Citizen scientist scuba divers shed light on the impact of warming oceans on marine life



File 20171019 1045 3eh0e1.jpg?ixlib=rb 1.1
A volunteer diver surveys marine life at Lord Howe Island.
Rick Stuart-Smith/Reef Life Survey, Author provided

Madeleine De Gabriele, The Conversation

Rising ocean temperatures may result in worldwide change for shallow reef ecosystems, according to research published yesterday in Science Advances.

The study, based on thousands of surveys carried out by volunteer scuba divers, gives new insights into the relationship of fish numbers to water temperatures – suggesting that warmer oceans may drive fish to significantly expand their habitat, displacing other sea creatures.

Citizen science

The study draws from Reef Life Survey, a 10-year citizen science project that trains volunteer scuba divers to survey marine plants and animals. Over the past ten years, more than 200 divers have surveyed 2,406 ocean sites in 44 countries, creating a uniquely comprehensive data set on ocean life.

Reef Life Survey takes volunteers on surveying expeditions at hard-to-reach coral reefs around the world.
Rick Stuart-Smith/Reef Life Survey, Author provided

Lead author Professor Graham Edgar, who founded Reef Life Survey, said the unprecedented scope of their survey allowed them to investigate global patterns in marine life. The abundance of life in warm regions (such as tropical rainforests and coral reefs) has long intrigued naturalists. At least 30 theories have been put forward, but most studies have been based on relatively limited surveys restricted to a single continent or group of species.

By tapping into the recreational scuba diving community, Reef Life Survey has vastly increased the amount of information researchers have to work with. Professor Edgar and his colleagues provide one-on-one training to volunteers, teaching them how to carry out comprehensive scans of plants and animals in specific areas.

Dr Adriana Vergés, a researcher at the University of New South Wales specialising in the impact of climate change on ocean ecosystems, said that the Reef Life Survey has already substantially improved our understanding of the marine environment.

“For example, Reef Life Survey data has greatly contributed to our understanding of the factors that determine the effectiveness of effectiveness of marine-protected areas worldwide. The team have made all their data publicly available and more and more research is increasingly making use of it to answer research questions,” she said.

Some of the divers have been working with Reef Life Survey for a decade, although others participate when they can. One volunteer, according to Professor Edgar, was so inspired by the project that he began a doctorate in marine biology (he graduated this year).

There’s a strong link between fish numbers and water warmth, which means warming oceans are likely to change global fish distribution.
Rick Stuart-Smith/Reef Life Survey, Author provided

Warming oceans means fish on the move

One of the important insights delivered by the Reef Life Survey datatbase is the relationship between water temperature and the ratio of fish to invertebrates in an ecosystem. Essentially, the warmer the water, the more fish. Conversely, colder waters contain more invertebrates like lobster, crabs and shrimp.

Professor Stewart Frusher, director of the Centre for Marine Socioecology at the University of Tasmania (and a former colleague of Professor Edgar) told The Conversation that he believes we will see wide-scale changes in fish distribution as climate change warms the oceans.

“Species are moving into either deeper water or towards the poles. We also know that not all species are moving at the same rate, and thus new mixtures of ecosystems will occur, with the fast-moving species of one ecosystem mixing with the slower moving of another,” he said.

As species migrate or expand into newly warmed waters, according to Professor Frusher, they will compete with and prey on the species already living in that area. And while it’s uncertain exactly how disruptive this will be, we do know that small ecosystem changes can rapidly lead to larger-scale impacts.

In order to predict and manage these global changes, scientists need reliable and detailed world-wide data. Professor Frusher said that, with research funding declining, scientists do not have the resources to monitor at the scales required.

The Conversation“Well-developed citizen science programs fill an important niche for improving our understanding of how the earth is responding to change,” he said.

Madeleine De Gabriele, Deputy Editor: Energy + Environment, The Conversation

This article was originally published on The Conversation. Read the original article.

Advertisements

What whales and dolphins can tell us about the health of our oceans



File 20170921 8179 260m8r.jpg?ixlib=rb 1.1
Dolphins contribute important knowledge about ocean health.
Shutterstock

Stephanie Plön, Nelson Mandela University

From the poles to the equator, marine mammals such as seals, dolphins and whales, play an important role in global ecosystems as apex predators, ecosystem engineers and even organic ocean fertilisers. The ocean off the coast of South Africa is home to a high diversity of these mammals and is recognised as a global marine biodiversity hotspot.

Marine mammals are often referred to as “sentinels” of ocean health. Numerous studies have explored the effects of both noise and chemical pollution, habitat degradation, changes in climate and food webs on these marine apex predators. Yet the interplay of these factors isn’t well understood.

Our research on the unfortunate dolphins incidentally caught in shark nets off South Africa’s KwaZulu-Natal coast has helped fill in some of the gaps. By assessing the health of these dolphins we have provided valuable baseline information on conditions affecting coastal dolphin populations in South Africa. This is the first systematic health assessment in incidentally caught dolphins in the Southern Hemisphere.

But to gain a fuller picture of the health of marine mammals in these waters I am now combining this contemporary field research with historical data, like the collection at the Port Elizabeth Museum Bayworld.

The combination of data on diet, reproduction, population structure and health helps us gain a better understanding of the pressures and changes these apex predator populations face. And it helps us understand it in relation to global change, including both climate change and pressures brought about by human behaviour.

My research sheds light on multiple factors: pollutant levels, parasites, and availability of prey, all have an impact on individuals as well as populations.

Understanding the health of these animals also gives us insight into the state of the world’s oceans. This is relevant because oceans affect the entire ecosystem including food security, climate and people’s health. This degree of connectedness is highlighted by recent discoveries about how whales act as ecosystem engineers.

The accumulation of this knowledge is important because the planet’s oceans aren’t being protected. Recent popular documentaries such as “Sonic Sea” and “Plastic Ocean” have highlighted their exploitation and pollution.

What’s missing

Without baseline knowledge it’s challenging to establish the potential effects that new anthropogenic developments (those caused by human behaviour) have on local whale and dolphin populations.

For example, we know that whales are sensitive to shipping noise, so what potential impact could a new deep water port have on mothers and their calves? Could it drive them away from these nursery areas, or could it lead to an increased risk of whales and ships colliding? To answer this and monitor the change that a new port brings with it, we are investigating the soundscape of two bays in the Eastern Cape (one with a new port, one without) in parallel with baleen whale mother-calf behaviour.

Another example is understanding how changes in the Sardine run over the past 15 years have affected the diets of these mammals. The Sardine run is an annual phenomenon when large shoals of Sardine migrate northwards along the coast into KwaZulu-Natal waters to spawn. Using long-term data and samples from the Port Elizabeth Museum research collection, we have been able to establish that over the the past 20 or so years the main predator in the Sardine run – the long-beaked common dolphin – has shifted its diet to mackerel. Although such changes in diet can have potential impacts on the health of the dolphins, parallel investigations on the trophic level these animals feed at (using isotope data from teeth) and the body condition of the dolphins (using long-term data on blubber thickness), indicated no adverse effects to the dolphins.

Our analysis highlights how marine mammals may be used as indicators of environmental change and why research is important.

Finding answers to intricate questions on environmental change is not always easy. But a better understanding and knowledge of the environment these animals live in has to be incorporated into studies contributing to their conservation and management. Such studies are becoming increasingly relevant as they highlight the fast degradation of the marine environment.

For example, a recent study identified antibiotic resistant bacteria in both sea water samples and exhaled breath samples from killer whales. This suggests that the marine environment has been contaminated with human waste which in turn has significant medical implications for humans.

Gaining such information is particularly important given the rapid changes taking place in the oceans, such as those on South Africa’s southern and eastern coastline. This includes increasing coastal development, new deep water ports being built or expanded, and parts of the deep sea being explored for oil and gas.

To assess these changes and what they mean for the environment, baseline studies need to be carried out so that potential effects can be assessed. Whales and dolphins are increasingly being recognised as indicators of ocean health in this endeavour.

And a continuation of the research we did on dolphins caught in nets will help document the cyclic changes that can be seen as normal variation in a population. This could prove important for assessing future catastrophic events, such as the Deep Horizon oil spill.

What next

The oceans absorb over 25% of the world’s carbon pollution as well as heat generated by global warming. They also produce at least 50% of the planet’s oxygen, and are home to 80% of all life on earth. Yet only 5% of this vital component of our planet has been explored.

The ConversationResearch on whales and dolphins contributes important knowledge about ocean health. Historical data increasingly provides a guideline to teasing out natural variations in populations and assessing the contribution that multiple factors have on these animals. In time, this will ensure that policy makers are being given sound scientific information. It will also provide us with a good barometer of the overall health of our oceans.

Stephanie Plön, Researcher, Earth Stewardship Science Research Institute, Nelson Mandela University

This article was originally published on The Conversation. Read the original article.

How to work out which coral reefs will bleach, and which might be spared


Clothilde Emilie Langlais, CSIRO; Andrew Lenton, CSIRO, and Scott Heron, National Oceanic and Atmospheric Administration

Regional variations in sea surface temperature, related to seasons and El Niño, could be crucial for the survival of coral reefs, according to our new research. This suggests that we should be able to identify the reefs most at risk of mass bleaching, and those that are more likely to survive unscathed.

Healthy coral reefs support diverse ecosystems, hosting 25% of all marine fish species. They provide food, coastal protection and livelihoods for at least 500 million people.

But global warming, coupled with other pressures such as nutrient and sediment input, changes in sea level, waves, storms, ventilation, hydrodynamics, and ocean acidification, could lead to the end of the world’s coral reefs in a couple of decades.


Read more: How much coral has died in the Great Barrier Reef’s worst bleaching event?


Climate warming is the major cause of stress for corals. The world just witnessed an event described as the “longest global coral die-off on record”, and scientists have been raising the alarm about coral bleaching for decades.

The first global-scale mass bleaching event happened in 1998, destroying 16% of the world coral reefs. Unless greenhouse emissions are drastically reduced, the question is no longer if coral bleaching will happen again, but when and how often?

To help protect coral reefs and their ecosystems, effective management and conservation strategies are crucial. Our research shows that understanding the relationship between natural variations of sea temperature and human-driven ocean warming will help us identify the areas that are most at risk, and also those that are best placed to provide safe haven.

A recurrent threat

Bleaching happens when sea temperatures are unusually high, causing the corals to expel the coloured algae that live within their tissues. Without these algae, corals are unable to reproduce or to build their skeletons properly, and can ultimately die.

The two most devastating global mass bleaching events on record – in 1998 and 2016 – were both triggered by El Niño. But when water temperatures drop back to normal, corals can often recover.

Certain types of coral can also acclimatise to rising sea temperatures. But as our planet warms, periods of bleaching risk will become more frequent and more severe. As a consequence, corals will have less and less time to recover between bleaching events.

We are already witnessing a decline in coral reefs. Global populations have declined by 1-2% per year in response to repeated bleaching events. Closer to home, the Great Barrier Reef lost 50% of its coral cover between 1985 and 2012.

A non-uniform response to warming

While the future of worldwide coral reefs looks dim, not all reefs will be at risk of recurrent bleaching at the same time. In particular, reefs located south of 15ºS (including the Great Barrier Reef, as well as islands in south Polynesia and Melanesia) are likely to be the last regions to be affected by harmful recurrent bleaching.

We used to think that Micronesia’s reefs would be among the first to die off, because the climate is warming faster there than in many other places. But our research, published today in Nature Climate Change, shows that the overall increase in temperature is not the only factor that affects coral bleaching response.

In fact, the key determinant of recurrent bleaching is the natural variability of ocean temperature. Under warming, temperature variations associated with seasons and climate processes like El Niño influence the pace of recurrent bleaching, and explain why some reefs will experience bleaching risk sooner than others in the future.

Different zones of the Pacific are likely to experience differing amounts of climate variability.
Author provided
Degrees of future bleaching risk for corals in the three main Pacific zones.
Author provided

Our results suggest that El Niño events will continue to be the major drivers of mass bleaching events in the central Pacific. As average ocean temperatures rise, even mild El Niño events will have the potential to trigger widespread bleaching, meaning that these regions could face severe bleaching every three to five years within just a few decades. In contrast, only the strongest El Niño events will cause mass bleaching in the South Pacific.

In the future, the risk of recurrent bleaching will be more seasonally driven in the South Pacific. Once the global warming signal pushes summer temperatures to dangerously warm levels, the coral reefs will experience bleaching events every summers. In the western Pacific, the absence of natural variations of temperatures initially protects the coral reefs, but only a small warming increase can rapidly transition the coral reefs from a safe haven to a permanent bleaching situation.


Read more: Feeling helpless about the Great Barrier Reef? Here’s one way you can help


One consequence is that, for future projections of coral bleaching risk, the global warming rate is important but the details of the regional warming are not so much. The absence of consensus about regional patterns of warming across climate models is therefore less of an obstacle than previously thought, because globally averaged warming provided by climate models combined with locally observed sea temperature variations will give us better projections anyway.

The ConversationUnderstanding the regional differences can help reef managers identify the reef areas that are at high risk of recurring bleaching events, and which ones are potential temporary safe havens. This can buy us valuable time in the battle to protect the world’s corals.

Clothilde Emilie Langlais, research scientist at CSIRO Oceans and Atmosphere, CSIRO; Andrew Lenton, Senior Research Scientist, Oceans and Atmosphere, CSIRO, and Scott Heron, Physical Scientist, National Oceanic and Atmospheric Administration

This article was originally published on The Conversation. Read the original article.

Debris from the 2011 tsunami carried hundreds of species across the Pacific Ocean



File 20170928 24177 15udpfb
Japanese vessel washed ashore on Long Beach, Washington being inspected by John Chapman.
Russ Lewis

Steven Chown, Monash University

When a foreign species arrives in a new environment and spreads to cause some form of economic, health, or ecological harm, it’s called a biological invasion. Often stowing away among the cargo of ships and aircraft, such invaders cause billions of dollars of economic loss annually across the globe and have devastating impacts on the environment.

While the number of introductions which eventually lead to such invasions is rising across the globe, most accidental introduction events involve small numbers of individuals and species showing up in a new area.

But new research published today in Science has found that hundreds of marine species travelled from Japan to North America in the wake of the 2011 Tōhoku earthquake and tsunami (which struck the east coast of Japan with devastating consequences).


Read more: Widespread invasive species control is a risky business


Marine introductions result from biofouling, the process by which organisms start growing on virtually any submerged surface. Within days a slimy bacterial film develops. After months to a few years (depending on the water temperature) fully formed communities may be found, including algae, molluscs such as mussels, bryozoans, crustaceans, and other animals.

Current biosecurity measures, such as antifouling on ships and border surveillance, are designed to deal with a steady stream of potential invaders. But they are ill-equipped to deal with an introduction event of the scale recorded along most of the North American coast. This would be just as true for Australia, with its extensive coastlines, as it is for North America.

Mass marine migration

Marine animals were transported vast distances on tsunami debris.
Carla Schaffer / AAAS

This research, led by James Carlton of Williams College, shows that over a few years after the 2011 earthquake and tsunami, many marine organisms arrived along the west coast of North America on debris derived from human activity. The debris ranged from small pieces of plastic to buoys, to floating docks and damaged marine vessels. All of these items harboured organisms. Across the full range of debris surveyed, scores of individuals from roughly 300 species of marine creatures arrived alive. Most of them were new to North America.

The tsunami swept coastal infrastructure and many human artefacts out to sea. Items that had already been in the water before the tsunami carried their marine communities along with them. The North Pacific Current then transported these living communities across the Pacific to Alaska, British Columbia, Oregon, Washington and California.

Japanese tsunami buoy with Japanese oyster Crassostrea gigas, found floating offshore of Alsea Bay, Oregon in 2012.
James T. Carlton

What makes this process unusual is the way a natural extreme event – the earthquake and associated tsunami – gave rise to an extraordinarily large introduction event because of its impact on coastal infrastructure. The researchers argue that this event is of unprecedented magnitude, constituting what they call “tsunami-driven megarafting”: rafting being the process by which organisms may travel across oceans on debris – natural or otherwise.

It’s not known how many of these new species will establish themselves and spread in their new environment. But, given what we know about the invasion process, it’s certain at least some will. Often, establishment and initial population growth is hidden, especially in marine species. Only once it is either costly or impossible to do something about a new species, is it detected.

Biosecurity surveillance systems are designed to overcome this problem, but surveillance of an entire coast for multiple species is a significant challenge.

Perhaps one of the largest questions the study raises is whether this was a once off event. Might similar future occurrences be expected? Given the rapid rate of coastal infrastructure development, the answer is clear: this adds a new dimension to coastal biosecurity that will have to be considered.

The ConversationInvestment in coastal planning and early warning systems will help, as will reductions in plastic pollution. But such investment may be of little value if action is not taken to adhere to, and then exceed, nationally determined contributions to the Paris Agreement. Without doing so, a climate change-driven sea level rise of more than 1 m by the end of the century may be expected. This will add significantly to the risks posed by the interactions between natural extreme events and the continued development of coastal infrastructure. In other words, this research has uncovered what might be an increasingly common new ecological process in the Anthropocene – the era of human-driven global change.

Steven Chown, Professor of Biological Sciences, Monash University

This article was originally published on The Conversation. Read the original article.

Antarctic Ocean and Climate Change


The link below is to an article that takes a look at the effects of a 1-degree rise in temperature of the Antarctic Ocean.

For more visit:
http://e360.yale.edu/digest/what-happens-to-the-antarctic-ocean-with-1-degrees-celsius-of-warming

Explainer: how does the sea ‘disappear’ when a hurricane passes by?


Darrell Strauss, Griffith University

You may have seen the media images of bays and coastlines along Hurricane Irma’s track, in which the ocean has eerily “disappeared”, leaving locals amazed and wildlife stranded. What exactly was happening?

//platform.twitter.com/widgets.js

These coastlines were experiencing a “negative storm surge” – one in which the storm pushes water away from the land, rather than towards it.


Read more: Irma and Harvey: very different storms, but both affected by climate change


Most people are familiar with the idea that the sea is not at the same level everywhere at the same time. It is an uneven surface, pulled around by gravity, such as the tidal effects of the Moon and Sun. This is why we see tides rise and fall at any given location.

At the same time, Earth’s atmosphere has regions where the air pressure is higher or lower than average, in ever-shifting patterns as weather systems move around. Areas of high atmospheric pressure actually push down on the ocean surface, lowering sea level, while low pressure allows the sea to rise slightly.

This is known as the “inverse barometer effect”. Roughly speaking, a 1 hectopascal change in atmospheric pressure (the global average pressure is 1,010hPa) causes the sea level to move by 1cm.

When a low-pressure system forms over warm tropical oceans under the right conditions, it can intensify to become a tropical depression, then a tropical storm, and ultimately a tropical cyclone – known as a hurricane in the North Atlantic or a typhoon in the northwest Pacific.

As this process unfolds, the atmospheric pressure drops ever lower and wind strength increases, because the pressure difference with surrounding areas causes more air to flow towards the storm.

In the northern hemisphere tropical cyclones rotate anticlockwise and officially become hurricanes once they reach a maximum sustained wind speed of around 120km per hour. If sustained wind speeds reach 178km per hour the storm is classed as a major hurricane.

Surging waters

A “normal” storm surge happens when a tropical cyclone reaches shallow coastal waters. In places where the wind is blowing onshore, water is pushed up against the land. At the same time the cyclone’s incredibly low air pressure allows the water to rise higher than normal. On top of all this, the high waves whipped up by the wind mean that even more water inundates the coast.

The anticlockwise rotation of Atlantic hurricanes means that the storm’s northern side produces winds blowing from the east, and its southern side brings westerly winds. In the case of Hurricane Irma, which tracked almost directly up the Florida panhandle, this meant that as it approached, the east coast of the Florida peninsula experienced easterly onshore winds and suffered a storm surge that caused severe inundation and flooding in areas such as Miami.

The negative surge

In contrast, these same easterly winds had the opposite effect on Florida’s west coast (the Gulf Coast), where water was pushed offshore, leading to a negative storm surge. This was most pronounced in areas such as Fort Myers and Tampa Bay, which normally has a relatively low tide range of less than 1m.

//platform.twitter.com/widgets.js

The negative surge developed over a period of about 12 hours and resulted in a water level up to 1.5m below the predicted low tide level. Combined with the fact that the sea is shallow in these areas anyway, it looked as if the sea had simply disappeared.


Read more: Predicting disaster: better hurricane forecasts buy vital time for residents.


As tropical cyclones rapidly lose energy when moving over land, the unusually low water level was expected to rapidly rise, which prompted authorities to issue a flash flood warning to alert onlookers to the potential danger. The negative surge was replaced by a storm surge of a similar magnitude within about 6 hours at Fort Myers and 12 hours later at Tampa Bay.

The ConversationRising waters are the deadliest aspect of hurricanes – even more than the ferocious winds. So while it may be tempting to explore the uncovered seabed, it’s certainly not wise to be there when the sea comes rushing back.

Darrell Strauss, Senior Research Fellow, Griffith University

This article was originally published on The Conversation. Read the original article.

I have always wondered: why is the sea salty?



File 20170905 9729 1xhzlu5
Salt flows down rivers to the ocean.
Shutterstock/Masonjar

Helen Phillips, University of Tasmania

This is an article from I Have Always Wondered, a new series where readers send in questions they’d like an expert to answer. Send your question to alwayswondered@theconversation.edu.au


Why is the sea salty? – Robert Moran, Middlecove


The short answer is that water dissolves the salts contained in rocks, and these salts are carried in the water to the sea.

As raindrops form, they absorb carbon dioxide from the air. The water (H₂O) and carbon dioxide (CO₂) react to form carbonic acid (H₂CO₃). The carbonic acid makes rainwater slightly acidic, with a pH of around 5.6. Pure water has a pH of 7, which is neutral.


Read More: I have always wondered: why are some fruits poisonous?


So, rain dissolves salts out of the rocks and these salts are carried via runoff to streams and rivers and finally to the sea. Rivers carry almost 4 billion tonnes of salt to the sea each year.

But rivers aren’t salty, right? Rivers are definitely not as salty as the sea, but they constantly carry their small salt content into the sea, and as a result the concentration of salt in the sea (which oceanographers call salinity) has built up over millions of years.

In fact, rivers aren’t the only source of sea salt. Rocks in the sea also play a role, and hydrothermal vents in the ocean floor and subsea volcanoes also supply dissolved salts to the sea.

Super-heated molten lava about to explode into the water.
NSF and NOAA

Over millions of years, the concentration of salts has increased from possibly almost fresh in the primeval sea to where it is now – an average of 35 grams of salt in every kilogram of seawater.

If all this salt could be taken out of the ocean and spread over Earth’s land surface, according to the US National Oceanic and Atmospheric Administration, it would form a layer more than 150 metres thick.

Why are some places saltier than others?

Salinity varies from place to place in the sea, depending on how close you are to rivers, how much rain falls, how much evaporation occurs, and whether ocean currents are bringing in saltier or fresher water.

In general, the sea is saltier in the subtropics, where evaporation is high due to warm air temperatures, steady trade winds, and very low humidity related to atmospheric circulation patterns called Hadley Cells.

The sea is fresher close to the Equator where rainfall is high, and in the Southern Ocean and Arctic Ocean, where sea ice melt in the summer adds fresh water.

NASA’s ‘Salt of the Earth’ Aquarius map.
NASA

Enclosed seas, such as the Mediterranean and Red Seas, can be very salty indeed. This is because the removal of fresh water by evaporation is much larger than the addition by rainfall, and lower-salinity waters from the deep sea can’t flow in as easily.

Ocean salinity as a rain gauge

While the total amount of salt in the sea is pretty constant, the distribution of the salt is changing. Broadly speaking, the salty parts of the ocean are becoming saltier, and the fresh parts fresher.

These salinity changes are caused by changing rainfall and evaporation patterns globally, where wet places are generally becoming wetter and dry places are getting drier.


Read More: I have always wondered: when do baby birds begin to breathe?


This amplification of the water cycle is a consequence of rising air temperatures due to climate change. Warm air can hold more moisture, so it can receive more evaporated water from the sea or land surface, and then release more when it rains.

Just how fast the water cycle is amplifying is a topic of current research.

Earth’s water cycle.

Rainfall and evaporation are difficult to measure accurately, particularly over the ocean where 78% of rain falls.

Ocean salinity, on the other hand, is easier to measure now that we have the global Argo program: an armada of profiling floats that measure salinity and temperature from the surface to a depth of 2,000m, and surface salinity measurements via satellite.

The ConversationOcean salinity measurements are not only being used to understand past changes in the water cycle and reduce uncertainty in climate models, they are helping to improve seasonal rain forecasts around the world.


  • Email your question to alwayswondered@theconversation.edu.au
  • Tell us on Twitter by tagging @ConversationEDU with the hashtag #alwayswondered, or
  • Tell us on Facebook

Helen Phillips, Senior Research Fellow, Institute for Marine and Antarctic Studies, University of Tasmania

This article was originally published on The Conversation. Read the original article.