Once again the time has come to gather around and take a well deserved hiatus from the politics of the day. Science talk is here. New discoveries, new takes on old knowledge, and other bits of news are all available for the perusing in today's information world. Over the fold are selections from the past week from a few of the many excellent science news sites around the world. Today's tidbits include following mass extinction with predators gone prey thrives, 'small-fry' fish just as vulnerable to population plunges as sharks and tuna, succulent plants waited for a cool, dry earth to make their mark, why more species live in the Amazon rainforests, sea level rise may return to North America's west coast after a three decade hiatus, sources of Mississippi River phosphorus, and at least for now US farmers dodge the impacts of global warming. Gather yourselves around. Pull up that comfy chair and bask in the sunshine. There is plenty of room for everyone. Get ready for one more session of Dr. Possum's science education and entertainment.
Featured Stories
Any change in the environment can be bad for certain animals within the current population. A mass extinction millions of years ago studied in the fossil record shows the benefits to certain creatures when predator species were eliminated.
Paleontologists know the Devonian Period, which spanned from 416 to 359 million years ago, as the Age of Fishes, a time of astonishing diversity for marine vertebrate species. That thriving world was devastated by the Hangenberg event, a mass extinction of unknown origin that set the stage for modern biodiversity.
But some species survived the carnage of the Hangenberg event. The next 15 million years in the fossil record are dominated by crinoids, species similar to modern sea lilies and related to starfish. So abundant and diverse were these marine animals that the period is known as the Age of the Crinoids; entire limestone deposits from the era are made up of crinoid fossils.
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As fish populations thrived in the Devonian, crinoid diversity and abundance remained low despite favorable conditions. But after the Hangenberg event devastated fish species, crinoids thrived, diversifying and multiplying. The data suggests the ripple effects of a mass extinction upon ecosystems can last millions of years.
Rapid population plunge among large fish species such as tuna and sharks is a well known phenomena.
Analyzing over 200 scientific assessments of fisheries around the globe, the team found that populations of small fish such as sardines and anchovies were at least as likely to have collapsed at some point in the last 50 years as stocks of large fish. A major cause of population crashes in all fisheries is overfishing.
That finding runs counter to the assumption of many scientists that the dramatic population declines suffered by large predatory fishes, including tuna, sharks and marlins, indicate they are at the greatest risk of extinction, just like large predators on land.
The cactus is a stalwart of the desert today but their species explosion waited for cool, dry times.
...cacti exploded onto the global scene then, about the same geologic time as other succulent plants and tropical grasses. The trigger: A global period marked by cooling and increaed aridity, possibly with lowered atmospheric carbon-dioxide levels.
The Amazon rainforests are noted for the number and diversity of species living within the region's boundaries.
The researchers compiled data on the number of treefrog species at 123 sites around the world and analyzed the data with a new evolutionary tree (based on DNA sequence data) for 360 treefrog species. They discovered that the richness of treefrog species in the Amazon rainforest sites is not explained by wet, tropical climatic conditions alone.
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Instead, the researchers discovered that the high biodiversity of Amazonian sites is related to different groups of treefrogs occurring together in the Amazon Basin for more than 60 million years—since before most dinosaurs became extinct. In contrast, those sites in tropical rainforests that have relatively few treefrog species are in areas that were colonized by treefrogs much more recently.
The west coast of North America has seen a three decade respite from the global sea rise.
Global sea level rose during the 20th Century at a rate of about two millimeters (.08 inches) per year. That rate increased by 50% during the 1990s to a global rate of three millimeters (.12 inches) per year, an uptick frequently linked to global warming. Rising sea level has consequences for coastal development, beach erosion and wetlands inundation. Higher sea levels could cause increased damage to coastal communities and beaches, especially during coincident high tides, storm surges and extreme wave conditions.
Scientists date the current phase of a Pacific Ocean climate cycle called the Pacific Decadal Oscillation (PDO) to the mid- to late-1970s. The current "warm" phase is characterized by the upward movement, or upwelling, of cold water toward the surface along the West Coast. Despite a few El Niño-induced surges in sea level during that time, the coastal sea level trend has mostly been steady.
(Left) Satellite altimetry sea-level height estimates over an 18-year period show upward trends in the western Pacific Ocean that are much larger than the global rise rate, but virtually no rise off the West Coast. (Right)Tide gauge data at Seattle, San Francisco and San Diego show sea level along the Pacific coast rising at about the global rate from 1930 to about 1980, but scant rise or even a lowering of sea level over the past three decades that is consistent with altimetry.
When the cycle shifts to its negative "cold" phase, coastal ocean waters will become characterized more by a downwelling regime, where the amount of colder, denser water currently brought to the surface will be reduced. Resulting warmer surface water will raise sea level.
Many people seek simple solutions to the problems of nitrogen and phosphorus pollution of our waterways.
Not surprisingly, counties with intensive row crop agriculture, such as those in the Upper Midwest Corn Belt states of Iowa, Illinois and Ohio, contributed the most phosphorus to rivers. However, these same counties often showed negative phosphorus balances, meaning that phosphorus outputs in crops exceeded inputs by farmers.
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In addition, although animal manure is considered a major phosphorus source to streams and rivers, it was relatively unimportant to phosphorus loading across the entire MRB (Mississippi River Basin).
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Phosphorus from human waste did prove significant. Counties encompassing Chicago and other major metropolitan areas “showed up as hot spots,” David says, because most municipalities don’t remove phosphorus from the otherwise clean sewage effluent they discharge into streams. The team further found that about half of the variation in phosphorus loadings was not explained by their models, suggesting that other factors also contribute, such as stream bank erosion and phosphorus deposits in river sediments.
Overall, the findings suggest that reducing phosphorus pollution will require broad adoption of practices that limit nutrient runoff, such as cover crops, buffer strips, and incorporation of fertilizers. It will also require limits on phosphorus discharge from cities.
The effects of global warming have brought drought and other severe weather changes around the globe but for now US farmers are dodging the impact.
(Researcher) Lobell and his colleagues examined temperature and precipitation records since 1980 for major crop-growing countries in the places and times of year when crops are grown. They then used crop models to estimate what worldwide crop yields would have been had temperature and precipitation had typical fluctuations around 1980 levels.
The researchers found that global wheat production was 5.5 percent lower than it would have been had the climate remained stable, and global corn production was lower by almost 4 percent. Global rice and soybean production were not significantly affected.
The United States, which is the world's largest producer of soybeans and corn, accounting for roughly 40 percent of global production, experienced a very slight cooling trend and no significant production impacts.
Outside of North America, most major producing countries were found to have experienced some decline in wheat and corn (or maize) yields related to the rise in global temperature. "Yields in most countries are still going up, but not as fast as we estimate they would be without climate trends," Lobell said.
Other Worthy Stories of the Week
Seeking life's imprint in shifting desert sand
Early human ancestor apparently chewed grass instead of nuts
Lichen evolved on two tracks, like mammals and marsupials
Hydrogen fuel technology gets a big boost from low cost, efficient catalyst
Eddies found to be deep, powerful modes of ocean transport
A billion tons of biomass a good goal, but at a high cost
Caves and their dripstones tell us about the uplift of mountains
Rice traced to single domestication event
Four planets huddle up before dawn on May 10
Two views of a lopsided galaxy
New mineral discovered: One of the earliest formed in the solar system
New piece added to plant evolutionary puzzle
Chemistry curbs spreading of carbon dioxide
'Swiss cheese' design enables thin film silicon solar cells with potentially higher efficiency
Tree rings tell a 1,100-year history of El Niño
For even more science news:
General Science Collectors:
Alpha-Galileo
BBC News Science and Environment
Eureka Science News
LiveScience
New Scientist
PhysOrg.com
SciDev.net
Science/AAAS
Science Alert
Science Centric
Science Daily
Scientific American
Space Daily
Blogs:
A Few Things Ill Considered Techie and Science News
Cantauri Dreams space exploration
Coctail Party Physics Physics with a twist.
Deep Sea News marine biology
Laelaps more vertebrate paleontology
List of Geoscience Blogs
ScienceBlogs
Space Review
Techonology Review
Tetrapod Zoologyvertebrate paleontology
Science Insider
Scientific Blogging.
Space.com
Wired News
Science RSS Feed: Medworm
The Skeptics Guide to the Universe--a combination of hard science and debunking crap
At Daily Kos:
This Week in Science by DarkSyde
Overnight News Digest:Science Saturday by Neon Vincent. OND tech Thursday by rfall.
Pique the Geek by Translator Sunday evenings about 9 Eastern time
All diaries with the DK GreenRoots Tag.
All diaries with the eKos Tag
A More Ancient World by matching mole
Astro Kos
SciTech at Dkos.
NASA picture of the day. For more see the NASA image gallery or the Astronomy Picture of the Day Archive.
Menkhiband California Galaxy, NASA, Public Domain