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The ecology of the Bahamian
(Abaco) pine forest
Part 1 of a series by John Hedden
For PART 2 -
Click
HERE
For PART
3 - Click
HERE
In this series
of articles we will eventually have a good look at the pine forest
community of Abaco and so try to understand its ecology and its
position in the living web of the Abaco environment. However,
to understand how the pine forest survives, we must also understand
a little about ecology, its terms and words. We must also appreciate
that ecology is an imperfect science. We all know that scientists
dream of being able to perform all sorts of experiments in a
well equipped laboratory where every imaginable scientific device
is available for use in a well controlled, artificial environment,
giving exact and perfect results every time!
Ecological experiments
are unfortunately not like that. The laboratory is the natural
living world outside where all sorts of uncontrollable events
take place. The length of time of the experiment may be anywhere
between several hundred years to over many thousand, making it
difficult for one scientist to begin and end the observations.
On top of that the scientists did not even design the experiment;
it was already taking place when they arrived in the laboratory!
Ecology is such
an imperfect science that ecologists are unable to predict accurately
what will be the long term effects of modern (last 100 years)
physical activities by mankind in the form of pollution, population
manipulation and breeding and topographical changes (roads, concrete,
cities, deforestation, among others). One thing we do know is
that a global environment means that NO geographical area and
NO (political) nation is isolated from the world environment.
In other words, what we do to nature here on Abaco will have
an effect through winds and the Gulf Stream on Florida and the
U.S. East Coast, Iceland, Western Europe and the British Isles.
More towards
the local scene, let us demonstrate some basic ecological principles
through observations of a living system. We will use our Abaco
wetland (Marls, South Side, North Side West Side, according to
where you are from).
The Bahamas is
made up of many islands the windward side of which are formed
of ridges (hills) laid down as sand dunes by winds some 100,000
years ago. On the leeward side the shallow sea and shore is populated
by four different types of "mangrove." (Sorry, taxonomists.)
These colonisers slowly but surely over the years turn open salt
water wilderness into dry land wilderness! A short journey into
the mangroves anywhere here will show you what is happening.
It all begins
with the long floating seedling, possible a foot long, which
arrives (perhaps from Andros or Eleuthera) bobbing up and down
on the ocean and becomes stuck in the mud not too far out from
the shore line. This seedling soon roots and grows into the familiar
RED MANGROVE which really does walk across the shallow water
by dropping new roots from its twisting trunk. Soon this tangle
traps debris, leaves, garbage and bits of wood, providing a home
for crabs, sponges, algae, fish, crawfish, oysters and such.
Water movement quickly becomes restricted, more solids are deposited
and before long a muddy slop is formed. However, the red mangrove
doesn't like this new environment it has created and so withers
away and is replaced by the just as familiar BLACK MANGROVE.
These are identifiable by the short breathing shoots they send
up from their roots through the mud and into the air, making
the mud flats look like a forest of sticks. The roots underneath
further bind the mud mass together forming a semi-hard ground
which by now has become unsuitable for the black mangrove. The
WHITE MANGROVE then moves in and displaces the black mangrove
forest. The white mangrove is distinctive with its salt releasing
glands at the bottom of the leaf on its stem. Over time the ground
becomes hard and solid and inhospitable for the white mangrove
which itself is displaced by the hardy salt-tolerant BUTTONWOOD
with its attractive leaves and trunks. Over time this solid land
experiences rainfall and movement of fresh water under it changes
the soil from salt to fresh. The buttonwood can no longer survive
and so relinquishes this land to the first of the mixed coppice
type vegetation.
So, over a period
of years we have moved from an open salt water community to a
solid rockland community in five definite steps. This orderly
change in communities is called ECOLOGICAL SUCCESSION. It begins
with the PIONEERING STAGE of the red mangrove and progresses
through the SERAL STAGES to the mature CLIMAX of the coppice.
The whole grouping of seral stages is called a SERE. Remember
that this succession is equivalent to the life (larval) stages
of an insect, finally ending in the mature adult. In fact, the
whole interaction between plants, animals and physical environment
of the community is regarded as a living organism rather than
a hodge podge of different life forms. These factors show us
that we have, in fact, a dynamic balance (growing and changing)
rather than a static (stopped) balance of nature. This, of course,
means that the system is healthy.
Remember the
above terms and ideas and think about the following two questions.
1. Is global warming taking place? 2. Would global warming have
an effect on the ecological succession of the mangrove community?
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