Key mangrove: A system in conflict

The maps on pages 144-145 depict changes that have occurred over a period of 30 years in a hypothetical wetlands area, Key Mangrove. Introduce the first map using the information given under "Change in a Mangrove Ecosystem." All the changes that occurred in this wetland area over the 30-year period are listed for you, but allow your students the opportunity to discover the changes themselves.

A mangrove swamp offers just one example of a wetlands ecosystem. You may prefer to adapt this exercise to focus on other wetlands types, like prairie potholes or bogs, instead.

PROCEDURE

1. Examine all four maps with your students. Use these questions to guide their observations and draw conclusions about the development that has taken place on the island.

a. Look at the first map. About what percentage of Key Mangrove was covered by mangrove swamp 30 years ago?

b. Look carefully at the development that has taken place at each 10-year interval. In each case, how has transportation increased? What industries have been added or expanded? How has the residential development increased? What recreational facilities have been added? What public services have been added to meet the needs of the residential and industrial development? What have been the effects of the mangrove swamp on the key itself? Why is the swamp important?

c. Compare Map #1 with Map #4. What is the percentage of mangrove swamp that remains? (Divide the areas to be compared into grids, then calculate the percentages from the number of grids in each area.)

d. What percentage of the original mangrove swamp was filled in at each 10-year interval?

e. What was built first? How did this stimulate the rest of the development?

f. What has been the effect of this development on the wetlands and the animals living and breeding there?

g. Do you think the shrimp industry has been affected by the increase in development? In what way?

h. In what ways could people use the mangrove swamp in its natural state for recreation? In what ways have people altered the mangrove swamp for recreational purposes? How have the recreational uses of the island changed over time?

i. What immediate benefits are the result of development of the wetland? What are the long-term benefits of this development? Who or what has been adversely affected by the development of the wetlands?

j. Where could development have taken place on this island without destroying the mangroves? Why do you think more development didn't take place in these areas?

k. Do you think people who moved in 30 years after development began really know why the island was named Key Mangrove?

2. Now your students are ready to create their own management plans for the island using the first map as their starting point. Generally, their plans should allow for the orderly development of the island and the conservation of its natural features.

a. Their plans must provide for human needs such as housing, food, schools, recreation, and waste disposal.

b. Their plans must still protect the natural system, recognizing its aesthetic, economic, and ecological importance.

SUMMARY

When students have completed their plans, share them as a class and use these questions to help them understand the process they used in developing their plans:

1. What development was not included in your plans? Why not?

2. Whose needs did you think were most important to consider as you developed your plan.

3. Did you have problems finding a balance between development and conservation?

4. Who do you think would object to your plan? Do you think their objections would be legitimate or would be raised simply to further their own interests?

5. Did you find cases in your planning processes in which the wishes of an individual or small group became more important than those of the whole group? In which cases?

6. What compromises did you make?

7. Look at the original maps. What changes would you make at each 10-year interval? Why?

CHANGE IN A MANGROVE ECOSYSTEM

You will notice that 30 years ago the hypothetical island, Key Mangrove, was largely uninhabited. Only four vacation estates had been built on the island. Much of the area was covered by mangrove swamp.

Red mangrove, a tree species adapted to brackish or salty water, covers large portions of this type of swamp. These trees grow easily in water and can be recognized by their arching, stilt-like roots, which are at least partially responsible for the growth of the island itself. The roots trap materials carried by ocean currents and protect the accumulating land mass from ocean waves or hurricanes. The mangrove drops leaves that provide nutrients for the accumulating soil. These dropped leaves also provide habitat and food for the plentiful animal life, from invertebrates to fish, birds, and occasionally, mammals.

A mangrove swamp is a breeding area and habitat for many marine animals, especially shrimp. Many varieties of birds live and breed here. Herons, wood storks, and other wading birds nest here in great numbers. Mollusks, such as coon oysters and Florida hornshells, are in these swamps. Bonefish come in with the tide to feed on the crabs and mollusks living in the shallow water.

Because of the abundance of wildlife and marine life, Key Mangrove was a fisher's and seafood lover's paradise for years. Shrimpers from a coastal town on the mainland fished the waters of Key Mangrove and took their catch to a large packing firm on the mainland for processing. The mangrove swamp is a fragile ecosystem, and its basis, the red mangrove trees, may be affected by slight variations in salinity and in nutrients carried in the water.

TEN YEARS LATER

* The ferry has been replaced by a bridge allowing easier access to the mainland.

* Some shrimp fishermen have moved permanently to the island now that a bridge connects it to the mainland.

* A shrimp packing plant has been built.

* A housing development has been built that furnishes homes for the workers at the shrimp packing plant.

* A sewage treatment plant has been built.

* A supermarket and a drug store have been built on the island.

TWENTY YEARS LATER

* An oil company has built a refinery on the island.
* The shrimp packing industry has grown and more workers are needed.
* A sanitary landfill has been established.
* More housing has been built for workers at the new plants.
* A shopping mall has been built.
* Two hotels and a marina have been built, increasing tourist trade.
* A school has been built near the new housing development.
* A golf course has been built.

THIRTY YEARS LATER

* Two more hotel complexes have been added and the area is becoming more popular as a vacation spot.

* A large public marina has been opened.

* Another golf course has been built on the eastern side of the island.

* The sanitary landfill has been enlarged.

* A housing development with boat ramps, attractive to sport fishers and water enthusiasts, has been built.

* Another school has been built to serve the growing population.

* A pond has been dredged on the golf course to attract migratory birds.