Geoscience Reference
In-Depth Information
1.6 Book approach and outline
governance and public policy (chapter 14).
The i nal section of this topic (Part V) provides
regional case studies focusing on the unique
social and physical characteristics of both large
and internationally renowned as well as smaller
wetland sites from the low latitudes (chapter
15), middle latitudes (chapter 16), and high alti-
tudes and latitudes (chapter 17).
In this topic, we recognize that a complete study
of wetland environments requires the assess-
ment of the physical and biological attributes,
properties and functions of these ecosystems,
and the economic, political and social aspects
that mediate their use globally. We adopt a
systems approach, which emphasizes simultane-
ously examining component parts of a system
in the context of the whole. Such an approach
allows us to consider the interactions between
the physical, biological and human elements of
wetland ecosystems. Moreover, selected exam-
ples from across the world are used to illustrate
wetland characteristics and interactions. Collec-
tively, these provide a broad understanding of
the global scope of wetlands, their contributions
to natural processes and human societies.
Part I of the topic provides a general over-
view and introduction to the study of wetlands.
Chapter 2 considers the physical and social
components of wetland systems, while chapter
3 discusses the methods used to study and
monitor these systems. Part II focuses on the
fundamental physical and biological aspects of
wetlands including wetland hydrology (chapter
4), soils (chapter 5), vegetation (chapter 6) and
wildlife (chapter 7). In Part III, we consider
short- and long-term changes in wetland envi-
ronments and their roles in environmental
cycles and feedback. Autogenic and allogenic
change and the inl uence of climate, i re, tec-
tonic activity, sea-level l uctuation, and animal
activity on wetlands are addressed in chapter 8,
while chapter 9 provides a long-term record of
wetland formation and development through
geologic time. The important role of wetlands
in biogeochemical cycles and climate regimes
by acting as carbon reservoirs is addressed in
chapter 10.
Part IV of the topic focuses on the human
use and governance of wetland environments.
Topics addressed in this section of the topic
include wetland services, resources and methods
for valuation (chapter 11), wetland conservation
planning and management practices (chapter
12), wetland restoration, enhancement and crea-
tion (chapter 13), and i nally global wetland
1.7 Summary
Wetlands include water, soil, vegetation and
wildlife, as modii ed and exploited by human
activities. Early civilizations arose in fertile river
valleys, and wetlands continue to be essential
for modern human society. Wetlands provide
many resources for people who live in or derive
economic benei ts from them. In addition, wet-
lands serve important, but less tangible func-
tions for water supplies and high levels of
biological productivity and biodiversity. As
major sources and sinks for carbon, wetlands
play critical roles in the global carbon cycle with
signii cant consequences for greenhouse gases
and potential climate change.
In spite of these direct and indirect values,
people have a difi cult time balancing their
own, local, economic gains with broader regional
or global issues concerning wetland develop-
ment. Humans modify wetlands for various pur-
poses in many ways, most commonly by artii cial
draining, i lling, and reducing inl ow or extract-
ing water. What may be good for upstream
water users, however, often leads to undesirable
effects for downstream wetland habitats, water
resources, and the people who depend on them.
The total extent of existing wetlands is esti-
mated to range from 7 to 12 million km
2
, depend-
ing upon the dei nition for what is included.
These wetlands are found primarily in two latitu-
dinal zones
-
boreal and sub-boreal (50-70°N)
and tropical (
15°), and many more wetlands of
diverse types are found in all other parts of the
world. Aquatic civilizations adapt to seasonal
resources in wetlands, such as annual l ood
cycles, in order to practice agriculture and extract
resources with lesser impacts on wetland envi-
ronments. Hydraulic civilizations, in contrast,
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