What is deforestation ?• Deforestation refers to the loss ordestruction of naturallyoccurring forests, primarily dueto human activities such aslogging, cutting trees for fuel,slash-and-burn agriculture,clearing land for livestockgrazing, mining operations, oilextraction, dam building, andurban sprawl or other types ofdevelopment and populationexpansion.
What are the main causesof deforestation ?There are 5 main causes ofdeforestation :• Logging• Industrialization• Agriculture• oil exploitation• human disasters
How Fast is DeforestationHappening?• Currently, 12 million hectares of forests arecleared annually.• At this rate all moist tropical forest could belost by the year 2050, except for isolatedareas in Amazonia, the Zaire basin, as well as afew protected areas within reserves andparks.
Hots• Do you think forests are important for theenvironment.• Trees too give out Carbon dioxide to theatmosphere does this have a role in globalwarming.
CONSEQUENCES OF DEFORESTATIONAlteration of local and global climatesthrough disruption of :a) The carbon cycle. Forests act as a major carbon storebecause carbon dioxide (CO2) is taken up from theatmosphere and used to produce the carbohydrates,fats, and proteins that make up the tree. When forestsare cleared, and the trees are either burnt or rot, thiscarbon is released as CO2. This leads to an increase inthe atmospheric CO2 concentration. CO2 is the majorcontributor to the greenhouse effect. It is estimated thatdeforestation contributes one-third of all CO2 releasescaused by people.
• b) The water cycle. Trees draw ground water upthrough their roots and release it into the atmosphere(transpiration). In Amazonia over half of all the watercirculating through the regions ecosystem remainswithin the plants. With removal of part of the forest,the region cannot hold as much water. The effect ofthis could be a drier climate.
Time to think critically• How are plants able to keep the environmentcold?
Flooding• Flooding. Deforestation can result to watershedsthat are no longer able to sustain and regulatewater flows from rivers and streams. Trees arehighly effective in absorbing water quantities,keeping the amount of water in watersheds to amanageable level. The forest also serves as acover against erosion. Once they are gone, toomuch water can result to downstream flooding,many of which have caused disasters in manyparts of the world
More effects ……• Soil erosion With the loss of a protectivecover of vegetation more soil is lost.• Silting of water courses, lakes and damsThis occurs as a result of soil erosion.• Extinction of species which depend on theforest for survival. Forests contain morethan half of all species on our planet - as thehabitat of these species is destroyed, so thenumber of species declines• Desertification The causes of desertificationare complex, but deforestation is one of thecontributing factors .
Summary• Define deforestation• List four causes of deforestation• Give three effects of deforestation on theenvironment.