southern hemisphere, Chapman recognizes (outside the tropics) a South American
Group and an Austro-New Zealand group. On the pacific coast of South America,
distinct effects of a climate gradient on the species compositions are shown by Fariña
et al. (2017). Here, the salt marshes are divided in arid coastal habitats dominated by
Sarcorcornia fruticosa as well as temperate habitats in the South with high Spartina
densiflora abundance. In Australia and New Zealand, salt marshes form extensive
habitats sometimes over 10 km wide, but mostly confined to estuarine environments
or barrier estuaries. Mangrove encroachment is one of the major threats for salt
marshes, mainly in northern Australia (Saintilan et al. 2009).
In many parts of the world, saltmarshes are directly or indirectly influenced by
human activities. Moreover, large areas are used for grazing (Fig. 2), hay making or
food harvesting. Especially in regions with protected saltmarshes, the question of the
intensity and reduction of grazing has intensively been discussed during the last
50 years. Many saltmarshes along the North Sea, for instance, are heavily overgrazed
by domestic animals (mainly sheep). Natural grazing takes place by geese and hares.
The majority of rather brackish plant communities found along the Baltic Sea coast
rely on (very) moderate grazing regimes (Pätsch et al. 2019) in combination with
other factors of which elevation is most dominant (Jutila 2001). Where grazing does
not take place, succession stages dominated by Bolboschoenus maritimus, Elytrigia
repens, Phragmites australis or Schedonorus arundinaceus, or even willow shrubland and Alnus glutinosa woodland, would be able to replace them. Moderate
grazing might facilitate coastal ground-breeding birds that profit from the structure
of salt pastures, as has been demonstrated in National Parks of the German Bight
(Looijen and Bakker 1987; Kirsch 1990).
3.5 Rocky Shores
Rocky shores are hard transitions from sea to land often accompanied with a steep
difference in altitude. Water currents and erosion form strongly accented coastlines,
sometime with cliffs rising hundreds of metres above sea level. Also, artificial
structures may show similar characteristics as rocky shores. Examples are docks,
dikes or even ships and buoys can function as comparable hard substrate for algae
and invertebrates.
The lifeforms living on rocks are distributed over several zones depending on
their contact with salt sea water and wave action. Brown and red algae, molluscs and
crustaceans like barnacles inhabit the sub-, low- and mid-tidal zones, while higher up
mussels and periwinkles are attached to the rocks in high tide zones. In the splash
zone lichens can start growing (Denny and Gaines 2007). On less inclined areas
between the rocks, rock pools can form with stagnant sea water. In these small pools,
many species of the lower zones or even marine species can find temporal refuge.
The limited size of the rock pools facilitates extreme conditions as salt levels rise due
to water evaporation. Higher up on the cliff, on the edges of the rock faces vegetation
with salt tolerant plants such as Armeria maritima develops. These rock edges are
Coastal Habitats, Shallow Seas and Inland Saline Steppes: Ecology,. . .
289
Group and an Austro-New Zealand group. On the pacific coast of South America,
distinct effects of a climate gradient on the species compositions are shown by Fariña
et al. (2017). Here, the salt marshes are divided in arid coastal habitats dominated by
Sarcorcornia fruticosa as well as temperate habitats in the South with high Spartina
densiflora abundance. In Australia and New Zealand, salt marshes form extensive
habitats sometimes over 10 km wide, but mostly confined to estuarine environments
or barrier estuaries. Mangrove encroachment is one of the major threats for salt
marshes, mainly in northern Australia (Saintilan et al. 2009).
In many parts of the world, saltmarshes are directly or indirectly influenced by
human activities. Moreover, large areas are used for grazing (Fig. 2), hay making or
food harvesting. Especially in regions with protected saltmarshes, the question of the
intensity and reduction of grazing has intensively been discussed during the last
50 years. Many saltmarshes along the North Sea, for instance, are heavily overgrazed
by domestic animals (mainly sheep). Natural grazing takes place by geese and hares.
The majority of rather brackish plant communities found along the Baltic Sea coast
rely on (very) moderate grazing regimes (Pätsch et al. 2019) in combination with
other factors of which elevation is most dominant (Jutila 2001). Where grazing does
not take place, succession stages dominated by Bolboschoenus maritimus, Elytrigia
repens, Phragmites australis or Schedonorus arundinaceus, or even willow shrubland and Alnus glutinosa woodland, would be able to replace them. Moderate
grazing might facilitate coastal ground-breeding birds that profit from the structure
of salt pastures, as has been demonstrated in National Parks of the German Bight
(Looijen and Bakker 1987; Kirsch 1990).
3.5 Rocky Shores
Rocky shores are hard transitions from sea to land often accompanied with a steep
difference in altitude. Water currents and erosion form strongly accented coastlines,
sometime with cliffs rising hundreds of metres above sea level. Also, artificial
structures may show similar characteristics as rocky shores. Examples are docks,
dikes or even ships and buoys can function as comparable hard substrate for algae
and invertebrates.
The lifeforms living on rocks are distributed over several zones depending on
their contact with salt sea water and wave action. Brown and red algae, molluscs and
crustaceans like barnacles inhabit the sub-, low- and mid-tidal zones, while higher up
mussels and periwinkles are attached to the rocks in high tide zones. In the splash
zone lichens can start growing (Denny and Gaines 2007). On less inclined areas
between the rocks, rock pools can form with stagnant sea water. In these small pools,
many species of the lower zones or even marine species can find temporal refuge.
The limited size of the rock pools facilitates extreme conditions as salt levels rise due
to water evaporation. Higher up on the cliff, on the edges of the rock faces vegetation
with salt tolerant plants such as Armeria maritima develops. These rock edges are
Coastal Habitats, Shallow Seas and Inland Saline Steppes: Ecology,. . .
289