The Cradle of Life — Curtis Whitwam

“Worlds Coming Together” watercolor 18x30

Mangroves: The Creators of Life

It may sound like a bold statement, but the Mangrove forests that line the coasts in the tropical regions of the world are among the most important ecosystems on earth. In a number of ways, these amazing and fascinating trees create the conditions that support much of the life that exists in the oceans. In this month’s blog, we will explore some of the ways these forests are able to accomplish so much in such a difficult environment.

The “prop” roots of the Red Mangrove trees reach out into the water to root into the fertile sediments.

Masters of Adaptation

Mangrove trees are able to thrive in the salty environments of bays and estuaries because of a series of adaptations that allow them to grow where almost no other trees can grow. There are three main species of Mangroves, Red Mangroves (Rhizophora mangle), Black Mangroves (Avicennia germinans), and White Mangroves (Laguncularia racemosa). Each of these types has its own way of handling the salty water that they live with. Red Mangroves exclude most of the salt in the water at its root surfaces through a powerful filtration system leaving only 1/70th of the salt in its sap compared with the surrounding water. Black Mangroves allow a lot more salt into their sap at 1/7th that of sea water and then they secrete a white bloom of salt out through the undersides of their leaves. You can see the salt crystals on black mangrove leaves. Indigenous people as well as settlers used to use these salt blooms to add salt to their diet and to salt cure foods.
White Mangroves also allow more salt into their tissues and secrete the salt out of a gland at the base of their leaves.
Sometimes the salt burden can be too great for even mangroves to handle (especially where there is a lot of evaporation of intermittent tidal pools) and in these places you will find salt barrens where little plant life exists.
Another way mangroves thrive in these salty environments is through their methods of reproduction. Mangroves do not produce seeds. They are “viviparous” which means to bring forth live young. They produce “propagules” which are complete, living baby plants on their stems. These dormant plants, once fully formed, drop from the trees and then either take root in the sediment where they land or they float in the water until they find new land to root. Red Mangrove propagules are long and cigar shaped and can float dormant for up to a year before finding sediment to root in. This enables these amazing plants to literally cross oceans.
Black Mangrove propagules look like large lima beans and White Mangrove propagules look like a large green kernel of corn. They can also remain dormant for a long time (although not as long as the reds) before rooting.
The root systems of Mangroves also make them especially adapted to the soft, muddy environments that they thrive in. Red Mangroves send out “prop roots” from their trunks and branches which enable them to create a broad base of support and take advantage of the nutrients at the surface levels of the soils. The prop roots also help these trees spread out into new territory into the shallow waters enabling more leafy branches to sprout and reach for the sunlight. Red Mangrove prop roots are a major source of inspiration in many of my paintings. Their patterns as well as their fascinating ability to allow the trees to “walk” make them a favorite subject of mine.
Black Mangrove roots have really amazing “aerial roots”or pneumatophores that sprout up above the soil and waters’ surface allowing the roots to receive oxygen.

One more way that mangroves adapt to their environment is by shedding massive quantities of their leaves into the water and sediment below. These leaves are broken down by fungi and other organisms and creates a highly fertile soil in which not only the mangroves thrive, but also creates the foundation of the web of life for millions and millions of other organisms.

“Root Refuge” watercolor 11x14. Juvenile Snook are just one of the many species of fish that use mangroves as their nursery.

Mangroves are Protectors

As the mangrove propagules newly take root and begin growing, these young plants send out their prop roots which anchor into the fresh sediment. More branches form which send out more prop roots. With each cycle of the tide water flows through these labyrinths of roots and sediment gets deposited at their base. As the mangrove root system and canopy expands they form “overwash islands” which allow tidal water to flow through the roots and continually build more sediments. Gradually, dry land is formed within the inner reaches of these islands. These islands not only create habitat for millions of invertebrates, fish, birds, and mammals, but they also protect exposed shorelines from storm surges as they provide a buffer to wave action. As fresh water falls from the sky onto the newly formed dry land, underground fresh water lense aquifers form as the freshwater floats above the saltwater, this enables new plants and trees to emerge which creates all new webs of life.

Fresh raccoon tracks within the intertidal edge of a mangrove forest. The mangroves provide all of the resources for these mammals to thrive in these ecosystems.

Mangroves are Providers

Mangrove roots provide a hard substrate in environments that would otherwise have only mostly soft, muddy surfaces. These hard substrates allow organisms such as oysters, tunicates, barnacles, algae species, mussels, and more to take hold and multiply. Not only are many of these organisms filter feeders that cleanse the water column, but they are also abundant food sources for a myriad of other animals. Mangrove roots create thousands of times more of this valuable hard substrate “real estate” than sea walls or dock pilings could ever hope to achieve. These surfaces are a critical component of healthy estuary ecosystems. Mangroves do all of this work 24 hours a day, 365 days a year and they do it all for free and they never complain.

Mangroves have Value

Imagining what would happen if Mangroves were gone is a scary prospect. The diverse array of birds that use mangroves as their nesting grounds would be gone. Storms would erode and destroy the coastlines. Without the fertile detritus in the soils of mangrove forests, astronomically high numbers of invertebrates critical to the base of the food webs would vanish. Shellfish and fish would dwindle. Life around the coral reefs would lose diversity and the reefs themselves would struggle as water quality would decrease. The worlds commercial and recreational fisheries would collapse.
It would be nothing short of catastrophic.
As the human populations along the coastlines continues to increase, mangrove forests are becoming increasingly under threat. There is no substitute for these intricate and critical forests. It is essential for us to support ways to protect these ecosystems.

Stay tuned to this page for more fun and fascinating news and facts about our natural world and don't forget that we support local environmental organizations working to protect the most vulnerable ecosystems and organisms. A percentage of all sales of artwork goes to the Florida Springs Institute and the Florida Springs Council

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Curtis Whitwam