Magnificent Mangroves

It’s common knowledge that trees are important. They provide oxygen, shade, habitat, food, and useful forest products. In tropical and subtropical areas, there is an important tree that is vanishing from coastal areas at an alarming rate- the mangrove.

Mangroves are annoying because they tend to live only at beaches that developers around the world want to develop. Mangroves are wonderful trees because in addition to the ecosystem functions they perform for nature, they also have ecosystem services for humans, if we would just leave them alone. They form a protective barrier against storm surges and trap sediments in their root systems, extending the coast outward as a buffer against sea level rise.

Mangrove forest (USFWS)

Mangrove species are able to tolerate brackish water. They have tall prop roots that keep the bulk of the tree above high tide. The root system slows water, allowing sediments to settle out. Eventually, enough sediment accumulates that the tree is on solid ground and new mangroves colonize the water in front. Small organisms like the safety that mangrove roots provide.

The tall prop roots are obvious at low tide (NOAA)

Mangroves are able to handle brackish water because they have a salt gland, so to speak. They excrete the salt through their leaves, bark, or roots. Some of the leaf excreters keep their leaves, which have a salty coating. Others accumulate salt in the leaf, and shed the leaf when it is saturated with salt. Those that excrete salt through their bark also use the shedding method to get rid of the salt.

Now that we’ve become aware of the mangroves’ benefits, we’re slowly making progress toward preserving the remaining forests. Here in the US, there are three mangrove species (red, black, and white) with a historic range being the Gulf coast and both of Florida’s coasts. Today, the best example of a mangrove forest can be in Florida at Everglades National Park. If you ever get to check out this important ecosystem, please do!

More great prop roots, this time on red mangroves (NPS)

This week's mangrove facts come from NOAA and American Museum of Natural History.