Dance Of The Planets 2013 : May 24 – 30

This year the show will be best seen from around May 24 – 30 2013 — with Venus, Jupiter, and Mercury all seeming to be right next to each other in the sunset/dusk sky. In reality though, they will be nowhere near each other, it’s simply how they will appear from the Earth on those days. Jupiter will be over half a million kilometers apart from the other two planets.

While Venus and Jupiter are often easily visible in the night’s sky, Mercury usually takes a bit more forethought/luck to see. As Mercury is rather close to the Sun, the only time that it is visible from the Earth is when the Sun’s light is dimmed greatly — such as at/after sunset.

So for those wanting to watch, the best time is about 45 minutes after sunset, though really anytime within an hour or so of then is good. You’ll be wanting to look low on the west northwestern horizon. There will be a couple of bright ‘stars’ in the area — one of which will be Jupiter, one Venus, one Mercury, and then a couple of other true stars. The graphics on this page should give you a very good idea.

A note, sometimes/and in some regions, you may need to use binoculars to see all three of the planets. It’s a beautiful show regardless though, even ‘just’ with the naked eye. Also, it will be somewhat low on the horizon, so you may need to find somewhere with a good view of the horizon — anywhere very flat, or high up — coasts work very well, as do tall buildings/hills.

For more information on this year’s other best astronomical events, see: Astronomy 2013, Comet ISON, Meteor Showers, Solar Eclipses, Supermoon, etc

Image Credits: Nathan August © ; After Sunset via Flickr CC

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But now, thanks to new research from the Institut de Recherche pour le Développement (IRD), the causes have become clear. The primary cause is overfishing, and with it the decline of many ecologically important species. Many significant predators of jellyfish, such as tuna and sea turtles, have seen their numbers plummet in recent years as a result of overfishing. And with their decline, jellyfish have begun to see their populations grow. But perhaps far more important than that decline, though, is the overfishing of small pelagic fish, such as sardines and herring, which are the main competitors of jellyfish.

“However, jellyfish are primarily taking advantage of the overfishing of small pelagic fish. Just like these cnidarians, sardines, herring, anchovies and more feed off zooplankton. Thus, they represent their main competition for food. In areas where too many of these fish are caught, they free up an ecological niche. Jellyfish now have free rein and can thrive. Furthermore, small fish eat the eggs and larvae of jellyfish. Therefore, under normal conditions, they regulate the population. In their absence, there is nothing to stop the proliferation of these gelatinous creatures.”

So, in short, overfishing is resulting in a decreased level of competition for the jellyfish, allowing their numbers to boom.

The new research was done by comparing “two ecosystems belonging to the same ocean current, the Benguela, which flows along the south of Africa. The first ecosystem is located off the coast of Namibia. Here, fish stock management measures are not very restrictive. The stocks are barely restored before fishing activities start up again. Jellyfish are currently colonising these coastal waters. The second ecosystem is located 1,000 km further south, off the coast of South Africa. Here, the opposite is true: fishing has been tightly controlled for 60 years. The jellyfish population has not increased.”

“A vicious circle is developing in affected areas. Under the water, the links in the food chain are much more flexible than on Earth: prey species can feed off their predators. As such, jellyfish devour larval fish. Their proliferation prevents the renewal of fishery resources. This invasive species in turn threatens fisheries. In Namibia, some 10 million tonnes of sardines in the 1960s made way for 12 million tonnes of jellyfish.”

The research makes it clear that a more better approach to fishing, one that takes whole ecosystems into account, is necessary if the health of the oceanic ecosystems is to be maintained. To put it a different way, management measures need to be put into practice which consider potential impacts across all levels of the trophic network. Otherwise, at some point in the not-too-distant future, the seas may be populated primarily by jellyfish, as they once were.

While there has been much anecdotal evidence of the jellyfish population boom, there is, as of now, no hard scientific data proving the increase. Data on overfishing is a different matter though…

“Overfishing has also been widely reported due to increases in the volume of fishing hauls to feed a quickly growing number of consumers. This has led to the breakdown of some sea ecosystems and several fishing industries whose catch has been greatly diminished. The extinction of many species has also been reported. According to a Food and Agriculture Organization estimate, over 70% of the world’s fish species are either fully exploited or depleted. According to the Secretary General of the 2002 World Summit on Sustainable Development, ‘Overfishing cannot continue, the depletion of fisheries poses a major threat to the food supply of millions of people.’”

“The cover story of the May 15, 2003 issue of the science journal Nature – with Dr. Ransom A. Myers, an internationally prominent fisheries biologist as the lead author – was devoted to a summary of the scientific information. The story asserted that, as compared with 1950 levels, only a remnant (in some instances, as little as 10%) of all large ocean-fish stocks are left in the seas.”

Some of the most prominent recent examples of overfishing:

- In the summer of 1992, the Northern Cod fisheries completely collapse, total biomass fell to 1% of its earlier level. “The collapse of the Northern Cod fishery marked a profound change in the ecological, economic and socio-cultural structure of Atlantic Canada. The change was expressed most acutely in Newfoundland, whose continental shelf lay under the region most heavily fished, and whose communities were nearly all of those who lost employment because of the moratorium. Considering the importance of the cod fishery to the livelihood of Canada’s coastal communities, and the Northern Cod’s initial abundance in the region, the fishery being mismanaged until it collapsed – from which to this day it has not recovered – is nothing short of shocking.” Not that shocking really…

To date, about two decades later, the fisheries there have only recovered to about 10% of the ‘original’ stock. Fisheries researchers have put the slow recovery down “to inadequate food supplies, cooling of the North Atlantic, and a poor genetic stock due to the overfishing of larger cod.”

- Sharks are rapidly going extinct — with some estimates saying that they may be extinct within only the next few decades. Over 100 million sharks are currently being killed every year, and possibly as many as 273 million according to recent research. This is largely as a result of the booming shark fin trade, being caught as by-catch, and recreational fishing. Many species of shark have seen their overall numbers and population range fall by as much as 90% in just the last 20-30 years.

- “The Peruvian coastal anchovy fisheries crashed in the 1970s after overfishing and an El Niño season largely depleted anchovies from its waters. Anchovies were a major natural resource in Peru; indeed, 1971 alone yielded 10.2 million metric tons of anchovies. However, the following five years saw the Peruvian fleet’s catch amount to only about 4 million tons.This was a major loss to Peru’s economy.”

- “The sole fisheries in the Irish Sea, the west English Channel, and other locations have become overfished to the point of virtual collapse, according to the UK government’s official Biodiversity Action Plan. The United Kingdom has created elements within this plan to attempt to restore this fishery, but the expanding global human population and the expanding demand for fish has reached a point where demand for food threatens the stability of these fisheries, if not the species’ survival.”

- “Many deep sea fish are at risk, such as orange roughy, Patagonian toothfish, and sablefish. The deep sea is almost completely dark, near freezing and has little food. Deep sea fish grow slowly because of limited food, have slow metabolisms, low reproductive rates, and many don’t reach breeding maturity for 30 to 40 years. A fillet of orange roughy at the store is probably at least 50 years old. Most deep sea fish are in international waters, where there are no legal protections. Most of these fish are caught by deep trawlers near seamounts, where they congregate because of food. Flash freezing allows the trawlers to work for days at a time, and modern fishfinders target the fish with ease.”

- “Blue walleye went extinct in the Great Lakes in the 1980s. Until the middle of the 20th century, it was a commercially valuable fish, with about a half million tonnes being landed during the period from about 1880 to the late 1950s, when the populations collapsed, apparently through a combination of overfishing, anthropogenic eutrophication, and competition with the introduced rainbow smelt.”

With regards to the causes of overfishing — beyond the simple maximization of profits, there is a large degree of mistrust of fisheries science by many fishermen. We’ll close with a quote from a fisheries scientist: “The subjective impression the fishermen get is always that there’s lots of fish – because they only go to places that still have them… fisheries scientists survey and compare entire areas, not only the productive fishing spots.”

The new research was published in the Bulletin of Marine Science.

Source: Institut de Recherche pour le Développement (IRD)

Image Credit: © IRD / L. Corsini; Purse Seine via Wikimedia Commons; Jellyfish via Flickr CC

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It’s a common assumption that because tropical regions currently contain the greatest diversity of life, that this must be where life on the Earth originated. But the reasons for there being a greater diversity of life in the tropics, than in the polar regions, are unrelated to the origination of life.

The main reason for there being a greater diversity of life in the “tropical” environments of the world is due to the greater continuity of such an environment in the Earth’s history. Whether located in the Arctic, or around the equator, environments similar to the current environment of the tropical regions of the world have been present throughout the Earth’s history, whereas colder environments have been more temporary, coming and going from the world completely, periodically.

The period of time after the End-Permian extinction 250 million years ago serves as a good example — the Arctic then was comparable to the tropical environments of today, the tropics were much hotter than today (too hot for most life), and the polar environments of today were simply not present at all.

So to get back on track — where did life actually originate then? What sort of an environment?

That remains something of an open question.

With regards to the new research, it’s first important to note that researchers really don’t know very much about brinicles. “Bruno Escribano and colleagues explain that scientists know surprisingly little about brinicles, which are hollow tubes of ice that can grow to several yards in length around streamers of cold seawater under pack ice. That’s because brinicles are difficult to study. The scientists set out to gather more information on the topic with an analysis of the growth process of brinicles.”

What the researchers found was that they are “analogous to a ‘chemical garden’, a standby demonstration in chemistry classes and children’s chemistry sets, in which tubes grow upward from metal salts dropped into silicate solution. But brinicles grow downward from the bottom of the ice pack.”

The research concluded that “brinicles provide an environment that could well have fostered the emergence of life on Earth billions of years ago, and could have done so on other planets. Beyond Earth, the brinicle formation mechanism may be important in the context of planets and moons with ice-covered oceans.”

It’s an interesting idea, whether or not there is any “truth” to it. It’s worth noting that “life” need not have originated in only one place/time, or even for it to have originated on the Earth. Or it even could be a common feature/quality of certain types of environments, wherever they are present, ubiquitous in any of them. It’s also unnecessary to think of the conception we currently refer to as “life” as something that has an “origination” at all.

Source: American Chemical Society

Image Credits: Screen Capture

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“Such widespread redistribution of Arctic vegetation would have impacts that reverberate through the global ecosystem,” said Richard Pearson, primary author of the paper and a researcher at the American Museum of Natural History’s Center for Biodiversity and Conservation.

Plant growth in the Arctic has been increasing over the past couple of decades, coinciding very clearly with rising temperatures. Temperatures in the Arctic have been climbing at nearly twice the rate of the global average, for a variety of reasons, and will continue to do so well into the future. For the new research, models were created to “statistically predict the types of plants that could grow under certain temperatures and precipitation. Although it comes with some uncertainty, this type of modeling is a robust way to study the Arctic because the harsh climate limits the range of plants that can grow, making this system simpler to model compared to other regions such as the tropics.”

What the models show, is that a massive redistribution of vegetation throughout the Arctic is possible. With as much as half of all vegetation switching to a different class, and an enormous increase in total tree cover. The researchers say that if you use Siberia as an example, forests could end up hundreds of miles north of where they are now.

“These impacts would extend far beyond the Arctic region,” Pearson said. “For example, some species of birds seasonally migrate from lower latitudes and rely on finding particular polar habitats, such as open space for ground-nesting.”

This rapid greening would greatly decrease the albedo of the region. Which means that, simply put, dark trees reflect much less sunlight that snow and ice do. This would lead to a further increase in the rate of warming in the Arctic.

“By incorporating observed relationships between plants and albedo, we show that vegetation distribution shifts will result in an overall positive feedback to climate that is likely to cause greater warming than has previously been predicted,” said co-author Scott Goetz, of the Woods Hole Research Center.

The research paper was published on March 31st in the journal Nature Climate Change.

Some things to note with regards to this new research:

With the increasing habitability of the Arctic, and the disappearing sea ice/opening lines of transportation, the Arctic is set to become one of the most important regions in the world. Large stores of valuable oil and natural gas exist in the region, that many of the countries surrounding the Arctic have an interest in. Conflict is possible, perhaps even probable, as the climate there warms, and the extraction of these resources becomes more economical.

A recent research paper from the University of Iceland that explored some of the ramifications of climate change in the Arctic, found that: With Arctic land temperatures expected to climb by 4-7 degrees Celsius by 2100, much of the world’s populations, agriculture, and infrastructure, will shift northwards. Much of the equatorial world will eventually become nearly uninhabitable, except in thin regions along the coasts. In time, it is likely that the Arctic Ocean and the countries bordering it will become the “center” of the world, featuring the majority of human activity.

How fast this migration towards the Arctic occurs will largely have to do how fast the Arctic becomes “habitable” and how fast some of the more southerly regions become unable to support large human populations. This loss of habitability in southerly regions will likely be as a result of diminishing agricultural productivity/increasing failures, increasing conflict, drought, and desertification. Though it is also likely that the increasing quantities/intensities of extreme weather events, and resource depletion/soil erosion/deforestation will factor in.

Source: American Museum of Natural History

Image Credits: www.amap.no; University of Iceland; Quaking Aspens via Flickr CC

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The placodonts lived for about 40 million years or so in the flat coastal regions of the Tethys Ocean, from around 250 million years ago to 210 million years ago. Possessing their “trademark” crushing teeth, they fed primarily on shellfish and crustaceans, but were likely opportunistic predators as well. The distinctive features of these teeth really make them stand out in the fossil record; “the upper jaw had two rows of flattened teeth – one on the palate and one on the jawbone – while the lower jaw only had one set of teeth ideal for crushing shellfish and crustaceans.”

Despite what we know about them, their origins have been somewhat unclear. But with this discovery of a juvenile’s skull in a 246-million-year-old sediment layer those origins are now becoming more clear. The new fossil skull found in Winterswijk (Netherlands) is very clearly the earliest form of all known placodonts, the ancestor of all of the later forms. And the fossil’s exceptional state of preservation really makes it stand out from previous finds, all of the characteristics of the 2-centimeter-long skull are apparent in fine detail

“Unlike all the other placodonts discovered to date, the Winterswijk specimen has conical, pointed teeth instead of flattened or ball-shaped crushing ones,” explains Torsten Scheyer, a paleontologist at the University of Zurich. “Which means the pointed teeth on the lower jaw slotted precisely into the gap between the palate and upper-jawbone teeth when biting.”

“The group’s trademark double row of teeth in the upper jaw is proof that the new find is actually a placodont. According to the researchers, the teeth of Palatodonta bleekeri, the scientific name given to the Winterswijk specimen, were specialized in gripping and piercing soft prey.”

“The double row of teeth in the new find combined with its considerable age lead us to conclude that it is a very early placodont, from which the later forms developed,” says Scheyer. The formation of crushing teeth and the specialization of a diet of shellfish and crustaceans thus developed later within placodont evolution.

This Palatodonta bleekeri skull is also helping to clarify the origins of the placodonts. Earlier finds had already narrowed down their likely-place-of-origin to the shelf sea areas off of either present-day Europe or China. With the very old age and basal form of this fossil found in the Netherlands, it is looking very likely that they originated in Europe.

It’s interesting to imagine the climate and time period that these animals lived in. 248 million years ago the world was beginning to emerge from the dead zone that followed the End-Permian mass extinction event. But the climate then was still pretty extreme, being “generally hot, arid, rainless and dry, and deserts were widespread.” The poles remained somewhat temperate though, offering a refuge for many life forms. There was an enormous loss of biodiversity during the End-Permian extinction event though, that took upwards of 30 million years to recover from, so the fauna that was present at the time was relatively homogenous. The tropical regions at the time were largely devoid of “complex” life, being inhabited mostly by animals such as mollusks.

In some ways, the early-Triassic may serve as a useful proxy to imagine the future effects of modern anthropogenic climate change. A shift towards the poles, mass extinctions, desertification, boom-and-bust cycles caused by population-booms and resource exploitation, and mass migrations/increased competition.

Source: University of Zurich

Image Credits: Rekonstruktionszeichnung: Jaime Chirinos; UZH; Triassic via Wikimedia Commons

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