Earthweek: A Diary of the Planet (April 26, 2013)

Nuclear Pests
Rats and snakes are just some of the local hazards threatening the decommissioning of Japan's crippled Fukushima nuclear power plant.  It's been more than three years since the facility was hit by a huge post-quake tsunami, which caused three of its reactors to melt down.  Officials estimate it could take 40 years to eventually tear down the plant.  In the meantime, water is being pumped into the reactors to keep the fuel from getting hot enough to cause additional melt downs.  But rats and snakes have been recently knocking out power to the pumps, for up to a day at a time.   While the plant's operators say it would take a few days for the fuel to become critically hot, nuclear power experts are urging them to replace the makeshift cooling systems with some that will last the decades needed to eventually resolve Japan's worst environmental disaster.
Diving Light
Whether a shark hunts near the surface or in the shadowy depths may depend on the season, the time of day and even the fullness of the moon.  By watching 39 gray reef sharks living near the coral reefs of the West Pacific nation of Palau, a group of Australian marine biologists observed that the sharks would typically swim at more shallow levels during winter than beneath the waxing sunlight of spring.  The sharks also seemed to vary their depth depending on the position and brightness of both the sun and the moon.  For example, the sharks tended to dive deepest at noon when sunlight penerates the farthest into the water.  But in the relative darkness of dawn and dusk, the sea animals would ascend to within 100 feet of the surface.  Likewise, the sharks were found to swim much deeper beneath a full moon than during a new moon.
Elusive Resolve
The goal of limiting global climate change to only 2 degress Celsius of warming since the start of the Industrial Revolution is slipping out of reach, according to a draft summary being prepared by climate experts.  Almost 200 nations agreed in 2010 to limit global warming to below that level.  The new 22-page draftsummary says that governments may have to find ways to artificially suck greenhouse gases from the air to stay on goal if they don't make deep cuts in carbon emissions by 2030.
Storm Fatality
A fierce storm on the night of April 17-18 blew down an ancient oak that had shaded the Ceirog Valley in northern Wales since the year 802.  The Pontfadog oak is said to have served as the rallying point for Welsh prince Owain Gwynedd's army, which defeated England's King Henry II in 1157.  The tree was spared eight years later when Henry had his men cut down the Ceirog woods.  But its massive trunk, which grew to 42 feet in girth, had been largely hollowed out by decay.  It hasn't been decided what to do with the wood from the 1,200-year-old tree, but it could be used to make benches or a monument for the village to put on display.
Earthquakes
China's most deadly earthquake in three years killed at least 196 people and injured 12,000 others as it wrecked thousands of buildings in the southwestern province of Sichuan.
*  At least 18 people died in eastern Afghanistan from a temblor that rocked a wide swarth of South Asia.
*  Earth movements were also felt in central Japan, central New Zealand and southwestern Mexico.
Dark Lightning
It turns out that there's much more going on inside a storm cloud than flashes of lightning and peals of thunder.  According to new research from the Florida Institute of Technology, thunderstorms also emit "dark lightning."  It is made up of energetic blasts of X-rays and gamma rays that possibly expose jet passengers to excessive doses of radiation.  Until recently, it was assumed that pules of these high-energy rays were coming from the edge of space.  "We now know that they come from deep within the atmosphere, from garden-variety thunderstorms," explains Joseph Dwyer, physicist and lead researcher for the study.  Dark lighning is thought to occur once in every thousand bolts of electric lightning.
Dolphin Measles
A viral strain that causes measles in humans has killed more than 100 dolphins that have washed up on the western coast of Italy so far this year, according to marine mammal experts.  "The deaths could be caused by food shortages that weaken the animal, making them more easily exposed to diseases and parasites," Italy's Ministry for the Environment said in a statement.  The country's National Institute of Marine Sciences said that the death rate among the striped dolphins has dropped abruptly this month, possibly indicating the outbreak has run its course.  The epidemic mostly affected young dolphins under the ages of 15 to 20 years.  "Animals born after the 1990-92 epidemic (of measles) are devoid of the antibodies needed to defend them against the disease," the institute said.