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 Joel Sartore
Although it has been written that we are but dust and to dust we
shall return, it would be far more accurate to say that we came
from water (our human bodies are nearly two-thirds water) and to
water we must eventually return. Water is one of the most abundant
compounds on Earth and one of the most critical components for
sustaining life on this planet. It is also one of the most
remarkable substances. No other common inorganic material is fluid
at temperatures that support life, making it possible for floating
and swimming organisms to have evolved and become mobile. Although
fluid, the viscosity of water allows for rowing or undulating body
movements to provide for easy mobility. Additionally, few natural
compounds are so resistant to temperature changes (its so-called
specific heat), which helps buffer living cells from rapid, perhaps
fatal heating and cooling and also limits the rate of evaporation.
Water dissolves essentially all the critical elements needed for
life, including all the basic nutritional salts as well as vital
gasses such as oxygen, hydrogen, and carbon dioxide. Its
biochemical presence is also needed for facilitating all the basic
photosynthetic and respiratory processes of living cells that
involve carbon, oxygen, and hydrogen.
Although water becomes denser as it cools and approaches
freezing, it actually expands as it freezes. Thus ice forms at the
tops of lakes and rivers first, rather than from the bottom up.
This curious fact allows aquatic organisms to survive in a fluid
environment while separated from subfreezing atmospheric conditions
above by a protective ice ceiling, thus enabling them to endure
long winters or even more prolonged arcticlike conditions. Although
water strongly resists freezing, it easily evaporates and by later
condensation is able to spread life-giving moisture across the
drier parts of the globe as various forms of precipitation.
Because cold water is relatively dense and sinks and warmer
water correspondingly rises, oceans develop vertical cycles. As a
result, warmer, low-latitude waters rise and replace sinking polar
waters, producing upwellings of deep, dissolved ocean nutrients,
access to which would otherwise be forever lost to plants and
animals. These oceanic cycles, aided by the energy of planetary
spin effects, produce enormous clockwise or counterclockwise
surface-level currents such as the Gulf Stream, which may either
warm or cool adjoining land masses, causing offshore or onshore
winds and resulting in increased or reduced coastal precipitation.
Oceanic currents therefore influence large-scale terrestrial wind
as well as precipitation variables and thereby control
continentwide climatic patterns, as recent cycles of La Niña and El
Niño have so effectively proven in recent years.
Even in smaller ecosystems and communities such as lakes,
marshes, and temporary wetlands, water strongly influences and
ultimately controls local species diversity and the overall
abundance of plants and animals. This control is largely brought
about by the influence of available water in allowing
photosynthesis to proceed and thus regulate the initial plant
production and subsequent storage of organic matter such as
carbohydrates. These materials are then successively funneled
through food chains in a predictable and diminishing sequence of
exploitation by consumer organisms such as herbivores and
carnivores. The consumers in turn are ultimately exploited and
transformed back again into their inorganic compounds by lowly
decomposer organisms such as bacteria. In short, the water that
helped to convert carbon dioxide to organic carbon molecules by
green plants is again finally released as water in the process of
respiration and decomposition by both plants and animals. As stated
earlier, water we are and to water we shall return.
Of all the wonders of Earth, nothing is more valuable than
water; without it Earth would be as lifeless as Mars. Nevertheless,
nothing on our planet seems to be wasted so flagrantly or polluted
so recklessly by humankind as water. Ultimately, we earthlings will
have to decide if we wish to share Mars’s fate; postulated
interplanetary attempts by NASA to reach and colonize it and to use
its possible subsurface ice supplies for human consumption and
industrial purposes would be roughly comparable to visiting Earth
as it may have appeared 3 billion years ago and hoping to set up a
profitable car-wash operation there. It would seem that conserving
water on Earth is far simpler, much more profitable, and immensely
more critical to our own survival than hoping to find and extract
water on Mars.
By permission of the University of
Nebraska Press. © 2001 by the University of Nebraska Press.
Available wherever books are sold or from the University of
Nebraska Press, 800.526.2617, and on the Web at
nebraskapress.unl.edu.
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