Case Study: Tropical Rainforest Deforestation

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Chapter 3: EcosystemsAPES 2013Date1Case Study: Tropical RainforestDeforestation Tropical Rainforest are found near the equator Cover about 2% of the Earth’s land surface, but contain up to half of the world’sknown terrestrial plant and animal species So far, at least half of these forests have been destroyed or disturbed. It is expectedthat most forests will be gone or severely damaged within your lifetime. Three major consequences: reduction of biodiversity accelerate climate change due to global warming change regional weather patterns which will permanently change theecosystem2Ecology Ecology is the study of how organisms interact with one another andwith their physical environment of matter and energy. Levels of organization: Population Community Ecosystem Biosphere3

Cells Cells - smallest and most fundamental structures of life Cell Theory - all living things are composed of cells Eukaryotic cell - membrane-bound structure that contains a nucleus(“eu” true, “karyote” nucleus) Prokaryotic cell - membrane-bound structure that contains no distinctnucleus (“pro” before, “karyote” nucleus)4Species Species - set of individuals that mate and produce fertile offspring So far, biologists have identified 1.8 million species. We have no idea how many species are present on the Earth.Estimates range from around 4 million to 100 million. The mostwidely accepted estimate is between 10 and 14 million distinctspecies. In 2007, scientists began a project to list and describe the 1.8 millionknown species in a free Internet encyclopedia (www.eol.org).5Ecology Ecology - how organisms interact with their biotic and abioticenvironments Biotic - living components (other organisms) Abiotic - non-living components (soil, water, and other forms ofmatter and energy)Ecologists focus on populations, communities, ecosystems, andbiosphere6

Fig. 3-4Populations Population - a group ofindividuals of the same speciesthat live in the same place atthe same time In a natural population thereare slight genetic differenceswhich is why the members donot all look and act exactlyalike. Genetic Diversity - variation ina population7Habitat Habitat - the place where a population or an individual organismnormally lives A habitat’s size varies based on the species. For a whale, it couldbe the entire ocean. For a bacterium, it could be the intestines of atermite.Each habitat has resources that the organisms need to survive (light,water, temperature.)8Communities Community - consists of all of the population of different species thatlive in a particular place Example: forestMembers of a community interact with each other (mainly in feedingrelationships)9

Ecosystems Ecosystem - a community of different species interacting with oneanother and with the nonliving components of the environment (soil,water, other forms of matter, and energy) Ecosystems can be very small (an old bucket full of water, a single tree),or very large (the Gobi Desert, the boreal forest) Ecosystems can be natural(undisturbed forest) or artificial (crop fields,tree farms, reservoirs). Matter and energy can move from one ecosystem to another Ex. Soil and sediment being washed away by a river Ex. Migration of animals10Focus on Insects Considered pests because they compete with us for food, spreaddisease, and are a general nuisance Insects have been around for over 400 million years and can evolve(adapt) relatively quickly in response to environmental changes. Insects actually sustain our lives (estimated value in US 57 billion) Pollination is a vital natural service Control other insect populations Renewal of soilFig. 3-A11Earth’s LifeSupport Systems Atmosphere - air Hydrosphere - water Geosphere - rock, soil,sediment Biosphere - living componentsFig. 3-612

AtmosphereAtmosphere - thin spherical envelope of gasses surrounding the Earth’s surface Troposphere - extends about 17 kilometers above sea level in equatorial regionsand 7 kilometers above sea level at the poles. Almost all of the Earth’s weather occurs here. Contains a majority of the air we breath and consists of: Nitrogen (78% byvolume); Oxygen (21% by volume); Remaining 1% is water vapor, carbondioxide, methane, and other greenhouse gasses (gasses that trap heat andwarm the lower atmosphere)Stratosphere - layer above the troposphere 17-50 kilometers above the Earth’s surface Lower portion contains ozone gas (O3) which filters out most of the sun’sharmful ultraviolet (UV) radiation13Hydrosphere Hydrosphere - consists of all the water on or near the earth’s surface Forms: Liquid water Ice Water vaporMost water is found in the oceans which cover 71% of the earth14Geosphere Geosphere - consists of the core, mantel, and crust of the interior ofthe earth Upper portion contains the nonrenewable fossil fuels and mineralswe use as well as some renewable chemicals organisms need tosurvive15

Biosphere Biosphere - includes the parts of the atmosphere, hydrosphere, andgeosphere where life exists Extends from about 9 kilometers above the earth’s surface to thebottom of the ocean In comparison, if the earth were an apple, the biosphere would be nothicker than the skin. The goal of ecology is to study this very thin layer and howorganisms interact on and with it.16Biomes Biomes - large regions with distinct climates and certain species adapted to them Aquatic life zones - watery parts of the biosphere Freshwater life zones Marine life zonesFig. 3-7North AmericanBiomes(39th Parallel)17Factors that Sustain Life One-way flow of high-quality energy from the sun Cycling of matter and nutrients (law of conservation of matter) Gravity18

Solar Energy Energy from the sun reaches the earth as electromagnetic waves mostlyas visible light, UV radiation, and infrared radiation (heat) Large quantities of this energy is reflected back into space by theatmosphere, clouds, and earth’s surface. Ozone gas (O3) in the lower stratosphere absorbs 95% of UV radiation The electromagnetic waves light the earth, warm the air, and cycles waterthrough the biosphere (evaporation) 1% of this energy also generates winds Green plants and algae use about 0.1% of this energy for photosynthesis19Solar Energy and the NaturalGreenhouse Effect Only about 1% of total solar radiation intercepted by theearth reaches the surface. Most is reflected as long-wavelength infrared radiationand travels back toward space encountering greenhousegasses (water vapor, carbon dioxide, methane, nitrousoxide, and ozone) which causes those molecules to vibrateand release IR radiation with even longer wavelengths. This vibration increases the molecules kinetic energywhich warms the lower atmosphere and earth’s surface. Without this, the earth would be too cold to support life. Human activities further add greenhouse gasses to theatmosphere. Clearing the rainforest further exacerbates the problembecause those forests would absorb huge amounts ofcarbon dioxideFig. 3-820Components of EcosystemsFig. 3-9 Two major components: Abiotic - nonliving components Biotic - living and once livingcomponents Biotic factors also includedead organisms, dead partsof organisms, and wasteproducts of organisms21

Energy in an Ecosystem Food Chain - sequence of organisms in which each organism serves asa source of food or energy for the nextFig. 3-1328Energy inan Ecosystem Food Web complexnetwork ofinterconnectedfood chainsFig. 3-1429Usable Energy Biomass - the dry weight of all organicmatter contained in organisms; this iswhat is transferred from one trophiclevel to another in a food chain Ecological Efficiency - the percentageof usable chemical energy transferredas biomass from one trophic level toanother This can be anywhere from2-40% efficient (loosing 60-98%) A safe bet is to assume about10% efficiency (90% loss)Fig. 3-1530

Productivity Gross Primary Productivity (GPP) - the rate at which an ecosystem’sproducers covert solar energy into chemical energy as biomass foundin their tissues Usually measured in energy production per unit area over agiven time span (ex. kilocalories per square meter per year kcal/m2/yr)Net Primary Productivity (NPP) - rate at which producers usephotosynthesis to produce and store chemical energy minus the rateat which they use some of this stored energy through aerobicrespiration (NPP GPP - R, where R is energy used in respiration)31Average NPP On land, NPP decreases from the equator to the poles because of theincreased availability of sunlight at the equator In the marine habitats, NPP is highest in estuaries where nutrientlevels are high, and the open ocean has the lowest because of a lack ofnutrients (except at upwellings where sediments at the bottom arebrought to the top). Open ocean does produce the most biomass (justbecause there is so much of it). It is estimated that humans use 20-32% of the earths NPP even thoughwe are only 1% of the biomass.32Nutrient Cycles Biogeochemical Cycles (nutrient cycles) - movement of nutrients through air,water, soil, rock, and living organisms Driven directly or indirectly by solar energy and gravity Include: hydrologic, carbon, nitrogen, phosphorus, and sulfurReservoirs - temporary storage sites (ex. atmosphere) where nutrient mayaccumulate33

Hydrologic Cycle Hydrologic cycle (water cycle) - collects, purifies, and distributes theearth’s fixed supply of water Powered by energy from the sun. The solar energy causesevaporation from oceans, lakes, rivers, and soil. Evaporationchanges liquid water into water vapor. Gravity then draws thewater back to the earth’s surface as precipitation. 84% of water vapor in the air comes from the oceans. 90% of the water that comes from the land is from transpiration(evaporation from the surfaces of plants)34Water Paths Surface Runoff - water that flows into streams and lakes whicheventually goes back to the ocean Glaciers - usually very long term Aquifers (groundwater) - precipitation ends up here when it sinksthrough soil and permeable rock to underground layers of rock, sand,and gravel35Purification Evaporation and precipitation distill the water Water flowing above ground and below ground is naturally filteredand partially purified by chemical and biological processes (mostly bydecomposer bacteria Only 0.024% of the earth’s water is available to us as liquid freshwater36

Altering the Water Cycle Humans draw large quantities of freshwater from lakes, streams, and undergroundsources (faster than nature can replace it) Humans clear vegetation from land for various reasons. This increases runoff,reduces infiltration that would normally recharge groundwater supplies, increaserisk of flooding, and excellerates soil erosion and landslides. Clearing vegetation can alter weather patterns by reducing transpiration Cutting down forests increase ground temperature (reduction of shade)Humans increase flooding by draining wetlands for farming and other purposes andcovering the land with impermeable barriers like roads and parking lots37Important Properties of Water Hydrogen Bonding (cohesion and adhesion) Liquid over wide temperature range Can store large amounts of heat without a large change in temperature Takes huge amounts of energy to evaporate because of hydrogen bonds Polarity allows it to dissolve many different compounds Filters out UV rays that would harm marine life Water expands when it freezes38Carbon Cycle Carbon cycle - the circulation of carbon through the biosphere, atmosphere, andhydrosphere Carbon cycle is based on CO2 which makes up 0.038% of the volume of theatmosphere and is also dissolved in water If the CO2 in the atmosphere changes even a little, it can cause huge changes intemperature. Producers remove CO2 from the atmosphere through photosynthesis. Insoluble carbonates at the bottom of the ocean are the earth’s largest store ofcarbon. Over millions of years, these buried deposits under high pressure andheat are converted to fossil fuels (coal, oil, and natural gas).39

Nitrogen Cycle Major nitrogen reservoir is the atmosphere where chemicallyunreactive nitrogen gas (N2) is 78% by volume. Nitrogen is crucial in many compounds (proteins, DNA, vitamins)but is not usable as nitrogen gas by plants or animals Two processes convert (fix) nitrogen into usable forms: Electrical discharges in the atmosphere (lightning) Nitrogen fixing bacteria40Nitrogen Fixing Bacteria Combine N2 with hydrogen to form ammonia (NH3) which thebacteria uses and excretes the rest into the environment Some of the ammonia is converted to ammonium (NH4 ) that can beused by plants Leftover ammonia and ammonium undergoes nitrification to nitrateions (NO3-) which can be taken up by plants The plants then use this nitrogen to form amino acids, proteins,vitamins, and nucleic acids Animals will consume these plants41Nitrogen Cycle Plants and animals return the nitrogen-rich organic compounds to theenvironment as waste and through the decomposition of their bodies Ammonification - specialized bacteria convert simple nitrogencontaining compounds into ammonia and ammonium Denitrificaiton - specialized bacteria in waterlogged soil and at thebottom of lakes, oceans, swamps, and bogs convert NH3 and NH4 back into nitrate and nitrate ions and eventually into gaseous nitrogen(N2) and nitrous oxide gas (N2O)42

Nitrogen Cycle and HumanInteraction Add large amount of nitric oxide (NO) into the atmosphere when N2 and O2 combinewhile burning fuel at high temperatures. This is converted to nitrogen dioxide gas(NO2) and nitric acid vapor (HNO3) which can return to the earth as acid rain (aciddeposition) Add nitrous oxide (N2O) to the atmosphere through anaerobic bacteria on animalwastes and inorganic fertilizers. These greenhouse gasses warm the atmosphere anddeplete ozone. Release nitrogen stored in the soil and plants through deforestation and destructionof natural habitats. Add excess nitrates to bodies of water through agricultural runoff and sewagedischarge. Remove nitrogen from topsoil when harvesting nitrogen-rich crops43HumanActivities Since 1950, human activitieshave more than doubled theannual release of nitrogen, andit is expected to double againby 2050.Fig. 3-2044Phosphorus Cycle Phosphorus is important in nucleic acids and energy carryingmolecules (ADP and ATP) as well as bones and teeth. Phosphorus circulates through water, the earth’s crust, an livingorganisms (does not include the atmosphere). Major reservoir for phosphorus is phosphate salts containingphosphate ions (PO43-) found in rock and ocean sediments Water picks up the phosphate ions, and the dissolved phosphate canbe taken up by plants. From there, it can be transfered up the foodweb.45

Phosphorus as a Limiting Factor Phosphorus is often in low concentrations in soil so it is a limitingfactor for plant growth. This means phosphate salts are used as inorganic fertilizers46Phosphorus Cycle and HumanInteraction Remove large amounts of phosphate salts from the ground forfertilizers Reduce phosphate in tropical soils because of clearing forests Soil that is eroded from fertilized crop fields carries large amounts ofphosphorus into rivers, lakes, and the ocean where it stimulate thegrowth (overgrowth) of producers47Sulfur Cycle Essential component of many proteins Most of earth’s sulfur is stored underground in rocks and minerals and as sulfate(SO42-) deep under the ocean sediments Sulfur enters the atmosphere through natural sources Hydrogen sulfide (H2S) - colorless, poisonous gas released from volcanosand organic matter broken down by anaerobic decomposers in floodedswamps, bogs, and tidal flats. Sulfur dioxide (SO2) - colorless, suffocating gas also from volcanos Sulfate (SO42-) - salt, often with ammonium; enters through the atmospherefrom sea spray, dust storm, and forest fires.48

Sulfur Cycle Algae creates large amounts of dimethyl sulfide (DMS) which serve asa nuclei for the condensation of water into the droplets that createclouds In the atmosphere the DMS is converted to sulfur dioxide or sulfurtrioxide and tiny droplets of sulfuric acid. When these droplets fall tothe earth it is as acid rain49Sulfur Cycle and HumanActivities Releasing large amounts of sulfur dioxide into the atmosphere Burning sulfur containing coal and oil to produce electric power Refine sulfur containing petroleum to make gasoline andheating oil Convert sulfur containing metallic minerals to free metals suchas copper and lead.50Nutrients andEutrophication Eutrophication Happens in agricultural and urbanareas (areas with large amounts ofnutrient runoff) Causes extensive eutrophication This leads to algal bloom This leads to large amounts of O2consumption This leads to a hypoxic environment This leads to animal death51

Date Chapter 3: Ecosystems APES 2013 Case Study: Tropical Rainforest Deforestation Tropical Rainforest are found near the equator Cover about 2% of the Earth’s land surface, but contain up to half of the world’s known terrestrial plant and animal species So far, at least half of these forests have been destroyed or disturbed. It is expected