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Permafrost Thaw | Earth Wise

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We’ve talked about permafrost before.  It is the frozen soil, rock, or sediment piled up in the Arctic that has been there at least for two years but, for the most part, for millennia or even over a million years.  Permafrost holds the carbon-filled remains of vegetation and animals that froze before they could start decomposing.   Estimates are that there are nearly 2,000 billion tons of carbon trapped in Arctic permafrost.  To put that in perspective, annual global carbon emissions are less than 40 billion tons.

Keeping all that carbon frozen plays a critical role in preventing the planet from rapidly heating. The ongoing warming of the Arctic is causing the subsurface ground to thaw and release long-held carbon to the atmosphere.

Scientists from Europe and the US are working together to better track permafrost carbon dynamics.  They are trying to understand the mechanisms that lead to abrupt thaws in the permafrost that have taken place in some locations.  These rapid thawing events are not well understood.  Researchers are also studying the effects of the increasingly frequent wildfires in the Arctic on the permafrost.

Researchers are using satellites to better understand the effects climate change is having on the Arctic environment and how these changes, in turn, are adding to the climate crisis.  Permafrost cannot be directly observed from space, so that its presence has to be inferred from measurements like land-surface temperature and soil moisture readings.  Terrestrial observations are also necessary for understanding how greenhouse gases – both CO2 and methane – are being emitted from the Arctic.

Thawing permafrost is a ticking timebomb for the environment that demands the growing attention of the scientific community.

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Permafrost thaw: it’s complicated

Photo, posted January 24, 2014, courtesy of Brandt Meixell / USGS via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Arctic Communities And Permafrost Thaw | Earth Wise

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Permafrost is frozen soil, rock or sediment that can be as much as a few thousand feet thick.  To qualify as permafrost , the material has to have been at or below the freezing point of water for two or more years.  Most of it is located in high latitudes in the Arctic and Antarctic regions.   Permafrost covers nearly a quarter of the exposed land in the Northern Hemisphere.

Permafrost contains enormous amounts of carbon in the form of frozen soil that includes remnants of plants and animals, in some cases that have been there for more than 20,000 years.

The Arctic region has been warming faster than any place else on earth and thawing permafrost is already unleashing methane and carbon dioxide to the atmosphere, adding to the global temperature rise.

Apart from the impact on the global climate, thawing permafrost is making the ground unstable and is causing serious problems for local communities.

Recent research using satellite observations provides an overview of the Arctic to identify communities and infrastructure that will be at risk over the next 30 years.

Using high-resolution data from the Copernicus Sentinel satellite missions along with ground-based data going back to 1997, researchers modeled the permafrost ground temperature trends and extrapolated them out to 2050.  The results were that 55% of the infrastructure currently located on permafrost and within 60 miles of the Arctic coastline – infrastructure on which many communities rely – is likely to be affected.

Most human activity in the Arctic takes place along permafrost coasts.  Permafrost thaw is exposing these coasts to rapid change that threatens biodiversity and puts pressure on communities.

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Satellites pinpoint communities at risk of permafrost thaw

Photo, posted January 24, 2014, courtesy of Brandt Meixell / USGS via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Biodiversity And Trawling Bans | Earth Wise

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Trawling is a method of commercial fishing that involves pulling or dragging a fishing net – called a trawl – through the water or across the seabed in hopes of catching fish.  Commercial fishing companies favor towing trawl nets because large quantities of fish can be caught in one go.  

However, the trouble with trawling is that it’s destructive to the seafloor and indiscriminate in what it catches.  When towing these large trawl nets, the largest of which is reportedly big enough to catch thirteen 747 jets, everything that happens to be in the way gets caught.  As a result, trawling results in lots of bycatch, a fishing industry term used to describe the deaths of non target species during the process. 

In 2012, the Hong Kong government implemented a territory-wide trawling ban in its waters in hopes of rehabilitating the marine benthic habitat.  The benthic zone refers to the ecological region at the bottom of the ocean. 

Researchers from City University of Hong Kong collected sediment samples from 28 locations six months before the trawl ban and two and a half years after the trawl ban to see whether such interventions can facilitate ecosystem recovery. 

According to the study, which was recently published in the journal Communications Biology, the ban on trawling significantly improved marine biodiversity.  The researchers observed substantial increases in the richness of species and the abundance of benthic marine organisms following the trawling ban.  And since small benthic organisms are the main source of food for large species like fish and crabs, the trawling ban actually helps support fisheries.

More governments should consider a trawl ban to promote sustainable fisheries and marine biodiversity conservation.

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Research confirms trawl ban substantially increases the abundance of marine organisms

Photo, posted December 4, 2018, courtesy of John via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

The Corn Belt Is Losing Topsoil | Earth Wise

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According to a new study published in the Proceedings of the National Academy of Sciences, more than a third of the farmland in the U.S. Corn Belt has completely lost its carbon-rich topsoil due to erosion.   The affected area is nearly 100 million acres and the amount of carbon loss is nearly 2 million tons.

The study, led by scientists at the University of Massachusetts, Amherst, found that the greatest loss of carbon-rich topsoil was on hilltops and ridgelines.  This indicates that tillage – the repeated plowing of fields – was the primary cause of the erosion because loosened soils move downslope.

The loss of topsoil has reduced corn and soybean yields in the Midwest by 6%, resulting in a loss of nearly $3 billion a year for farmers.  In addition, the loosening of the topsoil increases runoff of sediment and nutrients into nearly waterways, worsening water quality.

Previous studies have shown that no-till farming practices can have a significant impact on reducing erosion.  A study published last November found that if farmers shifted entirely to no-till practices, it would reduce soil erosion from U.S. agricultural fields by more than 70%, as well as significantly reducing nutrient and sediment runoff. 

No-till farming is the practice of planting crops without tilling the soil.  Instead, seeds are planted through the remains of previous crops by planters or drills that cut seed furrows, place the seeds, and close the furrow.  Currently less than 15% of farmland in the upper Mississippi River watershed is farmed with no-till practices. 

Even partial changes in tilling practices could produce positive results for topsoil retention and for waterways.

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One-Third of Farmland in the U.S. Corn Belt Has Lost Its Topsoil

Photo, posted September 15, 2010, courtesy of the United Soybean Board / Soybean Checkoff via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Rivers Changing Color | Earth Wise

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A recent study, published in Geophysical Research Letters, found that one-third of large American rivers have had significant changes of color over the past 30 years.  Rivers can appear to be shades of blue, green, and yellow and we tend to expect healthy rivers to have colors in shades of blue.  According to the new study, only 6% of American rivers are dominantly blue.

The study looked at 235,000 Landsat images taken from 1984 to 2018.  The results are that 56% of rivers studied were dominantly yellow, 38% dominantly green, and 6% blue.  Over the 34 years studied, 33% of the rivers had significant changes in color. About 21% became greener and 12% more yellow. 

The chief causes of color changes in rivers are farm fertilizer runoff, dams, efforts to fight soil erosion, and climate change.  Climate change increases water temperature and rain-related runoff.

Color changes are not necessarily a sign of poor river health, but dramatic changes could point to issues that need attention.  A river can change color based on the amount of sediment, algae, or dissolved organic carbon in the water.   If a river becomes greener, it can often mean large algae blooms are present that cause oxygen loss and can produce toxins.  On the other hand, rivers that are getting less yellow demonstrate the success of regulations to prevent soil erosion.

The study of river colors can pinpoint which rivers are undergoing rapid environmental change.  What the study does not provide is information on water quality.  Water quality measurements will be important to determine the health of many of the rapidly changing rivers.

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One Third of U.S. Rivers Changed Their Color, Three Decades of Satellite Images Show

Photo, posted July 6, 2016, courtesy of Jeffrey Beall via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Restoring Seagrass In Virginia | Earth Wise

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Seagrass is found in shallow waters in many parts of the world.  They are plants with roots, stems, and leaves, and produce flowers and seeds.  They can form dense underwater meadows that constitute some of the most productive ecosystems in the world.  Seagrasses provide shelter and food to a diverse community of animals including tiny invertebrates, fish, crabs, turtles, marine mammals and birds.

In the late 1920s, a pathogen began killing seagrasses off the coast of Virginia.  In 1933, a hurricane finished them off completely.  For nearly 70 years thereafter, the bay bottoms of the Virginia coast were muddy and barren, essentially devoid of fish, shellfish, mollusks and other creatures that inhabit seagrass meadows.  The local scallop industry was no more.

The largest seagrass restoration project ever attempted has changed all that.  During the past 21 years, scientists and volunteers have spread more than 70 million eelgrass seeds within four previously barren seaside lagoons.  This has spurred a natural propagation of meadows that have so for grown to almost 9,000 acres, the largest eelgrass habitat between North Carolina and Long Island Sound.

The long-term research conducted by the team from the University of Virginia shows that the success of the seagrass restoration project is improving water quality, substantially increasing the abundance of fish and shellfish in the bays, and capturing carbon from the water and atmosphere and storing it in the extensive root systems of the grasses and in the sediment below. 

The study shows that marine restorations are possible on scales that contribute directly to human well-being.

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Some Good News: Seagrass Restored to Eastern Shore Bays is Flourishing

Photo, posted May 17, 2019, courtesy of Virginia Sea Grant via Flickr. Photo credit: Aileen Devlin | Virginia Sea Grant.

Earth Wise is a production of WAMC Northeast Public Radio.

Mangrove Trees And Climate Change | Earth Wise

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Mangrove trees are small trees that grow in coastal saline or brackish water at tropical and subtropical latitudes.  Many mangrove trees can be identified by their dense tangle of prop roots.  These roots make the trees appear as if they are standing on stilts above the water.  The tangle of roots allows mangrove trees to handle the daily rise and fall of tides and to slow the movement of tidal waters.  

Mangrove forests provide many ecosystem services, including stabilizing the coastline by reducing erosion from storm surges, waves, and tides.  The intricate root system of mangrove trees are attractive to fish and other species seeking food and shelter from predators.  Mangrove forests also store large amounts of carbon.     

But according to a new study recently published in the journal Science, mangrove trees won’t survive sea level rise by 2050 if greenhouse gas emissions aren’t reduced.  

Using sediment data from 78 locations over the last 10,000 years, an international team of scientists led by Macquarie University in Australia estimated the chances of mangrove trees survival based on the projected rates of future sea-level rise.

When sea level rise rates exceeded 6 millimeters per year, which is similar to estimates under high-emissions scenarios for 2050, researchers found that mangrove trees were unlikely to keep pace with the rising water levels.  But when the annual increase was 5 millimeters or less – which is the projected low-emissions scenario this century – mangrove trees are much more likely to survive. 

These findings underscore the importance of reducing greenhouse gas emissions to mitigate rapid sea level rise.  The future of mangrove trees may depend on it.  

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Mangrove trees won’t survive sea-level rise by 2050 if emissions aren’t cut

Photo, posted December 17, 2012, courtesy of Edward Stojakovic via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Ocean Acidification And Mass Extinction

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Since the industrial revolution, the concentration of carbon dioxide in the atmosphere has increased due to the burning of fossil fuels and land use changes.  The ocean absorbs about 30% of the CO2 that is released in the atmosphere.  As the levels of atmospheric CO2 increase, so do the levels in the ocean.

When CO2 is absorbed by the ocean, a series of chemical reactions occur, resulting in seawater becoming more acidic.  Ocean acidification threatens calcifying organisms, such as clams and corals, as well as other marine animals, like fish.  When these organisms are at risk, the entire marine ecosystem may also be at risk.

In fact, according to research recently published in the journal Proceedings of the National Academy of Sciences, fossil evidence from 66 million years ago has revealed that ocean acidification can cause the mass extinction of marine life.  Researchers analyzed seashells in sediment laid down shortly after a giant meteorite hit earth.  This strike wiped out the dinosaurs and 75% of marine species.  Chemical analysis of the shells revealed a sharp drop in the PH of the ocean over hundreds of years after the meteorite strike.  The meteorite impact vaporized rocks, causing carbonic acid and sulphuric acid to rain down, acidifying the ocean.  The strike also resulted in mass die-off of plants on land, increasing atmospheric CO2.  

Researchers found that the pH dropped by 0.25 pH units in the 100 to 1,000 years after the meteorite strike.  Alarmingly, scientists expect the pH of the ocean to drop by 0.4 pH units by 2100 if our carbon emissions continue as projected. 

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Ocean acidification can cause mass extinctions, fossils reveal

Photo, posted March 16, 2017, courtesy of Zachary Martin via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Degraded Permafrost In The Arctic

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Permafrost is defined as rock or soil that has been at or below the freezing point of water for two or more years.  Most of it is located in high latitudes in and around the Arctic and Antarctic regions.   Permafrost covers nearly a quarter of the exposed land in the Northern Hemisphere.

Permafrost can contain many different materials including bedrock, sediment, organic matter, water and ice.  Because of the presence of organic matter, permafrost is potentially the source of significant methane emissions if it thaws and the trapped biomass begins to rot.

A recent study looked at the results of 30 years of aerial surveys and extensive ground mapping of an area of Canada’s high Arctic polar desert known as the Eureka Sound Lowlands.  This area has an extremely cold climate and the permafrost there is over 1/3 of a mile thick.  It has long been assumed that this landscape was stable.

Research led by McGill University in Montreal has found that this is not the case.  The increases in summer air temperatures seen in recent years are initiating widespread changes in the landscape.

A particular landform known as a retrogressive thaw slump that forms when ice within permafrost melts and the land slips down is widely occurring in the area.  The absence of vegetation and layers of organic soil in these polar deserts make permafrost in the area particularly vulnerable to increases in summer air temperatures.

The research indicates that despite the cold polar desert conditions that characterize much of the high Arctic, the interaction between ice-rich permafrost systems and climate factors is complex and the links between global warming and permafrost degradation are not well understood.

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Widespread permafrost degradation seen in high Arctic terrain

Photo, posted August 11, 2018, courtesy of Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Saving Beaches With Seagrass

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Almost a quarter of the Gross Domestic Product of places around the Caribbean Sea is earned from tourism.  Preserving the beaches in the region is an economic imperative.  With increasing coastal development, the natural flow of water and sand is disrupted, natural ecosystems are damaged, and many tropical beaches simply disappear into the sea.

With such high stakes, expensive coastal engineering efforts such as repeated replenishing of sand and the construction of concrete protective walls are common strategies.  Rising sea levels and increasingly powerful storms only increase the threat to tropical beaches.

Researchers from The Netherlands and Mexico recently published a study in the journal BioScience on the effectiveness of seagrass in holding onto sand and sediment along shorelines.

Seagrasses are so-named because most species have long green, grass-like leaves. They are often confused with seaweeds but are actually more closely related to flowering plants seen on land. Seagrasses have roots, stems and leaves, and produce flowers and seeds. Seagrasses can form dense underwater meadows and are one of the most productive ecosystems in the world. Seagrasses provide shelter and food to an incredibly diverse community of animals, from tiny invertebrates to large fish, crabs, turtles, marine mammals and birds.

The researchers performed measurements of the ability of seagrass along Mexico’s Yucatan Peninsula coastline to keep sand in place and prevent erosion.  They found that the amount of erosion was strongly linked to the amount of vegetation.  Quite often, seagrass beds have been regarded as a nuisance, rather than a valuable asset for preserving valuable coastlines.  The study opens opportunities for developing new tropical beach protection schemes in which ecology is integrated into engineering solutions.

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Seagrass Saves Beaches and Money

Photo, posted October 13, 2010, courtesy of NOAA via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

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