This model simulates the distribution of mangroves in coastal areas. There are 4
different species of mangroves (black, white, button, and red), each of which has
a different level of salinity tolerance. Black mangroves are the least tolerant
of high salinity, followed by white mangroves, button, and finally red mangroves,
which are the most tolerant.

The model shows a river flowing into the ocean, represented by two kinds of
turtles - freshwater and saltwater. At setup, all patches have zero salinity.
Freshwater turtles decrease by one the salinity level of the patches over which
they cross. Saltwater turtles increase it by one. As the fresh water mixes with
the saline ocean, a gradient of salinity is created.  Also, the salinity reaches
a small distance into the land.

Seeds of each kind of mangrove flow down the river, with a probability of
sticking to the banks. When a seed sticks to a bank, it determines whether the
salinity level is within its range of tolerance. If it is, then it turns into a
plant. Otherwise, it continues flowing down the river.

Each plant generates new seeds and disperses them around it. The new seeds check
whether they can tolerate the salinity of their patch. If they can, then they
turn into plants. Otherwise, they either continue to flow into the river, or get
moved by the wind to some other patch.


First of all, make sure that you drag (copy) the files named Patches 1 - 5, from 
the Mangroves folder to your StarLogoT application folder. Make
sure to put them into the folder of the StarLogoT application you are using, and
not a previous version of StarLogoT.


SETUP - Press SETUP once to set up the model.

GO - Press GO to start the model.

RIVER 1, RIVER 2, RIVER 3, etc. - Press one of these buttons to import the
drawing of the coastal area of your choice.  (If you don't like the one you see.)

DRAW YOUR OWN RIVER - Press this button and unleash your imagination: Draw your
own river by following the guidelines set forth in the info window section
"THINGS TO TRY" (see below).


RIVER-FLOW - Increase the river flow if you want more freshwater to flow down.
Decrease the river flow if you want less freshwater to flow down. Use this to
simulate real-world situations, such as the creation of a dam, or the diversion
of a river's water for irrigation purposes. See section "THINGS TO TRY" for more.

SALINITY - Increase or decrease the salinity level of the ocean as you wish.


distribution of species.

MANGROVE POPULATIONS BY SPECIES (2) - This shows how many plants of each species
are successful.


- Let the model run long enough for populations of the different species to build

- Observe how the shape of the river influences the salinity patterns and, as a
consequence, the patterns of mangrove vegetation.


- Increase or decrease the salinity level of the ocean and observe how the
salinity level and the patterns of vegetation change.

- Increase the river flow to simulate a larger river. Observe how the salinity
level and the patterns of vegetation change.

- Decrease the river flow to simulate the creation of a damp somewhere along the
river (of course, we cannot see the damn itself), or the diversion of the water
flow for irrigation purposes (in support of agriculture). Observe how the
salinity level, and thus the mangrove vegetation patterns, change!

- You can draw your own river by pressing the button DRAW RIVER. Or you can draw
new channels or block channels on an existing river picture.  Make sure to follow
the following directions: - Connect the source of the river to the ocean. - Use
color number 95 to draw the river. - Use color number 22 to draw the ground. - Do
not change the width of the first (the highest) line of the river. The first line
should have xcor >= -4 and xcor <= 6 ! - Make it relatively easy for the fresh
water and the seeds to flow down the river: don't make sharply curved banks;
don't make inlets that will make it hard for the freshwater and the seeds to
escape from, etc. In general, use common sense to draw a simple, but interesting,

-Can you change conditions so that a species become extinct?


Once you master the operation of this model, you could try one or more of the
following experiments:

- Change the code in order to allow plants to grow close to the banks, but not on
the banks! Mangroves have long roots that enable them to grow in shallow waters.

- Code underground water flows that enable fresh or saline water to flow across
the earth as groundwater and enable mangroves to grow further away from the banks
of the river.

Give the mangroves adaptive abilities -- say, a certain chance of changing their
salinity tolerance and spreading to other zones.


- Exporting/Importing Patches: You can make a drawing in the graphics window and
export patches (through the File Menu Bar). You can import patches whenever you
want to use this picture in the same or a different model. For example, in order
to export the patches of your model, you would use the export patches command
under the File Menu Bar and choose a name for your file. In order to import
patches saved in the file called "My Patches", you would first make sure that the
file is in the StarLogoT folder, and then type the command: import-patches "|My

- Turtle-Patch Interaction: Note how they are used in combination to simulate
flow.  The turtles are used to carry water across distances; the patches are used
to store persistent local conditions.  To do this, Turtles interact with patches
and change one of their variables.

- Breeds:  Salt water and fresh water are represented and transported as two
turtle breeds.  For example, if you want the river to cease to exist, i.e. the
freshwater turtles to die, you can type: ask-freshwater [die]


An excellent source of information on mangroves can be found online at

This website also includes an extensive list of suggested readings.

An extensive source of impressive images and Quicktime movies of mangroves can be
found online at