Environmental Engineering Reference
In-Depth Information
pands, the value of clean water will increase as demands escalate for a fi-
nite resource. Population growth is likely to increase demand on water
supplies, even in the face of uncertainty over climate in the future (Vörös-
marty et al., 2000). Increased efficiency has led to decreases in per capita
water use in the United States since the early 1980s (Fig. 1.3). Efforts to
increase conservation of water will become essential as water becomes
more valuable (Brown, 2000).
Despite the existence of technology to make water use more efficient
and maintain water quality, the ongoing negative human impact on aquatic
environments is widespread. Most uses of water compromise water qual-
ity and the integrity of aquatic ecosystems, and future human impact on
water quality and biodiversity is inevitable. An understanding of aquatic
ecology will assist humankind in making decisions to minimize adverse im-
pacts on our aquatic resources, and it will ultimately be required for poli-
cies that lead to sustainable water use practices (Gleick, 1998).
WHAT IS THE VALUE OF WATER QUALITY?
We have discussed availability of water, but the quality of water is also
important. Aquatic ecosystems provide us with numerous benefits in addi-
tion to direct use. Estimates of the global values of wetlands ($3.2 trillion
per year) and rivers and lakes ($1.7 trillion per year) indicate the key im-
portance of freshwaters to humans (Costanza et al., 1997). These estimates
suggest that the greatest values of natural continental aquatic systems are
derived from flood control, water supply, and waste treatment. The value
per hectare is greater for wetlands, streams, and rivers than for any ter-
restrial habitats. In this chapter, I explore values of aquatic ecosystems be-
cause monetary figures can influence their perceived importance. Methods
for assigning values to ecosystems can provide important evidence for peo-
ple advocating minimization of anthropogenic impacts on the environ-
ment. Ignoring ecosystem values can be particularly problematic because
perceived short-term gain often outweighs poorly quantified long-term
harm when political and bureaucratic decisions are made regarding re-
source use.
Quantification of some values of water is straightforward, including
determining the cost of drinking water, the value of irrigated crops, some
costs of pollution, and direct values of fisheries. Others may be more dif-
ficult to quantify. What is the value of a canoe ride on a clean lake at
sunset or of fishing for catfish on a lazy river? What is the worth of the
species that inhabit continental waters including nongame species? These
values may be difficult to quantify, but methods are being developed to
establish nonmarket values and integrate environmental dimensions to
economic analyses (Costanza, 1996). These methods include estimating
how much money people spend to travel to an aquatic habitat, the sta-
tistical relationship between an attribute of the system and economic ben-
efit, and surveys of how much money people believe an aquatic resource
is worth (Wilson and Carpenter, 1999). In an example of determining a
relationship between an economic benefit and an ecosystem attribute,
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