Geoscience Reference
In-Depth Information
concept of 'ecological status' enshrined within the
Directive is not synonymous with 'conservation
value', yet the WFD has much to offer nature
conservation (Boon and Lee, 2005). Article 1 of the
WFD summarizes the main aims of the Directive:
to prevent further deterioration of aquatic
ecosystems and to protect and enhance their status
(including wetlands directly depending on aquatic
ecosystems);
between upstream and downstream reaches;
between river channels, riparian zones and
floodplains; and between the surface of the river
bed and sub-surface regions.
In the early to mid 20th century, research on
running waters looked inward to the ecological
factors that affect the distribution of organisms
(Percival and Whitehead, 1929; Macan, 1963).
Much of the credit for looking outward, for
broadening the appreciation of rivers as integral
parts of the landscape, should be given to
Noel Hynes' brief but influential paper on 'the
stream and its valley' (Hynes, 1975). His succinct
description of the way 'the valley rules the
stream' - with river communities shaped by their
underlying geology, soils, precipitation, and organic
inputs - has been expanded by many others over
the past 35 years to provide the scientific basis
for integrated catchment management (ICM). It is
only comparatively recently, however, that ICM
has become the basis of a statutory requirement
throughout the European Union following the
adoption of the WFD. Yet the WFD takes a rather
patchy approach to scale and to connectivity.
On the one hand, there is a requirement to
produce river basin management plans, to monitor
the status of water bodies, and to put in place
'programmes of measures' to ensure that the
environmental objectives of the Directive are met.
On the other, the assessment of ecological status
does not recognize explicitly the three types of
connectivity described above. The importance of
longitudinal connectivity is recognized but only in
forming part of the assessment of rivers at the
highest level of ecological status. To be classified as
such, 'The continuity of the river [should not be]
disturbed by anthropogenic activities and allows
undisturbed migration of aquatic organisms and
sediment transport.' The same level of assessment
also applies to lateral connectivity between a river
and its riparian zone. Floodplain habitats are not
included explicitly although wetlands dependent
on aquatic ecosystems are covered to some extent
by the WFD.
Research on the hyporheic zones of rivers (the
vertical dimension) has increased rapidly over the
last 20 years; papers have now been published on
to promote sustainable water use;
to
reduce
pollution
to
groundwater
and
to
surface water;
to contribute to mitigating the effects of floods
and droughts.
A 'departure from naturalness', which lies at
the heart of the Directive and assessed in terms
of ecological status, is an important component
(perhaps the most important component) of
conservation value but it is not the only one
(Ratcliffe, 1977; Boon
et al
., 1997, 2002; Boon,
2000; Dunn, 2004).
Consequently, while the HD and the WFD
both have a valuable role to play in furthering
river conservation in Europe, this role is limited.
Assessing the conservation value of rivers only to
meet the requirements of European legislation will
produce an unbalanced picture. The last 20 years
have seen many new approaches to evaluating
fresh waters in general, and rivers in particular
(Boon and Pringle, 2009). Some methods have
been designed to help select a representative
set of rivers for protection (Chadderton
et al
.,
2004; Leathwick
et al
., this volume) while others
have broader objectives (Kleynhans, 1996; Boon
et al
., 1997). One overriding aim, in all cases,
has been to move from decisions based largely
on subjective judgements to those supported by
scientific evidence.
Scale and connectivity
Understanding of the significance of scale in
the way rivers function, and therefore in their
conservation and management, has grown
impressively over the last 20 years. Just before the
1990 conference, a paper by Ward (1989) on the
'four-dimensional nature of lotic ecosystems' drew
attention
to
the
importance
of
'connectivity' -
