"Urban transport systems based on a combination of rail lines, bus lines, bicycle pathways, and pedestrian walkways offer the best of all possible worlds in providing mobility, low-cost transportation, and a healthy urban environment." –Lester R. Brown, Plan B 4.0: Mobilizing to Save Civilization.
Chapter 3. Signs of Stress: The Biological Base: Synergies and Surprises
One concern of environmental scientists is that some trends of environmental degradation will reinforce each other, accelerating the process. Chris Bright of Worldwatch Institute has analyzed several of these synergistic relationships among environmental trends, both local and global. One such concern is with ice melting. When land is covered with ice and snow, much of the sunlight reaching the earth's surface is simply bounced back into space by the high reflectivity of the surface. Once the snow and ice melts, the soil or the water beneath absorbs much of the energy in the sunlight, raising temperatures. The higher temperature leads to more melting, and the process begins to feed on itself in what scientists call a positive feedback loop.84
This is of particular concern in the Arctic Sea, where ice is melting, shrinking the reflective area. (See Chapter 2.) The synergistic relationship between rising temperatures and reduced reflectivity may now have reached the point of no return in the Arctic, suggesting a future when Arctic sea ice may disappear entirely during the summer months. This rise in temperature in the polar region may also help explain why the Greenland ice sheet is beginning to melt.85
Another set of synergies is threatening the earth's forests by fire. Intact, healthy rainforests do not burn, but forests weakened by logging or slash-and-burn farming become vulnerable to fire. The more they burn, the more vulnerable they become. The process, which feeds on itself, reinforces the global warming trend. As higher temperatures due to climate change lead to the drying out of forests and more burning, more carbon is emitted into the atmosphere. Rising atmospheric carbon dioxide levels accelerate the process of global warming. The trends of rising temperatures and burning forests begin to reinforce each other.86
One consequence of many interacting changes is that they can lead to developments that surprise even the scientific community. One such event came in August 2000, as described in Chapter 2, when the icebreaker cruise ship discovered open water at the North Pole. Yet another recent surprise is the dieoff of coral reefs. Again, the reasons for the coral dieoff are complex, but a rise in surface water temperature may be responsible. What is surprising is that a temperature rise in sea surface water of less than 1 degree Celsius can lead to reef deaths. If the reefs continue to die, oceanic ecosystems will be altered, directly affecting the fisheries that depend on the coral reefs as nursery grounds.87
These are but a few of the surprises and synergies that have been encountered in recent years. No one knows how many the new century will bring. And unfortunately, synergistic trends such as those just described are often irreversible. As Chris Bright observes, "Nature has no reset buttons."88
84. Chris Bright, "The Nemesis Effect," World Watch, May/June 1999, pp. 12-23.
85. D.A. Rothrock, Y. Yu, and G.A. Maykut, "Thinning of Arctic Sea-Ice Cover," Geophysical Research Letters, 1 December 1999, pp. 3469-72; W. Krabill et al., "Greenland Ice Sheet: High-Elevation Balance and Peripheral Thinning," Science, 21 July 2000.
86. Burning of forests from Matthews et al., op. cit. note 4, pp. 24-26.
87. John Noble Wilford, "Ages-Old Icecap at North Pole Is Now Liquid, Scientists Find," New York Times, 19 August 2000; coral reefs from Lisa Mastny, "World's Coral Reefs Dying Off," in Worldwatch Institute, op. cit. note 77, pp. 92-93.
88. Chris Bright, "Anticipating Environmental 'Surprise,'" in Lester R. Brown et al., State of the World 2000 (New York: W.W. Norton & Company, 2000), p. 37.
Copyright © 2001 Earth Policy Institute