Newsletter and Technical Publications
Freshwater Management Series No. 5
Guidelines for the Integrated Management of
- Phytotechnology and Ecohydrology -
Climate and land cover are
major factors that regulate the
hydrological cycle, in sense that water, mineral sediments, and biogenic
substances are dynamic elements in the river basin landscape.
During the last 300 years,
most river basins were dramatically modified due to human disturbances such as
agriculture, grazing, deforestation, and urbanisation. These disturbances also
have been changing the Earthís albedo and, consequently, its surface energy
budget, affecting local and regional climate, and, ultimately, the amount and
quality of water in the river basins of the world.
The one of the fundamental tenets of the
concept of sustainable development is the maintenance of an homeostatic
equilibrium within the ecosystem. Over-exploitation, or biotic structure
degradation, alters the ecosystem processes to the point where the ecosystemís
ability to produce desired resources is seriously diminished. A decline in
water quality and biodiversity, observed at the global scale in both developed
and developing countries, has provided sobering evidence that a purely
"mechanistic" and fragmented approach to water resources management, based
largely on hydrotechnical solutions such as application of sewage treatment
technologies and regulation of hydrological processes through flood control and
drought mitigation measures, has been less than successful. While elements of
this approach remain valid and viable, a technical solution alone is clearly
insufficient for the sustainable use of the worldís water resources.
|The human persistence and biodiversity
on the Earth is dependent on our ability to
maintain the integrity of ecological processes, which have been developed in
the course of biogeochemical evolution, expressed and measurable as energy,
volume of water, and nutrient mass dynamics on the basin scale.
A. The urgent need for a new approach for integrated river basin management
At the beginning of 21st century, the increasing human population and its
aspirations has become a major factor in progressive environmental degradation
on the global scale. Degradation of biological structures and ecological
processes means a reduction in the ecosystemís carrying capacity. As a
consequence, during the next 30 to 60 years, the human imperatives may clash with
the carrying capacity of global environment. Such a clash would be nothing less
than catastrophic for humanity.
It is a well-known phenomenon in ecological
handbooks that overpopulation, and exhaustion of the resources upon which the
population depends, leads to population collapse. This phenomenon appears in
many types of populations and across a range of scales, from protozoans in an
experimental bottle to deer population introduced to a coastal island. The
final effect of such experiments is always the same - over-exploitation of
biotic resources lead to sharp decline of population size.
It is worth
underlining, however, that the carrying capacity of each ecological system
within the mega-ecosystem -the biogeosphere we know as Earth - is not fixed.
It can be reduced by pollution and over-exploitation of resources (e.g.,
through harvesting of biomass, or pollution of water). Likewise, it can be
restored and expanded through good husbandry and management (Figure 1.1).
The optimistic aspect of this story is that if, during periods of sharply increased
population growth, the carrying capacity of the environment is increased, the
population possesses additional time during which homeostatic regulatory
mechanisms may be established to achieve a state of dynamic equilibrium between
the density of the population and the carrying capacity of ecosystem. One
example of such homeostatic feedback regulation is well known. In case of fish
populations, when food resources become limiting, females do not produce eggs.
This results in a reduction in the population and the recreation of an
equilibrium between resource availability, necessary to sustain the population,
and the population itself. Thus, the question becomes one of providing an
answer to the question of how to achieve and sustain this equilibrium, or,
better yet, of how to expand the carrying capacity of global ecosystem to
sustain an increasing population?
|Fig. 1.1. A. The various
scenarios of the effect of doubling CO2 emissions on a temperate,
European river basin (Pilica River), based upon the two most prominent
computation scenarios - the Goddard Institute for Space Studies (GISS) and the
Geophysical Fluid Dynamics Laboratory (GFDL) models|
|Fig. 1.1. B. The potential effect of changes in the global ecosystemís
carying capacity on human population growth (Zalewski, M., G. A. Janauer &
G. Jolankai 1997, changed)(lager image)|
The answer is through developing an understanding of ecological
processes at different spatial and temporal scales. Such an understanding can
be achieved by integrating the different sectors or branches of the