December 22, 2008
Here on the long, low, sandy ridge between the ocean and the mangroves most plants and animals are exquisitely adapted to the very hot, salty, sandy- soiled habitat. Precisely because the habitat is so severe, however, species diversity along the ridge is fairly low. If you walk along the sandy road atop the sandy ridge you'll see only a fraction of bird species, for instance, to be seen along a similar little road through hacked-over thornforest back in Yokdzonot or Sabacché. So: Here there are relatively few species, but the species present often are unusual and wonderful to see.
Saturday morning I realized that nearly a week after sending out my last Newsletter I'd not photographed a single new bird species, and I like to feature at least one bird in each Newsletter. Therefore, while I should have been stringing acorns and bamboo sections for a hotel curtain, I went walking, hoping to see any kind of bird not yet featured. Just about when I was about to give up hope, finally something caught my eye, something good. I'd almost walked right past him because he was being very quiet, lurking in the shadows of a flowering Wild Papaya tree, as shown at http://www.backyardnature.net/n/08/081222mc.jpg.
That's a Mangrove Cuckoo, COCCYZUS MINOR PALLORIS, a denizen of humid tropical lowlands from Mexico to northern South America, plus there's a population in southern Florida. A frontal view would have shown large, white spots on the tail's black undersurface, like a North American Yellow-billed Cuckoo's. The throat's buff color continues onto the underparts.
In the picture you can see two features typical of members of the Cuckoo Family. First, members often but not always have slightly decurved bills. More diagnostic is the fact that cuckoos look like regular songbirds, or passerines, but their feet are zygodactyl -- have two toes projected forward and two backwards, instead of three forward, one backward, typical of songbirds. In the picture you can barely make out a foot's zygodactylness.
At my previous two locations we saw that Mangrove Cuckoo's aren't found exclusively next to mangroves. In the Yucatan they extend a good distance into the interior.
I've told you about seabeans -- seeds that float great distances and end up washed onto beaches. Certain folks have lots of fun looking for seabeans, identifying them, figuring out where they came from, and maybe even making jewelry from them. Last week some very serious seabeaners stayed at Mayan Beach Gardens and they seabeaned every day. That drew me to the topic of Hamburger Beans, for Hamburger Beans are seabeaning stables. They're something rare enough to be interesting but common enough to be obtainable. Several found by our visitors are shown at http://www.backyardnature.net/n/08/081222mu.jpg.
Two plant species are represented in that picture, both in the genus MUCUNA. About 160 species of Mucuna are recognized worldwide, most being climbing vines or shrubs. They're members of the Bean Family, the Fabacea, and produce alternate, 3-lobed leaves and bean-type flowers (papilionaceous) typical of Bean Family. The legumes producing the beans typically are clothed in stinging hairs. Back in my botanist days at the Missouri Botanical Gardens I learned about the genus Mucuna fast because anytime we dealt with a dried, pressed herbarium specimen, despite any care we took, we'd always end up scratching because of those stinging hairs.
In the picture, the two grayish hamburger beans up front were produced by Mucuna sloanei, and sometimes are called Brown Hamburger Beans or Horse Eyes. The species lives in swamp forests, at borders of rivers and lakes, in savanna woodland and wet places in secondary vegetation over a vast distribution area including Africa, the Caribbean and Pacific islands. A black dye is obtained from all parts of the plant.
More commonly found here than the Brown species are the two reddish-brown beans in the background. They're Mucuna urens, Red Hamburger Beans, distributed throughout much of the American Tropics as well as on Pacific islands.
These species don't live on sandy beaches. Hamburger beans found on our beaches sometimes are sprouting, but they don't grow into vines. However, if they wash into the ocean they're probably doomed, even if they're still alive after a transoceanic float. No Mucunas are listed as native to this state, Quintana Roo.
Your own seabeans can be identified on the web at the "Sea-Bean Guide" page at http://www.seabean.com/guide/.
AUSTRALIAN PINE CHRISTMAS TREE
This week I drew the chore of going out to cut a Christmas tree to be set up in the hotel's reception room. Normally I don't cut wild trees for Christmas service, but this time when I set off down the narrow sand road carrying a bucksaw I actually felt pretty good about it.
For, the obvious candidate for Christmas-tree service around here is what's shown vigorously growing on the dry sand ridge next to Hurrican-Dean-savaged mangrove at http://www.backyardnature.net/n/08/081222ca.jpg.
That looks a lot like Loblolly Pine back in Mississippi and one of its English names is Australian Pine, but its similarity to any pine tree is purely incidental. It's CASUARINA EQUISETIFOLIA, a member of what could be called the Australian Pine Family, the Casuarinaceae. Pines are gymnosperms but Australian Pines are flower-producing angiosperms. On the phylogenetic Tree of Life this family stands close to oaks, birches, walnuts and beeches.
If you look closely at an Australian Pine's "needles" you see that they're not like pine needles at all. See http://www.backyardnature.net/n/08/081222cb.jpg.
What appears to be Australian Pine's "needles" are actually slender, much-branched, green to grey-green, toothpick-wide stems bearing minute scale-leaves in whorls of 68. Remembering that the leaves are tiny, scale-like things in whorls of 6-8, you can figure out where they are in the close-up shown in the inset at the picture's lower left.
I didn't feel too bad about cutting an Australian Pine because it's a serious invasive here and through much of the world, and the species is highly "allelopathic" -- it produces chemicals that inhibit the growth of other species. Once Australian Pine gets established it tends to form pure stands with few other plants able to survive near them, and offering relatively little food and shelter to wildlife. Dense stands of Australian Pine look lush and green, but ecologically they are deserts.
Therefore, Australian Pine is listed as a Category I invasive exotic species by the Florida Exotic Pest Plant Council. Possession, collection, transportation, cultivation and importation of Australian Pine are prohibited by the Florida Department of Environmental Protection.
On the other hand, Australian Pine is very tolerant to sand, sun and salt spray, stabilizes sandy, windblown soil, and grows quickly producing firewood in places where few other tree species can grow. I've seen it referred to as "the best firewood in the world."
I'm told that around the hotel there were no Australian Pines before Hurricane Dean, but now I see that they're abundant all up and down this sandy beach. Efforts have been made to remove them from the Sian Ka'an Biosphere Reserve just to our north.
From what I can see, those efforts are doomed to fail.
"Seagrass" is a general term commonly applied to long, slender aquatic plants rooted on the seafloor. Not far offshore here the seafloor is solidly mantled with seagrass. Up the beach about a mile dark patches of seagrass occur close to shore, then the water turns dark where pure seagrass begins, as shown at http://www.backyardnature.net/n/08/081222sx.jpg.
At low tide patches of seagrass close to shore may rise above all but the larger waves. When the water is lowest, often beautiful tropical fish shelter at the mats' edges and make brief forays across the shallow water above the mats. There are hours when thin sheets of clear water flow over the dark mats and the seagrass first points this way, then that way, depending on water flow direction, as at http://www.backyardnature.net/n/08/081222sw.jpg.
Best I can figure out, the fuzzy, greenish stuff at the bases of some of those slender stems is alga growing on the seagrass, while the whiteness covering the seagrass stems' top parts, mostly to the left, is carbonate gunk that chips off as the "grass" moves. Breaks in the pale gunk give the plant stems a segmented look, but the stems aren't segmented.
Based on technical literature and pictures on the Internet, this "grass" is Manatee-grass, SYRINGODIUM FILIFORME, not a grass at all but rather a member of the monocot Manateegrass Family, the Cymodoceaceae.
Ecologically an important thing about Manatee-grass is that its roots penetrate and stabilize offshore sand. Some landowners along this beach, wanting the turquoise water you see above naked, submerged, white sand, send workers out with machetes to uproot the Manatee-grass. They are encouraging the sea to wash away their beaches. The irregularly shaped, dark mats in the first picture stand about two feet above the naked sand surrounding them.
Right up the beach from here, for years a resort has systematically removed seagrass from before its beach. You can see a picture of the way that looks now at http://www.backyardnature.net/n/08/081222sy.jpg.
Ten years ago, I'm told, nearly all of the water you see in that picture was sandy beach with large Coconut Palms growing on it. It ran almost parallel with the rocky point seen at the distance. Beach erosion began immediately after removal of the seagrass began. The resulting little bay was already in place when Hurricane Dean came through last year.
Not only Manatee Grass but also the Turtle Grass, Thalassia testudinum, I told you about some Newsletters ago, host nitrogen-fixing anaerobic microbes on their roots and rhizomes, thus, like members of the Bean Family on dry land, in the sea these plants "fertilize" other aquatic plants in the area with usable nitrogen.
Several plants with large blossoms with slender petals and/or long-exerted stamens are called "spider lily." Back in Mississippi a red-flowered plant blossoming in late July and early August, Lycoris radiata, of the Amaryllis Family, is the main "spider lily." Back home in Kentucky the main wild "spider lily," also a member of the Amaryllis Family, is Hymenocallis occidentalis.
Down here one of the most spectacular as well as most commonly encountered plants on the sandy ridge separating the ocean from the mangroves is a "spider lily" with flowers very similar to the white Kentucky species. In fact, it's in the same genus. It's HYMENOCALLIS LITTORALIS, often known in English as the Beach Spiderlily. A cluster of blossoms standing guard outside my tent door recently is shown at http://www.backyardnature.net/n/08/081222hy.jpg.
In the picture notice the conspicuous "staminal cup" -- the flaring, white, cuplike "crown" from which the stamens arise, growing inside and a little above the long, slender, white, recurving, petal-like items. The staminal crown is a distinctive feature of several closely related genera in the Amaryllis Family, such as Narcissus and our Mississippi Lycoris. You can recognize the stamens by their brown, curved, pollen-producing anthers attached by the centers of their backs to long, stiff, greenish filaments arising from the staminal cup's rim.
WHITE WATER OFFSHORE
At http://www.backyardnature.net/n/08/081222cr.jpg you see the beach view for which people from all over the world come to the Costa Maya to see. Of interest to us right now is the line of white water about half a mile offshore. (It looks closer than that because I was using a small telephoto lens.)
At night when I'm sleeping on the beach I hear two distinct wave sounds. There's the close-up, washing, rhythmic thunder reaching a crescendo maybe every five seconds when waves break on the beach. Beneath that sound lies a continual roar like a big waterfall, created when waves form and collapse out where you see the white water in the picture.
That's where our coral reef is. Waves travel great distances across the Caribbean, then when they encounter the reef they break, creating the roaring white water.
To understand why waves break when they pass over shallow water offshore you have to go into wave physics. Basically, a wave is what you see plus an inverted-cone area of activity below the wave. That area of activity is like an underwater leg. When the "leg" hits the ocean floor or a reef it "trips," causing the wave to rise, rush forward, and collapse. The process is described and diagrammed more technically at the "How Stuff Works" website, on a page explaining to surfers why waves break, at http://adventure.howstuffworks.com/surfing6.htm.
Between the coral reef and the beach there's a broad lagoon about 15 feet deep, mostly densely vegetated with various species of seagrass, Turtle Grass, and similar aquatic plants.
STANDLY'S "FLORA OF YUCATAN"
This week I stumbled upon Paul Standley's 1930 publication "Flora of Yucatan" archived online at http://www.archive.org/details/floraofyucatanfistan.
The work is very outdated, incomplete and has no illustrations, but -- as far as I know -- for those of us with no institutional affiliation, it's the best thing available to give us a toehold in understanding which plants live in the Yucatan.
Marcia, one of the hotel's owners, issues a monthly, nicely illustrated "Property Owner's Newsletter" focusing on life on the eastern Yucatan coast. If you have a special interest in this area you might find it worth subscribing to and checking out the archives at http://www.mayanbeachgarden.com/PropertyOwners_Newsletter.html.
WHY I'M AGAINST NUCLEAR POWER
The opposition I stated against nuclear power a few Newsletters back brought a flurry of letters supporting it, and requests that I explain my reasoning. Here goes:
Radiation damages and destroys DNA. Radiation is one of the few poisons that can not only make sick or kill an organism but also alter a species' genome by inserting mutations and other genetic anomalies into the DNA.
Literature on this matter is dense and confusing. However, when we focus just on damage to inherited genes, here are some generally accepted facts relating to the USSR's 1986 Chernobyl nuclear power station failure:
Researchers from Israel and Ukraine examined the children of irradiated parents now living in those countries. The number of genetic mutations was seven times higher in those children than in siblings conceived before the accident.
Among people irradiated during that disaster a DNA mutation rate 50 per cent higher than normal was passed on to subsequent generations.
These facts and many others are documented online at http://www.chernobyl.info/index.php?userhash=&navID=30&lID=2.
At Semipalatinsk in the former USSR where nuclear weapons were tested from 1949 to 1956, genetic mutations among people living in the region have nearly doubled. The paper documenting this is at http://www.stuk.fi/stuk/tiedotteet/2002/en_GB/news_204/.
Probably the most dangerous emissions of radioactive compounds during the Chernobyl disaster were those that accumulate in the food chain, such as certain isotopes of iodine and strontium.
The half-life of Iodine-129, primarily formed from the fission of uranium and plutonium in nuclear reactors, is 15.7 million years. With such a long half-life, even tiny leakages into the environment accumulate rapidly.
Anyone can find such documentation by using a search engine and such keywords as "nuclear radiation genetic mutations."
I am against saddling living things with unnaturally high mutation rates over the next millions of years, so I am against any activity that introduces nuclear waste onto Planet Earth.
My opposition to nuclear power is much more than an intellectual stance. There are spiritual reasons for opposing it, as well.
For, as soon as the newly formed Earth grew cool enough to support life, life arose and began evolving. To me this reveals two facts that serve as the basis of my everyday spirituality:
First, that to the Creator of the Universe, life is important.
Second, that to the Creator of the Universe, evolution is important.
The Creator has spent billions of years evolving Life on Earth to where it is now. The very machinery of evolution consists of genes and chromosomes in which the instructions for making and evolving Life are written in terms of DNA sequences.
Thinking like this, the inherited genetic material of all species... reveals itself as sacred. It is the closest thing we have to "The Written Word of God."
Radiation is the most deadly of all poisons to which inherited genetic material is vulnerable.
The deliberate creation of radiation that almost certainly eventually will be accidentally leaked or purposefully introduced into the planetary biosphere, then, can be described as "sinful."
Best wishes to all Newsletter subscribers,