Tropical Rainforest

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Tropical RainforestWhat are tropical rainforests?Thick, evergreen forests found in areas with high rainfall and temperature throughout the year.Structure of tropical rainforestEmergent LayerTrees rise through the canopy and tower above other treesCan grow up to 50 m tall. Some even 80 m tallFormed by crowns of the treesAdaptation: Emergent trees have tall, straight and smooth trunks with few branches to obtain maximum amount of sunlightSmooth bark allow rainwater to flow easily from crown to root of treesCanopy LayerTrees grow up to 20-30m to reach for sunlightTheir crowns form an almost continuous coverLooks like an Cover is like an umbrella, block out up to 90% of sun's rays from reaching forest floorDense, unbroken canopy catches much of the rain as it fallsUndergrowth LayerDark; much of the sun's rays are blocked by canopy layerAdaption: Plants have larger leaves compare to plants in other layers to catch sun's raysPlants are small, thin and widely-spaced; lack of sunlightSparse vegetation near forest floorHot and wet environment cause rapid decomposition, living thin layer of decompositionRich in biodiversityAdaptation of plantsLeavesBroad in order to catch sunlightWaxy, leathery or hairy surfaces to minimise loss o fmoisture through transpiration due to high temperature Narrow,downward-pointing tips(drip tips) allow rainwater to run off easily. Prevents fungi and bacteria from growing on themFruit and flowersColourful and strong-smelling to attract insects and animals for dispersal or pollinationRootsButtress roots grow from 1-5 m above ground to support the trees' heavy weightRoots are shallow as nutrients are mostly found in top layer of soilRapid decomposition of fallen leaves and branches provides nutrients in soilShallow roots as water is availible throughout the yearUses of tropical rainforestsWater catchmentArea drained by river and the smaller rivers that flows into itWater from the trees slowly seep into the ground and stored as groundwaterImpurities in rainwater are trapped in soil before water flows into reservoirsWater provide clean water supplySupplies water for human daily needsGreen lungs of EarthAbsorbs carbon dioxide from atmosphere and release oxygen through photosynthesisMore than 20% of Earth's oxygen is estimated to be generated by the Amazon rainforestEarth's natural air purifierDense vegetation keeps Earth coolHabitat to flora and faunaHome to more than 2 million species of living thingsAmple sunlight is converted by plants into energy and food through photosynthesis. This allows plants to thrive. Plants are eaten by animals for survivalContinuous canopy is a habitat where plants can grow and animals can live inHabitat to indigenous peopleAbout 60 million indigenous people depend wholly on the rainforestHave been living in rainforest for thousands of years Rainforest provide daily necessities for these peopleObtain food by:Hunting and gatheringHunter-gatherers hunt, fish and gather wild fruits and nutsAgricultureGrowing of crops for human useShifting cultivators grow their own plants for food and medicineBurn vegetation to provide nutrients to fertilise plantsAfter using up nutrients in soil and soil cannot support any more plants, shifting cultivators move to another plot of land Original plot left to regain fertility naturallySource of timberRainforests provide wood for fuel in countries where people depended on fire to cookTo build or make thingsMedical applicationMany food from tropical rainforests have cancer-fighting propertiesIn the Amazon rainforest, nearly 3000 plant species have been identified to have such propertiesPotential medicinal value of plants in tropical rainforests is largely untapped25% of all modern medicines come from these plantsLess than 1% of these plants have been tested for their pharmaceutical propertiesEarth's oldest living ecosystemsDeforestationWhat is deforestation?Cutting down and removal of all or most trees in a forested areaWhy does deforestation occur?Agricultural activitiesSubsistence farming activities have been the traditional cause of deforestation in the tropicsVegetation is able to regrow as shifting cultivators move to another plot of landDo not pose a major threat to forestRate of deforestation increased with introduction of large-scale commercial activities on plantationsPlantations obtained by burning and clearing large areas of rainforestCattle ranchingLarge areas of rainforest cleared to create land for cattle to grazeLoggingCommercial logging of tropical hardwoods is a major cause of deforestation in SEA and Africa Timber used to make furniture, building materials and charcoalMiningMetals and gemstones are found beneath many tropical rainforestsForests cleared to establish mines and construct roads to transport the mineralsHow does deforestation impact people and environment?Environmental impactLoss of biodiversityLoss of variety of plants and animalsEstimated that millions of plant and animal species have become extinctVariety of resources human can obtain from rainforests will be goneChanges in biodiversity may increase occurrence of insect-borne diseasesLoss of water catchment areasCountries surrounding Amazon rainforest depend on water from Amazon Basin during dry seasonsClearing trees disrupts water cycleDisrupted water cycle leads to drier climate and drier soils; will no longer contain and receive as much waterDecreased water supply and higher water pricesIncreased risks of flooding, soil erosion and sedimentationRainwater falling directly on the ground flowing over bare surface more rapidly as surface runoff causes flooding in surrounding areas Soil erosion Removal of top layers of soil by rainwater, wind and destructive human activitiesRain is intercepted by different forest layers before hitting groundRemoval of trees cause the land to become exposedSedimentationEroded soil washed into rivers increased the amount of sediments in riversWater quality and aquatic life is affected Increased amount of sediments smothers fish eggs results in lower hatch ratesWater turns cloudy preventing sunlight from penetrating waterCoral reefs can be suffocated by sedimentsEnhanced greenhouse effectAmount of greenhouse gases in atmosphere increased due to human activities Scientists think that it had led to a rise in Earth's average temperature as more heat is trapped in the atmosphereDeforestation contributes to enhanced greenhouse effectsDeforestation increases amount of carbon dioxide in atmosphereLess trees means less carbon dioxide is absorbed and more of it remains in the atmosphereDeforestation contributes significantly to total amount of carbon dioxide released into atmosphereCauses ice caps to melt and result in rise of sea levels and flooding of low lying coastal areasEconomic impactDepletion of natural resources Rapid deforestation often destroys the rainforest faster than it can replenish itselfMany natural resources provide by rainforest are being depletedAffects earnings of industries that rely on rainforest resourcesSocial impactEffects on indigenous peopleCutting down rainforests to create land for plantations or mining affects the lives of indigenous peopleLost their homes to plantationsForced to adapt to new way of livingLoss of tropical rainforests means that they have to find other ways to surviveCauses indigenous tribes to disperse and cultures to disappearHow to manage deforestation in Singapore?Protection of forested areasMain areas where tropical rainforests are found today are protected as nature reserves by Parks and Trees Act 2005Parks and Tress Act 2005 contains guidelines for visitors to nature reserves to minimise disturbance to rainforestsReforestationProjects were carried out to improve condition of forests Students, volunteers and organisations join efforts to replant saplings of native speciesMany reforestation projects are intended to conserve and recover native plant speciesPublic educationSingapore government aims to promote people's understanding by:Increasing appreciation, awareness and understanding of nature through public seminars, road shows and eventsPromoting volunteerism through biodiversity interest groupsIncorporating elements of biodiversity conservation into the school curriculum Trails and guide walks in the nature reserves inform public about biodiversity of rainforests Plant types were printed in brochuresVarious websites contain articles, photographs and information on upcoming nature-related events Singaporeans can participate as volunteers in conserving Singapore's nature