Understanding and Managing Climate Change Effects on River Ecosystems - River Conservation and Management - page 108

network aspects of river systems. At even more
basic levels, understanding the eco-physiological
effects of changing temperature, discharge and
changing oxygen dynamics is still limited by data
availability for many organisms (Elliott and Elliott,
2010; Stamp et al. , 2010).

temperature, discharge, stream nutrient dynamics
(Caruso, 2001, 2002; Hong et al. , 2005), habitat
availability (Cattaneo et al. , 2004), and impaired
recovery from the effects of acid deposition

(Durance and Ormerod, 2009).

Adaptive management
Adaptive management is the third major priority,
and in many respects the most crucial yet
surprising gap. Accepting that continued climate
change is now inevitable, far better evidence
is required from which to support and develop
adaptive strategies that will reduce adverse effects
are far as possible. Again, available knowledge
is scant and still largely speculative (Ormerod,
2009; Palmer et al. , 2009; Wilby et al. , 2010).
Principal recommendations for adaptation include:
(i) improving predictions of ecological effects so
that these effects can be anticipated and managed,
while the most sensitive locations can be protected
as far as possible; (ii) reducing the associated
stressors with which climate might interact, such
as point or diffuse pollution and water abstraction;
(iii) increasing the lengths of river designated
for their nature conservation value, targeted for
restoration or included in catchment-sensitive
agri-environment land-use incentives aimed at
benefits for rivers, riparian zones or river corridors;
(iv) buffering rivers against temperature gain
through the use of judicious riparian shading; (v)
maintaining environmental flows in rivers to the
extent that desirable organisms and key biological
communities are maintained and functional links
with catchments and floodplains are restored; (vi)
increasing ecological resilience and resistance to
climate change - i.e. enhancing features that
allow communities of river organisms to withstand
climate trends, or to re-organize and bounce back
in ways that sustain natural functions; and (vii)
improving connectivity among river basins as well
as of the processes within them.
All these cases require better supporting
evidence, but understanding is still rudimentary.
For example, the basic characteristics that increase
resistance or resilience at genetic, population,
community or ecosystem levels are still poorly
understood. This is most unfortunate because
potentially there are large benefits in all these

Interacting pressures
A further major dimension of climate change
is that effects on rivers will arise not only
directly, but also indirectly through the many other
processes linking atmospheric systems, catchments,
floodplains and riparian zones to river ecosystems.
Potential effects of this nature have been postulated
widely, involving the possibilities that climate will
have widespread effects on land use, point and
diffuse sources of water pollution, eutrophication,
acidification, invasive species, water abstraction
and a range of other stressors (Wilby et al. , 2006;
papers in Ormerod et al. , 2010). Effects extend
also to interactions between anthropogenic climate
change and existing, large-scale climatic effects
such as the Arctic Oscillation, North Atlantic
Oscillation and El Ni no/La Ni na that already cause
variations in discharge or temperature in river
systems large enough to have biological effects
(Puckridge et al. , 2000; Elliott et al. , 2000; Bradley
and Ormerod, 2001). In any of these cases,
existing stressors or pressures could exacerbate or
compound climate change effects; they could mask
or hide climate change effects; or they could act
as the indirect pathway through which climate
change effects are expressed. Ironically, this last
case includes instances where land-use change
or technological solutions in response to climate
change (e.g. renewable energy generation along
rivers) serve to cause problems that are locally at
least as large as those caused by climate change
(Aprahamian et al. , 2010).
So far, the scientific understanding of
interactions between climate change and other
pressures is limited. In some cases, climate
change effects have been most detectable at sites
where other problems, such as water quality, are
either absent or well understood (Daufresne and
Boet, 2007; Dewson et al. , 2007; Durance and
Ormerod, 2007, 2009; Viney et al. , 2007). In other
cases, interactions have been shown between