Amboseli National Park B&K Fig 3.1 Loss of woodlands First attributed to farmers clearing land or elephants Systems approach showed that dry phase of climate cycle changed habitat.

System Defined a set of components or parts that function together to act as a whole a single organism, a sewage treatment plant, a city, a river open or closed – ocean vs earth respond to inputs and have outputs

A Systems Approach Allows us to do the following: Understand complex processes Identify separate components that interact: Predators & prey Organic & Inorganic components Residents & Visitors Study the Earth as a dynamic system Compare one system to another

Feedback Mechanisms (how systems change) Feedback Mechanisms are how a system responds to input: in some cases, the output can then again serve as the input and cause a change in the System. Negative Feedback drives the system in the opposite direction of the output (e.g., spending money you earn). A large output serves to decrease subsequent outputs. A buffering effect; tends to stabilize a system. Positive Feedback drives the system in the same direction as the output (e.g., saving money you earn). A large output serves to increase subsequent outputs. An amplification effect; tends to destabilize a system.

Feedback: A Wilderness Example

Exponential Growth is a Form of Positive Feedback The Population Explosion is a form of Positive Feedback in which the Rate of Growth feeds on itself: more people leads to more births Doubling Time = the time for the quantity being measured to double! For humans, about 70 / growth rate.

What do these items have to do with exponential growth?

ENVIRONMENTAL UNITY  Environmental unity is shorthand for the concept that everything in the environment is connected, directly or indirectly, to everything else.  Any change in a system is likely to produce secondary and tertiary effects within that system and connected systems.

Change in the Earth System: Uniformitarianism Another principle important to understanding how the Earth as a system changes is uniformitarianism. Defined: principle that the physical and biological processes presently active in forming and modifying Earth can help explain the geologic and evolutionary history of the Earth. In other words: the same processes have been operating on our planet for countless years (mountains in Colorado grow 1mm/yr). changing-surface/the-forces-that-change-the-face-of-earthhttp://beyondpenguins.ehe.osu.edu/issue/earths- changing-surface/the-forces-that-change-the-face-of-earth Simply stated: “the present is the key to the past”

© 2003 John Wiley and Sons Publishers

Why Solving Environmental Problems is Often Difficult Hydrosphere, lithosphere, biosphere, and atmosphere = major parts of global environmental system 1. Nonlinear responses – exponential growth, rate at which CO 2 in the atmosphere dissolves in lakes, rivers, and oceans

Current Exponential Growth of the Human Population % per year At this annual rate of exponential growth, it takes only about a) 4 days to add the number of Americans killed in all U.S. wars b) 16 years to add 1.27 billion people(the population of China in 2001) - How much is a billion? If you could live for a billion minutes, you would be 1,902 years old.

Solving problems(con’t) 2. Lag time – delay between a cause and the appearance of its effect Ex) a) logging on steep slopes in dry environments/erosion b) long lag times may lead to overshoot and collapse

Hubbard Brook Experimental Forest

3. Irreversible consequences – ex) soil erosion “A nation that destroys its soil destroys itself.” - Franklin D. Roosevelt s/3/34/Dust-storm-Texas-1935.png _2785e9656f_o.jpg

Critical Thinking Some economists argue that population growth is good because it provides more workers, consumers, and problem solvers to keep the global economy growing. Environmentalists argue that population growth threatens economies and the earth’s life-support systems through increased pollution and environmental degradation. What is your position? Why?