Transcript Mangrove or “Mangal” - People Server at UNCW

Mangrove Ecology
with a case study from Ecuador
Introduction to Coastal Management
Mangrove or “Mangal”
Red Mangroves (Rhizophora mangle)
• Definition
– Tropical hardwood trees
adapted to grow in marine
intertidal environments
• Develop only on
shorelines protected
from wave action
(estuaries, bays,
lagoons)
• Common throughout
the tropical regions of
the world
• Typically flooded once
or twice per day
Distribution of Mangroves
• Generally occur between
30 degrees N.L. and 30
degrees S.L.
• Generally follow the 24
degree C. (75 degrees F.)
isotherm of sea surface
temperature
• Tolerate little or no frost
• Uncommon along arid
Distribution of mangroves (green) in southern
North American and Northern South America
coasts
Mangrove or “Mangal”
Characteristics
•
•
•
•
Low diversity of plant and animal species
Canopy high and monotonous
Soils waterlogged and anaerobic
Substrate variable (muds, sand, rock,
organic)
Mangrove or “Mangal”
Characteristics
• Mangrove species show characteristics
of pioneer species in their reproductive
biology
– r-selection properties in finding a
habitat
• Mangrove species show characteristics
of mature phase species in aspects of
community structure and vegetative
growth
– K-selection properties in maintaining
Mangrove Specializations
• Most species have some part
of root system exposed to
atmosphere
• Leaves large, thick, leathery
and evergreen
• Many are capable of
excreting salts from leaves
• Most cannot be propagated
vegetatively
• Most have no growth rings
• All mangroves distributed by
water and propagules float
Mangrove Characteristics
• Fauna
Frigate Bird
(Fregata
magnificens)
– highly variable; not
characteristic
– insects common
– birds--few
– mud skippers, crabs, oysters,
snails
– crocodiles, snakes (few
poisonous)
– tiger (Ganges River mangal is
refuge)
Raccoon (Procyon lotor)
– deer, raccoon, bats (bats are
White-tailed
Deer
(Odocoilus
____)
Mangrove Characteristics
• Once the mangrove
becomes established:
– little structure to the
community
– succession not
documented
– no understory
– no stratification
– species distributed by
edaphic factors (soil type,
soil salinity)
Utilization and Exploitation of
Mangroves
• Forestry
– boat building an fish traps
– poles
– firewood (charcoal)
– tannins and dyes
– chip and sell as cellulose base
Utilization and Exploitation of
Mangroves
• Agriculture
– typical agricultural plants cannot
survive in mangrove environments
– rice fields
– mariculture (shrimp, finfish,
shellfish)
Utilization and Exploitation of
Mangroves
• Fisheries
– documented as
nutrient source for
nearshore fisheries
– stabilize shorelines;
reduce
sedimentation into
estuaries
– habitat for juvenile
fish
– habitat for oysters
Utilization and Exploitation of
Mangroves
• Salt conversion
• Sewage treatment (garbage dump)
• Coastal protection (storm buffer, stabilize
shoreline)
• Wildlife management (deer, crocodiles,
tigers)
Ecuadorian Shrimp Mariculture
• Shrimp farming developed in the late
1960s
• By 1982, 44% of fish exports were shrimp
Ecuadorian children seining
for gravid female shrimp
Ecuadorian shrimp farms
created by removing mangrove
forests along estuarine
shoreline
Ecuadorian worker seining for
shrimp in man-made ponds
Shrimp Exports to the United States from
Ecuador, Panama and Mexico (1977-82)
Year
Ecuador
Panama
Mexico
1977
8 .61
10.07
7 6 .2 5
1979
1 3 .7 0
12.20
7 1 .8 9
1980
2 0 .1 9
13.73
7 6 .0 6
1981
2 4 .7 3
15.92
7 0 .8 7
1982
3 6 .1 2
17.62
8 0 .1 7
Percent
Change
320
75
5
Tradeoffs for Intensive versus
Extensive Mariculture
M ariculture
Approach
Yield per
Costs in
Technology
unit area money and
energy
Space
Requirements
I ntensive
high
high
high
low
Extensive
low
low
low
high
Solutions?
• Intensify mariculture to increase yields
• Discourage location of ponds in
mangroves
• Train extension agents
• Link research and field applications
• Discourage international funding for new
sites
• Charge single agency with mariculture
management