Environmental Science Midterm 2013 Fall

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Environmental Science
Carl Mitchell

Environmental Science Mid-term Notes Lecture 2 The Base Cause of Environmental Degradation My opinion (probably the same as most Environmental Scientists: World population growth, consumption, far above what we can be replaced Our Future: Cornucopians vs. Cassandras Cornucopia: horn of plenty – Human ingenuity will see us through our environmental problems via new technologies and the such. Cassandra: mythical princess of Troy who prophesized about dire future scenarios – All is lost because of our impact on the environment. IPAT(S) Model • 1974: Paul Ehrlich and John Holdren I P A T S
 • Impact is largely POLLUTION, RESOURCE DEPLETION, or both. Population = individuals need space and resources Affluence = greater per capita resource use Technology = increased exploitation of resources or ways of better dealing with our need for resources Sensitivity = how sensitive an area is to human pressure The First Humans Oldest known homonid (human-like) fossils: Ethiopia: 4.1 Doubling Time ln(2)´100 70 tD= = growthrate(%) growthrate(%) • The number of years it takes, given a specific rate of increase, for a number (such as population to double.)   1979 China growth rate = 2.8% (popl’n at )me: 1B) Current global growth rate = 1.2% (now: ~6.9B) Current Canada growth rate (natural and net immigration together) = 0.9% (now: 33.5M) Carrying Capacity • “The maximum population size of a species that a given environment can sustain.” • Limiting factors • Births ≈ deaths • Earth’s carrying capacity? Between 10 million and 33 billion. Cultural Revolution/Paleolithic Period: • Development of tools; stone, bone, wood – (Note animal tool use – crows) Environmental Science Mid-term Notes • Omnivorous diet • Manipulation of fire • Development of speech and communication • Toolmaking: – Ethiopia: 2.6 My bp – Tanzania: 1.75 My bp • Little evidence of population at time. Agricultural Revolution: • Start ~ 10-12,000 years bp • Transition from nomadic hunter-gatherer to settled farmer (environmental manipulation to meet needs) • Consequences: – Reduction of area needed per person – 500 X population density – Excess of food production over minimum – Whole population need not be in food production or acquisition – Establishment of settlements – Social structures – priests – accountants – salesmen – “Fertile Crescent” – note soil salinization & collapse of society • Easier to meet needs (food, safety, ease of raising children) = population increase Industrial Revolution • Began mid-1700’s (Great Britain) • Transition from rural, basic farming to manufacturing, urban society and massive use of energy • Consequences: • Improved sanitation and medicine • Major advance in agriculture (powered machinery-driven) leads to increases in food production • Greater supply of energy, resources, labour • Accumulation of wealth and market for manufactured goods Medical-Technological Revolution • We are in the middle of this one • Characteristics: • Developments in medicine and pharmaceuticals • Improved sanitation • Global communication • Green Revolution (agriculture advances) Environmental Science Mid-term Notes • Consequences: • People live longer, healthier lives • Gap between rich and poor widened Demography: The study of human population - Considerations: • Population size • Population density and distribution • Age structure • Sex ratios • Birth, death, immigration, and emigration rates ^Shape a population’s environmental impact. In the United Arab Emirates and Qatar, the ratio is closer to 200 to 100. Such ratios are bound to lower population growth rates. • It has occurred in Europe, U.S., Canada, Japan, and other nations over the past 200-300 years • The transition could fail in cultures that – Place greater value on childbirth – Grant women fewer freedoms – Factors Affecting Population Growth Education and the status of women (family planning), Poverty, Disease, (HIV/AIDS) Lecture 3 Difficult to find closed system Open system: ex. Automobile inputs and outputs energy, matter Closed system: inputs energy, outputs energy Negative feedback loops: output from system becomes input to a system, moving system in opposite direction (don’t let things change too much)  Ex. Rabbit and lynx population depleting and growing in a cycle Positive feedback loops: output from system exacerbates the system response by moving it further toward one extreme  Ex. Sea ice melting Emergent properties: characteristics of a system not evident (perceivable) from its components alone or individually  The rate (amount per time) if energy (joules) received at a surface called power (Js ^-1). This is Watt (W) Environmental Science Mid-term Notes  Power per surface area is an Energy Flux measured in W m^-2  The rate of energy emitted by a substance is governed by the Stefan-Boltzmann Law Solar constant: the rate at which isolation is received at the outer atmosphere of Earth Environmental Systems • Ecosystems • Hydrologic Cycle (next class) • Global Energy Balance (next class) • Biogeochemical Cycles: – Carbon Cycle – Nitrogen Cycle – Phosphorus Cycle – Sulphur Cycle – Mercury Cycle and lots of others Ecosystem: All organisms and nonliving entities that occur and interact in a particular area at the same time – Includes abiotic and biotic components – Energy flows and matter cycles among these components – Generally, the smallest ecologically “self-sufficient” space • BIG POINT: Energy enters, flows through, and exits this system, but matter is cycled within it. Conversion of Energy to Biomass in Ecosystems • Biomass: organic material that makes up living organisms. • Autotroph: an organism that produces complex organic compounds from sunlight and inorganic molecules (i.e., plants and some bacteria). • Gross Primary Production (GPP): Overall conversion of solar energy into chemical energy by autotrophs. • Respiration: metabolism. • Net Primary Productivity (NPP): Energy remaining after respiration, that goes toward accumulating biomass. • Net Ecosystem Productivity (NEP): NPP minus heterotrophic respiration and herbivory. Key Chemical Equations: Photosynthesis occurs in the presence of light and chlorophyll: Respiration involves the use of accumulated carbon to produce needed energy (below is the aerobic process): Environmental Science Mid-term Notes NPP vs. NEP • NEP = NPP – Ecosystem Respiration • Ecosystem respiration includes both the respiration of carbon above the surface and from soil. Factors Affecting NEP: 1. Nutrients • Nutrients (especially macronutrients like nitrogen and phosphorus) can be limiting factors for productivity. • Nitrogen usually limiting factor in marine systems, usually phosphorus in freshwater systems. 2. Oxygen Aerobic respiration: Energy Produced = 2872 kJ per mol glucose Biogeochemical Cycles • Earth is a “closed” system. Open to energy, but matter “cycles” (is circulated) within it over and over again (some VERY minor exceptions). • Matter circulates between pools or reservoirs. • The volume of material moving among reservoirs per unit time (a rate) is called a flux. • Fluxes are not necessarily stable (e.g., we have greatly affected the flux of C to the atmosphere). • Residence time (T ): Rverage amount of time a molecule or atom stays in a pool. • Sources vs. Sinks. • Lots of feedbacks in biogeochemical cycling. Importance of Nitrogen • 78% of atmosphere th • 6 most abundant element on earth • Key ingredient in proteins and DNA • Essential nutrient for plant growth Key Processes in the N Cycle • Nitrogen Fixation: combination of nitrogen gas (N ) with 2ydrogen to form ammonia (NH ) an3 subsequently, the biologically available and soluble ammonium ion (NH ). 4 • Two driving processes: lightning and nitrogen-fixing bacteria. • Nitrification: Conversion of NH to N4 and then2NO by specializ3d bacteria. Plants take up NO . - 3 - • Denitrification: Conversion of NO back 3o N gas by s2ecialized bacterial Environmental Science Mid-term Notes communities. Human Alteration of N Cycle • Doubling of nitrogen fixation. Due to Haber-Bosch process (fertilizer production) and increased production of legumes (soybeans). • Increased atmospheric N O 2greenhouse gas) and other NO (produxe smog). Due to fossil fuel burning and animal waste decomposition. • Depletion of micronutrients (Ca, K) from soils (N fertilizers make them more mobile and they flush out). • Acid rain. • Eutrophication  devastating to fisheries (especially coastal marine fisheries). • Increased plant growth and carbon storage. Eutrophication: The process of nutrient over-enrichment, blooms of algae, increased production of organic matter, and ecosystem degradation Importance of Phosphorus • Key component of cell membranes, DNA, and ATP (energy). • Often limiting nutrient for autotroph growth. • Biogeochemical cycle is largely restricted to lithosphere and hydrosphere (NOT atmosphere). • Cycle is largely driven by: – solubilization – precipitation – assimilati
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