Geoscience Reference
In-Depth Information
spatial dynamics; Hanski 1999; Freckleton & Watkinson 2002) that cannot be
attained in restored sites in fragmented or otherwise heavily modified landscapes
(Hanski 1994). This is an issue that requires careful consideration in the planning
of restoration projects, and requires further investigation for general guidelines.
In addition, it is important to consider connections and dispersal abilities in
the context of climate change. Climate change may not only affect reference
conditions (as discussed above) but may also alter connections between sites and
dispersal abilities of species. Important mechanisms through which climate
change is anticipated to alter the connectivity of freshwater ecosystems are
(i) changed hydrodynamics of streams and rivers due to more extreme rain events
(see Chapter 4) which will alter the connections between sites by surface water
flows. For example, changes in river flooding events will change connections
between sites via seed dispersal by water, because seed deposition during flooding
events will be affected (Goodson
et al
. 2003); (ii) faster drying of ponds and
shallow lakes, due to warmer and drier summers, which will reduce 'stepping
stone' connections between wetlands. For example, the disappearance of ponds
increases the isolation of pond habitats and reduces zooplankton dispersal
between ponds (Allen 2007). Wind-dispersed organisms will be dispersed over
longer distances when storms increase in intensity and frequency, but this effect
is predicted to be relatively small (Soons
et al
. 2004b). In summary, measures of
the effects of climate change on the connectivity among freshwater ecosystems
are needed to predict future impacts on the success of restoration measures.
However, general guidelines are difficult to provide because effects are likely to
be highly specific per site and landscape, and will require landscape-scale
predictions of climate change and detailed knowledge of the spatial configuration
and connections in the landscape. A landscape-scale approach to restoration that
addresses these spatial issues, such as the OLU approach, in combination with
climate change predictions at the same working scale, will result in more
successful, realistic and 'climate change-proof ' restoration activities.
Operational landscape units: an approach
for enhancing success of wetland restoration
Nature conservation and restoration has focused traditionally on protecting
individual sites. However, in parts of the world where the natural landscape has
been severely altered for agricultural or urban use, individual patches are often
too small and isolated to ensure effective nature protection. Dispersal of organisms
and the balance between local extinction and recolonization are impeded,
resulting in populations, even as metapopulations, being less stable and more
subject to species loss. Another effect of landscape fragmentation is that natural
linkages in the landscape, such as water flows, are severed due to modifications
in geomorphology and hydrology.
Lateral connections in landscapes maintain biodiversity and ecological
functioning at a much higher level than is possible in separate ecosystems without
these spatial interactions. Lateral connections include corridors between landscape
patches, such as riparian forests connecting extensive floodplain forests, but
also connections by water flow or wind. Hence, conservation efforts should
Search WWH ::
Custom Search