Geoscience Reference
In-Depth Information
economically important North Atlantic salmon
along the New England coastline of the United
States.
In some cases, natural events may inadvert-
ently and unexpectedly speed up the process of
restoration. A recent example is the accidental
1990 breaching of the Sieperda Polder in
the Scheldt River estuary of the Netherlands
(Eertman et al. 2002). Polders date back several
centuries and are an example of deliberate
human drainage of coastal landscapes. These
reclaimed areas are often lower than sea level
and are protected from l ooding by a series of
sea walls and levees, canal-and-lock systems,
and draining mechanisms that make them suit-
able for agriculture or human settlement.
Some i ve years after the 1990 accidental
breaching of the Sieperda Polder during an
intense storm, tidal activity quickly re-established
a marsh ecosystem with mudl ats and brackish
vegetation communities where agricultural crops
were once grown (Eertman et al. 2002). The
expansion of tidal channels through deliberate
restoration efforts further enhanced a vibrant
coastal marsh system, which now supports a
diversity of biota. While this was not a planned
restoration project, given the right conditions
the Scheldt River estuary demonstrates just
how quickly natural tidal processes re-
established wetland l ora and fauna (Eertman
et al. 2002).
Considerable effort has been made in Canada
to restore and reclaim cutover peatlands (Quinty
and Rochefort 2003). In order to restore func-
tional peat accumulation two steps are essential:
a) re-establishing viable plant cover including
Sphagnum
mosses, and b) raising and stabiliz-
ing the water table near the surface. These
objectives are reached through the following
operations: preparing the surface, collecting and
spreading plants, spreading straw cover, fertiliz-
ing, and blocking drainage.
The Bois-des-Bel site in southeastern Quebec
exemplii es this approach. The site had been
abandoned for two decades prior to the begin-
ning of restoration in 1999. An area of 8 ha
was treated by leveling i elds, i lling ditches,
building berms, and creating pools. Vegeta-
tion became re-established rapidly, and fauna
returned to the pools. This experimental site is
monitored for long-term consequences of resto-
ration particularly on its biodiversity (Peatland
Ecology Research Group 2009). Many other sites
have been restored or reclaimed in Quebec and
New Brunswick as well as the Canadian prairie
provinces, with variable results (Quinty and
Rochefort 2003).
Other bioengineering or soft engineering
approaches include stream-bank stabilization
using biodegradable matting or dead tree trunks,
constructing habitat and nesting sites, and
restoring connections and habitat links between
patches of wetlands through riparian buffers or
vegetated corridor connectors. These connectors
allow animal species to move freely between
wetland patches. The actual coni guration and
close proximity of pools and ponds within a
wetland site are also important considerations
when attempting to restore habitat for amphib-
ians (Knutsen et al. 1999). Other approaches try
to restore patches of wetlands in relatively close
proximity to each other even if they are not
connected through vegetated corridors. Such
patches may serve as important bird feeding
areas and stopover points along migratory
routes.
Active approaches to restoration and enhance-
ment are time-consuming and i nancially
demanding. They also require considerable
expertise and careful long-term planning. The
results of active restoration approaches often
take a longer time to manifest. Hence, a moni-
toring and evaluation system must be imple-
mented to ensure that results are in keeping
with goals and expectations (IWWR 2003).
13.5.2 Passive and hybrid approaches
Passive approaches involve restoration or
enhancement through the removal of factors
that reduce a wetland's resilience and viability.
This approach allows a wetland to regenerate
naturally by removing any problematic factors
or reducing the sources of degradation (U.S.
Environmental Protection Agency 2000; IWWR
2003). Restricting access to a wetland site either
by humans or domesticated animals to allow
native l ora to re-establish is one example of a
