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What happened to the sea stars?

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Billions of sea stars off the Pacific coast of North America from Mexico to Alaska have died from a wasting disease since 2013.  This die-off is considered to be the largest ever marine epidemic.  Over 90% of the population of sunflower sea stars has succumbed to the disease.

The result has been an explosion in the population of the sea urchins that the sea stars feed on.  In turn, the sea urchins have devoured kelp forests that provide habitat for thousands of marine creatures.  These kelp forests support a multi-million-dollar economy through fisheries and tourism as well as sequestering carbon dioxide and protecting vulnerable coastlines. 

The disease begins with lesions and eventually kills sea stars by seemingly melting their tissues over a period of about two weeks.  Sea stars with the disease become contorted and lose their arms.

For years, the definitive cause of the wasting disease has been elusive.  But researchers from the University of British Columbia, the Hakai Institute, and the University of Washington have now identified a bacterium that is the disease-causing agent.

A strain of the Vibrio pectenicida bacteria – named FHCF-3 – is responsible.  The Vibrio genus of bacteria includes pathogens that infect corals, shellfish, and even humans.  Vibrio cholerae is the cause of cholera.

Research is now underway to understand the link between the disease and warming ocean temperatures due to climate change.  The hope is that the discovery of the cause of the wasting disease will help guide management and recovery efforts for sea stars and impacted ecosystems.

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‘Disease detectives’ discover cause of sea star wasting disease that wiped out billions of sea stars

Photo, posted April 16, 2011, courtesy of Brian Gratwicke via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

More trouble from sea urchins

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Sea Urchins are real troublemakers.  On the West Coast, the sea urchin population exploded when the sunflower sea stars that eat them were decimated by a wasting disease.  Urchins devour kelp and they ate up 96% of the region’s kelp forests.  Kelp forests serve as shelter and food for a vast array of marine life and kelp sequesters as much as 20 times more carbon than terrestrial forests.

A new study by researchers at North Carolina State University looked at the health of the coral reef in Honaunau Bay on Hawaii’s Big Island and found that ballooning sea urchin populations are endangering the survival of the reef.

Fishing in these areas has greatly reduced the numbers of fish that feed on sea urchins and urchin populations have grown significantly.   There are areas of the reef where there are 51 sea urchins in every square meter.

The reef is already not growing at a healthy rate as a result of water pollution and overheating created by climate change.  These result in a poor environment for coral to reproduce and grow, which leaves the reef unable to keep up with the pace of erosion caused by urchins.

Reef growth is measured in terms of net carbonate production – namely the amount of calcium carbonate produced over time.  In the 1980s, healthy reefs in Hawaii produced about 15 kilograms of carbonate a year per square meter.  The Honaunau Reef today shows an average net carbonate production of only 0.5 kilograms per square meter.  The reef is growing very slowly and can’t keep up with urchin erosion.

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Huge sea-urchin populations are overwhelming Hawaii’s coral reefs

Photo, posted October 29, 2017, courtesy of Rickard Zerpe via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

How warm is It?

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As of June, the world had seen 13 consecutive months of record-breaking heat.  The average global temperature over the last 12 of those months measured 1.5 degrees Celsius warmer than the preindustrial era. This means that the world has at least temporarily exceeded the temperature target set forth in the Paris Climate Agreement.

Does this mean that climate change has gotten to the point where keeping temperatures below that goal is no longer possible? Not necessarily. Temperatures could drop below the 1.5-degree level in the near future.

The world has certainly been warming as a result of climate change, but the spike in temperature for the past year has also been driven by an El Niño condition in the Pacific, which leads to warmer temperatures.  How much of the warming is a result of each factor is not known.

But scientists say that El Niño has ended in June and a La Niña condition is likely to take shape between August and October. This would lead to cooler temperatures in many places.

Despite the extensive and lingering heatwaves in the US in July, on a global scale, temperatures have actually started falling in July.  July may end up being the first month since June 2023 to not set a new monthly global temperature record.  Nevertheless, the long streak of record-high temperatures is no statistical anomaly.  It is indicative of a large and continuing shift in the climate.   Whether conditions in the Pacific produce an El Niño or a La Niña, the steady long-term warming will continue as long as human-generated carbon emissions continue.

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How Bad Is Warming? La Niña May Reveal

Photo, posted September 19, 2022, courtesy of Paul Sableman via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Global coral bleaching

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The world’s coral reefs are in the midst of a global bleaching event being driven by extraordinarily high ocean temperatures.  This is the fourth such global event on record and is predicted to be the largest one ever.  Coral bleaching occurs when corals are stressed by heat and eject the symbiotic algae within them that they need to survive.  Bleached corals can recover if water temperatures cool soon enough.  Otherwise, they die.

Each of the three previous coral bleaching events has been worse than the last.  The first, in 1998, affected 20% of the world’s reefs.  The second, in 2010, affected 35%.  The third, from 2014 to 2017, affected 56% of reefs.

The current bleaching event was confirmed by satellite observations early in April and was already seen to be affecting more than half of the world’s coral areas across the Pacific, Indian, and Atlantic Oceans.  The ongoing event is expected to be the worst bleaching ever experienced by Australia’s Great Barrier Reef.  A small saving grace is that the current bleaching event is not expected to be of extremely long duration because the El Niño in the Pacific has abated.

Coral bleaching events are becoming more severe and frequent due to increased marine heat waves driven by climate change.  Last year was particularly difficult for corals as global sea temperatures reached record high levels for several months.

Widespread coral bleaching impacts economies, livelihoods, food security, and more.  Coral reefs provide ecosystem services essential to marine life and human populations as well.  Global action will be needed for coral interventions and restorations.

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Satellites watch as 4th global coral bleaching event unfolds

Photo, posted March 23, 2012, courtesy of Oregon State University via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

The hottest year on record

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Barring some sort of massive global deep freeze late in the year, it was increasingly obvious by November that 2023 was going to be the hottest year ever recorded.  After analyzing data that showed the world saw its warmest ever November, experts around the world made the call early in December.

According to the European Union’s Copernicus Climate Change Service, from January to November 2023, global average temperatures were the highest on record – 1.46 degrees Celsius or 2.6 degrees Fahrenheit above the pre-industrial average.  Given that the Paris Climate Accord has the goal of keeping warming below 1.5 degrees Celsius, 2023 has been an alarmingly hot year.

November itself was 1.75 degrees warmer than the pre-industrial average.  The average surface air temperature for the planet was 14.22 degrees Celsius or about 57.6 degrees Fahrenheit.  Now 57 degrees doesn’t sound all that warm, but we are not accustomed to thinking in terms of the average temperature for the entire planet.  Keep in mind that the planetary average includes Antarctica and the polar north. The year as a whole had six record-breaking months and two record-breaking seasons. 

There is no reason to hope that the warming in 2023 was an anomalous occurrence and that 2024 is apt to be cooler.  With an El Niño in place in the Pacific, the new year might even be warmer than the previous one.  With continued warming, extreme weather events are likely to become even more frequent and intense, exacerbating the damage and loss of life from droughts, floods, hurricanes, and wildfires.

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2023 is officially the hottest year ever recorded, and scientists say “the temperature will keep rising”

Photo, posted June 7, 2012, courtesy of NASA/Kathryn Hansen via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

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Plastics In The Air | Earth Wise

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Plastic pollution is a big deal.  There are plastics clogging up landfills and waterways and accumulating in the oceans, choking turtles and seabirds.  Annual production of plastics has grown from 2 million tons a year in 1950 to more than 450 million tons today.

As if plastic problems weren’t already big enough, it is becoming increasingly clear that there are growing amounts of microplastic particles in the air. Bits of plastic are lofted into the sky from seafoam bubbles and from spinning tires on highways.  The particles are so light that they can travel for thousands of miles, far from where they originate.

Studies in recent years documented the presence of plastic particles even in places like the Pyrenees in Europe and in federally protected areas of the US.  Other studies have measured the quantity of plastic in the air of various locations and have looked at the origins of the particles.

In the western US, over 80% of microplastics came from roads where vehicles kick up particles from tires and brakes.   In remote areas of the Pacific, there is less than a single particle of plastic per cubic meter of air.  In cities like London and Beijing, on the other hand, there can be several thousand particles per cubic meter.

Microplastics can act as airborne aerosols, like dust, salt, soot, volcanic ash, and other particles.  Aerosols play an important role in the formation of clouds and in temperature regulation on the earth.  At low concentrations, such as exist in most places, microplastic aerosols don’t have much of an effect.  But there are more in the atmosphere all the time and, at this point, scientists don’t really know what effect they will have.

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Microplastics Are Filling the Skies. Will They Affect the Climate?

Photo, posted August 28, 2014, courtesy of Alan Levine via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

The Hottest Summer | Earth Wise

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It was a very rainy and relatively cool summer in much of New England as well as in New York’s Capital Region, where Earth Wise originates.  Despite that fact, according to NASA scientists, the summer of 2023 was the Earth’s hottest since global record keeping began in 1880.

The months of June, July, and August taken together were .41 degrees Fahrenheit warmer than any other summer on record as well as being 2.1 degrees warmer than the average summer between 1951 and 1980.

The record summer heat was marked by heatwaves in South America, Japan, Europe, and the US.  The heat exacerbated wildfires in Canada that dumped smoke across much of the northern tier of our country and also led to severe rainfall in Europe.  All sorts of temperature records were set in places across the globe.

According to NASA, exceptionally high sea surface temperatures, fueled in part by the reemergence of El Niño in the Pacific, were a major factor in the summer’s record warmth.

The record-breaking heat of this summer continues a long-term trend of warming.  Scientists around the world have been tracking the warming that is driven primarily by human-caused greenhouse gas emissions.  The combination of this background warming and the marine heatwaves set the stage for new temperature records.  The El Niño was enough to tip the scales. 

In the current environment, heat waves will last longer, be hotter, and be more punishing.  The atmosphere can hold more water producing hot and humid conditions that are harder for the human body to endure.

Scientists are expecting the biggest impacts of El Niño in the early parts of next year.  We can expect to see extreme weather of many kinds over the next year.

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NASA Announces Summer 2023 Hottest on Record

Photo, posted June 8, 2023, courtesy of Anthony Quintano via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Why Was the Summer So Hot? | Earth Wise

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Many places around the world have experienced extraordinary heat waves this summer.  The 31 days of high temperatures 110 degrees or more in Phoenix is a prime example but many other places suffered from extreme and relentless heat.  Why did this happen?

The overarching reason is climate change, which has warmed the Earth by 2.2 degrees Fahrenheit since the preindustrial era.  This change on a global level is enough to make heatwaves far more likely.  For example, the concurrent heatwaves in Europe and North America were 1000 times more likely to have occurred because of climate change.

But there hasn’t been a sudden increase in global temperature that would make this summer so much hotter.  Instead, what really has happened is three other factors all came into play at the same time.

The first is the 2022 eruption of Hunga Tonga-Hunga Ha-apai, which is an underwater volcano in the South Pacific.  That eruption did not produce much in the way of planet-cooling aerosols in the atmosphere.  Instead, it vaporized huge amounts of seawater, sending water vapor into the atmosphere, which helps trap heat.

The second is a change in the amount of energy radiating from the sun.  That actually rises and falls a small amount every 11 years.  Currently, it is in the upswing and will reach its next peak in 2025.

Finally, there is the arrival of the El Niño in the Pacific, whose balmy ocean waters radiate heat into the air.

The combination of all these factors when added to the already warming climate is a recipe for temperatures to soar to uncharted highs.  We can expect more heat waves, forest fires, flash floods, and other sorts of extreme weather.

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It’s Not Just Climate Change: Three Other Factors Driving This Summer’s Extreme Heat

Photo, posted February 27, 2017, courtesy of Giuseppe Milo via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

El Niño Will Likely Return | Earth Wise

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El Niño, a weather phenomenon triggered by warm waters in the eastern Pacific, is likely to return this year, according to the World Meteorological Organization.  The Pacific has been in the cooler La Niña phase for the past 3 years, which is unusual, but that appears to be coming to a close.  According to the WMO, there is an 80% chance that the Pacific will shift to the El Niño phase before fall.

Record hot years typically coincide with El Niño, which adds to the ongoing warming trend in the climate.   There is not yet a clear picture of how strong the forthcoming El Niño event will be or how long it might last, but even a mild El Niño could affect precipitation and temperature patterns around the world.

The hottest year on record, 2016, occurred during a particularly strong El Niño.  Experts expect that 2024 is likely to see soaring temperatures again.  El Niño generally leads to drier conditions in Australia, Indonesia, and southern Asia, but greater amounts of rainfall in South America, the U.S., and parts of Africa.  Despite the presence of a cooling La Niña for the past three years, the last eight years have been the hottest on record.

El Niño and La Niña form an intermittent cycle known as the El Niño Southern Oscillation, or ENSO, that is highly influential in shaping the year-to-year variations in weather conditions around the world.  ENSO is a natural phenomenon and scientists are still trying to understand how human-caused climate change might be impacting the behavior and dynamics of the cycle.

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‘A New Spike’ in Global Temperatures in the Forecast

Photo, posted October 11, 2015, courtesy of Harshil Shah via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

2022 Temperature Report | Earth Wise

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The average surface temperature for the Earth in 2022 tied with 2015 as the fifth warmest on record.  The warming trend for the planet continued with global temperatures 1.6 degrees Fahrenheit above the average baseline for 1951-1980 that NASA uses for its studies. Compared with the late 19th century average used in setting climate goals, global temperatures are up about 1.1 degrees Celsius, or 2 degrees Fahrenheit.

Overall, the past nine years have been the warmest since modern recordkeeping began in 1880.   The rising temperatures have moved in concert with rising levels of greenhouse gases entering the atmosphere from human activity.  Many factors can affect the average temperature in any given year including El Nino and La Nina conditions in the Pacific.  But the longer-term trend is quite clear.  Global temperatures continue to rise.

Greenhouse gas emissions have reached all-time high levels despite increasing efforts to reduce them.  There was a real drop in levels in 2020 due to reduced activity during COVID-19 lockdowns, but they rebounded soon thereafter. 

The Arctic region continues to experience the strongest warming trends, as much as four times the global average.  Arctic warming has a major impact on weather at lower latitudes as it changes the behavior of the jet stream as well as affecting ocean currents and water temperatures.

As global temperatures continue to rise, rainfall and tropical storms have become more intense, droughts have become more severe, and ocean storm surges have had increasing impact.  From torrential monsoons in Asia to megadroughts in the U.S. Southwest, extreme weather has become the new normal.

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NASA Says 2022 Fifth Warmest Year on Record, Warming Trend Continues

Photo, posted June 20, 2020, courtesy of Daxis via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Some Good News For The Great Barrier Reef | Earth Wise

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It seems like there has been nothing but dire news from Australia’s Great Barrier Reef.  Earlier this year, there was yet another mass bleaching event – the fourth in seven years and the first ever to strike during a cooler La Niña phase in the Pacific.  But this bleaching event was less severe than other recent ones, which makes it possible for parts of the reef to bounce back.

In particular, in the northern and central stretches of the reef, scientists have recorded the most extensive coral cover seen in 36 years of study.  In areas where coral cover has expanded, it is mostly fast-growing Acropora corals driving the growth.  That isn’t the best outcome, given that Acropora are particularly vulnerable to strong waves, highly susceptible to bleaching, and are the preferred target of crown-of-thorns starfish.

Those creatures are a major problem for the Great Barrier Reef.  In contrast to the upper stretches of the reef, the southern third actually saw coral cover drop from 38 to 34 percent over the course of the past year.  Scientists blame the decline on an outbreak of crown-of-thorns starfish, which prey on corals.  The starfish grow faster and eat more in warmer, more acidic waters.   Carbon emissions are both raising ocean temperatures and turning waters more acidic.

The large increases in hard coral cover in the reef are certainly good news, but it is important to understand that they can be quickly negated by disturbance on reefs where Acropora corals predominate.  Warming temperatures and mass bleaching events continue to pose a critical threat to all reefs, especially when there are crown-of-thorns starfish outbreaks and increasing frequency of tropical cyclones.

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Parts of Great Barrier Reef See Most Extensive Coral Cover In 36 Years

Photo, posted July 15, 2019, courtesy of Kenneth Lu via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Marine Predation And Climate Change | Earth Wise

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Climate change is taking a toll on forests, farms, freshwater resources, and economies all around the world.  But ocean ecosystems remain the center of global warming.

Despite their vast ability to absorb heat and carbon dioxide, oceans are warming.  In fact, according to scientists, the oceans have absorbed 90% of all the warming that has occurred during the past 50 years. 

The ocean’s surface layer, which is home to most marine life, takes most of this heat.  As a result, the top 2,300 feet of global ocean water has warmed approximately 1.5°F since 1901.

Well it turns out that a hotter ocean is also a hungrier ocean.  According to a new study recently published in the journal Science, researchers discovered that predator impacts in the Atlantic and Pacific oceans peak at higher temperatures.  The effects of more intense marine predation could disrupt ecosystem balances that have existed for millennia. 

An international research team led by the Smithsonian Institution and Temple University analyzed predator and prey data collected from 36 sites, running along the Atlantic and Pacific coasts from Alaska in the north to Tierra de Fuego at the tip of South America.  The research team found that, in warmer waters, predators’ more voracious appetites left outsized marks on the prey community.  Total prey biomass plunged in warmer waters when prey were left unprotected.  However, in the coldest zones, leaving prey exposed or protected made nearly no difference at all.  

As the oceans continue to warm, more intense predation will create winners and losers and could jeopardize the overall health of marine ecosystems.  

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As the ocean heats up hungrier predators take control

Photo, posted July 14, 2017, courtesy of Jonathan Chen via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Alaskan Icemageddon | Earth Wise

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December saw some wild weather in Alaska.  A combination of record high temperatures and torrential rainstorms resulted in the coining of the term “Icemageddon” to describe what was going on with the weather.

Kodiak Island in southern Alaska saw a high temperature of 67 degrees on December 26, which was warmer than it was in Southern California that same day.  This set an all-time record for the warmest December day in Alaska.  Such a high temperature is amazing considering how little sunlight Alaska gets at this time of year.  And with warmer air comes wetter air, as the atmosphere is capable of holding more water vapor as temperatures increase.

As a result, that same day saw the interior of the state get an inch of rain in just a few hours, something that hadn’t happened for decades.  But then, when temperatures plummeted again, all that rainwater froze.

Huge sheets of ice blocked roads and choked traffic in Fairbanks, Alaska’s second largest city.  Indeed, it was the state’s transportation department that came up with the term icemageddon to describe the situation.

The extreme warmth in December is related to the same weather pattern that brought cold, wintry weather to the Pacific Northwest and Northern California.  Those weather conditions resulted in hundreds of cancelled flights in Seattle, where temperatures dropped into the 20s, and in massive amounts of snowfall in the Sierra Nevada mountains in California.  A strong area of high pressure anchored in the Northern Pacific resulted in a clockwise flow around it drawing warmer, more tropical air from the Pacific up to Alaska.

Climate change continues to push the envelope on what sort of weather is possible all over the world.

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Alaska faces ‘Icemageddon’ as temperatures swing wildly

Photo, posted April 30, 2015, courtesy of Naql via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Coral Reef Status Report | Earth Wise

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In October, the Global Coral Reef Monitoring Network released the first-ever report collecting global statistics on the world’s corals.  It documents the status of reefs across 12,000 sites in 73 countries over 40 years.  Overall, the news is not good, but there were some bright spots.

From 2009 to 2018, the world has lost 14% of its corals, corresponding to about 4,500 square miles of coral.  Global warming has led to prolonged marine heatwaves that trigger coral bleaching.  Local pollution has also damaged reefs.   The International Panel on Climate Change has reported that 2 degrees Celsius of global warming would wipe out 99% of the world’s corals.

The report does show that corals can recover globally if given a decade of cooler waters.  Some places in the world – particularly the Coral Triangle in Asia, which contains nearly a third of the world’s coral – have actually seen coral growth over the past decade. 

The Global Coral Reef Monitoring network started collecting data in 1978.  Coral health was fairly steady until 1998 when the first mass bleaching event occurred, triggered by a powerful El Niño event.  For the next 12 years, corals recovered nicely, but then bleaching events in 2010 and 2015-17 took their toll.

The Pacific, Australia, and the Caribbean have all seen major decreases in coral.  The Coral Triangle is a major exception which is thought to be a result of genetic diversity among the region’s corals.

Coral conservationists globally are working to protect corals and to actively restore them.  The situation is fairly dire, but there continue to be reasons for hope.

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Finding Bright Spots in the Global Coral Reef Catastrophe

Photo, posted October 13, 2015, courtesy of Albert Straub via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Coral Reefs And Fish Survival | Earth Wise

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The precarious state of the world’s coral reefs has been a highly visible subject for a decade or more.  Mostly what we hear about is the loss of some of the most beautiful sights on the planet. But there is far more at stake than scenic wonders.

The warming and acidifying of ocean waters are causing corals to increasingly bleach and often die.  Corals provide a unique food source for some species of fish and a three-dimensional habitat for many others.  The fish that depend on corals are often prey for fish that don’t depend directly on corals and so on up the food chain.

What happens to fish when coral reefs disappear?  The fish species that feed on corals will starve while others will seek alternative rocky habitats.

A new study by the University of Helsinki uses statistical methods to predict how fish diversity will respond to declines in coral diversity. It concludes that a future coral loss might cause a 40% reduction in reef fish diversity globally.  This is more than a loss of colorful sights for snorkelers; reef fishes provide essential protein for millions of people around the world.

The estimate of potential loss of fish species greatly exceeds the number of species known to depend directly or even indirectly on coral.  The implication is that coral reef food webs will begin to unravel if corals go extinct.  This unraveling is expected to be worse in some places than others.  The Central Pacific, for example, could lose 60% of its reef fish.

For both snorkelers and for the millions who depend upon reef fishes for food, the need for greater efforts to conserve and restore coral reefs is apparent.

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A fu­ture ocean that is too warm for cor­als might have half as many fish spe­cies

Photo, posted September 27, 2009, courtesy of Matt Kieffer via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

California Offshore Wind | Earth Wise

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Offshore wind has been pretty much a non-starter in the U.S. until recently.  Now there is considerable activity in the Northeast Atlantic with major projects getting started off the coasts of Massachusetts, New York, and other eastern states.  The prospects for wind farms in the Pacific, on the other hand, have been pretty dismal.  There are significant logistical problems posed by a deep ocean floor and also opposition from the Navy that does not want obstacles for its ships.

A combination of progress in floating wind turbine technology and the arrival of an administration highly supportive of renewable energy technology has changed the situation.  In late May, the Navy abandoned its opposition to Pacific offshore wind and joined the Interior Department in giving support to allowing two areas off the California coast to be developed for wind turbines.

The plan allows commercial offshore wind farms in a 400-square-mile area in Morro Bay in central California, and in another area off the Humboldt Coast in Northern California.

The two California sites could support enough wind turbines to generate electricity to power 1.6 million homes.  That would make the California coast one of the largest generators of wind power in the world.  The forthcoming Vineyard Wind farm in Massachusetts is expected to have 84 giant turbines.  The two California sites could hold more than 300 turbines.

The offshore wind industry is booming around the world, especially near the coasts of Norway and the UK, where the water is shallow, and turbines can be anchored to the ocean floor.  By contrast, the Pacific Ocean floor drops steeply from the coastline, making it too deep to anchor wind towers.  The newly emerging technology of floating turbines is the key to establishing offshore wind in the Pacific.

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Biden Opens California’s Coast to Wind Farms

Photo, posted August 7, 2013, courtesy of Ray Bouknight via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Sharks On The Decline | Earth Wise

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During the past 70 years, global shark populations have been on the decline.   Many species have become threatened or endangered.  Conservation efforts have been underway in many places, but shark populations continue to be at risk because of over-fishing and habitat loss.

A comprehensive study by marine biologists at Texas A&M University deployed more than 15,000 baited remote underwater video stations on 371 coral reefs in 58 countries.   The study included 59 different shark species in the Atlantic, Pacific and Indian Oceans.  The researchers were surprised to find that no sharks at all were detected in almost 20% of the locations surveyed and were almost completely absent from coral reefs in several nations. 

Scientists believe that demand for shark products, such as fins and meat, and bycatch (that is, sharks captured in nets by fisherman trapping other kinds of fish) are strong contributors to the widespread declines in shark numbers around the world.

The study shows that if corrective steps are not taken in regions where marine management is still ineffective, continued depletion of shark populations is highly likely. 

Sharks have important roles in marine ecosystems.  When their habitats deteriorate and their populations decrease, ecosystem stability and health is degraded because sharks help regulate prey populations.

Some countries, notably the Bahamas, are combating the problem by providing sanctuaries for sharks where fishing and harvesting is prohibited.  Such places support some of the healthiest shark populations in the world.  However, the decline of coral reefs is just another challenge facing shark populations around the world.

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Study Shows Alarming Decline In Shark Numbers Around The World

Photo, posted January 9, 2017, courtesy of Kris-Mikael Krister via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Why The Arctic Is Warming So Fast | Earth Wise

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The Arctic has been warming at the fastest rate of any place on Earth.  There have long been observations of amplification of Arctic warming, meaning that its temperature increases have been well above what would be expected from the global temperature rise.

Many climate models have attributed this warming to the melting of sea ice.  As the bright white ice disappears for longer periods of the year, the dark surface waters that are exposed absorb sunlight rather than reflecting it back into space the way the ice does.  This is known as the ice-albedo feedback.  But it does not entirely explain the amount of warming in the Arctic.

Researchers at the Scripps Institution of Oceanography have developed a new theory that helps to explain what is going on.

In the areas of the Arctic Ocean where there is sea ice, the water is actually warmer at depth and colder near the surface.  The deeper waters are fed by the relatively warm Pacific and Atlantic Oceans while the surface water is cooled by the ice.  The increasing temperature difference between surface and deeper water causes a greater upward flow of heat.  This was first observed in research cruises that revealed evidence that the Arctic Ocean water was becoming more turbulent over time.

According to computer modeling, this phenomenon is responsible for about 20% of the amplification of global warming that occurs in the Arctic.

There are multiple ongoing studies looking at the Arctic warming trend.  Other factors that have contributed over time are the presence of chlorfluorocarbons in the atmosphere.   That contribution is waning since the use of CFCs has been phasing out over time.

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Researchers Find New Reason Why Arctic is Warming So Fast

Photo, posted April 19, 2017, courtesy of Markus Trienke via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Fish And Ships

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Solutions to overfishing of certain tuna and shark populations have been hindered by some significant unknowns:  where the fishing is happening, and where the fish are.  But researchers from Stanford University have recently shed some light on this mystery. 

According to a paper recently published in the journal Science Advances, the researchers have developed a map of shark, tuna, and ship movements that could help ocean managers identify regions of the sea where vulnerable species may be at risk. 

The researchers’ work builds on a 2018 study in which four years of satellite vessel movement data was used to develop a machine learning algorithm that mapped the footprint of 70,000 different fishing vessels around the world.  In their paper, the researchers zeroed in on the activities of 900 vessels from 12 countries in the northeast Pacific Ocean to figure out to what degree fishing fleets, sharks, and tunas overlapped. 

The researchers combined the vessel data with the ocean habitat preferences of sharks and tunas obtained from a decade-long tracking program called Tagging of Pacific Predators (or TOPP).  According to the IUCN, most of the 876 individuals tagged in TOPP belong to species that are either threatened or near-threatened.

By synthesizing this data, researchers were able to map where sharks and tunas would have the highest overlap with commercial fishing vessels.  Increasing the transparency of where fish meets fleets will allow ocean managers to determine where international protections may be needed. 

The United Nations is currently developing the world’s first legally binding treaty to protect international waters.  The Stanford University researchers hope their findings can help with this treaty’s formulation. 

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Tunas, sharks and ships at sea

Photo, posted June 20, 2011, courtesy of Mike Baird via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

WAMC Northeast Public Radio

WAMC/Northeast Public Radio is a regional public radio network serving parts of seven northeastern states (more...)