Hydro-ecological relations in the Delta Waters

that chwged farnor reed mrshes and tidal flats fnto wet grasslands,
the numbers of these wintering geese conld stabilize and even rise.
In the new areas also important botanical values arid. The most
striking example Is the developcent of: a wet dune-slack vegetation with
rEre species like Parnassia painstris, Blackstonia gerfoliata and
several species of orchids. This type of habitaf originally occurred in
the lower parts of the coastal aunes. There it dieap~eated, however,
almost totally because of the lowering of the greundwator level.
Especially on sandy soils with a stehle groundwater regime in the Lakes
Be- and Grevelingen hundreds of hectares of this particular
vegetatipn type could develop and in the future probably also in the
Krammer-VolLerak.
However, the new ereas are still in a dmamic state and the above-
mestioned values mag be temposaq. The decllne of shote birds in the
Grevelingen (Fig. 5) is a good exgmple M thSs. We also see that shrubs
and trees begin to caJoniee the dune-slack habitats and displace the
characteristic herbs. In a late* phase parts of the actual duna-slack
enviro~nt will probably change because of decalcif4catiofi. In certain
cases it is possible to stop or slow down natural succession by grazfng
or mowing, thua conserving certain development stages by appropriate
management methadv. However, we hme to realize that it ia not possible
to keep the former estuarine landscape in a young stage, because there
are ne cyclic dynamic processes to renew abiotic envimnment. In the
long run the ecosystems will grow to a more mature stage and this will
inevitably lead to a decline of certain species and the appearawe of
others, AL the moment it will be possible to keep certain species by
grazing or mowing Eor a certain the. However, in the longer run theg
will bisappeaz.
Anyhow. it is qnite eLear that a grazing management will lead te
ecasystems totally different from those of spontaneous development or a
wing regime. And from that point of view the decision lies with the
etologists and the nature management: what type of nature do we wane on
the new emerged land?