David Tenenbaum – GEOG 110 – UNC-CH Fall 2005Modeling and Environmental Science: An Introduction• Environmental Science – It sounds like a modern idea, but if you view it broadly, it’s a very old idea:• Our ancestors’ survival depended on their knowledge of the environment• “Science is a process, a way of knowing”• It results in conclusions, generalizations, and sometimes scientific theories and even scientific laws• People often confuse the process of science with a fixed set of beliefs – the results• BUT science does not lead to so much to a fixed set of beliefs as to a set of beliefs that, at the present time, account for all known observationsabout a kind of phenomenonDavid Tenenbaum – GEOG 110 – UNC-CH Fall 2005Science Æ Change• Science is a process of discovery, thus scientific ideas change through time, and this can make applying the results of science frustrating. For example:1. Scientists cannot agree what is the best diet for people.2. A chemical can be considered as dangerous in the environment for a while, and then later be determined not be3. Wild fire was considered to be undesirabledisturbance, and then it was decided that it is an important and necessary natural phenomenon• It is more accurate to think of science as a continuing adventure with ever improving approximations of how the world worksDavid Tenenbaum – GEOG 110 – UNC-CH Fall 2005How Does Science Work?• Science begins with “Observations” of the world• From these observations, scientists formulate hypotheses that can be tested• Modern science does not deal with things that cannot be tested by observations, such as the existence of a supernatural being• It is generally agreed today that the essence of the scientific method is “disprovability”• A statement can be said to be scientific if someone can state a method by which it can be disprovedDavid Tenenbaum – GEOG 110 – UNC-CH Fall 2005Scientific Statements• Let’s come up with a few scientific statements• How could we disprove them?• For example: “Deforestation changes stream water flow peaks and water quality”• This is a scientific statement as we can come up with an experiment to disprove it or test if the above statement is true or false• In some sense, progress in science is not so much limited by our ability to conceive of scientific statements, but our ability to come up with ways to test them …David Tenenbaum – GEOG 110 – UNC-CH Fall 2005Assumptions of Science1. Events in the natural world follow patterns that can be understood through careful observation and analysis2. The basic patterns, or rules, that describe the behavior of events in the natural world are the same everywhere3. Science is based on a type of reasoning known as induction; it begins with specific observations about the natural world and extends to generalizations4. Generalizations can be subjected to tests that may disprove them; if such a test cannot be devised, then a generalization cannot be treated as a scientific statement5. Although new evidence can disprove existing scientific theories, science can never provide absolute proof of the truth of its theoriesDavid Tenenbaum – GEOG 110 – UNC-CH Fall 2005The Methods of ScienceYesNoObservation of Nature (Context: Current scientific theories and social values)1Form some Inferencesabout How We Think Things Work2Create a Model that relates the Inferences in Order to Explain the Observations3Hypothesis Deduced from the Model4Test the Hypothesis5Perform Data Collection to Allow us to Conduct the Test6RejectHypothesis7David Tenenbaum – GEOG 110 – UNC-CH Fall 2005Principles of Environmental Systems• Before we get to the systems view of the environment, we need to set out some supporting ideas:1. The Earth is a dynamic and evolving system2. The Earth is the only suitable habitat we have3. Understanding is key to solving env. problems4. The Earth has been profoundly altered by life5. Sustained life on Earth6. The nature of population sizes through time7. Human activities cause changes in the environment8. Land-use/land-cover change tends to be cumulative9. The Principle of Environmental UnityDavid Tenenbaum – GEOG 110 – UNC-CH Fall 20051. The Earth is a Dynamic and Evolving System•The age of Earth: ~ 4.6 billion years• Life on Earth: ~ 2 billion years• Human ancestors: Several million years• Our ancestors set the stage for the eventual dominationof human beings on EarthDavid Tenenbaum – GEOG 110 – UNC-CH Fall 20051. The Earth is a Dynamic and Evolving System• Matter and energy are constantly being transferred and are changing in form• Energy: The Earth is nearly in a steady state in energyIOI = O• That is, the Earth receivesenergy from the Sun and releases an equal amount of energy to space. There is no net gain or loss of energy for the Earth. This is not true over a day or year, but in the long termDavid Tenenbaum – GEOG 110 – UNC-CH Fall 20051. The Earth is a Dynamic and Evolving System• Matter: The Earth is almost a closed systemwhen it comes to matter• That is to say, that much like energy if you compare how much is coming in versus going out over the long term, the difference is negligible• Matter fluxes with respect to the magnitude of the Earth are quite smallIOI = ODavid Tenenbaum – GEOG 110 – UNC-CH Fall 20052. The Earth is the Only Suitable Habitat We Have• Because the Earth is the only suitable habitat we have available to us (barring some future where we can successfully move elsewhere), we have a strong, motivated self-interest in how this dynamic and evolving system is going to change• We know the resources of the Earth to be finite– Energy is more or less in a steady state– With respect to matter, the Earth is almost a closed system• With this in mind …David Tenenbaum – GEOG 110 – UNC-CH Fall 20053. Understanding is Key to Solving Environmental Problems• When faced with problems concerning the environment, understanding environmental systems, their feedback cycles and rates of change are often the key to finding a solution:• For example, let’s consider the sustainable use of forest resources: Given a particular tract of forested land, how much should we harvest each year in order to use the resource sustainably?• What items of information do we need in order to make a decision here?David Tenenbaum – GEOG 110 – UNC-CH Fall 20053. Understanding is Key to