interconnected, providing mutual protection and sustenance. Each of these ecosystems also creates biotastructured environments, where the organisms themselves
provide and build the physical structure among which
associated life is nurtured and sheltered. Without this living structure, these habitats and the many organisms
dependent on them simply would not exist. This essentially identifies how such a large group of plants and animals are so vulnerable.
For example, bordering mangrove coasts, colonial
coral reefs often flourish in the shallow warm seas created
and protected from land runoff by mangrove vegetation
(Duke and Wolanski, 2001). Mangroves absorb unwanted
nutrients and sediments of turbid waters to stabilize eroding and depositional shorelines. In modern human times,
this buffering role also includes the capture of harmful
chemicals in runoff waters from agricultural lands. The
specialized plant assemblages of mangrove coasts provide
a broad range of essential, and often undervalued, ecosystem services along with their more acknowledged roles as
habitats of high productivity and as fishery nursery sites
(Robertson and Duke, 1990). In such ways, the consequences of disturbing mangrove coast habitats are
expected to have far-reaching implications and impacts
on neighboring ecosystems and dependent biota.
Uniquely vulnerable mangroves require special
management
Ancestral mangroves are believed to have reinvaded
marine environments in multiple episodes from diverse
earlier lineages of land-based, flowering plants over the
previous 50–100 million years, culminating in today’s
mangrove flora. The evolution of mangrove plants
appears constrained by key functional attributes essential
to their survival in characteristically saline, inundated settings where isotonic extremes, desiccation, and hydrologic exposure combine as uniquely harsh restrictions on
organisms living in the tidal zone and within estuaries
(Duke et al., 1998). Such is the mangrove coast. This
land-sea interface is also a highly dynamic environment,
where even subtle changes in climate, sea-level, sediment,
and nutrient inputs have dramatic consequences for the
survival, distribution, and health of organisms living there.
Specifically, the predominant direct human disturbances
affecting mangrove coasts include: eutrophication, pollution, dredging, landfill, overfishing, and sedimentation.
The combination of these pressures, coupled with changes
in global climate and sea-level rise, has resulted in once
healthy mangrove areas becoming endangered communities with local extinction evident in some places (Duke
et al., 2007). Lessons from various rehabilitation projects
demonstrate that restoration is costly and unlikely to succeed. This places even greater urgency on managers to
develop and apply effective protective measures beforehand, to avoid irreplaceable losses and further degradation
of remaining, remnant mangrove coast ecosystems.
Over the past two centuries, human progress and development have increased dramatically. And, human society
has prospered and flourished accordingly. These great
human achievements have come at a huge environmental
cost though, with massive alterations to natural landscapes
to accommodate demands of expanding industry, trade,
and population. Mangrove coasts are particularly vulnerable because of their naturally highly dynamic geophysical
circumstances, coupled with a preference by human communities for development along coastlines and waterways.
This explains why there have been significant losses of
tidal wetland habitats in most coastal areas. But, the
longer-term consequences and implications have only
been partially considered. It is reasonable to ask, does it
really matter? Are remaining ecosystems sustainable?
And, how do we quantify and monitor changes so we
might manage both the changes and the consequences better? The answers can only come from knowing more about
the factors that affect functioning of habitats along mangrove coasts.
Factors influencing mangrove coasts: a strategy
There is an urgent need for local resource managers and
environmental enthusiasts to learn more about the range
of factors influencing mangroves and tidal wetlands in
their area. Help is also needed for optimization of sustainable management outcomes, with best-practice assessment methods to direct how mangrove coasts might best
be managed in view of current sociopolitical, economic,
and environmental pressures.
To achieve such outcomes, six key strategies are
recommended:
1. Identification and quantification of the type and biota
of tidal wetlands
2. Surveys of past changes in extent and character of wetland areas
3. Assessment of ecosystem health and how these ecosystems are changing
4. Identification of the chief drivers of change and assessment of longer-term implications
5. Determination of what will be lost in terms of ecosystem goods and services
6. Decisions on management options based on assessments of extent, change, health, pressures, and values
The far greatest problem facing tidal wetlands is the
ever-growing global population with its predictable, continually expanding demand for natural resources and
space, including mangrove coasts. One key consequence
also is that our global climate is changing dramatically,
and the loss of vital natural habitats and biological
resources is a direct result (Duke et al., 2007). Where we
acknowledge the value of these natural ecosystems for
the numerous direct and indirect services they provide,
then we must act urgently to become their diligent guardians. It is imperative that communities are aware of the
changes taking place, and what is being lost, so they can
414
MANGROVE COASTS
provide and build the physical structure among which
associated life is nurtured and sheltered. Without this living structure, these habitats and the many organisms
dependent on them simply would not exist. This essentially identifies how such a large group of plants and animals are so vulnerable.
For example, bordering mangrove coasts, colonial
coral reefs often flourish in the shallow warm seas created
and protected from land runoff by mangrove vegetation
(Duke and Wolanski, 2001). Mangroves absorb unwanted
nutrients and sediments of turbid waters to stabilize eroding and depositional shorelines. In modern human times,
this buffering role also includes the capture of harmful
chemicals in runoff waters from agricultural lands. The
specialized plant assemblages of mangrove coasts provide
a broad range of essential, and often undervalued, ecosystem services along with their more acknowledged roles as
habitats of high productivity and as fishery nursery sites
(Robertson and Duke, 1990). In such ways, the consequences of disturbing mangrove coast habitats are
expected to have far-reaching implications and impacts
on neighboring ecosystems and dependent biota.
Uniquely vulnerable mangroves require special
management
Ancestral mangroves are believed to have reinvaded
marine environments in multiple episodes from diverse
earlier lineages of land-based, flowering plants over the
previous 50–100 million years, culminating in today’s
mangrove flora. The evolution of mangrove plants
appears constrained by key functional attributes essential
to their survival in characteristically saline, inundated settings where isotonic extremes, desiccation, and hydrologic exposure combine as uniquely harsh restrictions on
organisms living in the tidal zone and within estuaries
(Duke et al., 1998). Such is the mangrove coast. This
land-sea interface is also a highly dynamic environment,
where even subtle changes in climate, sea-level, sediment,
and nutrient inputs have dramatic consequences for the
survival, distribution, and health of organisms living there.
Specifically, the predominant direct human disturbances
affecting mangrove coasts include: eutrophication, pollution, dredging, landfill, overfishing, and sedimentation.
The combination of these pressures, coupled with changes
in global climate and sea-level rise, has resulted in once
healthy mangrove areas becoming endangered communities with local extinction evident in some places (Duke
et al., 2007). Lessons from various rehabilitation projects
demonstrate that restoration is costly and unlikely to succeed. This places even greater urgency on managers to
develop and apply effective protective measures beforehand, to avoid irreplaceable losses and further degradation
of remaining, remnant mangrove coast ecosystems.
Over the past two centuries, human progress and development have increased dramatically. And, human society
has prospered and flourished accordingly. These great
human achievements have come at a huge environmental
cost though, with massive alterations to natural landscapes
to accommodate demands of expanding industry, trade,
and population. Mangrove coasts are particularly vulnerable because of their naturally highly dynamic geophysical
circumstances, coupled with a preference by human communities for development along coastlines and waterways.
This explains why there have been significant losses of
tidal wetland habitats in most coastal areas. But, the
longer-term consequences and implications have only
been partially considered. It is reasonable to ask, does it
really matter? Are remaining ecosystems sustainable?
And, how do we quantify and monitor changes so we
might manage both the changes and the consequences better? The answers can only come from knowing more about
the factors that affect functioning of habitats along mangrove coasts.
Factors influencing mangrove coasts: a strategy
There is an urgent need for local resource managers and
environmental enthusiasts to learn more about the range
of factors influencing mangroves and tidal wetlands in
their area. Help is also needed for optimization of sustainable management outcomes, with best-practice assessment methods to direct how mangrove coasts might best
be managed in view of current sociopolitical, economic,
and environmental pressures.
To achieve such outcomes, six key strategies are
recommended:
1. Identification and quantification of the type and biota
of tidal wetlands
2. Surveys of past changes in extent and character of wetland areas
3. Assessment of ecosystem health and how these ecosystems are changing
4. Identification of the chief drivers of change and assessment of longer-term implications
5. Determination of what will be lost in terms of ecosystem goods and services
6. Decisions on management options based on assessments of extent, change, health, pressures, and values
The far greatest problem facing tidal wetlands is the
ever-growing global population with its predictable, continually expanding demand for natural resources and
space, including mangrove coasts. One key consequence
also is that our global climate is changing dramatically,
and the loss of vital natural habitats and biological
resources is a direct result (Duke et al., 2007). Where we
acknowledge the value of these natural ecosystems for
the numerous direct and indirect services they provide,
then we must act urgently to become their diligent guardians. It is imperative that communities are aware of the
changes taking place, and what is being lost, so they can
414
MANGROVE COASTS