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viernes, 7 de febrero de 2014

The world's 10 oldest living trees

There are colonies of clonal trees that have lived for tens of thousands of years, but there's something majestic about a single tree able to stand on its own for millennia. These ancient trees have bore witness to the rise and fall of civilizations, survived changing climates, and even persevered through the fervent development of human industry. They are a testament to the long view that Mother Nature takes in tending the Earth. With that in mind, consider the world's 10 oldest living trees.

Photo:zest-pk/Flickr

Methuselah
At 4,841 years old, this ancient bristlecone pine is the oldest known non-clonal organism on Earth. Located in the White Mountains of California, in Inyo National Forest, Methuselah's exact location is kept a close secret in order to protect it from the public. (An older specimen named Prometheus, which was about 4,900 years old, was cut down by a researcher in 1964 with the U.S. Forest Service's permission.) Today you can visit the grove where Methuselah hides, but you'll have to guess at which tree it is. Could this one be it?
Photo:Rick Goldwasser/Flickr



Sarv-e Abarqu
Sarv-e Abarqu, also called the "Zoroastrian Sarv," is a cypress tree in Yazd province, Iran. The tree is estimated to be at least 4,000 years old and, having lived through the dawn of human civilization not far away, it is considered an Iranian national monument. Many have noted that Sarv-e Abarqu is most likely the oldest living thing in Asia.

Photo:iranian.com


Llangernyw Yew

This incredible yew resides in a small churchyard of St. Dygain's Church in Llangernyw village, north Wales. About 4,000 years old, the Llangernyw Yew was planted sometime in the prehistoric Bronze Age — and it's still growing! In 2002, in celebration of the golden jubilee of Queen Elizabeth II, the tree was designated as one of 50 Great British trees by the Tree Council.
Photo:Wiki Commons


Alerce
The Alerce is a common name for Fitzroya cupressoides, a towering tree species native to the Andes mountains. There's almost no telling how old these trees can get, since most of the larger specimens were heavily logged in the 19th and 20th centuries. Many botanists believe they are the second-longest living trees on Earth aside from the bristlecone pine of North America. To date, the oldest known living specimen is 3,640 years old.
Photo:Wiki Commons/GNU


The Senator

The Senator, located in Florida, is the largest bald cypress tree in the United States, and it is widely considered the oldest of its species known to exist. It is likely the largest U.S. tree of any species east of the Mississippi River. Estimated to be around 3,500 years old, the Senator was used as a landmark for the Seminole indians and other native tribes. The Senator's size is particularly impressive because it has endured many hurricanes, including one in 1925 which reduced its height by 40 feet.

The tree gets its name from from Sen. M.O. Overstreet, who donated the tree and surrounding land in 1927.

Update 1.17.12: It is with a heavy heart that we report that 'The Senator' has burned to the ground. 
Árbol de 3500 años se incendia y colapsa por imprudencia de adicta a drogas
Photo:Ashley Schmidt/Wiki Commons

Patriarca da Floresta

This tree, an example of the species Cariniana legalis named Patriarca da Floresta in Brazil, is estimated to be about 3,000 years old, making it the oldest non-conifer in Brazil. The tree is believed to be sacred, but its species is widely threatened due to forest clearing in Brazil, Colombia and Venezuela.
Photo:bocaberta.org


Olive Tree of Vouves

This ancient olive tree is located on the Greek island of Crete and is one of seven olive trees in the Mediterranean believed to be at least 2,000 to 3,000 years old. Although its exact age cannot be verified, the Olive Tree of Vouves might be the oldest among them, estimated at over 3,000 years old. It still produces olives, and they are highly prized. Olive trees are hardy and drought-, disease- and fire-resistant — part of the reason for their longevity and their widespread use in the region.

 
Photo: Carmel Jane Doak/Panorami


Jōmon Sugi

Jōmon Sugi, located in Yakushima, Japan, is the oldest and largest cryptomeria tree on the island, and is one of many reasons why the island was named a UNESCO World Heritage Site. The tree dates to at least 2,000 years old, but some experts believe it could be older than 5,000 years old. Under that theory, it's possible that Jōmon Sugi is the oldest tree in the world — even older than Methuselah. Regardless of the numbers, it's a tree that deserves mention here.
  
Photo:Wiki Commons/GNU


Chestnut Tree of One Hundred Horses

This tree, located on Mount Etna in Sicily, is the largest and oldest known chestnut tree in the world. Believed to be between 2,000 and 4,000 years old, this tree's age is particularly impressive because Mount Etna is one of the most active volcanoes in the world. The tree sits only 5 miles from Etna's crater. The tree's name originated from a legend in which a company of 100 knights were caught in a severe thunderstorm. According to the legend, all of them were able to take shelter under the massive tree. It is listed by Guinness World Records as having the "greatest tree girth ever," at 190 feet in circumference.
  
Photo:Wiki Commons/GNU


General Sherman
Believed to be around 2,500 years old, General Sherman is the mightiest giant sequoia still standing. The volume of its trunk alone makes it the largest non-clonal tree by volume in the world, even though its largest branch broke off in 2006, smashing part of its enclosing fence and cratering the pavement of the surrounding walkway. Perhaps this was a sign that General Sherman could not be caged in? Sherman can be found in Sequoia National Park in California, where five of the 10 largest trees in the world exist.
 
Photo:Wiki Commons

ORIGINAL:
Mother Nature Network
Apr 07, 2010

viernes, 6 de abril de 2012

Submerged Forests off the coast of Wales: a Climate Change Snapshot

ORIGINAL: SkepticalScience
by John Mason
7 April 2012 

Sea-level rise over the past 10,000 years is recorded in Cardigan Bay, off the western seaboard of Wales, UK. Peat-beds complete with the remains of trees are today exposed over low tide along several of the Bay's beaches. Incredibly, a new exposure of peat has recently yielded human footprints, made some 3000 years or more ago by the people who witnessed the final stages of the drowning of the land.
The deglaciation that followed the Last Glacial Maximum, twenty thousand years ago, was accompanied by a global sea-level rise that averaged out at some 120 metres. Around the British Isles, there are many areas covered by shallow seas, 10-20 metres in depth, and Cardigan Bay, off the west-facing coast of Wales, is one of them. Sailing due west from the local coastal ports such as Aberystwyth and Aberdyfi, it is a good ten nautical miles before the 20m submarine contour is reached. The sea-bed is a sandy table-land, divided by several great ridges of gravel and boulders - the Sarnau (Welsh for Roads) - that mark the lateral moraines of the valley-glaciers that flowed out westward to join the Irish Sea Ice-Sheet.
View across Cardigan Bay with one of the Sarnau in the foreground
above: view across Cardigan Bay to the Snowdonia mountains, with one of the Sarnau, Sarn Cynfelyn, in the foreground. It extends out beneath the sea as a steep-sided reef for over six nautical miles. Photo: author.
The process of post-glacial sea-level rise has been well-charted, and with respect to this corner of the world, the inundation of the land to form much of Cardigan Bay was within the last 10,000 years. We have additional local evidence for this timescale: peat samples, dredged from the seabed not far from Aberystwyth, at a depth of 18.5 metres, yielded a radiocarbon date of 8740 +/- 100 years before present (Haynes et al, 1977). It should be noted in passing that this part of the UK is regarded as having been essentially neutral with respect to post-glacial isostatic rebound: to the north, where the main ice-sheets were formerly located, the land rose whilst to the south, which was mostly ice-free, the land sank.
post-glacial sea-level rise
above: the post-glacial rise in sea-level, adapted from Fleming et al (1998), with dates relevant to this article annotated in red.
8740 years: let's just place that date in context. The Younger Dryas had come and gone (12,900-11,800 years BP), and the Mesolithic was about halfway through. The people who lived in the region were gradually turning from full-time hunter-gatherers to the combination of these with agriculture, something which by the Neolithic was developing various degrees of sophistication. By then, the rate of sea-level rise had slowed, but it continued to advance throughout the Neolithic and the following Bronze Age, and there is impressive evidence from that process right here on the Welsh coast.


timeline
above: timeline annotated with the period during which Cardigan Bay was inundated.

So-called Submerged Forests are known from various parts of the world, but the one at Borth, on the Cardigan Bay Coast of Wales, is a particularly fine example. Every winter, after storms have scoured away parts of its extensive sands, large areas of peat appear, littered with fallen tree-trunks and with stumps in growth position. Although it is sometimes referred to as the "Fossil Forest", the wood is not fossilised as such: it looks and feels just like what one might expect waterworn and waterlogged wood to look and feel like. The peat is hard and compact: walking on its surface barely leaves a mark.
Submerged Forest, Borth
above: part of the Submerged Forest at Borth. Photo: author.
The basal peat, upon which the tree-stumps are situated, is around 6,500 years old. Above it, where erosion has not removed it, there lies a layer of bluish-grey clay and, at the south end of the beach, atop the clay is a second, thinner peat. The succession records the transition from forest to salt-marsh, between 6,500 and 3,000 years ago, which is late Mesolithic through to mid Bronze Age. It is thought that, originally, the coastline, with its shingle storm-beach and dunes, was over a kilometre to the west (seawards): during this period, the storm-beach advanced towards the land and its immediate hinterland became salt-marsh: the trees became waterlogged with brackish water and died. The retreat of the coast would likely have continued were it not for the establishment of the fishing-village of Borth and various sea-defences, the most recent of which is just nearing completion. Local people living here are constantly reminded of sea-level rise when they look out across the beach at low tide and see the trees emerging from the waves.
The Submerged Forest has recently been in the news. In February 2012, retired geology lecturer Dr Denis Bates, of Aberystwyth, noticed that a new area of ancient peat had become visible along the southernmost part of the beach. Taking a closer look, he discovered that the peat contained scatters of burnt stone - an archaeological feature typical of Bronze Age sites. Burnt stone consists of sharp, angular fragments of bleached-looking rock produced by heating large pebbles in fires and then immersing them in water: it was the instant cooling that shattered them. Why they did this is not clear: one theory is that it was a means of heating-up the water whilst some archaeologists have connected the practise with sweat-lodges, as in the Native American tradition.

Dr Martin Bates, Denis' son, is an archaeologist based at the University of Wales, Lampeter, and was therefore quickly on hand to undertake a detailed investigation of this find. Despite the peat and clay beds spanning an important period of human activity in the area, they have to date yielded few remains: an Aurochs skeleton was discovered many years ago and a small number of flint and bone implements have been recorded over the years. But when surveying commenced, the site proved to be of even greater interest, as upon the surface of the upper peat layer, and impacting into the clay below, the surveyors discovered footprints. There were the circular depressions made by the hooves of cattle, sheep and goats and, incredibly, human prints. It appears that the adults were foot-clad, but one print was found that belonged to a child aged approximately four years, which showed the impressions of bare toes. I visited the site over low tide a few days ago: standing next to such impressions, my heavy rigger-boots hardly left a mark: back when the prints were made this would have been squelchy marsh that you could go up to your knees in if unlucky.

human footprint, borth submerged forest
above: photographed whilst still underwater, a human footprint in now hard and compact peat at the Submerged Forest, Borth. Photo: author.
Interestingly, coastal West Wales has its very own Flood Legend, which goes as follows:

Cantre'r Gwaelod (also known as Cantref Gwaelod or Cantref y Gwaelod) translates into English as the Lowland Hundred. It is the legendary sunken kingdom that is said to have long ago occupied a tract of fertile land in what is now Cardigan Bay. Cantre'r Gwaelod's capital was Caer Wyddno, seat of the ruler Gwyddno Garanhir. The land is usually described as being defended from the sea by a dyke, complete with sluice-gates, managed by one Seithennin, who, it was said, was fond of his drink. One dark and stormy night, the gates were neglected during drunken festivities and as the tide rose, so the sea swept in, ruining the land.


The UK, Ireland and N France, ten thousand years ago
above: lost landscapes? A map of the UK, Ireland and N France ten thousand years ago, at the start of the Mesolithic, when sea levels, though rising, had not yet reached their full post-glacial extent. The brown areas are lands that have since been lost. Redrawn from Lambeck, 1995 (PDF).

Mere folklore, yes, but it is often wondered locally whether the legend recalls stories handed down over many generations, via the oral tradition, of lands that produced good hunting and gathering, but which by the start of the Neolithic had largely been lost to the advancing sea. The generations of people who followed-on from those who left the footprints would certainly have witnessed the environmental changes that led to the loss of the forests described above: they would have walked through what had become salt-marsh beneath dead and dying oaks and pines. They would have seen environmental change as starkly as anyone.

So what is in store for this small corner of the planet in the coming decades? According to Vermeer and Rahmsdorf (2009), the worst-case scenario would be a rise of 190cm by 2100. Using Alex Tingle's handy plotter, this is what a rise of 2m would look like:
2m sea level rise Borth
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And a rise of 6m, which would occur if parts of both the Greenland and West Antarctica ice-sheets continued to melt, would look like this:
6m sea-level rise
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Borth and Aberdyfi would be overwhelmed and even my hometown some distance inland would be affected: the fertile agricultural lands along the Dyfi flood-plain would be replaced by the relatively poor grazing offered by salt-marsh and another legend of flood would be born. Being rather fond of these places and the communities that live in them, I would personally prefer an outcome that did not involve such inundation. Future generations have just as much right to enjoy them as I do at present. It is such considerations that come to mind when people ask me why I blog.