Mangrove Cove

Delta
Mangrove Cove Management Plan
In the case of Mangrove Cove, the speed of this change has been high, and the number of
young mangrove trees sprouting amongst the saltmarsh plants suggests that the pace of this
expansion is not slowing. The site has a very gentle slope and it would not be unreasonable
to suggest that within another twenty years mangroves would have reached beyond the edge
of the reserve to where the deeper channel starts (shown in Figure 4 of Section 5.2.1.1
Evolution of the landscape).
There are two responses to this change - observe and interpret the change in habitat as
mangroves gradually reclaim the site, or actively manage the site to maintain the highest
range of biodiversity and cultural values.
Change is a natural process in intertidal communities, and watching it occur is an important
educational facet of environmental awareness. It takes man from the ‘controlling centre’ of
the universe and places him in his niche – a small cog in a large wheel. This is a valuable
lesson, and the mangroves at Ethelton may be used to illustrate several salient points – sealevel
change, land subsidence, the temporary nature of even quite large structures such as
boats and the importance of providing saltmarsh retreat areas for not only the plants but also
the animals and migratory birds that depend on them.
The negative side of allowing change to occur in this instance is the resulting reduction in
biodiversity value (vegetation species diversity, mud flat infauna and wader bird habitat) and
cultural values (shipwrecks, log pool piles and the ‘swim through sculptures’, indigenous
values). Where the ‘observe’ option is selected, interpretive signage is recommended to assist
the public in recognising what is occurring on the site.
As noted above, a monoculture of mangrove has lower biodiversity value than an area that
includes both mangroves and salt marsh. The obvious differences are observable in vegetation
diversity and wader bird habitat, both of which are smaller in a mangrove monoculture.
Mangroves are normally limited in their incursion into saltmarshes by the increased soil
salinity. In areas such as Mutton Cove, a restricted tidal entrance allows control of the water
levels and resulting soil salinity. In other parts of Barker Inlet such control is not available. In
some small areas there is land available for saltmarsh retreat (Little Para) but in most areas the
saltmarsh will be over run by mangroves. The Mangrove Cove saltmarshes are very small and
have no tidal restrictions, however they could possibly be managed by salting the saltmarsh
areas and wrecks. This should be a low impact, low cost method of slowing the advance of
the mangroves, leaving open area for the wrecks, saltmarshes and migratory birds.
The negative side of undertaking such an action is the essentially artificial nature of the
control. The process is experimental, so determining the degree of intervention may be
iterative. Also, it is unknown how effective the process would be. While the process is likely
to work to slow the mangrove expansion down in the short term (10-20 years) it may not be
sufficient to prevent the change in the case of extreme sea-level change over the longer term.
Indeed, should sea-level change be very large, even the mangroves may not survive.
Stakeholders have selected ‘active management’ as a management tool in Mangrove Cove,
however they recognise that this is an experimental procedure. It is recommended that the
salting program be designed as an experiment, monitored over several years and interpretation
provided.
LMC-MCR-001-PC/RE Page 34