Stretching along 14 miles of Biscayne
National Park's western edge is a
mysterious place that can remind one
of the jungles seen in old movies.
From the water, you see an unbroken
line of trees with their beautiful, dark
green leaves reaching almost to the
water. As you get closer, you see that
between the water and the leaves is a
seemingly impenetrable tangle of prop
roots, arching from the tree's trunk to
the water. You have reached our
mangrove forest - one of the longest
continuous stretches of mangroves left
on the east coast of Florida.
Mangroves flourish in salty environments
because they are able to obtain freshwater
from saltwater. Some have the ability to
block absorption of salt at their roots while
others secrete excess salt through their
leaves, allowing them to flourish where
other trees would die.
These mangroves, with their impenetrable
root system, help to keep Biscayne's waters
clean and clear by slowing the water that
flows into the bay from the land, allowing
the sediment carried by the runoff to settle
out. These roots also provide shelter and
protection for a host of marine organisms,
especially the very young and small, while
the trees branches above provide breeding
and nesting areas for many birds, including
the brown pelican.
Leaves fall from the mangrove's branches all year
round. These leaves break down to become food
for many marine organisms which, in turn, become
food for larger organisms including commercially
important species of fish, pink shrimp, and the
Florida spiny lobster. Without healthy mangrove
forests, Florida's vital recreational and commercial
fisheries would drastically decline.
Three types of mangroves inhabit the shoreline here.
Starting from the water and working inland, you
will find red, black, then white mangroves.
The Red Mangrove (Rhizophora mangle)
This tree was once found all along the Florida shoreline. It thrives along
muddy coastlines where you find its spreading roots reaching outward
toward the sea in water as deep as three feet. One could almost imagine
this tree walking into the water with its stilt-like prop roots. These prop
roots grow in mass thickets, which make them virtually impenetrable.
Because of this, developers destroyed miles and miles of these trees to
gain access to the shore and the water for condos, hotels, and
manmade beaches. Today, this destruction has slowed as the
mangroves are now protected throughout the state, even on private
The red mangrove's seeds, known as propagules and resembling large
beans or green cigars, germinate on the tree. When they drop from the
tree they can float in the water for up to a year before becoming lodged
along the shore where they start growing into a new trees.
The Black Mangrove (Avicennia
The black mangrove finds its home in mostly salty, silty, saturated soils
found along the tidal shoreline. It prefers higher and dryer soils than the
red mangrove. This mangrove is characterized by the many cigar-like "
pneumatophores" sticking out of the soil all around the trunk. These
pneumatophores can extend 6 or more inches above the saturated soil,
allowing the submerged roots to obtain surface oxygen even as the tide
comes in. Like the red mangrove, the black mangrove's green seed will
germinate while still on the tree and can float in saltwater for up to 4
months before finding a suitable place to grow.
The White Mangrove (Laguncularia
The white mangrove is normally found further inland than the red or black
mangroves. The base of its leaves have two salt-excreting glands near
the leaf blade which allow it to get rid of excess salt. All of the
mangroves have trouble with cold weather and freezes, but the white
mangrove is the least cold tolerant of the three.
These mangrove trees are also found along the shores of the park's
islands, separated from the mainland by the shallow waters of Biscayne