olelog

The Philippines are hit by 20-30 typhoons annually. Most of us probably still remember the typhoon Fengshen (or Frank) in June 2008 that killed at least 1350 people. A special tragedy was that 800 of the 856 people on board the ferry Princess of the Stars were killed when the ship capsized.

The replanting of mangroves on the coasts of the Philippines could help save many of the lives lost in the typhoons. A study published online in the journal Wetlands Ecology and Management says low-cost local replanting programs are more successful than large-scale government projects. In a comparison of a number of replanting initiatives, the authors found that the most successful projects had been low budget and locally led.

The mangrove forests along the Philippines' 36,300 km of coastline play an important role in fisheries, forestry and wildlife as well as providing protection from typhoons and storm surges, erosion and floods. In the last century they have, however, declined from 450,000 ha to 120,000 ha, mostly due to their development into culture ponds - fish/shrimp culture ponds have indeed increased to 232,000 ha.

In large-scale projects for massive rehabilitation of mangrove forests the long-term survival rates of mangroves are generally as low as 10–20%. Poor survival can be mainly traced to two factors: inappropriate species and site selection, as a distinct lack of ecological knowledge results in the wrong species of mangrove consistently being planted in inappropriate sites. It is obviously important that the (local) community involved has a shared interest in the survival of the mangroves and live next to the plantation site, which makes maintenance easy.


Reference:
Primavera and Esteban (2008), A review of mangrove rehabilitation in the Philippines: successes, failures and future prospects, Wetlands Ecology and Management (DOI 10.1007/s11273-008-9101-y)


• http://www.springerlink.com/content/x6155715188v774k/
• http://www.eurekalert.org/pub_releases/2008-07/s-mkt072108.php

See also my posts
Mangrove as Flood Protection and Trees against floods - in the Bay of Bengal

The formation of the Isthmus of Panama may be one of the most important geologic events in the last 60 million years. Even though only a small sliver of land relative to the sizes of continents, the Isthmus of Panama had an enormous impact on Earth's climate and its environment. By shutting down the flow of water between the two oceans, the land bridge re-routed ocean currents in both the Atlantic and Pacific Oceans. Atlantic currents were forced northward, and eventually settled into a new current pattern, namely the Gulf Stream. With warm Caribbean waters flowing toward the northeast Atlantic, the climate of northwestern Europe grew warmer. (Winters there would be as much as 10°C colder in winter without the transport of heat from the Gulf Stream.) The Atlantic, no longer mingling with the Pacific, grew saltier. Each of these changes helped establish the global ocean circulation pattern in place today.

Before the present-day isthmus was created a significant body of water (referred to as the Central American Seaway^*)) separated the continents of North and South America. Beneath the surface, two plates of the Earth's crust were slowly colliding, forcing the Pacific Plate to slide under the Caribbean Plate. The pressure and heat caused by this collision led to the formation of underwater volcanoes, some of which grew large enough to form islands as early as 15 million years ago. Eventually the volcanic activity formed a thin strip of land linking the Americas and separating the Pacific and Atlantic oceans. So far it was believed that the isthmus finally had formed between North and South America about 3 million years ago - but is that so?


Engineers digging to widen the Panama Canal have uncovered more than 500 fossils from animals that lived before the land bridge linked North and South America. By comparing the Panama discoveries to fossil records from each continent, palaeontologists hope to determine where the individual animals came from. Volcanic debris embedded in the same layer of rock as the fossils will help pinpoint the time when the animal was found on either side of the land bridge. Determining exactly when this closure happened could be key to understanding the link between major changes in ocean currents and our climate, providing insight into the impact of global warming. Was the closure linked to the start of the ice age is one of the questions.

• http://www.msnbc.msn.com/id/25726314/

*)
The Central American Seaway, also called the Panamanic Seaway or Inter-American Seaway formed in the Mesozoic (200-154 million years ago) during the separation of the Pangaean supercontinent.

See also my post on Ocean (and atmospheric) circulation.



PS: In 2004 Oceanus posted a great article on line titled How the Isthmus of Panama Put Ice in the Arctic with more in depth information.

Oceanic anoxic events or Anoxic events occur when the Earth's oceans become completely depleted of oxygen (O₂) below the surface levels.

Detailed stratigraphic studies of Cretaceous black shales from many parts of the world have indicated that two Oceanic Anoxic Events were particularly significant in terms of their impact, one in the early Aptian (~120 Ma), sometimes called the Selli Event (or OAE 1a) after the Italian geologist, Raimondo Selli (1916–1983), and another at the Cenomanian–Turonian boundary (~93 million years ago), sometimes called the Bonarelli Event (or OAE 2) after the Italian geologist, Guido Bonarelli (1871–1951).

OAE2 was the big one. It was the most global, the most dramatic of a half-dozen OAEs during the exceptional warmth of the mid-Cretaceous period 120 million to 80 million years ago. The young Atlantic Ocean was as narrow as a few hundred kilometers, the sea ran free between Europe and Africa and into the western Pacific, and high sea levels drove the ocean up onto the continents.

Palm trees grew in what would be Alaska, large reptiles roamed in northern Canada and the ice-free Arctic Ocean warmed to the equivalent of a tepid swimming pool. But the depths of the ocean suddenly became starved of oxygen, wiping out swathes of marine life - a mass extinction. The sea floor around the globe became a lethal black ooze, that much later turned into black shale and partly transformed into oil.

After the extinction, levels of greenhouse gases in the atmosphere dropped and Earth lurched into a sudden, but short-lived, period of cooling. What was the cause of this extraordinary event? Palaeoceanographers looking for triggers of OAEs, especially OAE2, have long turned their attention to large volcanic eruptions. A shift in lead isotopes recorded at the very onset of OAE2 in Italy supported that idea (Science, 27 April 2007, p. 527 - Humongous Eruptions Linked to Dramatic Environmental Changes), but the evidence remained regional in scale.

In the journal Nature of 16 July 2008, palaeoceanographers report geographically broad-based isotopic evidence for a volcano-OAE2 link. They measured the element osmium (a rare metal) in sediments across OAE2 from Italy—which was in the Tethys seaway between Europe and Africa at the time—and just off northeast South America, which was then in the opening Atlantic. At both sites, they found that the ratio of osmium-187 to osmium-188 dropped dramatically just before the extinction event. The drop indicates that a huge amount of molten magma, carrying a higher proportion of the heavier isotope, was discharged into the oceans.

During that time period, the only volcanic site large enough to spew forth the necessary amount of magma in a few hundred of thousand years was a known volcanic plateau underneath the modern-day Caribbean. However, the researchers say that the huge lava flows thought to have been involved (and forming the bed of the present-day Caribbean) would have preceded the extinction by up to 23,000 years.

Next big question: what caused the huge eruption in the first place?

References
Turgeon, S. C. & Creaser, R. A. Nature 454, 323–326 (2008)
Kerr, Caribbean Megaeruptions Drove a Global Ocean Crisis, Science of 18 july 2008, p. 327.

• http://www.physorg.com/news135432196.html
• http://www.terradaily.com/reports/Death_in_the_deep_Volcanoes_blamed_for_mass_extinction_999.html
• http://news.bbc.co.uk/2/hi/science/nature/7510541.stm
• http://www.nature.com/news/2008/080716/full/news.2008.957.html