Restoration of Salt Marshes - Restoration Ecology: The New Frontier - page 260

were revealed to be most successful with respect to the
re-establishment of halophytic plant species after de-
embankment were all grazed (Wolters et al . 2005 ).
This can be attributed to breaking up monospecifi c
swards and reducing competition. In fact, these
restored marshes ' behave ' as aforementioned existing
salt marshes.

35

France

Denmark
Netherlands / Belgium
United Kingdom

30

25

20

15

19.4.3 Increase of tidal amplitude

10

5

In Connecticut, United States, tidal fl ows were rein-
stated by placement of a 1.5 m diameter culvert in an
impoundment. Restoration targets were expressed in
terms of inundation, salinity, productivity and com-
munity structure. Vegetation integrates a number of
factors; however, food chain support as manifested by
macro - invertebrates, fi sh and birds was also taken into
account. In 1988, 10 years after the start of the resto-
ration, the existing freshwater species Typha angustifo-
lia had declined from 75% to 15%, whereas Spartina
alternifl ora had increased from <1% to 45%. In addi-
tion, high - marsh species had re - established and
covered 20% of the site, but Phragmites australis had
also spread. After 1988 Phragmites declined and salt
marsh vegetation had increased to cover 85%.
Although the restoration exhibits a striking result, the
restored marsh only moderately resembles the pre-
impoundment marsh (Fell et al . 2000 ). Monitoring
between 5 and 20 years of nine sites after increased
tidal amplitude along the coast of Connecticut revealed
different results for various parameters. Rapid recovery
of vegetation was related to sites with low elevation,
greater inundation and higher groundwater tables as
a result of greater colonization potential. Recovery of
other organisms was not always related to that of the
vegetation. A viable population of the native, high-
marsh snail Melamopus bidentatus took 20 years to
recover in a site where the vegetation recovered much
faster. Characteristic fi sh species assemblages were
found in creeks and ditches within 5 years. Populations
of breeding birds typical of salt marshes had estab-
lished after 15 years in the restored sites (Warren et al .
2002). Hence, within 20 years, successful restoration
by the increase of tidal amplitude is possible in this site
with these conditions. However, possibilities and time
scales for other salt marsh functions, such as carbon
storage and wave attenuation, are not known.
The polder Beltringharder Koog, Germany, was
embanked in 1987 in order to have a reservoir to

0

Percentage of target species

Figure 19.6 Frequency distribution of scores of
percentage of charteristic salt-marsh plant species related to
the regional species pool of over 70 de-embanked sites in
north-west Europe. Note the absence of monitoring in about
50% of the sites. (Modifi ed from Wolters et al . 2005 .)

reconstruction, from an area of 300 m × 300 m in an
intensively ditched salt marsh in Germany, revealed
that the claypit refi lled with a rate of 15 cm yr − 1 during
the fi rst 2 years to less than 4 cm yr − 1 after 8 years,
when it exceeded Mean High Tide. In the mean time, a
meandering creek pattern had developed (Karle & Bar-
tholomä 2008). Of course, all de-embankment meas-
ures and plans for removal of artifi cial sand dikes are
carried out within the framework of maintaining ade-
quate coastal defence for the hinterland.
In organogenic coastal areas such as along the Baltic
Sea, embankment resulted in lowering of the polder
because of agricultural exploitation and oxidation.
Hence, removal of the summer dike might result in
permanent stagnant pools containing slightly brackish
water without any vegetation, after die-off of the fresh-
water community. This sequence of events was indeed
observed at Karrendorfer Wiesen on the German Baltic
Coast (M ü ller - Motzfeld 1997 ). De - embankment of an
estuarine summer - polder in the south - western Nether-
lands revealed that Phragmites australis took over in the
absence of livestock grazing, whereas Plantago mar-
itima became dominant in a grazed site, and the lower
lying pools remained without vegetation (Bakker et al .
2002b). These differences emphasize the effect of man-
agement regime on the outcome of de-embankment.
This is in fact a widespread phenomenon. The sites that