November 21, 2019

Planting the Mangrove Forest


 
Mangroves are woody trees or shrubs belonging to several plant families. Their lifestyle allows them to live along tropical coastlines and the banks of rivers where salt and freshwater intermingle. Growing in dense stands and forests, tropical mangrove habitats are critical to provide proper ecosystem functions, the creation of new land, and in mitigating the effects of storms, flooding, and other disruptive effects of rising sea levels.
 
Image by Lanare Sevi
Each species commonly grouped together under the mangrove lifestyle has differing tolerances to saltwater; they use various strategies to block absorption or to excrete dangerous salt from their tissues. They also grow in slightly different environments. Mangroves don’t need saltwater to live, they just tolerate it much better than other plants. It’s a great advantage and an evolutionary strategy that rids them of competitors.  Some must have primarily freshwater or water that is only slightly brackish to survive.
National Park Service/Image by G. Gardner
Other mangroves are found closer to the sea, and some can grow in pure seawater. Many mangroves excrete excess salt via pores along the undersides of their leaves or from their twigs, while others have impermeable leaf surfaces that physically block the salt.
Mangrove forests are imperiled worldwide due to coastal development, harvesting for timber and fuel, and the catastrophic effects of increasingly powerful hurricanes. Mangroves have declined in most areas due to human activities, but the warming climate is allowing them to colonize places that, until recently, were too cold for them to survive.


National Park Service/Image by G. Gardner
The forests historically covered much of coastal South Florida, its offshore barrier islands, and the Keys. Rising sea levels will allow them to grow on land that was last submerged 2.5 million years ago. Drive along U.S. highway 41, the Tamiami Trail, west of the Big Cypress Swamp to see stunted Red Mangroves, the recent pioneers of a swamp that is gradually turning salty.

Sometime within this century, most, if not all, of low-lying South Florida will once again become submerged by a shallow sea, as it has been at least four previous times in the geological history of North America.


Pinecrest Gardens’ artist-in-residence, Xavier Cortada, has developed a conceptual project to remind us of this. As part of The Mangrove Project, he has distributed mangrove seedlings, painted a Garden mural depicting Red Mangroves, and collaborated with the Gardens to plant the world’s first upland mangrove forest. Hundreds of Red, Black, and White Mangroves have been installed adjacent to the mural. It’s thought that the cultivated mangrove forest will survive to grow, in the future, in the newly-returned sea. 
     

November 14, 2019

The Mangrove Palm



Image by Dr. Neahga Leonard
 
"If there are no mangrove forests, then the sea will have no meaning. It is like having a tree with no roots, for the mangroves are the roots of the sea."

 Unknown fisherman, Trang Province, Southern Thailand 

Mangroves are woody trees or shrubs that are salt-tolerant and grow along coasts in tropical and subtropical regions. Their distinctive and ecologically important communities consist of members of a number of plant families. Mangrove species can be said to have a common lifestyle, rather than being taxonomically related.
Image by Luis Argerich
The Nipa Palm, Nypa fruticans, is naturally distributed along Asian and Northern Australian rivers and brackish estuarian environments, often in dense stands that can extend for miles. In many areas the palm is a significant and sometimes dominant component of mangrove forests. It’s quite unusual, as palms go. Characteristic of the species is its mild salinity tolerance, which is generally uncommon among palms. The trees develop subterranean, horizontally branching trunks in their muddy, shallow-water habitat. Nipas form spiky clusters of fruit that resemble medieval weapons. Their seeds are designed to float, like coconuts. Sometimes the seeds will begin germinating before they settle in the mud or sand.
Image by Tanetahi



Nipa Palm is both ecologically and economically useful. It provides habitat for aquatic organisms; it stabilizes and protects land from storms and flooding, just like other mangroves. Its leaves make a durable building thatch; its copious sweet sap is harvested to make palm wine and syrup. The fruit is also popularly eaten. Because of the high sugar content of the plant’s tissues, it's an outstanding source of ethanol for fuel production. Nipa stands are environmentally sustainable and require no chemical fertilizer or pesticide inputs.

Male and Female Flowers

November 1, 2019

The Strangest Plant on Earth


 

“He wrote that he was so astonished that he knelt on the hot sand in bewilderment, thinking that his fantasies had taken flight.”
Chris Bornman, describing the reaction of Friedrich Welwitsch upon seeing Welwitschia mirabilis for the first time.

A fine candidate for the most world’s most biologically unique plant, Welwitschia mirabilis is the sole member of the family Welwitschiaceae. This strange cone-bearing plant was first brought to the attention of science by the plant explorer for whom it was named.


Friedrich Welwitsch was an Austrian, trained in medicine and botany, who disappointed his parents by not developing a law career. Instead, after briefly working as a physician, he pursued his interests in plants, working for important botanical gardens in Portugal and England. His African explorations resulted in the discovery of several new species. Welwitsch died in 1872 but left a fine collection of many thousands of dried herbarium specimens. Three hundred and twenty nine species of plants and animals have been named in his honor.

Namib Desert Fog. Image by Juliane Ziedler
Welwitschia is related to other cone-bearing plants, such as cycads and the relic family of trees and vines, the Gnetaceae. From evidence in the fossil record, the ancestors of Welwitschia diverged from other conifers at least 114 million years ago. The ancestral Welwitchias' forest habitat dried and vanished; the modern species seems like a fanciful creation from the imagination of Dr. Seuss. Welwitschia mirabilis is a woody, two-leaved dwarf “tree” that ekes out it existence in parts of the Namib Desert of Angola and Namibia in areas that can receive no rain at all for several consecutive years. As in western South America, the plant communities of the coastal Namib Desert have evolved to rely upon the nightly fogs that are generated by cold ocean currents. Welwitschia’s metabolism requires some foggy humidity to function, but the species ultimately survives by tapping into deeper soil moisture that is recharged by infrequent rainfall. 
Male and female plants bear cones  on short branches; the winged seeds need a bit of surface soil moisture to germinate. Consequently, the reproductive success rate is low. Outlandish claims are often made concerning Welwtschia’s longevity. More accurately, by measuring the growth rates of their leaves, it’s estimated that individual plants can live 500 to 1000 years.

Welwitschia seedling. Image by H. Maurer
 Welwitchia Seedlings grow two tough strap-like leaves that elongate throughout the plants’ lives. Desert winds twist and shred the long, tough leaves. After many decades the tangled, unkempt mature plants resemble dirty piles of rubbish.

Welwitschia near Swakopmund, Namibia. Image By Joh Henschel
  
Image by Thomas Schoch