Geoscience Reference
In-Depth Information
tions, some of which are likely to be highly rele-
vant in the future.
Joined-up
working
The Manifesto
and party pressure
Dogma
Ideas
Timing
Public commitments
and targets
Evidence
10.5.2.1 Trawling
Events and crises
Practicality/
delivery
Devolution
Science and
technology
Legality
Many countries' economies and populations rely
heavily upon trawling on their continental shelves,
for example, in 2001, the Great Barrier Reef
(GBR) shelf was worth AU$4.2 million to the
Australian economy, and another AU$0.3 mil-
lion through recreational and commercial fish-
ing (Productivity Commission 2003). On some
shelves, trawling is already heavily regulated,
primarily to protect fish-stocks or allow their
recovery, but with the added advantage of
moderating impacts upon the sea bed. Moves
towards enforcing marine zonation of various
types are also occurring. Perhaps the most
advanced in this process is the GBR shelf, where
the wish to minimize potential human impacts
has led to the shelf being divided up into a series
of complex biophysical zones, within which
restrictions apply to various human activities
such as anchoring, line fishing and trawling.
Such zonation is driven by perceived ecosystem
consequences rather than sedimentary ones
per
se
, and there remains a need for fundamental
research relating the shelf sedimentary environ-
ment to the ecology.
Parliament
Policy
Public opinion
Think tanks
The media
Cost and
resources
Global pressures
Specialist
lobbying
Ministers'
ambition/
ability/
willpower
EU
obligations
Organizational
culture
Fig. 10.15
Graphic illustrating 22 factors that can influence
the decisions taken by UK Government ministers. Note that
'science and technology' forms only one factor. (Used with
permission of McNeil Robertson Development.)
directly influence chemical and biological pro-
cesses and operate on a variety of spatial and
temporal scales, which may be hard to sample
effectively. In addition, where two or more human
activities coincide to influence the sediments, the
combined impact may be a complex function of
the nature of the individual impacts (e.g. trawl-
ing in an area of aggregate dredging). There
are also practical difficulties and great expense
involved in obtaining information about the
shelf sea-bed and its sedimentary processes.
Further, management regimes need to be
based on the best available science, so science
knowledge needs to be transformed effectively
into policy and management actions to prevent
environmental damage. Very real constraints
exist on our ability to do this, not least because
of the difficulty of proving cause and effect, and
of dealing with the uncertainties involved. It is
also noteworthy that science knowledge is only
one of a broad range of factors that can be taken
into account when forming policy (Fig. 10.15)
10.5.2.2 Aggregate dredging
World-wide, the demand for marine aggregates
is largely a function of construction activity.
For the UK, most marine sand and gravel is
currently extracted from the east and south-
east coasts of England, but new discoveries in
the eastern English Channel, near the median
line with France, are planned for exploitation.
The UK's past and predicted requirement is
around 25
10
6
tyr
−1
until 2016, of which these
new deposits could provide
×
50% (DEFRA
2005). Licence conditions include commit-
ments towards environmental protection and
monitoring, so that trends in the sedimentary
impacts of marine aggregate extraction will be
supported by increasing volumes of relevant
sedimentary data.
>
10.5.2 Sedimentary impacts of sea-bed
disturbance
The main current issues of anthropogenic sea-
bed disturbance were examined in above sec-
