Environmental problems – An overview - Environmental Deterioration and Contamination: Problems and their Management - page 5

In order to study ecosystems, the world of “living'' is organized hierarchically,
ranging in scale from genes to cells, tissues, organs, organisms, species, communities
up to the level of the biosphere. Ecosystems exhibit a nonlinear behavior, referring
to the fact that cause and effect are disproportionate. Therefore, even small changes
in critical variables may lead to disproportionate, perhaps irreversible, changes in the
system properties (Levin, 1999).
The most commonly used general characteristic of the state of an ecosystem is
biodiversity. The Convention on Biological Diversity (CBD, 1992) defines biodiversity
as the variability among living organisms from all sources, including, “inter alia,'' ter-
restrial, marine, and other aquatic ecosystems, and the ecological complexes of which
they are a part. This includes diversity within species, between species and of ecosys-
tems. The decrease of biodiversity can be explained by five reasons, namely, habitat
destruction, invasive species, pollution, human overpopulation, and overharvesting
(Torrance, 2010). Because all species have their own role in the self-supporting and
self-regulating system of the ecosystem, the decrease in biodiversity usually indicates
that the original composition and equilibrium of the ecosystem has been altered and
consequently, the whole ecosystem becomes simpler and more vulnerable. The disap-
pearance of the most sensible parts of a certain flora and fauna indicates that the living
conditions of the ecosystem have decayed.
The fundament of today's ecoscience and environmental management is our under-
standing that ecosystems are sustained by the biodiversity within themselves. There is
a close interaction between living (biotic) and nonliving (abiotic) components of the
ecosystem. Feedback loops regulate global biogeochemical cycles, climate and ecosys-
tem properties such as abundance and community structure. An ecosystem cannot be
predicted or understood by the summation of its individual components. Any quali-
tative change in the composition results in quantitative changes in the whole system,
i.e., the system is able to evolve. The main processes which characterize ecosystems are
life processes and adaptation, abundance and distribution of organisms, succession,
biodiversity, material and energy flow, and finally, information flow.
Biodiversity includes species diversity, ecosystem diversity, genetic diversity, and
the complex processes operating at and among these respective levels. Biodiversity can
be characterized by the quality and quantity of the metagenome (the sum of DNA
and genes in a certain ecosystem), or any of the higher hierarchical components of the
ecosystem. High-level cooperation between communities results in increased efficiency
in the utilization of material and energy resources, which eventually leads to home-
ostasis. Biodiversity plays an important role in ecological health as much as it does
for human health. Understanding biodiversity and its conservation is the main focus
of ecosystem management and environmental management. For more information on
the topic see the Encyclopedia of Biodiversity (Levin, 2000, updated 2007).
Preventing the extinction of species is the best-known tool today to preserve biodi-
versity, but it is far from being enough to support ecosystem sustainability. The habitat
of the ecosystem (i.e., the environment) itself needs much more attention. Finding the
harmony between ecosystem use and human land uses may help to avoid losing the
ecosystem services essential for human life.
As mentioned, living and nonliving parts of the ecosystem are non-separable; their
coordinated cooperation is integrated in ecological systems with different development,
efficiency, and size. Some microorganisms may form a micro-sized ecosystem habitat