Page 670 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

634 part IV Soils, ecosystems, and Biomes
condensation (discussed in Chapter 7). As the warm, moist air moves onshore and reaches the mountains, the air lifts and cools, and condensation occurs at higher elevations than before. Extra moisture means more cloud cover, and these clouds affect the daily tempera- ture range: Clouds at night, acting like insulation, raise nighttime minimum temperatures, whereas clouds dur- ing the day act as reflectors, lowering daytime maxi- mum temperatures (discussed in Chapter 4).
Optimal conditions for the non-native chytrid fun- gus occur when temperatures are between 17°C and 25°C. The new cloud cover keeps the daytime maximum below 25°C at the forest floor. In these more favourable conditions, the disease pathogen flourishes. Harlequin frogs have moist, porous skin that the fungus pen- etrates, killing the frog. Some researchers suggest that the spread of this fungus may be related to other factors in addition to climate change, including human popula- tion growth. More research is clearly needed to find a definitive cause. Between 1986 and 2006, approximately 67% of the 110 known species of harlequin frogs went extinct.
species and Ecosystem Restoration Since the 1990s, species restoration efforts in North America have focused on returning predators such as wolves and con- dors to parts of the western United States and, recently, jaguars to the U.S. Southwest. Other efforts have resulted in rising populations of black-footed ferrets and whoop- ing cranes in the prairie regions and shortnose sturgeon along the Atlantic seaboard. These projects have reintro- duced captive-bred animals or relocated wild animals into their former habitats, while at the same time lim- iting practices such as hunting that once caused spe- cies decline. The preservation of large habitats has also
played a critical role in restoring these, and other, en- dangered species worldwide.
Recent efforts at ecosystem restoration have had some success in restoring or preserving biodiversity, al- though questions remain about the effects of such work on overall ecosystem functioning. Numerous river resto- ration projects, such as the dam removals discussed in Chapter 15, are successfully restoring natural conditions for fisheries and riparian wetlands in the short term. In the Florida Everglades, a $9.5 billion restoration proj- ect began in 2000 and is ongoing. The goal is to return freshwater flow into the south Florida swamplands to revive the dying ecosystem. The Everglades restoration is the largest and most ambitious watershed restoration project in history (see www.evergladesplan.org/index.aspx).
Restoration of the Great Lakes ecosystems began in the 1970s and is ongoing. Focus Study 19.2 discusses the various environmental issues that have plagued this region of intense human use and development, and the management strategies in use to restore natural condi- tions. However, the question remains in these and many other ecosystems as to what is “natural.” The goal of returning ecosystems to the conditions that prevailed before human intervention is now being expanded to include the possibility of creating “novel ecosystems,” human-built or human-modified ecosystems that may have species and habitats that have never occurred to- gether. These novel systems have no natural analogs on which to base scientific hypotheses or restoration strategies—and yet, to sustain biodiversity and ecosys- tem function in our changing world it may be necessary to consider and manage such ecosystems. The intercon- nectedness of life processes and complexity of Earth’s support systems demand that we consider the whole when we study the web of life (Figure 19.25).
◀Figure 19.25 The web of life. Study the spider web as you read the following quotation:
life devours itself: everything that eats is itself eaten; everything that can be eaten is eaten; every chemical that is made by life can be broken down by life; all the sunlight that can be used is used. . . . The web of life has so many threads that a few can be broken without mak- ing it all unravel, and if this were not so, life could not have survived the normal accidents of weather and time, but still the snapping of each thread makes the whole web shudder, and weakens it. . . . you can never do just one thing: the effects of what you do in the world will always spread out like ripples in a pond.
[Photo by robert Christopherson; quotation from Friends of the earth and amory lovins, The U.n. Stockholm Conference, Only One Earth (london, england: earth island limited, 1972), p. 20.]