Planet Earth Weekly

Climate Change and Renewable Energy: Saving Our Planet for Future Generations


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Climate Change over the last Millennium: The Medieval Warm Period

Global warming

Climate Change in the last 1000 years.

“A great variety of information and data indicate there were major fluctuations in the global climate during the last 1000 years.”

By Dr. John J. Hidore

September 3, 2018—-A great variety of information and data indicate there were major fluctuations in the global climate during the last 1000 years. There were periods when it was warmer than now and others when it was colder. Fluctuating temperatures brought significant changes in the global environment.

The Medieval Warm Period or Little Climatic Optimum

One distinctive climatic period during this time is what is known as the Medieval Warm period or Little Climatic Optimum. The period extended from about 950 to 1250 AD. This time was unusually warm for the millennium and was warmer even by present global temperatures. With the increase in temperature came increased precipitation in many areas. This increased lake levels. The Caspian Sea rose by some 18 meters (59 feet).

The medieval warm period was a global phenomenon. Perhaps the best evidence of this was that sea level rose. This had a widespread impact on the human population at the time. The rise in sea level forced the migration of large numbers of people away from the coast and into areas already occupied. This resulted in clashes between different groups and cultures. There was an expansion of Eskimo cultures around the arctic. Central Asian cultures also expanded into areas they had not previously occupied.

Climate Change

Global Warming over time.

Climate of the Western Arctic Basin

Contemporary literature from Iceland has aided in reconstructing of one of the most complete sequences of the Arctic Basin climate over the last thousand years. There is much data for Iceland from the following sources:

900-1590: information from Icelandic sagas about times of severe weather and related famine.
1591-1780: historical records combined with incomplete drift ice data.
1781-1845: a reconstruction of weather conditions as derived from the relative severity and frequency of drift ice near Iceland.
1846 to present: actual meteorological instruments.

Climate Change

The earth’s overall temperatures are increasing every year.

Iceland and Greenland’s Changing Climate

The Vikings settled Iceland in the ninth century. Evidence of agriculture and other activities indicate the climate that existed at the time. When the Vikings settled Greenland, it was quite warm, as Eric the Red discovered in Greenland in 982 A.D. In 984 A.D. the Norse founded the colony of Osterbygd on Greenland. While an icy land, it supported enough vegetation (dwarf willow, birch, bush berries, pasture land) for settlement.

The settlers brought cattle and sheep that not only survived but thrived for a considerable period. They established two colonies and began to farm. The outposts thrived and regular communications existed with Iceland. Between 1250 and 1450 AD climate deteriorated over wide areas. Iceland’s population declined. Grains that grew there in the tenth century would no longer grow. Greenland became isolated from outside contact. Extensive drift ice prevented ships from reaching the settlements.

Global Greenhouse Gases

Climate Change

Europe’s Changing Climate

In Europe storminess resulted in the formation of the Zuider Zee and the excessively wet, damp conditions led to a high incidence of the disease St. Anthony’s Fire (ergotism.). Chronicles contain many references to weather conditions of the time, including the Arctic Basin. William of Malmsbury, writing in 1125 about the Gloucester region of England stated “the area exhibits a greater number of vineyards than any other county in England, yielding abundant crops of superior quality….they may also bear comparison with the growths of France.” What is significant about this statement is that by the fifteenth century there was no wine industry in England. The most probable reason is a cooling of the climate since the twelfth century.

Climate Changed in the Interior of North America

There is ample evidence that the warmer conditions affected continental areas as well. Research shows that Indians in the Great Plains of the United States migrated as a result of changes in precipitation. A study by archaeologists and climatologists show for example, that Indians of the Mill Creek culture of Iowa deserted a thriving community about 1200 A.D. Precipitation declined rapidly at the time.

The abandonment of settlements in the southwest United States probably was due to drought. The historic settlements of Chaco Canyon and Mesa Verde indicate that they supported large and prosperous communities. By 1300 A.D., these settlements were deserted.

Reasons other than drought certainly may account for the abandonment. However, tree-ring analysis shows that between 1276 A.D. and 1299 A.D, practically no rain fell in these areas.

Climate Change

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The Arctic Basin: Warming Faster than the Planet in its Entirety

Arctic Ocean

Melting of the Arctic Sea Ice

“The arctic basin is warming faster than most of the earth’s surface.”

By Dr. John J. Hidore
June 8, 2018—–The Arctic Basin consists of the Arctic Sea and the surrounding land. The climate of the basin is warming faster than any other area of Earth’s surface. Air temperature over the arctic has increased an average of nearly three degrees Celsius (five degrees Fahrenheit) over the last century. This is almost double that of the global average.

The Energy Exchange in Change of State Between Ice and Water

One very important feature of the energy balance distinguishes the Arctic Basin. Over 95% of the earth’s surface, the major change in the state of water in the environment is between liquid and gas. This entails evaporation and condensation. In the Arctic it is between solid and liquid. There is an energy exchange of about 80 calories per gram between solid and liquid. For the rest of the earth the energy exchange is much higher. The energy exchange between liquid and gas is 590 calories per gram. This is nearly seven times that of ice and water.

The implication of this is that melting or freezing takes place with relative small changes in heat added or heat lost in the environment!

The energy exchange in melting artic

Melting of the Arctic

Energy Exchange in the Tundra

Surrounding the Arctic sea is a grassland, generally known as the tundra. Such a grassland is found primarily only in the Northern Hemisphere. The southern margin of the tundra is delimited by the polar margin of a coniferous forest. Specific regions that contain tundra are the northern coast of North America, Iceland, Spitsbergen, coastal Greenland, and the Arctic borderlands of Eurasia.

A significant feature of the tundra is permafrost. Permafrost is permanently frozen ground. Extensive area of land in the basin are covered with it. Permafrost can vary from centimeters to many meters thick.

Ice and snow are highly reflective of solar radiation. However, in the summer months some of the solar radiation melts the permafrost. The surface layer of permafrost thaws leaving the deeper layer frozen. The result is that lakes and ponds are a characteristic of the tundra. Once the permafrost melts at the surface, the wet ground absorbs much more radiation and the thawing increases. However, except on the margins of the permafrost, there remains frozen ground beneath the surface.

How deep the permafrost melts will vary. The point is that once the surface thaws the solar energy that is absorbed goes up substantially. This in turn increases the rate of the thawing of the permafrost. As the earth’s atmosphere slowly warms this process is being accelerated.

climate change

The exchange of energy is causing rapid arctic melting.

Energy Exchange in the Arctic Sea

The Arctic Sea is a part of the world ocean that is frozen much of the year but increasingly is open during the summer months. The season when melting occurs has increased by three weeks since records began. At present, even in the summer, there is a large area that remains frozen. As the atmosphere slowly warms more of the ice cover melts. Open water absorbs much more radiation than the ice and this increases the temperature of the water which then increases melting of the ice. As a result, over recent decades, the sea ice has been thinning or melting entirely over large areas. Just as on land the conversion from sea ice to open water is increasing at an increasing rate.

Climate change

The rapidly melting artic

In summary, the arctic basin is warming faster than most of the earth’s surface. Part of the explanation lies in the fact that the amount of energy it takes to change the state of water between solid and liquid is much less than it takes to change the state between liquid to gas. There is thus a net gain in heat that is proportionately higher than that of the rest of the planet. As the summer season increases in length more heat is absorbed in the environment adding to the general global warming!

Warming of the Arctic


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The Warming of Planet Earth Varies from Place to Place

Melting of the Arctic

The Arctic sea ice is melting at a record rate.

“The Arctic Region is the Most Rapidly Warming Region in the Northern Hemisphere.”

By Dr. John J. Hidore

April 10, 2018—–There is no doubt that Planet Earth is warming relatively fast! Data supports this allegation. The data supporting global warming include biological, geological, hydrological and climatological. 

The year 1880 has been established as the beginning of a period of accelerated warming due to the increased use of fossil fuels and a growing population. From 1880 to 1979, the global temperature increased 0.1°F (0.05ºC) above the pre-industrial average. By 2016 the global temperature had climbed 1.4°F(0.6ºC).

Land and Sea Warm at Different Rates

The warming of our planet is not the same from place to place over the surface. With the possible exception of Antarctica, the continents are warming faster than the oceans. The main reason is the difference in specific heat between land and ocean. The specific heat of a substance is the amount of energy it takes to raise the temperature of one gram of the substance 1°C (1.8ºF). The specific heat of water is used as the base for measuring specific heat and has a value of 1.0. The specific heat for some other substances are ice=0.5, air=0.24, and sand=0.19.

The significance in the difference in specific heat is that a given unit of energy will raise the temperature of earth materials about five times as much as a unit of water. Thus, land surfaces warm faster than water when an equal amount of energy is added.

Glacier National Park

Global warming is causing disappearing glaciers.

Northern Hemisphere is Warming Faster Than the Southern

Climate normals are periods of 30 years that move forward every 10 years. The current normal being used is that of the period 1980-2010.When compared to the 30 year global average for the period 1980-2010, the northern hemisphere is warming faster than the average for the earth as a whole. It is also warming faster than the southern hemisphere. The Northern Hemisphere temperature increased more than two degrees Fahrenheit. The reason the Northern Hemisphere is warming faster than the southern Hemisphere is due to the fact that most of the earth’s land mass is in the Northern Hemisphere.

Disease and melting ice caps

Consequences of Global Warming

The Arctic Region is Rapidly Warming

The Arctic is the coldest region in the Northern Hemisphere. The region consists of the sea surrounding the North Pole and land that rings the sea. The arctic is warming faster than mid-latitude or tropical regions. It is warming more than twice as fast as the average for the earth. The reason for this is that as ice and snow melt on the fringes of the arctic the ratio between reflection and absorption of solar energy changes drastically.

In the winter the sea is covered by a veneer of ice and the surrounding land is generally covered by snow. With the onset of summer, the increased solar radiation results in the melting of ice and snow melting off the land. The more snow and ice that melts, the faster the arctic warms. This change results in what is known as a positive feedback mechanism. More and more energy is absorbed rather than reflected or used to melt the ice. As the melting season lengthens the land and atmosphere above it warm faster than areas further south.

While the Arctic is still the coldest region in the Northern Hemisphere, it is warming more rapidly than other areas!

Global Warming

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Why Coastal Cities Must Build Sustainably

Soft shoreline vs. Hardshoreline

Soft shorelines create spaces for the water to go.

Obama Presidential Adviser, John Holdren, said of the challenge of climate change, “We will end up with a mix of prevention, adaptation and suffering. It is for us to determine the ratio.”

By Linn Smith

September 18, 2017 ——With the recent flooding in Texas and Florida, it is evident that the rising seas from climate change will affect us by chronic flooding, which will become more frequent. There will be continued flooding and devastation from weather as our climate and seas warm up.
The Union of Concerned Scientists ask the question, “If flooding continues, how many times does it have to happen before you stop thinking of rebuilding and start thinking of relocation? Each community has a threshold for sea level rise and chronic flooding beyond which sustaining normal routines becomes impossible.”

climate change

Mitigation Vs. Prevention

Mitigation or Prevention

Scientist have worried for years that melting sea ice and ocean warming would cause a rise in sea levels, extreme weather and more severe and frequent hurricanes. What is our government’s responsibility? Do we continue to spend our tax dollars on mitigation, cleaning up the aftermath of the increasingly destructive power of storms? Do we continue to rebuild coastal areas that are vulnerable to climate change or do we have a responsibility to reconstruct cities and coastal areas against the coming vulnerability of our changing climate?

William V. Sweet, Scientist with the National Oceanic and Atmospheric Administration stated, “Once impacts become noticeable, heavy rains and extensive flooding are going to be upon us quickly. It’s not 100 years off anymore.” Higher seas mean higher storm surges. As seas rise in an area, the coastal creeks and marshes will rise and bring salt water inland. Many coastal trees will be affected by the saltwater rise.

Storm Surges

Protection from Storm Surges

Reducing the Impact of Rising Seas

What are our choices? Keep spending tax dollars on rebuilding coastal properties or rebuild naturally to reduce the impact of rising seas. A soft shoreline maintains the natural dynamics of the shoreline, with a healthy movement of the sand and improving habitats of sea life. It allows the coastline to do what it does naturally, without the build-up of asphalt and man-made dwellings. A living coastline has natural barriers, vegetation and salt marshes that make it a stronger buffer, against flooding, but also moves and changes as any undeveloped shoreline would.

Obama Presidential Adviser, John Holdren, said of the challenge of climate change, “We will end up with a mix of prevention, adaptation and suffering. It is for us to determine the ration.” There are consequences of inaction!

Hard Structures vs. Soft Defenses Against Wave Energy

What we’ve done with much of our coastal lines to deter flooding is to construct impervious surfaces and blockages to dissipate the wave energy. But there are natural designs that absorb water from storms and channel it back into nature, creating spaces that navagate the water naturally.
The current method of deterring sea wave energy are hard structures. Hard structures, such as sea walls, deflect the wave energy to adjacent areas, redirecting the wave to a neighboring property. These properties witness a greater destructive energy than the original destination of the wave. Walls can fail and waves can erode sand at the base of the seawalls. Walls can also be destructive to the surrounding flora and fauna, which may be preventing a more serious flooding disaster. Hard structures won’t save our cities from rising seas!

The better approach according to Rachel Gittman, Ecologist, is to create living shorelines. A living shoreline is site specific according to the natural habitat of the location. She states that for calmer waters, build water absorbing marshes with sill-like ledges made of rocks, oyster shells or coconut fiber logs. A shoreline may also benefit from planting mangroves, which firmly anchor the shoreline in place.

Rising Seas

Cities affected by the rising waters.

Natural Barriers of Wave Energy

Steven Scyphers, Coastal Scientist, states, “It starts with a good understanding of what the natural conditions along the shoreline once were. It could mean restoring what existed on the shore, whether oyster reefs, coral reefs or other living breakers that can dissipate the wave energy. These natural barriers become more suitable over time as the plants, roots and reefs grow.”

By 2100, 490 communities could be chronically flooded including Boston, L.A. and most of NYC. Communities will have to decide what will be best for them, flood walls, living shorelines, elevating structures or to retreat. Cities that are below sea level probably won’t be benefited from natural shorelines.

In the meantime we need to change our behaviors to slow down climate change!

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From Global Warming to Global Environmental Change

Global Greenhouse Gases

Climate Change

There will always be those that deny that humans have any effect on the earth’s environment. But the evidence is in! It is time to focus not on whether we are altering the global system but how we can best slow the rate of changes.

By John J. Hidore
June 2, 2015–More than 100 years ago (1896) Svante Arrenius, a Nobel Laureate, made a study of the relationship between carbon dioxide and global temperatures. He concluded that the burning of fossil fuels could result in increasing temperatures.

In the 1930’s, a meteorologist named G.S Callendar, examined the temperature data from around the world and determined atmospheric temperatures were increasing. He also believed that the use of fossil fuels would lead to a warmer planet. In the 1950’s Charles Keating and Roger Revelle demonstrated that a large part of the carbon dioxide emissions from burning fossil fuels was accumulating in the atmosphere.

Rising Temperatures

About this time global temperature measurements began to show a slow and erratic increase. Over time the increase became well documented and the rising temperatures began to alter many natural processes on Earth. In the past several decades the concentration of carbon dioxide and other greenhouse gases has accelerated.

Global Warming

Global Warming and Declining Sea Ice

The Koyoto conference

In 1997 in Koyoto, Japan, an international conference on what was then being called global warming was convened. Many nations were represented at the Koyoto conference indicating a global awareness of the problem related to the additional greenhouse gases in our atmosphere. But–the largest contingent at the conference was that of energy corporations. They lobbied with the premise that global warming was a natural event and human activity had nothing to do with global warming. These deniers nearly prevailed! Only the efforts of then Senator Al Gore and a few others bought about a plan to reduce the greenhouse gases. Many nations set goals for reducing their contributions of carbon dioxide.

Working toward 100% renewables

Working Toward Renewable Energy

Global Warming vs. Climate Change

The reference to the process of global warming gradually was replaced by the phrase climate change. Climate change does not imply any hazard, just change! In one sense, the phrase “climate change” is more benign than global warming. Global warming has a more definite connotation of a threat than does climate change. However, implicit in climate change is the fact that there is more involved in change in the atmosphere than just temperature.

Climate consists of all different kinds of weather that occur in any area. It includes average temperatures, and seasonal changes. Climate also includes extremes that may occur in terms of temperature and precipitation. Temperature extremes may include extreme heat or cold. Climate also includes extreme precipitation and propensity to drought. Thus, climate change implies there are many more changes taking place in the atmosphere other than just temperature. The result of massive data collection around the earth documents both global warming and climate change.

Climate Change and the Effect on Regional Systems

It has now become apparent that the changes in climate, that are currently taking place, effect all aspects of the environment. Every region is made up of the atmospheric conditions, the flora and fauna, the water supply, and the land surface itself. Climate change is altering many regional systems such as the tropical rainforests, the grasslands, and even the world deserts.

Walruses need Sea ice

Walruses Cling to Melting Sea Ice.

The Effect of Ocean Temperature on Planet Temperatures

The Arctic basin is a good example. Not only has the region warmed but the Arctic Sea has changed from being largely frozen summer and winter to more and more ice free in the summer. This has greatly altered the lives of most inhabitants of the region. Perhaps most significant are the changes in the world ocean. The world ocean covers the majority of Earth’s surface and it is warming and becoming more acidic. These ocean temperatures determine the average air temperature of the planet! The height of the ocean is also rising, reducing the amount of land surface.

This connectedness in earth’s regional systems has resulted in the coining of the term “Gaia”. The term implies that the earth is a living, ever changing system. The concept of it being a living system has been questioned. However, it is well established that when a region of our planet experiences change in some aspect of the environment, it results in changes in the entire system.

Global Environmental Change

What began as the discovery of global rising temperatures has now morphed into a much broader and more inclusive recognition of 21st Century global environmental change. Human activity no effects the entire planet from pole to pole. The most important question of our time this: How much longer can we continue on the present path before the global system can no longer function in a manner that has supported life on the planet for millions of years. All indications point to the fact that time is running for making major changes in world policies.

There will always be those that deny that humans have any effect on the earth’s environment. But the evidence is in! It is time to focus not on whether we are altering the global system but how we can best slow the rate of changes.

Climate Change: Altering Our Global System


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Climate Change Threatens Polar Bears

Polar bears and declining sea ice.

Reduction of sea has made it difficult for polar bears to find food.

While the reduction in sea ice has created economic benefits for some, it has caused serious problems for many species of animals.

By Dr. John J. Hidore

March 1, 2015—In the Arctic Sea, summer sea ice has been retreating from the shore rapidly in the past few decades. In the last few years, the ice has retreated far enough from shore, and thinned enough that the Northwest Passage is open for commercial shipping. This has resulted in considerable economic benefit for the shipping industry—but at the expense of wildlife in the region!

Polar Bears Use the Sea Ice as a Base to Hunt Food

While the reduction in sea ice has created economic benefits for some, it has caused serious problems for many species of animals—one being the polar bear. Polar bears live on the sea ice much of the year and use the sea ice as a base from which to hunt for food. Climate change has caused the ice to retreat further from the coast, making it more difficult for the animals to swim to the ice and back. The Polar bear needs food that is high in fat—and seals provide such a food. However, the population of seals, which is the primary food for polar bears, is declining because the fish population, on which the seals depend, is also declining because of the change in water temperature.

Polar bears and declining sea ice.

Polar bear cubs are decreasing because of lack of food.

Extinction of the Polar Bear

Polar bears are found across the boundary between the southern limits of sea ice and the northern hemisphere land mass. This area includes Russia, Norway, Greenland, Canada, and the United States. There are more than 15 different groups of polar bear scattered around the arctic sea, and the population numbers for many of these groups is not known, but the total number of bears found in these regions is believed to be declining. Total numbers may be as many as 25,000. The International Union for the Conservation of Nature has listed the polar bear as vulnerable.

Polar Bears of the Beaufort Sea

Three-fourths of the global polar bear population is found in North America. Polar bears of the Beaufort Sea, which is the southern boundary for the bear, have decreased by 40% since the beginning of the 21st Century. Since the southern areas are warming faster and the sea ice is retreating further from shore, it is here that the problem for the polar bear is the worst. The number of Polar bears living in the southern Beaufort Sea dropped from an estimated 1500 in 2001, to only 900 in 2010. In a four year period, from 2003 to 2007, scientists tagged 80 cubs of which only two survived.

Sea Ice: Too Thin and Too Far from Land

Two-thirds of the Northern Alaskan female polar bears are being forced to make their dens on land rather than on the sea ice, which is their normal location. The sea ice has become too thin and too far from land in the winter. The female polar bear has been documented as swimming more than 300 miles from ice to land and many do not survive the long swim. If the Arctic ice continues melting far from shore, it may drive the polar bear to extinction. Projections show that the population could decline by more than 30 percent by 2050. In May of 2006, the World Conservation Union declared the species to have a high risk of extinction in the wild. Worst case scenarios forecast the global population to drop by 2/3 by 2060.

Hudson Bay also harbors a group of bear which is declining. Canadian scientists in 2013 estimated this population was down 25% since 1988. Data indicates the weight of the female polar bear here has dropped approximately 88 pounds and the number of cubs are decreasing and becoming smaller. The western Hudson Bay is now freezing later in the season and melting approximately three week earlier than several decades ago. This has reduced the bear’s hunting season on the ice by several weeks. The critical period for hunting is in the spring when the females are giving birth. Over the hunting season the bears are adding less fat to get them through the winter. Due to increasing malnutrition the group could become extinct by 2050.

Survival of the Polar Bear

Whether the polar bear can survive on food found on land is doubtful. Existing food found along the Arctic coast is not enough to sustain the animals. As an alternate source of marine food, some bears have attached themselves to walrus herds. While they do not attack adult walrus, they may capture their young. Some polar bears are beginning to scavenger the carcasses of dead bear and whales for food.

In 2008, the U.S. listed the polar bear as threatened under the Endangered Species Act.


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Declining Sea Ice Threatens Walruses

Walruses need Sea ice

Walruses Cling to Melting Sea Ice.

By Dr. John J. Hidore

The Rising Temperatures of the Arctic

February 22, 2014—World temperatures are warming at a record rate and the global climate is changing rapidly due to rising temperatures of our planet. Though the planet is warming, the rate at which it is warming is inconsistent from place to place. Temperature changes in the Arctic are taking place faster than anywhere else on the planet. The warming is affecting both the physical and biological character in this region. The most widely known affect is the melting of sea ice. The melting of the sea ice is significant, but the melting has many side effects.

Climate Change and the Walrus

The changing arctic climate has started to change much of the arctic wildlife. Among the species affected is the walrus. Walruses are large marine mammals that may weigh up to 2700 lbs or more. They spend nearly two-thirds of their lives in cold water. A walrus carries large tusks which are used to root out food living on the ocean floor. The tusks are also used to help move around on the slippery ocean floor. Off shore of the land masses surrounding the Arctic Ocean. the ocean floor drops slowly on what is generally referred to as the continental shelf. Beyond the edge of the continental shelf the depth to the ocean floor drops to several thousand feet in places. Walruses mainly feed on the continental shelf in water less than 300 feet deep. They will, however, feed as deep as 600 feet.

Declining Sea Ice

Sea ice plays a critical part in the lives of the walrus. Walruses cannot swim indefinitely like some seals, and must rest between forays searching for prey. They use sea ice as a platform for searching for food and as a place to rest during their annual migration. Females also use the sea ice during the summer as a place to give birth and nurse their infants. When the walruses are on the sea ice they tend to spread out over large areas. In late summer they migrate to warmer waters. In the past they tended to move onto land in late August during their migration. There are two species of walrus in the arctic. One is the Pacific walrus which inhabits the Bering, Chukchi, and Laptev seas. The other is the Atlantic walrus which is found along northeastern Canada and Greenland.

The Arctic region is now the warmest it has been in 40,000 years. The sea ice has melted to record lows. This has limited the area where walrus can haul out on the ice if it melts too far from land. When the sea ice retreats beyond the edge of the continental shelf and over deeper water, instead of hauling out onto the ice, the walruses head for land and congregate.

Walruses: Herding On Land

Huge gatherings of Pacific walrus have taken place in the last decade. In 2007, an estimated 6,000 walruses gathered along the Alaskan coast. In the fall of 2008, few walruses came on shore as some sea ice remained near shore. In September of 2009, some 3,500 Walruses were near Icy Cape on the Chuckchi Sea 140 miles southwest of Barrow. In 2011, some 30,000 congregated on a beach about a mile long. Large numbers of walruses have also been seen on shore at Cape Lisbourne. Large congregations have occurred in the years since. The same phenomenon is taking place on the Arctic coast of Russia near the Chukchi sea. Herds of tens of thousands were gathering on this coast. Near Point Schmidt, a herd of some 40,000 was sighted. The total population of Pacific walrus is not known, but estimates place it at about 200,000.

The large herds on land are a threat to the walruses. The threat comes from several sources. One is that they tend to stampede when some unusual event startles them. Individuals are often killed during the stampede. Russian biologists reported several thousand, mostly young, were crushed to death in one stampede. For example, noise from hunting weapons and polar bear attacks can cause a stampede. Pilots of small, low flying aircraft are being warned to stay away from the herds as the noise can cause them to stampede. Large gatherings in a limited space also are more favorable for the outbreak of disease. The concentration of such large numbers also has a severe effect on the clam population offshore from the herds. This extensive harvesting may result in an unsustainable population of their food supply.

The decline of sea ice and the changing environment are not only a threat to the walrus population but serve as further evidence of a warming planet. Biologists are asking for the walrus to be declared an endangered species since the outcome of declining sea ice on the species is not yet clear.