Laboratory Manual for Introductory Geology 4e

FIGURE 18.9 Estimated number of people (in millions) whose homes would be below
sea level if global temperatures rose by 2° to 4°, for the ten countries that would have the
greatest number of residents affected.
China
64
145
India
55
20
Bangladesh
48
12
Vietnam
26
46
Indonesia
16
44
Japan
18
34
United States
12
25
Philippines
20
7
Egypt
19
9
4°C 2°C
Brazil
9
16
0 30 60 90 120 150
Population (in millions)
Chapter 17 examined effects of sea-level rise at the regional level. Here, we look
more closely at what individual areas are facing. The United Nations estimates that
40% of the world’s population (~3.0 billion people!) lives within 100 km of a coast.
The goal of current international climate change treaties is to limit global warming
to 2°C—half the temperature increase that is predicted to occur if no actions
are taken—by cutting anthropogenic greenhouse gas emissions. But even a 2°C
increase will cause enormous damage, as some island nations in the Indian and
Pacific oceans will disappear entirely in the near future, like the Maldives in the
Indian Ocean, whose highest elevation is only 8 feet above sea level.
At this point, little can be done to protect those nations. Large parts of other
countries will be flooded, including Qatar, several Caribbean nations, and the Netherlands,
where many areas already below sea level are habitable only because of an
extensive and expensive system of dikes and seawalls. The countries with the largest
populations living in areas that will fall below sea level are shown in FIGURE 18.9.
The cost of relocating the threatened populations in those nations is almost inconceivably
large.
Closer to home, NOAA estimates that 39% of the U.S. population (126 million
people) lives in coastal counties that are vulnerable to sea-level rise. Twenty-one
small U.S. coastal towns have already had to be relocated—five in low-lying areas of
Louisiana and Washington and twelve in Alaska—at a cost of hundreds of millions
of dollars. These were small communities; how much would it cost if major U.S.
coastal cities had to be abandoned? FIGURE 18.10 dramatically shows projected sealevel
rise scenarios for five large U.S. coastal cities (see also Fig. 17.23 for projected
sea-level rise in New Orleans, Louisiana). The 5-foot rise is predicted to occur within
100–200 years, depending on the rate of global warming. The 12-foot estimate is
for the year 2300 and assumes that all nations initiate moderate greenhouse gas
controls.
Exercise 18.4 looks at the numbers of people who would be affected by sea-level
rise in the U.S. coastal cities shown in Figure 18.10.
18.2.5 Changes in the Biosphere
The biosphere must evolve to adapt to the changes in the atmosphere, cryosphere,
and hydrosphere we’ve discussed above. Whether or not organisms can survive
those changes depends on how rapidly they can adjust to the changing conditions;
18.2 CHANGES IN THE EARTH SYSTEM
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