Sunday, February 16, 2014

Tortoise poop


Thanks to Charles Darwin, the Galapagos Islands are known as a biological wonderland. After all, it was the relationships between its species which enabled Darwin to understand how different species could arise from a common ancestor.

But from a different perspective; the Galapagos actually aren’t species-rich; visitors to the islands often are surprised at how limited the number of species there really are compared to the mainland. The islands are remote, nearly 1000 kilometers from the mainland, and only a handful of species could ever make that trip.

In that setup…it turns out that the Galapagos tortoises wound up playing the role of a keystone species, one which the entire ecosystem depended on.

In new research, Dr. Cynthia Froyd of Swansea University took samples of soils throughout the Galapagos and tested them for the types of environments recorded and the species present.

They found that, prior to 500 years ago; they found “dung-affiliated” fungi, suggesting a large, plant-eating organism dominated the area. Since there aren’t other options living in the Galapagos wetlands, the only option was the tortoises.

Prior to the arrival of man, tortoises roamed freely across the islands, but starting in the 16th century, their numbers declined from 250,000 to 14,000 by 1970, and 5 of the original 14 subspecies have gone extinct.

At the same time, wetlands began drying up, a change recorded by the soil samples. About 500 years ago, the tortoise feces vanish, and at the same time, the plants change. The freshwater wetlands that once populated large areas of the Galapagos dried and the plants supported by those wetlands began dying, disappearing, and even going extinct.

The plants which supported those wetlands relied on the tortoises in several ways, including fertilization and churning up the ground as they walked through. The tortoises were a keystone species; once they began dying, the entire ecosystem surrounding them died with them.

Today, efforts are underway to protect the remaining tortoises and to introduce them into their previous environments, but many of the areas where the tortoises used to live simply don’t exist anymore. Once the tortoises died or were killed, the wetlands died with them, and reestablishing the entire ecosystem will be a difficult, long-term task.


Image credit: Wikimedia commons
http://en.wikipedia.org/wiki/File:Galapagos_tortoise_bathing.jpg

Original paper:
http://onlinelibrary.wiley.com/doi/10.1111/ele.12203/abstract

Baffin Island melting unprecedented


This photo shows one of the many glaciers on Baffin Island, in the far northern reaches of Canada. New research from this island tells a stark story of how unstable these glaciers are becoming.

Baffin Island is in the middle of the area strongly affected by Milankovitch cycles. As the Earth wobbles in its orbit, northern Canada is seeing particularly large swings in the amount of sunlight it receives, making it a key contributor to the expanding and melting of ice sheets.

Right now, we’re at a point where solar input to Canada is declining. About 11,700 years ago, the solar energy input to this area was about 9% greater than it is today; at about the same time, the large ice sheets covering Canada were collapsing.

Not every glacier in Canada collapsed, particularly here in Baffin Island, just the large ice sheet. But, since these glaciers aren’t linked to the large ice sheet, one would expect that Baffin Island is a place on Earth that should be cooling right now. It is getting less sunlight than it did 10,000 years ago, so if any place on Earth should be slowly cooling, it should be right here.

A new study led by Dr. Gifford Miller at CU Boulder found something remarkable. These glaciers are melting slowly at their edges, releasing some plants and rocks that have been trapped in the ice. These scientists sampled some of those plants, expecting that their radiocarbon ages would be a sign for how long the plants had been trapped in the ice. Using that information, they could estimate how much the glaciers of Baffin Island grew as the solar input decreased.

When they got a radiocarbon date on those formerly-frozen plants, they found that to their surprise the age was infinite. Radiocarbon dating doesn’t provide solid answers past about 40,000 years even in the best labs – beyond that the calculated age goes to infinity, so these plants must have been much older than 40,000 years – a time when all of Canada was covered by ice sheets.

Their conclusion is that these plants were trapped in ice during a previous time in-between the formation of ice sheets. The most recent inter-glacial time was about 125,000 years ago – a likely time for these plants to be trapped.

The presence of these plants means a couple things. First, ice that hasn’t melted in at least 125,000 years is melting today. Second, that ice is melting even though the amount of sun coming in to Baffin Island today is decreasing – the changing global climate is overwhelming the decreasing solar input.

Finally…125,000 years ago, the ice sheets on Greenland and Antarctica melted a lot more than they did in this inter-glacial period. If these plants are from that time…they come from a time when sea level was between 5 and 9 meters higher than it is today. To say that a different way, the last time the these plants were outside of a glacier, sea level was about twice the height of the hurricane Sandy storm surge in New York.


Image credit:
http://commons.wikimedia.org/wiki/File:Glacier,_Glacial_Lake,_and_Terminal_Moraine,_Baffin_Island_-a.jpg
Original paper:
http://dx.doi.org/10.1002/2013GL057188
Press report:
http://instaar.colorado.edu/news-events/instaar-news/instaar-study-shows-unprecedented-warmth-in-arctic/

Reach for the Skies: Colombia’s Giant Wax Palm Trees


Soaring over 60 m (≈200 ft) high in Colombia’s Cocora Valley is the giant wax palm: the tallest palm tree in the world. Growing at elevations as upward as 3150 m (>10,300 ft) above sea level, the wax palm trees live in seclusion in Colombia’s Andes Mountains, where they grow alongside coffee plants and other exotic vegetation. If a daring soul were to climb to the top (surely with a harness I’d hope), they may also be lucky enough to witness an endangered Yellow-eared parrot. The parrots are known to nest in the hollowed out trunks and leaf beds of the wax palms but they are extremely hard to find.

The wax palms get their name from a natural wax that covers their trunks which was also used for candles until the Colombian government passed a law that now protects the vulnerable trees. In addition to their waxy coating, the palm trees have also in the past been hunted for the Catholic holiday, Palm Sunday, as well as for architectural purposes.

The trees are now protected though, and it is not uncommon for Cocora Valley to be covered in fog, which gives the valley somewhat of a “Jack and the bean stalk” sort of feel to it. Standing below the palm trees and losing their green caps in a heavy fog can be almost as impressive as the sight of the palm trees on a clear day. However, there is nothing more humbling than standing directly beneath the palm tree that makes the mountains look small.


Photo Credit:
Alex Treadway, National Geographic
http://on.natgeo.com/1bEDG2b

References:
1.http://www.academia.edu/1865247/Colombia_national_tree_the_wax_palm_Ceroxylon_quindiuense_and_its_relative
2. http://www.colombiaexplorer.com/destinations/coffee-triangle/cocora-valley/
3. http://www.bbc.com/travel/feature/20130219-colombias-valley-of-the-palms

Sunday, February 2, 2014

Will the Canaries Collapse?


If you’ve ever watched geology-related television shows, one favorite story to tell is the idea of a mega-tsunami in the Atlantic Ocean caused when of one of the Canary Islands collapses.

The Canary Islands are islands off the coast of northwest Africa built by volcanoes. These volcanoes grow when magma, generated in the Earth’s mantle, forces its way upwards through the above rocks, fracturing them and pushing them apart.

Volcanoes like these literally break themselves in half. On several of these islands, most notably the island of La Palma, there are a series of faults (A good chance one of them is seen in the foreground here, the sharp break in the slope) where parts of the island are sliding into the sea. Every time magma comes up it pushes on faults like this, forcing part of the island outwards.

Surrounding all of the Canary Islands (and others in places like Hawaii) there are large debris fields made of up rocks that broke off the islands and slid into the sea. If you total up the size of these debris fields, they would have been massive – so massive that if all that material fell into the ocean at once, it would generate an enormous tsunami wave, one that could still be 50 meters high when it reached New York.

It’s a great story for TV; it’s plausible, you can go to the place where such a breakaway would happen and put your finger on it, and then you can animate that wave hitting New York, Boston, and Washington D.C.

The good news for most people is that the threat of such a mega-landslide is almost certainly overstated for one reason; the islands usually don’t collapse like that.

A paper published last year by Dr. J.E. Hunt and colleagues at the University of Southampton, UK, performed a detailed mapping study of the landslides over the last 1.5 million years. When they looked carefully at the largest landslide deposits, they found that instead of being one large landslide, they were each composed of several smaller units with large time breaks in-between.

In other words, these big landslides didn’t come down all at once, they came down slowly. The largest slide they found was about ¼ the volume of the full debris area on the side of an island.

Tsunami heights don’t scale directly with landslide volume, but it takes a really enormous landslide in the Canaries to do major damage to the U.S. East Coast. The largest slide they found would still cause a tsunami that would damage the islands themselves and possibly the coasts of Africa and Spain, but it wouldn’t be a major threat to far-flung population centers.

This research, of course, does not mean that such a giant collapse is impossible. Unique things do happen, and just because the previous collapses were small doesn’t 100% guarantee that any future ones will be also.

But, if you hear someone say “this island will collapse in the next few thousand years and cause a tsunami” or any version of that…that’s not how things have happened for the last 1.5 million years, and if we’re planning for the future, it’s not something we need to fear happening any time soon.


Image credit: Wikimedia commons
http://commons.wikimedia.org/wiki/File:Plantation_banana_La_Palma.jpg

Original paper (Subscription):
http://onlinelibrary.wiley.com/doi/10.1002/ggge.20138/abstract

Article:
http://blogs.agu.org/landslideblog/2013/12/13/canary-islands-tsunami/

Sinabung explodes…again and again.


We’ve covered the ongoing eruption at Sinabung volcano on the western side of the Indonesian island of Sumatra several times here at the Earth Story. The volcano erupted in 2010 following several centuries of inactivity and then entered a much more active phase in September of 2013. This weekend saw yet another phase of extreme activity from the volcano and an enlargement of the evacuation zone again, moving an additional 5000 people from their homes.

The volcano had about 30 separate explosions reported during the day on Saturday, with some of the largest outpourings of lava seen in the years of this eruption. The largest ash plumes reportedly went over 4000 meters into the sky.

The total evacuations associated with this eruption now exceed 20,000.

Previous posts: http://tinyurl.com/k8uv35j, http://tinyurl.com/ov6swbw, http://tinyurl.com/nevogf9 and http://tinyurl.com/lctx9tg


Image credit: Binsar Bakkara/AP
http://blogs.ft.com/photo-diary/tag/eruption/

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