Geoscience Reference
In-Depth Information
2004). New techniques that can map vegetation
from satellite images (Apan
et al.
, 2002; Read
et al.
,
2003) and data from Laser Imaging Detection and
Ranging (LiDAR) (Lefsky
et al
., 2002), are being
tested to produce vegetation maps at different
spatial scales for nature conservation at a pan-
European level (Bock
et al
., 2005). Although
remote sensing is invaluable because it can cover
large areas and distinguish major phyto-sociological
associations (Merters, 2002) ground-truth survey
information is required for validation and to
assess the structure and composition of vegetation
formations (Farid
et al.
, 2006; Goetz, 2006).
Hardwood alluvial forests are widely recognized
as important habitats for the conservation of
several species (Tockner and Ward, 1999; Sabo
et al.
, 2005) and maintaining river ecosystem
functioning (Wallace
et al.
, 1999; McClain
et al.
,
2003; Pettit and Naiman, 2005). Consequently,
riparian vegetation characteristics are assessed in
several river survey protocols (Fern andez
et al.
,
2011). However, very few studies have considered
the conservation status assessment of alder-ash
alluvial forests, even though European Member
States are obliged to report the status of this priority
habitat under Article 17 of the Habitats Directive
(Council of the European Communities, 1992).
So far, these reports (Joint Nature Conservation
Committee, 2007; Søgaard
et al.
, 2007) have
followed traditional guidelines for conservation
status assessment within the
Natura 2000
network
based on habitat range, area, structure and
function, typical species and human pressures
(European Commission, 2006). Many of the
reports have assessed alder-ash alluvial forest as
being at favourable conservation status, reflecting
our conclusions, but the baseline information from
several Member States is not always reliable.
Suitability maps for different vegetation formations
(Echevarria
et al.
, 2008; M ucher
et al.
, 2009) would
assist in establishing reference range and area
and this would provide a much more reliable
assessment of conservation status in relation to
habitat changes caused by human activities.
For habitat structure and function, alder-ash
alluvial forest has been classified as 'unknown'
or
Nature Conservation Committee, 2007; Søgaard
et al.
, 2007). However, the assessment of human
pressures has been largely qualitative and with
no geographical context, so the most effective
management action required is unclear. Our
results show that invasive and transformer species
(
sensu
Richardson
et al.
, 2000) and fragmentation
are the main reasons preventing achievement
of favourable conservation status for alder-ash
alluvial forest along Cantabrian rivers. Identifying
affected areas using Geographical Information
System (GIS) polygons can help to target effective
restoration and conservation measures. Linking
impacts (e.g. embankments, bank reinforcements,
water abstraction, flow regulation and point and
diffuse pollution) to specific management action
would provide a much better basis for river
conservation and management at the appropriate
geographical scale.
Atlantic salmon conservation status
Our conclusion about salmon conservation status
is similar to that in previous studies which
demonstrated that most populations were either
extinct, endangered (the Nansa and Deva rivers),
or critically endangered (As on and Pas rivers;
Garcıa de Le aniz
et al.
, 1992). In Spain as a
whole, salmon is considered endangered (Doadrio,
2001), while in Europe it is classified as 'near
threatened' (Elvira, 2001). Salmon in northern
Spain are at the southern limit of their natural
range (McCrimmon and Gots, 1979), and the
Cantabrian populations have been subject to a
variety of major pressures during the last 50
years (Garcıa de Le aniz
et al.
, 1992). Even in
the As on, Pas and Deva rivers where distribution
range was considered favourable, populations are
very vulnerable to point and diffuse pollution,
water abstraction, barriers to migration, habitat
degradation and angling.
Catch records suggest that none of the salmon
populations achieves a sustainable minimum level
(cf. metapopulation effective size; Kuparinen
et al.
,
2010). Although the Miera and Deva rivers showed
larger number of salmon towards the end of the
15-year period (Figure 16.6), catch records usually
underestimate fish population sizes (O'Connell,
'inadequate'
across
most
of
Europe
(Joint
