HW2_Solutions - DEPARTMENT OF CIVIL AND ENVIRONMENTAL...

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1 DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING UNIVERSITY OF CALIFORNIA, BERKELEY CE11 ENGINEERED SYSTEMS AND SUSTAINABILITY, SPRING 2009 H OMEWORK 2: E NVIRONMENTAL T RENDS AND N ATURAL R ESOURCES D UE W EDNESDAY , F EBRUARY 11, 2009 (T OTAL : 100 P OINTS ) ***SOLUTIONS*** Improving and Deteriorating Environmental Trends Problem 1 a. Please give two examples supporting the pessimistic view of environmental trends not shown in your HO#4. (20 points) On a global scale, most of the environmental trends supporting the pessimistic view are well known. Among them are the increase of CO 2 concentration into the atmosphere (cf. Fig 1), the reduction of world forest area (cf. Fig 2) and the reduction of world fish stocks (cf. Fig 3 & 4). The case of CO 2 is well known. CO 2 is a non toxic gas. In small quantities (< 1%), it has no toxicological effects on living species. However, its greenhouse effect and thus its related global warming effect and influence on climate change (even if the magnitude is still difficult to estimate) are fairly accepted in the scientific world. More complex to evaluate and thus more debatable are the possible negative outcomes of global warming and their magnitudes. The alarming thing is the speed with which the CO 2 concentration is currently increasing into the atmosphere (cf. Fig 1). As shown in Fig 1, in the last 1’000 years (up to 1800), the concentration of CO 2 in the atmosphere was fairly constant around 280 ppm. However, in less than 200 years, the concentration increased up to close to 380 ppm nowadays. The speed and magnitude of increase is an alarming trend. It is strongly suspected that most of this increase is caused by the important combustion of fossil energy by our society. Fig 1. CO 2 concentration in the atmosphere (IPPC, 2001). On a global scale, another alarming trend is the decrease in world forest surface area (cf. Fig 2). Forests are one of the main features of our world concerning the state of the environment. Indeed, among other important roles, they shelter an important fraction of the world’s biodiversity (this is especially the case for equatorial forests) and act as an important sink of atmospheric CO 2 (this is especially the case for boreal forests). The decreasing in world forest area seriously affects the world’s biodiversity and its capacity to absorb atmospheric CO 2 . Even if this later trend is less alarming because boreal forests do not diminish in size, the combustion of tropical and equatorial forests release important amount of CO 2 (in the order of several billions tons per year).
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2 Fig 2 shows the change, between 1980 and 1995, of forest areas in different parts of the world. Even if some indicators are positive (for the developed countries), the overall trend is negative. Indeed, the reduction of area in the developing countries is faster than the increase in developed countries, in percentage (cf. Fig 2) and amount of hectares. Indeed, forests experience a net annual loss of
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HW2_Solutions - DEPARTMENT OF CIVIL AND ENVIRONMENTAL...

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