Environmental Engineering Reference
In-Depth Information
Ecosystem Engineers, Keystone Species - This contribution focuses on two eco-
logical phenomena. The first is “keystone species” which is defined as a species
(mostly of high trophic status) whose activities exert a disproportionate influence
on the patterns of species occurrence, distribution, and density in a community. The
second is the concept of “ecosystem engineers” defined as organisms that directly
or indirectly modulate the availability of resources (other than themselves) to other
species by causing physical state changes in biotic or abiotic materials. Models
have shown that the loss of species with a large number of trophic interactions can
trigger high numbers of secondary extinctions with serious consequences for
species persistence. The importance of keystone species can also be strongly linked
with ecosystem engineering. For example, the large impact of sea otters in kelp
forest ecosystems results from the coupling between engineering effects and
a trophic cascade.
Ecosystem Services - This entry provides an overview of issues concerning the
identification, biophysical and economic characterization, and safeguarding of
ecosystem services. The concept of ecosystem services has a long written history,
reaching back at least as far as Plato. This review history focuses on recent
advances such as the Millennium Ecosystem Assessment, and advances in spatial
modeling, economic valuation, and policy implementation. Examples of novel
finance and policy mechanisms, including water funds, marine spatial planning,
land-use planning and human development, and global policy efforts are presented.
The entry concludes with a discussion of the largest research and implementation
challenges in this field, identifying the issues that will frame the future growth of
the concept of ecosystem services.
Ecosystems and Spatial patterns - Ecological processes such as forest disturbances
act on ecosystems at multiple spatial and temporal scales to generate complex
spatial patterns. These patterns in turn influence ecosystem dynamics and have
important consequences for ecosystem sustainability. Analysis of ecosystem spa-
tial structure is a first step toward understanding these dynamics and the uncertain
interactions among processes. Quantitative characterization of spatial patterns and
their rates of change in natural environments are essential to understanding
ecological processes and to inform sustainable management techniques that aim
to minimize degradation and alteration of ecosystem dynamics. This entry covers:
sources of heterogeneity, spatial analysis, spatial analyses within the ecosystem
and spatial analyses among ecosystems.
Ecosystem Flow Analysis - It is necessary to understand the ecosystem as
a thermodynamic system and how the energy flows enter, interconnect, and disperse
from the environmental system. Ecological network methodologies exist to inves-
tigate and analyze these flows. In particular, partitioning the flow into boundary
input, non-cycled internal flow, and cycled internal flow shows the extent to which
reuse and recycling arise in ecosystems. The intricate, complex network structures
are responsible for these processes all within the given thermodynamic constraints.
Design of sustainable human systems could be informed by these organizational
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