Geoscience Reference
In-Depth Information
of the relevant sedimentary processes. Maps
of the sea-bed facies are essential background
information and also provide the basis for the
classification of sea-bed habitats. Clearly, it is
desirable that programmes should be available
for scientific scrutiny, so that the outcomes are
transparent and scientifically defensible. It is
increasingly important that information and data
are rapidly disseminated. Finally, the importance
of performance criteria cannot be overempha-
sized - there may be little point in undertaking
work unless progress towards the objectives can
be measured and the effectiveness of manage-
ment actions can be assessed.
There are good recent examples of shelf map-
ping projects. Extensive mapping work is being
undertaken in Australia (www.oceans.gov.au/
auscan), which was designed to assist the
ecosystem-based approach to environmental
management (section 10.4.8) by improving
understanding of the links between the physical
and biological components. Work in the Irish
Sea is developing a physical basis for the con-
servation of marine habitats (The Joint Nature
Conservation Committee 2004). The Irish Na-
tional Sea-bed Survey is also underway; using
techniques including multibeam and single-beam
echo sounders, sub-bottom profiling, gravity,
magnetics, with ground-truthing performed using
box core samples (http://www.gsisea-bed.ie).
A pan European project (Mapping European
Sea-bed Habitats (MESH) aims to produce
sea-bed habitat maps for much of the north-
west European shelf, and will improve the input
of such data into environmental management
within national regulatory frameworks (http://
www.searchmesh.net). Complementary regional
studies of the composition of shelf sediments
(e.g. Stevenson 2001) are also useful, especially
when dealing with issues of disposal at sea.
by no means universal, there is increasingly an
'ecosystem' approach taken to environmental
management of many ecosystems, including
those on continental shelves (e.g. European
Marine Strategy 2005). Essentially, such an
approach means that, rather than viewing a
human impact and its management in isolation,
account is taken of the range of components of
the system in question, the relevant processes
and interactions between components, the envir-
onmental factors that influence the system and
those factors that might be affected by anthro-
pogenic intervention. For example, except for
aggregates or marine minerals, the distribution
of shelf sediments and their associated processes
is not generally seen as having an inherent
value. Rather, sediments are important as a
substrate for benthic organisms and as a com-
ponent of the broader marine ecosystem. Thus,
assessment and monitoring of sediments are
often performed with regard to their role in
forming and maintaining marine habitats.
The ecosystem-based approach requires an
understanding of the overall sedimentary phys-
ical system. Most continental shelves are huge
physical systems, so that there is little practical
difference most human activities can make to the
systems as a whole, at least in terms of sediment
budgets. Consequently, local and subregional
scales tend to be most relevant, with biological,
chemical and social factors of importance. Map-
ping the sea-bed is a high priority for the future.
10.5
FUTURE ISSUES
10.5.1 Challenges of managing the impacts of
human activities on shelf sedimentation
Study, assessment and management of the
impacts of human activities on the sediments
of continental shelf environments represent a
significant challenge. The reasons include the
many physical processes that influence the shelf
sedimentary environment (Figs 10.2 & 10.3),
ranging from turbulence (scales of seconds and
centimetres) through to major sea-level cycles
(scales of
c
. 100,000 yr and
c
. 100 m). These
10.4.8 Taking an ecosystem-based approach
Marine systems are naturally dynamic and dis-
play natural variability, and the human pressures
on them vary with different patterns of human
activity. Protection of marine environments
needs to be flexible and adaptable. Although
