Homework 2-Environmental Systems and Ther inteatoh Environmentol Sclence: Earth
ID: 152966 • Letter: H
Question
Homework 2-Environmental Systems and Ther inteatoh Environmentol Sclence: Earth as a Living Planet, 9th Ed.-Chapters 4 and 5 1. Explain the phrase dynamic equilibrium. Why is the idea of equilbrium in systems somewhat misleading in regard to environmental questions? Provide an example of the average residence time (ART) of a pollutant in the environment, and describe how knowing the ART is important in protecting humans or other organisms. 2. What is the difference between positive feedback and negative feedback in environmental systems? Provide one example of each type of feedback for the environment. 3. 4. What is the main concern with exponential growth patterns for organisms, such as humans?Explanation / Answer
1. Dynamic equilibrium refers to the balanced state of incoming and outgoing fluxes from a system. If the exchanges are occurring at a uniform rate in a system, then the system is said to be in dynamic equilibrium.
The idea of equilibrium in systems is misleading in environmental questions because of the possibility of anthropogenic changes in natural landscapes and the associated ecosystems. The balance in exchanges from ecosystems may not last over longer periods of time due to human influences.
2. Average residence time is the amount of time spent by a substance in its reservoir. A pollutant such as methane spends about 12 years in the atmosphere. Mitigation efforts to reduce the methane emissions on a global scale may minimize the impact of sea level rise on coastal ecosystems. Since the impact of methane as a greenhouse gas is global, curbing the emissions of a relatively long-lived gas may reduce the rate of warming in oceans globally on a long term.
3. Positive feedback refers to the loop in which a system output drives a process in the same direction as the initial change. For example, an increase in methane emissions leads to an increase in the temperature of permafrost regions which further increases the emission of methane. Thus, an increase in methane emissions may further increase its emissions.
Negative feedback refers to the loop in which a system output drives a process in the opposite direction as the initial change. For example, an increase in methane emissions may lead to an increase in evaporation from oceans induced by the greenhouse effect, producing more low-level clouds capable of reflecting solar radiation and a lesser land surface temperature. Thus, an increase in methane emissions may further decrease its emissions from land.
4. The main concern with exponential growth patterns for humans is that the human population may not be left with sufficient resources needed for survival. An increase in population beyond a threshold level may affect an environment's ability to provide resources such as food, water, shelter to the entire population inhabiting in that environment.
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