Module 1_Introduction PDF

This material has been reproduced and communicated to you by or on behalf of University of the Philippines pursuant to PART IV: The Law on Copyright of Republic Act (RA) 8293 of the “Intellectual Property Code of the Philippines”. The University does not authorize you to reprodu...

This material has been reproduced and communicated to you by or on behalf of University of the Philippines pursuant to PART IV: The Law on Copyright of Republic Act (RA) 8293 of the “Intellectual Property Code of the Philippines”. The University does not authorize you to reproduce or communicate this material. The Material may contain works that are subject to copyright protection under RA 8293. Any reproduction and/or communication of the material by you may be subject to copyright infringement and the copyright owners have the right to take legal action against such infringement. Do not remove this notice. © Institute of Environmental Science & Meteorology, College of Science, University of the Philippines Diliman 1 Module 1 Env Sci 1 (Environment and Society) Introduction to Environmental Science Image credit: Google Earth Pro  Learning Outcomes ! Distinguish the gaps & overlaps of Environmental Science with other disciplines ! Demonstrate a capacity for the scientific method in the context of environmental science ! Discuss the processes that affect the environment & the connections among the processes 3 © C.L.Ringor Environment is everything around us. It includes the living and the nonliving things with which we interact in a complex web of relationships that connect us to one another and to the world we live in. Image credit: IStock by Getty Images 4 https://www.istockphoto.com/  e. As you’ll learn in reading this book, this field visit http://EnvironmentalScience-Cunningham.blogspot.com. Environmental t Is Environmental Science? Science ays inhabited two worlds. One is the natural world s, soils, air, and water that preceded interdisciplinary study of howus humans by billions interact with hich we are a part. The other is the world of social It the living & nonliving parts of their environment. integrates information & ideas from: rtifacts that we create for ourselves using science, political organization. Both worlds are essential to grating them successfully causes enduring tensions. r people had limited ability to alter their surround- e power to extract and consume resources, produce fy our world in ways NATthat threaten natural sciences - e.g. biology, both our contin- SCI chemistry, geology, physics that of many organisms with which we share the a sustainable future for ourselves and future genera- understand something about how our world works, g to it, and what we can SOC do tosocial protect and -improve sciences it. e.g. geography, SCI economics, political science nt (from the French environner: to encircle or sur- fined as (1) the circumstances or conditions that nism or group of organisms, or (2) the complex ral conditions that affect anhumanities individual or commu- - ethics HUM ns inhabit the natural world as well as the “built” social, and cultural world, all constitute impor- environment (fig. 1.2). tal science, then, is the systematic study of our Image credit: Cunningham & Cunningham (2012) FIGURE 1.2 Many kinds of knowledge contribute to solutions our proper place 5in it. A relatively new field, envi- in environmental science. A few examples are shown. e is highly interdisciplinary, integrating natural sci- nces, and humanities in a broad, holistic study of the but not how to persuade factories to install the necessary equipment. In contrast to more theoretical disciplines, environ- City planners know how to build housing and design safe drinking mission-oriented. That is, it seeks new, valid, con- water systems, but not how to make them affordable for the poor- e about the natural world and our impacts on it, but est members of society. The solutions to these problems increasingly ormation creates a responsibility to get involved in involve human social systems as well as natural science. thing about the problems we have created. As you study environmental science, you should learn the shed economist Barbara Ward pointed out, for an following: er of environmental issues, the difficulty is not to awareness and appreciation of the natural and built environment;. Remedies are now well understood. The problem knowledge of natural systems and ecological concepts; socially, economically, and politically acceptable. ow to plant trees, but not how to establish condi- understanding of current environmental issues; and h villagers in developing countries can manage the ability to use critical-thinking and problem-solving skills https://www.dreamstime.com/illustration/ http://www.clker.com/clipart-742551.html emselves. Engineers know how to control pollution, on environmental issues. animals-earth.html https://www.123rf.com/clipart-vector/ PTER 1 Goals of Understanding Our Environment sustainable_living.html?sti=m1yu968kh7se4dt3m8| http://www.mhhe.com/cunningham12e Environmental Science (1) to learn how life on the earth has survived and thrived, (2) to understand how we interact with the environment, and (3) to find ways to deal with environmental problems and live more sustainably 6  Limitations of Environmental Science Scientists cannot prove or disprove anything absolutely, because there is always some degree of uncertainty in scientific measurements, observations, & models. They try to establish that a particular scientific theory has a very high probability or certainty (typically 90% to 95%) of being useful for understanding some aspect of the natural world. Scientists are human, thus are not totally free of bias about their own results & hypotheses. The high standards of evidence required through peer review can help to uncover or greatly reduce personal bias & expose occasional scientists who falsify their results. Many systems in the natural world involve a huge number of variables with complex interactions. This makes it too difficult, costly, & time consuming to test one variable at a time in controlled experiments. Scientists develop mathematical models that can take into account the interactions of many variables. Scientists use statistical tools since not all environmental changes & events can be measured accurately. They use statistical sampling & mathematical methods to estimate measurements. 7 https://www.dreamstime.com/illustration/environmental-science.html 2.1 Understanding What Science Is—and What It Isn’t 25 Understanding Table 2.1 FACTOR IN KNOWLEDGE IN EVERYDAY LIFE COMPARED WITH KNOWLEDGE IN SCIENCE EVERYDAY LIFE AND IN SCIENCE What Science Is Goal Requirements To lead a satisfying life (implicit) Context-specific knowledge; no complex To know, predict, and explain (explicit) General knowledge; complex, logical — and What It series of inferences; can tolerate ambiguities sequences of inferences, must be precise and lack of precision and unambiguous Resolution of questions Through discussion, compromise, consensus Through observation, experimentation, logic Isn’t Understanding Validity Acquired spontaneously through interacting with world and people; criteria not well defined Assumed, no strong need to check; based on Pursued deliberately; criteria clearly specified Must be checked; based on replications, observations, common sense, tradition, converging evidence, formal proofs, How does science differ from other authorities, experts, social mores, faith statistics, logic ways of knowing? How can we use Organization of knowledge Network of concepts acquired through Organized, coherent, hierarchical, logical; science to answer practical questions experience; local, not integrated global, integrated Acquisition of knowledge Perception, patterns, qualitative; subjective Plus formal rules, procedures, symbols, about our effects on nature & what statistics, mental models; objective actions we should take to solve Quality control Informal correction of errors Strict requirements for eliminating errors and environmental problems? making sources of error explicit Source: Based on F. Reif and J.H. Larkin, “Cognition in Scientific and Everyday Domains: Comparison and Learning Implications,” Journal of Research in Science Teaching 28(9), pp. 733–760. Copyright © 1991 by National Association for Research in Science Teaching. Reprinted by Our cultural heritage gives us two ways permission of John Wiley & Sons. of thinking about the environment: the Knowledge in everyday life compared with knowledge in science. Image credit: Botkin & Keller (2011). kind of thinking we do in everyday life & Science as a Way of Knowing in A Closer Look 2.1. One Web site says that some people the kind of thinking scientists try to do. believe the crop circles are a “spiritual nudge... designed Science is a process, a way of knowing. It results in con- to awaken us to our larger context and milieu, which is There are crucial differences between choices, & are not open clusions, generalizations, to disproof and sometimes in theo- scientific Modern none otherscience than our does notearth collective deal with soul.” Whether or these two ways of thinking, & ignoring the riesscientific sense.laws. and even scientific TheScience distinction begins with questions things not this that is true,cannot beseem it does not tested bydisproof. open to these differences can lead to invalid arising from curiosity about the natural world, such as: How Science is a such process of between a scientific statement & a many birds nest at Mono Lake? What species of algae live observation, asdiscovery—a the ultimate continuing process whose essence is change in ideas. The fact that scientific ideas conclusions & serious errors in making nonscientific statement in the lake? Under is not what conditions doathey value live? purpose of life orWhy change is frustrating. thecan’t existence of aon what is scientists agree critical decisions about the environment. judgment—there Modern science does is not nodeal implication thatcannot be with things that supernatural being. the best diet for people? WhyScience also is a chemical does dan- considered tested by observation, such as the ultimate purpose of life or the gerous in the environment for a while science is the only “good” kind of existence of a supernatural being. Science also does not deal not deal with questions thatand then determined involve not to be? Why do scientists in one decade consider forest We can look at the world from many knowledge. with questions that involve values, such as standards of beauty values, such disturbances fires undesirable as standards and inof beauty a later decadeordecide points of view, including religious, or issues of good and evil—for example, whether the scenery issues ofare forest fires good naturaland and evil. in fact important? Are we caus- at Mono Lake is beautiful. On the other hand, the state- ing global warming or not? And on and on. Can’t scientists aesthetic, & moral. They are not science Science ment thatis“more a process, than 50% a of way of knowing. the people who visit Mono just find out the truth and give us the final word on all because they are based ultimately on Science Lake findbegins with the scenery questions beautiful” arising(discussed is a hypothesis these questions once and for all, and agree on it? faith, beliefs, & cultural & personal later)curiosity from that can be about tested bythe public-opinion surveys and can natural world. The answer is no—because science is a continuing ad- be treated as a scientific statement if the surveys confirm it. venture during which scientists make better and better ap- proximations of how the world works. Sometimes changes 8 Disprovability in ideas are small, and the major context remains the same. Sometimes a science undergoes a fundamental revolution Here’s the key to science: It is generally agreed today that in ideas. the essence of the scientific method is disprovability (see Science makes certain assumptions about the natu- Figure 2.3, a diagram that will be helpful throughout this ral world: that events in the natural world follow patterns  Science is a process of discovery—a continuing process whose essence is change in ideas. It is a continuing adventure during which scientists make better approximations of how the world works. Sometimes changes in ideas are small, & the major context remains the same. Sometimes a science undergoes paradigm shift. Science makes certain assumptions about the natural world: that events in the natural world follow patterns that can be understood through careful observation & scientific analysis, & that these basic patterns & the rules that describe them are the same throughout the universe. 9 Using Critical Thinking in Environmental Science "I analyze information & ideas, judge their validity, & make decisions # distinguish between facts & opinions, evaluate evidence & arguments, & take & defend informed positions on issues $ integrate information, to see relationships, & to apply your knowledge to dealing with various problems & decisions https://talentlens.in/critical-thinking-essence-decisive-mind-works/ 10 Question everything & everybody. Be skeptical. Do not believe everything you hear & read (including this), without evaluating the information you receive. Seek other sources & opinions. Identify & evaluate your personal biases & beliefs. Each of us has biases & beliefs taught to us by our parents, teachers, friends, role models, & our own experience. What are your basic beliefs, values, & biases? Where did they come from? What assumptions are they based on? How sure are you that your beliefs, values, & assumptions are right & why? Be open to considering different points of view. Suspend judgment until questioning. “It ain’t what you don’t be valid but need further testing? Is the you gather more evidence, & be willing know that gets you into trouble. It’s what information based on a few isolated to change your mind. Recognize that you know for sure that just ain’t so.” stories or experiences or on carefully there may be a number of useful & controlled studies that have been acceptable solutions to a problem, & Find out how the information related reviewed by experts in the field that very few issues are either black or to an issue was obtained. Are the involved? white. There are trade-offs involved in statements you heard or read based on dealing with any environmental issue. firsthand knowledge & research or on Question the evidence & hearsay? Are unnamed sources used? conclusions presented. What are the Be humble about what you know. Is the information based on reproducible conclusions or claims based on the Some people are so confident in what & widely accepted scientific studies or information you’re considering? What they know that they stop thinking & on preliminary scientific results that may evidence is presented to support them? 11 Does the evidence support them? Is Expect & tolerate uncertainty. Do not believe everything you read there a need to gather more evidence to Recognize that scientists cannot on the Internet. Evaluating information test the conclusions? Are there other, establish absolute proof or certainty on the Internet is one of the best ways more reasonable conclusions? about anything. However, the results of to put into practice the principles of science have varying degrees of critical thinking. Use & enjoy the Try to uncover differences in basic certainty. Internet, but think critically & proceed beliefs & assumptions. Many with caution. disagreements are based on different (& Check the arguments you hear & often hidden) basic assumptions read for logical fallacies & debating Become a seeker of wisdom, not a concerning how we look at & interpret tricks. Here are six of many examples vessel of information. Many people the world around us. Uncovering these of such debating tricks: (1) attack the believe that the main goal of their basic differences can allow the parties presenter of an argument rather than education is to learn as much as they involved to understand one another’s the argument itself; (2) appeal to can by gathering more & more viewpoints & to agree to disagree about emotion rather than facts & logic; (3) information. The primary goal is to learn their basic assumptions, beliefs, or claim that if one piece of evidence or how to sift through mountains of facts & principles. one conclusion is false then all other ideas to find the few nuggets of wisdom related pieces of evidence & that are the most useful for Try to identify & assess any motives conclusions are false; (4) say that a understanding the world & for making on the part of those presenting conclusion is false because it has not decisions. Facts & numbers are useful evidence & drawing conclusions. been scientifically proven. (Scientists only to the extent that they lead to an What is their expertise in this area? Do never prove anything absolutely, but understanding of key ideas, concepts, they have any unstated assumptions, they can often establish high degrees of connections, & scientific laws & theories beliefs, biases, or values? Do they have certainty.); (5) inject irrelevant or a personal agenda? Can they benefit misleading information to divert attention financially or politically from acceptance from important points; & (6) present only of their evidence & conclusions? Would either/or alternatives when there may be investigators with different basic a number of options assumptions or beliefs take the same data & come to different conclusions? 12 Science and Values Precautionary Principle Deciding what to do about an environmental problem involves both values & science. We must choose what we want the environment to be. But to make this choice requires knowing the scientific data & understanding its implications. What we choose should not only be dictated by our values. Science & values come to the forefront when we think about what action to take about a perceived environmental problem for which the science is only partially known. For this reason, in 1992 the Rio Earth Summit on Sustainable Development listed as one of its principles what we now call the Precautionary Principle —when there is a threat of serious, perhaps even irreversible, environmental damage, we should not wait for scientific proof before taking precautionary steps to prevent potential harm to the environment. The Precautionary Principle requires us to think ahead & predict potential consequences before they occur. It is a proactive, rather than reactive, tool— that is, we can use it when we see real trouble coming, rather than reacting after the trouble arises. 13 © CLRingor Solar Energy Sustainability: The Environmental Goal The variety of life on Earth has been sustained for at least 3.8 billion years in the face of catastrophic changes in environmental conditions. Three major interdependent natural factors have played the key roles in the long-term sustainability of life on this planet - scientific principles of sustainability: Image credit: Miller & Spoolman (2016). (1) Dependence on solar energy. The sun’s input of energy, called solar energy, warms the planet & provides energy that plants use to produce nutrients, the chemicals necessary for their own life processes & for those of most other animals, including humans. The sun also powers indirect forms of solar energy such as wind and flowing water, which we use to produce electricity. https://simple.wikipedia.org/wiki/ https://www.amwater.com/tnaw/water-information/water- Photosynthesis learning-center/the-water-cycle/ 14  Biodiversity (2) Biodiversity (short for biological diversity) is the variety of genes, organisms, species, & ecosystems in which organisms exist & interact. The interactions among species, especially the feeding relationships, provide vital ecosystem services & keep any population from growing too large. Biodiversity also provides countless ways FIGURE 1.2 Three Solar Energy of sustainability b for life to adapt to changing environmental has sustained a hug conditions, even catastrophic changes that wipe the earth for 3.8 bi out large numbers of species. drastic changes in e conditions (Concep (3) Chemical cycling or nutrient cycling is the circulation of chemicals necessary for life from the environment (mostly from soil & water) through © Cengage Learning organisms & back to the environment. The earth Image credit: Miller & Spoolman (2016). receives a continuous supply of energy from the sun, but it receives no new supplies Chemical of life- Cycling Biodiversity Chemical Cycling supporting chemicals. Through their complex interactions with their living & nonliving environment, organisms cycling. The earth receives must continually a continuous supplyinofnature,Sustainability Has Certain Key Components recycle energy from the sun, but it receives no new supplies the chemicals they need in order to survive. This of life-supporting chemicals. Thus through their waste = useful Sustainability, the central integrating theme of this book, means that there is littlecomplex waste interactions in nature, other resourceshas several critical components that we use as subthemes. with their living and nonliving than in the human world, because the wastes & environment, organisms must continually recycle the One such component is natural capital—the natural decayed bodies of anychemicals organismthey become need in order to survive. This means resources and ecosystem services that keep us and other species alive and support human economies (Figure 1.3). nutrients or raw materialsthatfor other there organisms. is little waste in nature, other than in the human world, because the wastes and decayed bodies Natural resources are materials and energy in na- of any organism become nutrients or raw materials for ture that are essential or useful to humans. They are often other organisms. In nature, classified as inexhaustible resources (such as energy from the sun and wind), renewable resources (such as air, water, waste = useful resources topsoil, plants, and animals) or nonrenewable or depletable Ecology and environmental science reveal that interde- resources (such as copper, oil, and coal). Ecosystem ser- pendence, not independence, is what sustains life and allows it vices are processes provided by healthy ecosystems that to adapt to a continually changing set of environmental support life and human economies at no monetary cost to conditions. Many environmental scientists argue that un- us. Examples include purification of air and water, re- derstanding this interdependence is the key to learning newal of topsoil, nutrient cycling, pollination, and pest how to live more sustainably. control. 15 Chemical Cycling Biodiversity 6 CHAPTER 1 ENVIRONMENTAL PROBLEMS, THEIR CAUSES, AND SUSTAINABILITY cycling. The earth receives a continuous supply of Sustainability Has Certain K Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). energy from the sun, but it receives no new supplies Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. of life-supporting chemicals. Thus through their Sustainability, the central integrating complex interactions with their living and nonliving has several critical components that environment, organisms must continually recycle the One such component is natural While environmental scientists 90446_ch01_002-023.indd 6 search for scientific solutions to chemicals they need in order to survive. This means resources and8:13 8/13/14 ecosystem AM services th problems, social scientists are looking for economic & political that there is little waste in nature, other than in the species alive and support human eco Natural resources are materia solutions. The search for solutions often involves conflicts. human world, because the wastes and decayed bodies Resources Are Inexhaustible, Renewable, of any organism become nutrients or raw materials or Nonrenewable for ture that are essential or useful to hu Dealing with such conflicts often involves making trade-offs, or classified as inexhaustible resources ( other organisms. In nature, A resource is anything that we can obtain from the envi- compromises, whether as a group or as an individual. Our ronment to meet theoursun and needs andwind), wants. renewable resourc Some resources, waste = useful resources study of environmental problems, proposed solutions, & trade- such as surface topsoil, plants, water, trees, and animals) and edible or are wild plants, nonr Ecology and environmental science reveal thatdirectly interde-availableresources (suchresources, for use. Other as copper,suchoil, and co as petro- offs has led us to propose three social science principles of Left: Minerva Studio/Shutterstock.com. Center: mikeledray/Shutterstock.com. Right: Kali Nine LLC/istockphoto.com. leum,itminerals, pendence, not independence, is what sustains life and allows wind,are vices andprocesses underground water, become provided by hea sustainability: to adapt to a continually changing set of environmental useful to us only with some effort and technological support life and human economies a ingenuity. conditions. Many environmental scientists argue that un- us. Examples Resources include can be classified purification o as inexhaustible, (1) Full-cost pricing (from economics): Many economists derstanding this interdependence is the key to learning renewable, ECONOMICS newal or of topsoil, nutrient nonrenewable cycling, (exhaustible) how to live more sustainably. (Figure 1.6). Solar energy is called an inex- control. recommend to include the harmful environmental & health haustible resource because its continuous Full-cost pricing costs of producing & using goods & services in their market supply is expected to last for at least 6 bil- lion years until the sun dies. It also pro- prices—a practice called full-cost pricing. This would give 6 CHAPTER 1 ENVIRONMENTAL PROBLEMS, THEIR CAUSES, AND SUSTAINABILITY vides us with inexhaustible wind and consumers better information about the environmental impacts flowing water that we use to produce rat to s electricity. A renewable resource is ion Wi of their lifestyles, & it would allow them to make more informed ure nsi S ge bility PO in r fut espo THIC n-w Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due toone that electronic can rights, somebethirdreplenished bysuppressed party content may be nat- fro LIT esu ne choices about the goods & services they use. Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if su ural processes within hours to ICS lts E centuries, as long as we do not R use it up faster than natural (2) Win-win solutions (from political science): We can learn90446_ch01_002-023.indd 6 processes can renew it. Exam- ples include forests, grasslands, to work together in dealing with environmental problems by fishes, fertile topsoil, clean air, recognizing our interdependent connections with others & and freshwater. The highest rate at which we can use a renewable with our life-support system. This means shifting from a win- resource indefinitely without re- lose approach based on competition & dominance of other ducing its available supply is called its sustainable yield. FIGURE 1.5 Three social science principles of sustainability can help us make humans & of ecosystems to win-win solutions that are based Social Science Principles of Sustainability a transition to a more environmentally and economically sustainable future. on compromise in light of our interdependence & that benefit both people & the environment Image credit: Miller & Spoolman (2016). Left: Carole Castelli/Shutterstock. Center: Alexander Kalina/Shutterstock. (3) A responsibility to future generations (from ethics): We should leave the planet’s life-support systems in at least as good a condition as that which we now enjoy, if not better, for future generations. 16 Inexhaustible Renewable Nonrenewable (Exhaustible)  Geosphere Atmosphere 3.1 Basic Systems Concept 45 Biosphere steady-state system, the inputs (of anything of interest) If the water input equals the water output and evaporation are equal to the outputs, so the amount stored within is not considered, the water level in the lake does not the system is constant. An idealized example of a steady- change, and so, in regard to water, the lake is in a steady state system is a dam and lake into which water enters state. (Additional characteristics of systems are discussed from a river and out of which water flows (Figure 3.4). in A Closer Look 3.1.) A CLOSER LOOK 3.1 Hydrosphere Earth as a System Simple Systems A system is a set of components, or parts, that function together as a whole. A simple way to think about a system is to view it as a series Input (I ) Output (O) of compartments (also called “reservoirs,” and we will use these terms interchangeably), each of which can store a certain (a) Compartment X amount 17of something you are interested in, and each of which Humanosphere receives input from other compartments and transfers some of e.g., water from a spigot e.g., water in a bathtub e.g., water down the drain its stored material to other compartments (Figure 3.6a). The general equation is The change in the amount stored in (∆S ) of X is the difference between the input I and the output O mathematically, and t is the unit time say an hour, I = O ± ∆S day or year. ∆St=It-Ot or It=Ot_∆St where I is input into a compartment; O is output, and ∆S is Basic Systems change in storage. This equation defines a budget for what is No change Tree farm A simple way to think about a system is to view it being considered. For example, if your checking account has (b) $1,000 in it (no interest rate) and you earn $500 per month in size of that plants as a series of compartments or reservoirs, each of reservoir one tree for which can store & receive from other reservoirs & Concepts at the bookstore, input is $500 per month. If you spend $500 every one cut Input equal to Output transfer some of its stored material to other per month, the amount in your account will be $1,000 at the Steady-state reservoirs. Image credit: Botkin & Keller (2011). end of the month (no change in storage). If you spend less than $500 per month, your account will grow (+∆S). If you spend more than $500 per month, the amount of money in Reservoir yourAaccount system can be(-∆open will decrease S). or closed. In an (c) is Use of fossil fuels reduced open system,water An environmental some energy engineer could oruse material this kind of systems diagram (solid, (Figure liquid, or3.6a) gas) to plan movesthe size of the into orvarious out of Input less than Output dams to be built on the Missouri River, taking into account Negative change the the system. desired total storage a closed In among the dams system, noand (Figure 3.4) the such transfers role of each take place. dam in managing the river’sFor flowour (refer Reservoir Pollution of back to the opening case study and also see Figure 3.7). In purposes, a materially closed system Figure 3.7, the amount stored in a dam’s reservoir is listed as (d) grows lake with pesticides Xn,is oneX isinthewhich where amountno matter of water storedmoves and n is theinnumber & Input greater than Output outcompartment. of the of the system, although (In this case the dams are energy numbered & in Positive change order from upstream to downstream.) Water flows from the F IGU RE 3.6 (a) General equation for ways in which a compart- information can move across the environment—tributaries, watersheds, and direct rainfall— stability. Such a system has a constant ment of some material can change. (Source: Modified from P.R. equal to the outputs, so the amount intosystem’s boundaries.and eachEarth is a to the Ehrlich, A.H. Ehrlich, and J.P. Holvren, Ecoscience: Population, each of the reservoirs, is connected stored within the system is constant. A condition, and if it is disturbed from that Resources, Environment, 3rd ed. [San Francisco: W.H. Freeman, materially adjacent reservoirsclosed system by the river. (for Finally, all all Missouri’s of the practical 1977].) Row (b) represents steady-state conditions; rows (c) and water flows into the Mississippi, which carries it to the Gulf condition, it returns to it once the (d) are examples of negative and positive changes in storage. steady state (dynamic equilibrium), purposes). of Mexico. disturbing factor is removed. also called balance of nature, is For this water-flow system, we can make a complete flow and do a scientific analysis of many environmental problems, seldom attained or maintained for very Systems diagram. This kindrespond to inputs of diagramming helps us to&think have about so you will find such diagrams throughout this book. long. Rather, systems are characterized Populations, species, ecosystems, & outputs. For example, increasing Earth’s entire biosphere are dynamic not only by human-induced greenhouse gases (input) in the lower systems, always changing & always disturbances but also by natural atmosphere is the primary cause of the requiring change. disturbances. Disturbances due to present global warming (output). natural events, are necessary for the With few exceptions, all real systems maintenance of those systems. Systems Systems maybe static or dynamic. A that we deal with in the environment are change naturally. If we are going to static system has a fixed condition & open to the flow of matter, energy, & manage systems for the betterment of tends to remain in that exact condition. information. An important distinction for the environment, we need to gain a A dynamic system changes, often open systems is whether they are better understanding of how they continually, over time. An important kind steady-state or non-steady-state. In change. of static system is one with classical a steady-state system, the inputs are 18  Systems of 3.1 Basic Systems Concept 49 Change ORV use The output of a system also depends on how long, on average, an input will remain in a reservoir — average Loss of vegetation residence time. This has important implications for environmental systems. + A system such as a small lake with an inlet & an outlet & a high transfer rate of + Erosion, gullies, ruts water has a short residence time for water. That makes the lake especially vulnerable to change because change can happen quickly. But, any pollutants Widening of ORV paths soon leave the lake. In large systems with a slow rate of transfer of water, such as oceans, water has a long residence time. Such systems are much Example of a positive feedback. Off-road vehicles (ORV) may Increase in cause positive feedback to soil erosion. ORV erosion (a) erode the soil & uproot plants. Without vegetation, the soil erodes faster, exposing even more soil (positive less vulnerable to quick change. feedback). As more soil is exposed, rainwater carves out ruts & gullies (more positive feedback). Drivers of However, once polluted, large systems = positive ORV then avoid the ruts & gullies by driving on feedback adjacent sections thatloop are not as eroded, widening paths & with slow transfer rates are difficult to + (b) erosion because they further increasing erosion (more positive feedback). The gullies themselves increase clean up. concentrate runoff & have steep side slopes. Once formed, gullies tend to get longer, wider, & deeper, FIGURE causing additional 3.10 erosion How (even moreoff-road positive feedback). (a) create vehicles Image credit:positive feedback Botkin & Keller (2011). on soil erosion (b) and (c). When the output of a system (or a reservoir in a system) affects its input, state systems can remain in a constant further increase in output. Also called a feedback occurs. There are two kinds condition. Positive feedback occurs “vicious cycle,” it is destabilizing. of feedback: negative & positive. increases air and water pollution, disease, crime, and dis- when an increase in output leads to a Negative feedback is self-regulating, c