires to remove flammable trees and under-brush in the highest-risk forest areas.

2nd APPROACH: Is to allow many fires on public lands to burn, thereby removing flammable underbrush and smaller trees, as long as the fires do not threaten human structures and life.

3rd APPROACH: Is to protect houses and other buildings in fire-prone areas by thinning a zone of about 60 meters(200 feet) around them and eliminating the use of flammable materials such as wooden roofs.

4 fires in the Amazon basin are changing weather patterns by raising temperature and reducing rainfall. th APPROACH: Is to thin forest areas vulnerable to fire by clearing away small fire-prone trees and underbrush under careful environmental controls. Many forest fire scientist warn that such thinning should not involve removing economically valuable medium size and large trees for two reasons.

First reason: These are the most fire-resistant trees.Second reason: Their removal encourages dense growth of more flammable young trees and underbrush leaves behind highly flammable slash, or brush and deadwood left over after thinning.

  • WE CAN REDUCE THE DEMAND FOR HARVESTED TREES fires in the Amazon basin are changing weather patterns by raising temperature and reducing rainfall.

  • Reduce wood waste

  •  According to the Worldwatch Institute and forestry analysts, up to 60% of the wood consumed in the united states is wasted unnecessarily.

  • Other nontree fibers to provide pulp for making paper

  •  One reason for cutting trees to provide pulp for making paper, but paper can be made from fiber that does not come from trees. China uses rice straw and other agricultural residues to make much of its papers. USA uses kenaf(Kuh-NAHF) fiber in a small amount of tree-free paper they produce. Kenafis a rapidly growing woody annual plant. Another is Hemp that yields more paper pulp per hectare than tree farms do and require fewer pesticides and herbicides.

It is estimated that within 2-3 decades, we could essentially eliminate the need to use trees to make paper.


  • Debt-for-nature swap  which can make it financially attractive for countries to protect their tropical forests. In such swaps, participating countries act as custodians of protected forest reserves in return for foreign aid or debt relief.

  • Conservation Concessions

  • Governments or private conservation organizations pay nations for agreeing to preserve their natural resources.

  • Another similar approach is to allow corporations and countries that emit large amounts of greenhouse gases such as CO2 to help offset such emissions by protecting CO2-absorbing forests in

  • In tropical and other areas. essentially eliminate the need to use trees to make paper.

  • Another way to use tropical forests more sustainably is to use strip cutting to harvest tropical trees for lumber. Loggers can also be more careful when cutting individual trees.

  • Individuals can plant trees.

  • Finally, each of us can use substitutes for wood such as bamboo and building materials made from recycled plastic or recycled waste lumber. We can also buy only lumber and wood products that are certified as sustainably produced.

SOLUTIONS essentially eliminate the need to use trees to make paper.

Sustaining Tropical Forests


Encourage regrowth through secondary succession

Rehabilitate degraded areas

Concentrate farming and ranching in already-cleared areas


Protect the most diverse and endangered species

Educate settlers about sustainable agriculture and forestry

Subsidize only sustainable forest use

Protect forests with debt-for-nature swaps and conservation concessions

Certify sustainably grown timber

Reduce poverty

Slow population growth

HOW SHOULD WE MANAGE AND SUSTAIN GRASSLANDS? essentially eliminate the need to use trees to make paper.

We can sustain the productivity of grasslands by controlling the number and distribution of grazing livestock and by restoring degraded grasslands.

Some Rangelands Are Overgrazed

Grassland provide many important ecological services, including soil formation. Erosion, control, nutrient cycling, storage of atmospheric carbon dioxide in biomass, and maintenance of biodiversity.

Rangelands are unfenced grasslands in temperate and tropical climates that supply forage, or vegetation for grazing(grass-eating) and browsing(shrub-eating) animals.

Livestock also graze in Pastures, which are managed grasslands or enclosed meadows usually planted with domesticated grasses or other forage.

Overgrazing essentially eliminate the need to use trees to make paper. occurs when too many animals graze for too long and exceed the carrying capacity of a rangeland area.



WE CAN MANAGE RANGELANDS MORE SUSTAINABLY essentially eliminate the need to use trees to make paper.

The most widely used method for more sustainable management of rangeland is to control the number of grazing animals and the duration of their grazing in a given area so the carrying capacity of the area is not exceeded.

One way of doing this is rotational grazing in which cattle are confined by portable fencing to one area for a short time(often1-2days) and then moved to a new location. Riparian zones are streams or rivers lined by thin strips of lush vegetation.

A more expensive and less widely used method of rangeland management is to suppress the growth of unwanted invader plants by use of herbicides, mechanical removal, or controlled burning.A cheaper way to discourage unwanted vegetation in some areas is through controlled. Short-term trampling by large numbers of livestock.

In the mid – 1980’s, cattle had degraded the vegetation and soil on this stream bank along the San Pedro River in the U.S state of Arizona. Within 10 years, the area was restored through natural regeneration after grazing and off-road vehicle use were banned.

HOW SHOULD WE MANAGE AND SUSTAIN PARKS AND NATURE RESERVES? and soil on this stream bank along the San Pedro River in the U.S state of Arizona. Within 10 years, the area was restored through natural regeneration after grazing and off-road vehicle use were banned.

We need to put more resources into sustaining existing parks and nature reserves and into protecting much more of the earth’s remaining undisturbed land are.

National parks face many environmental threatstoday, more than 1,100 major national parks are located in more than 120 countries. However, most of these national parks are too small to sustain many large animal species and many parks suffer from invasions by nonnative species that compete with and reduce the population of native species.

Parks in developing cities have the greatest biodiversity of all parks, but only about 1% of these parklands are protected.

Protecting Wilderness Is an important Way to preserve Biodiversity

One way to protect undeveloped lands from human exploitation is by legally setting them aside as large areas of undeveloped land called wilderness.

Two important reasons for protecting wilderness and other areas from exploitation.

One is to preserve biodiversity, as a vital part of the earths natural capital.

Second is to protect wilderness area as centers for evolution.


We can help to sustain terrestrial biodiversity by identifying and protecting severely threatened areas(biodiversity hotspots), rehabilitating damaged ecosystems(using restoration ecology), and sharing with other species much of the land we dominate(using reconciliation ecology).

  • Three Principles to BiodiversityProtect Ecosystems

  • Map the world’s terrestrial and aquatic ecosystems and create an inventory of the species contained in each of them and the ecosystem services they provide.

  • Locate and protect the most endangered ecosystems and species, with emphasis on protecting plant biodiversity and ecosystem services.

  • Seek to restore as many degraded ecosystems as possible.

Protecting Global Biodiversity Hotspots Is an Urgent Priority

To protect much of the earth’s remaining biodiversity as possible, some biodiversity scientists urge adoption of an emergency action strategy to identify and quickly protect biodiversity hotspots. An idea first proposed in 1988 by environmental scientist Norman Myers.

There are 34 global terrestrial biodiversity hotspots identified by biologists. Although these hotspots cover only a little more than 2% of the earth’s land surface, they contain an estimated 50% of the worlds flowering plant species and 42% of all terrestrial vertebrates(mammals, birds, reptiles and amphibians) and are also home to a large majority of the world’s endangered or critically endangered species.

Rehabilitate and Restore Ecosystems That We Have Damaged Priority

Ecological Restoration the process of repairing damage caused by humans to the biodiversity and dynamics of natural ecosystems. Examples: replanting forests, restoring grasslands, reintroducing invasive species, and freeing river flows by removing dams.

Variety of approaches in repair operations:

Restoration: Returning a particular degraded habitat or ecosystem to a condition as similar as possible to its natural state.

Rehabilitation: Turning a degraded ecosystem into a functional or useful ecosystem without trying to restore it to its original condition. Example: removing pollutants and replanting soil erosion in abandoned mining and landfills and in clear-cut forests.

  • Replacement: PriorityReplacing a degraded ecosystem with another type of ecosystem. Example: a degraded forest could be replaced by a productive pasture or tree plantation.

  • Creating artificial ecosystems: for example, creating artificial wetlands to help reduce flooding or to treat sewage.

  • Researchers have suggested a science-based four-step strategy for carrying out most forms of ecological restoration and rehabilitation:

  • Identify the causes of the degradation(such as pollution, farming, overgrazing, mining, or invasive species)

  • Stop the abuse by eliminating or sharply reducing these factors. This would include removing toxic soil pollutants, improving depleted soil by adding nutrients and new topsoil, preventing fires, and controlling or eliminating disruptive nonnative species.

  • If necessary, reintroduce species – especially pioneer, keystone, and foundation species- to help restore natural ecological processes.

  • Protect the area from further degradation and allow secondary ecological succession to occur.

  • We Can Share Areas We Dominate with Other Species

  • Reconciliation Ecology A science that focuses on venting, establishing, and maintaining new habitats to conserve species diversity in places where people live, wok, or play. In other words, we need to learn how to share with other species some of the spaces we dominate.

What Can You Do? secondary ecological succession to occur.

  • Sustaining Terrestrial Biodiversity

  • Adopt a forest

  • Plant trees and take care of them

  • Recycle paper and buy recycled paper products

  • Buy sustainably produced wood and wood products

  • Choose wood substitutes such as bamboo furniture and recycled plastic outdoor furniture, decking and fencing.

  • Help to restore a nearby degraded forest or grassland

  • Landscape your yard with a diversity of plants natural to the area

HOW CAN WE HELP TO SUSTAIN AQUATIC BIODIVERSITY? secondary ecological succession to occur.

We can help to sustain aquatic biodiversity by establishing protected sanctuaries, managing costal development, reducing water pollution, and preventing overfishing.

Human Activities Are Destroying and Degrading Aquatic Biodiversity

Human activities have destroyed a large portion of the world’s coastal wetlands, coral reefs, mangroves, and ocean bottom, and disrupted many of the world’s freshwater ecosystems. By 2006, Scientist claim that costal habitats are disappearing 2-10 times higher. ‘

Another major threat is ,loss and degradation of many-sea-bottom habitats caused by dredging operations and trawler fishing boats.

FISHERY: Is a concentration of a particular aquatic species (usually fish or shellfish) suitable for commercial harvesting in a given ocean area or inland body of water.

Methods of Fishing secondary ecological succession to occur.

Trawler Fishing  is used to catch fish and shellfish-especially shrimp, cod, flounder and scallops-that live on or near the ocean floor. It involves dragging a funnel-shaped net held open at the neck along the ocean bottom; the net is weighted down with chains or metal plates. This process is clear-cutting the ocean floor. Newer trawling nets are large enough to swallow 12 jumbo jet planes and even larger ones are on the way.

  • Purse-Seine Fishing secondary ecological succession to occur.

  • Is used to catch surface dwelling species such as tuna, mackerel, anchovies, and herring, which tend to feed in schools near the surface or in shallow areas. After a spotter plane locates a school, the fishing vessel encloses it with a large net called a purse seine. Nets used to capture yellow fin tuna in the eastern tropical Pacific Ocean have killed large numbers of dolphins that swim on the surface above schools of tuna.

  • Longlining secondary ecological succession to occur.

  • Also used by fishing vessels, it involves putting out lines up to 130 kilometers (80miles) long, hung with thousands of baited hooks. The depth of the lines can be adjusted to catch open-ocean fish species such as swordfish, tuna, and sharks or bottom fish such as halibut and cod. Longlines also hook and kill large numbers of endangered turtles, dolphins and seabirds each year. Making simple modifications to fishing gear and fishing practices can decrease seabird deaths.

Drift-Net fishing secondary ecological succession to occur.

 With this method fish are caught by huge drifting nets that can hang as deep as 15 meters (50 feet) below the surface and extend to 64 kilometers (40miles) long. This method can lead to overfishing of the desired species and may trap and kill large quantities of unwanted fish, marine mammals, sea turtles, and seabirds.

SOLUTIONS secondary ecological succession to occur.

Managing Fisheries


Use side-meshed nets to allow escape of smaller fish

Use net escape devices for seabirds and sea turtles

Ban throwing edible and marketable fish back into the sea

Fishery Regulations

Set catch limits well below the maximum sustainable yield

Improve monitoring and enforcement of regulations

SOLUTIONS secondary ecological succession to occur.

Managing Fisheries

Economic Approaches

Sharply reduce or eliminate fishing subsidies

Charge fees for harvesting fish and shellfish from publicly owned offshore waters

Certify sustainable fisheries


Restrict coastal locations for fish farms

Control pollution more strictly

Depend more on herbivorous fish species

SOLUTIONS secondary ecological succession to occur.

Protect Areas

Establish no-fishing areas

Establish more marine protected areas

Rely more on integrated coastal management

Consumer Information

Label sustainably harvested fish

Publicize overfished and threatened species.

Nonnative Invasions

Kill organisms in ship ballast water

Filter organisms from ship ballast water

Dump ballast water far at sea and replace with deep-sea water