A simple EC that is aimed at teaching you about the Mangroves and how they effect the land around us and how that in turn effects us.
What is a Mangrove forest?
To start I guess it is important to understand what a mangrove is. well according to Wikipedia a mangroves are "Mangroves are various large and extensive types of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics." further more "Mangroves are salt tolerant trees (halophytes) adapted to live in harsh coastal conditions. They contain a complex salt filtration system and complex root system to cope with salt water immersion and wave action. They are adapted to the low oxygen (anoxic) conditions of waterlogged mud." Now you know what a Mangrove, lets go into a little more detail (not too much) according to naturefoundationsxm.org there are four kinds of mangroves: the Red mangrove, Black mangrove, White mangrove and the Silver/Buttonwood mangrove. The red mangrove grows in the water followed by the Black mangrove that is partly in the water. Next are the White mangrove and the Buttonwood that are found higher up on land. All of these can be seen from GZ quite clearly although when the water level drops the Red mangrove is left rather high and dry at times. Simple enough but what does this have to do with you and me?
Why Are the Mangroves important?
Mangroves play a very important roll in the formation of soil along the shorelines. The above ground roots act as sieves which reduce the currents speed and shear which causes the sediment in the water to deposit and also helps retain the sediment that has already deposited previously. Mangroves also create their own sediment from organic mater they drop, this gets mixed into the trapped sediment over time, the continued depositing will eventually change the coastline unless something happens that changes the water flow speed or depth. Some of this Sediment will become compressed over time by the sediment that is deposited on top of it and eventually become sedimentary rock, quite often this is where you find some really great fossils as a leaf or even a animal that has died may fall into this sediment and become covered by the next layer that is deposited on top. slowly the sediment hardens and traps the leaf or dead animal in the newly formed rock, which in turn due to the transformation around it may too become rock, leaving the fossils that get found. The Mangroves can remain small (like the one you can see at GZ) or they can grow really large as more land is reclaimed (like the Sundarbans mangrove which is 140,000 ha).
If you look on the map you can see how the mangroves effect the land/earth. If you look at the satellite map view of the Sandarbans Mangrove you can see how the soil that has been washed down river has been slowed and deposited making what looks like 100's of islands almost like a shattered jigsaw. looking beyond this into the water you can see the amount of sand that is being deposited which will later if not to heavily eroded by waves will turn into more islands increasing the size of the "Delta" as this type of land formation/expansion is called over time this will keep growing and some of the smaller rivers will close up and area's may become dry fertile land. Unfortunately Man effects these Delta's in a very negative way which can be seen in this land cover animation of Mississippi River delta , since man has come into the area and destroyed the mangroves that were there 595697 ha has been lost back to the sea due to erosion.
This clearly shows the effects that the mangroves are having on the changing landscape of the earth around the world. Is this important to you? Well maybe you dont care about the reclaiming of land and the prevention of erosion or even the formation of fossils, well there is also the fact that the Mangroves improve our water quality
How Do Mangroves Effect Water Quality?
Mangrove habitats maintain water quality. By trapping sediments in the mangrove root system, these and other solids are kept from offshore waters, thereby protecting other coastal ecosystems from excessive sedimentation. This process also removes agrochemical and heavy-metal pollutants from the water, since these contaminants adhere to sediment particles. They also improve water quality by removing organic and inorganic nutrients from the water this lowers nitrate and phosphorus concentrations in contaminated water. Now that does effect you to a degree
Due to the recent water shortages the municipality and a lot of home owners are drilling and using boreholes, unfortunately boreholes decrease the amount of ground water ad will cause the water in the mangroves to dry up or move away from the mangroves towards the middle of the rivers, meaning the filtration of the water no longer takes place, and the contaminants are now more likely to end up in our water that we drink.
This is the reason I put this earthcache into play to make you think, and make you understand the impact our actions are having, not only on us but also on those around us and the future generations that will be affected by the rushed choices and actions we make now.
Questions:
1) Go to the edge of the water (away from the normal beach sand) and notice the sand texture and grain size, what do you notice about the sediment that the mangroves have caused to be deposited?
2) Looking at the edges of the river around GZ including the river mouth, using what you see do you think the mangroves are winning the land reclamation process here or do you think the erosion process is winning - give reasons for you answers
3) (optional) Take a photo of the something that shows the state / health of the Mangroves at the time of your visit
4) (Bonus Question) In you opinion do you think Boreholes are a good way to go or what would be your ideas to help get water to the population that you feel will have less of an impact ?
Please send your answers to us via the Geocaching messaging system or via email from our profile
References:
Wikipedea.org
naturefoundationsxm.org
eoearth.org
nhmi.org
Climate Change and Island and Coastal Vulnerability (ISBN 978-94-007-6015-8)
and the photo by Peter Chadwick