Arctic ecology
Encyclopedia
Arctic ecology
is the scientific study of the relationships between biotic
and abiotic factors in the arctic
, the region north of the Arctic Circle
(66 33’). This is a region characterized by stressful conditions as a result of extreme cold, low precipitation, a limited growing season (50–90 days) and virtually no sunlight throughout the winter. The Arctic consists of taiga
(or boreal forest) and tundra
biomes, which also dominate very high elevations, even in the tropics. Sensitive ecosystems exist throughout the Arctic region, which are being impacted dramatically by global warming
.
Sea ice
is frozen seawater that moves with oceanic currents; it provides important habitat and a resting place for animals, particularly during the winter months. Over time, small pockets of salty seawater get trapped in the ice, and the salt is squeezed out. This causes the ice to become progressively less salty. Sea ice persists throughout the year, but there is less ice available during summer months.
Large portions of the land are also frozen during the year. Permafrost
is substrate that has been frozen for a minimum of 2 years. There are two types of permafrost: discontinuous and continuous. Discontinuous permafrost is found in areas where the mean annual air temperature is only slightly below freezing (0 °C (32 °F)); this forms in sheltered locations. In areas where the mean annual soil surface temperature is below -5 °C, continuous permafrost forms. This is not limited to sheltered areas and ranges from a few inches below the surface to over 300 m (984.3 ft) deep. The top layer is called the active layer
. It thaws in the summer and is critical to plant life.
and boreal forests. The water in this region is generally frozen and evaporation
rates are very low. Species diversity, nutrient
availability, precipitation, and average temperatures increase as you move from the tundra to boreal forests and then to deciduous
temperate
ecosystems, which are found south of these Arctic biomes.
and supports larger species diversity
, an increase in canopy height, vegetation density, and biomass
. Boreal conditions can be found across northern North America and Eurasia. The boreal forests in the interior of the continents grow on top of permafrost due to very cold winters (see drunken trees
), while much of the boreal forest has patchy permafrost or lack permafrost completely. The short (3–4 month) growing season in boreal forests is sustained by greater levels of rainfall (between 30 and 85 cm (11.8 and 33.5 in) per year) than the tundra receives; This biome is dominated by closed canopy forests of evergreen conifers, especially spruces, fir, pine and tamarack with some diffuse-porous hardwoods. Shrubs, herbs, ferns, mosses, and lichens are also important species. Stand-replacing crown fires are very important to this biome, occurring as frequently as every 50–100 years in some parts.
, or the adjustment to new conditions, appears to be the most common form of adaptation to cold environments. No genetic advantage has been found when different people groups or races are compared. There is no evidence that fat is grown in response to cold, although its presence is advantageous. Amazingly, most people living in the Arctic region live a lifestyle very connected to the environment, spending significant time outside and depending heavily on hunting and fishing.
and caribou. Many of the animals in the Arctic are larger than their temperate counterparts (Bergmann’s rule), taking advantage of the smaller ratio of surface area to volume that comes with increasing size. This increases the ability to conserve heat. Layers of fat, plumage, and fur are also very effective insulators to help retain warmth and are common in Arctic animals including polar bears and marine mammals. Some animals also have digestive adaptations to improve their ability to digest woody plants either with or without the aid of microbial organisms. This is highly advantageous during the winter months when most soft vegetation is beneath the snow pack.
Not all Arctic animals directly face the rigors of winter. Many migrate to warmer climates at lower latitudes, while others avoid the difficulties of winter by hibernating
until spring. Although these options might seem to be easy solutions to the diffictulties of surviving an extreme environment, both are very expensive in terms of energy and risk of predation.
, water is able to remain in its liquid state down to -38 °C (compared to its usual 0 °C (32 °F) freezing point). After water reaches -38 °C, it spontaneously freezes and plant tissue is destroyed. This is called the nucleation point. The nucleation point can be lowered if dissolved solute
s are present.
If a plant has taken the tolerance route, it has several different ways to tolerate freezing. Some plants allow freezing by allowing extracellular
, but not intracellular
freezing. Plants let water freeze in extracellular spaces, which creates a high vapor deficit that pulls water vapor out of the cell. This process dehydrates the cell and allows it to survive temperatures well below -38 °C.
Another problem associated with extreme cold is cavitation. Ring-porous wood is susceptible to cavitation
because the large pores that are used for water transport easily freeze. Cavitation
is much less of problem in trees with ring-diffuse wood. In ring-diffuse wood, there is a reduced risk of cavitation, as transport pores are smaller. The trade-off is that these species are not able to transport water as efficiently.
First, thermohaline circulation
is a series of underwater oceanic currents fueled by the salinity and temperature of seawater. Melting ice sheets would introduce vast amounts of fresh water into the North Atlantic, causing a change in density which could disrupt the currents. If this circulation slowed or stopped, the climates of northern Europe and North America would be strongly impacted.
Second, the melting of glaciers and sea ice is disrupting the lifestyles of a wide range of species. Polar bear
s live on the sea ice for much of the year and find their food in the surrounding ocean waters. Recent projections suggest that global warming will lead to the disappearance of most summer sea ice within 40 years.
A third practical concern is the melting of permafrost due to climate change. Degradation of this permafrost is leading to major ground surface subsidence and pounding. The ground is literally melting away in many regions of the Arctic. The locations of towns and communities that have been inhabited for centuries are now in jeopardy. A condition known as drunken tree syndrome is being caused by this melting. Ground water and river runoffs are being negatively impacted as well. Although warming conditions might increase CO2 uptake for photosynthetic organisms in some places, scientists are concerned that melting permafrost will also release large amounts of carbon locked in permafrost.
Finally, the impacts of the release of carbon from the permafrost could be amplified by high levels of deforestation
in the Boreal forests in Eurasia and Canada. This biome currently serves as a large carbon sink, sequestering large amounts of carbon dioxide. However, over half of the original forest has been or in danger of harvesting, largely for export. Carbon Dioxide is a greenhouse gas, which facilitates increased warming of the earth.
appeared in the bibliography, the Arctic and Antarctic Polar regions were found to be still unexplored. In addition, the North Pacific Ocean (Pacific Northeast and Pacific Northwest), still has few citations in comparison to its large size. This limits our perception of the world’s aquatic biodiversity. Consequently we do not have sufficient information about biodiversity in most places on earth. Even though biodiversity declines from the equator to the poles in terrestrial ecosystems, this is still a hypothesis to be tested in aquatic and especially marine ecosystems where causes of this phenomenon are unclear. In addition, particularly in marine ecosystems, there are several well stated cases where diversity in higher latitudes actually increases (Moustakas & Karakassis 2005). Therefore, the lack of information on biodiversity of Arctic Regions prevents scientific conclusions on the distribution of the world’s aquatic biodiversity.
Life in the Cold
Ecology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...
is the scientific study of the relationships between biotic
Biotic component
Biotic components are the living things that shape an ecosystem. A biotic factor is any living component that affects another organism, including animals that consume the organism in question, and the living food that the organism consumes. Each biotic factor needs energy to do work and food for...
and abiotic factors in the arctic
Arctic
The Arctic is a region located at the northern-most part of the Earth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia, Greenland, the United States, Norway, Sweden, Finland, and Iceland. The Arctic region consists of a vast, ice-covered ocean, surrounded by treeless permafrost...
, the region north of the Arctic Circle
Arctic Circle
The Arctic Circle is one of the five major circles of latitude that mark maps of the Earth. For Epoch 2011, it is the parallel of latitude that runs north of the Equator....
(66 33’). This is a region characterized by stressful conditions as a result of extreme cold, low precipitation, a limited growing season (50–90 days) and virtually no sunlight throughout the winter. The Arctic consists of taiga
Taiga
Taiga , also known as the boreal forest, is a biome characterized by coniferous forests.Taiga is the world's largest terrestrial biome. In North America it covers most of inland Canada and Alaska as well as parts of the extreme northern continental United States and is known as the Northwoods...
(or boreal forest) and tundra
Tundra
In physical geography, tundra is a biome where the tree growth is hindered by low temperatures and short growing seasons. The term tundra comes through Russian тундра from the Kildin Sami word tūndâr "uplands," "treeless mountain tract." There are three types of tundra: Arctic tundra, alpine...
biomes, which also dominate very high elevations, even in the tropics. Sensitive ecosystems exist throughout the Arctic region, which are being impacted dramatically by global warming
Global warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...
.
Arctic environment
To understand Arctic ecology, it is important to consider both the terrestrial and oceanic aspects of the region. A few important parts of this environment are sea ice and permafrost.Sea ice
Sea ice
Sea ice is largely formed from seawater that freezes. Because the oceans consist of saltwater, this occurs below the freezing point of pure water, at about -1.8 °C ....
is frozen seawater that moves with oceanic currents; it provides important habitat and a resting place for animals, particularly during the winter months. Over time, small pockets of salty seawater get trapped in the ice, and the salt is squeezed out. This causes the ice to become progressively less salty. Sea ice persists throughout the year, but there is less ice available during summer months.
Large portions of the land are also frozen during the year. Permafrost
Permafrost
In geology, permafrost, cryotic soil or permafrost soil is soil at or below the freezing point of water for two or more years. Ice is not always present, as may be in the case of nonporous bedrock, but it frequently occurs and it may be in amounts exceeding the potential hydraulic saturation of...
is substrate that has been frozen for a minimum of 2 years. There are two types of permafrost: discontinuous and continuous. Discontinuous permafrost is found in areas where the mean annual air temperature is only slightly below freezing (0 °C (32 °F)); this forms in sheltered locations. In areas where the mean annual soil surface temperature is below -5 °C, continuous permafrost forms. This is not limited to sheltered areas and ranges from a few inches below the surface to over 300 m (984.3 ft) deep. The top layer is called the active layer
Active layer
In environments containing permafrost, the active layer is the top layer of soil that thaws during the summer and freezes again during the autumn. In all climates, whether they contain permafrost or not, the temperature in the lower levels of the soil will remain more stable than that at the...
. It thaws in the summer and is critical to plant life.
Biomes
Moisture and temperature are major physical drivers of natural ecosystems. The more arid and colder conditions found at higher northern latitudes (and high elevations elsewhere) support tundraTundra
In physical geography, tundra is a biome where the tree growth is hindered by low temperatures and short growing seasons. The term tundra comes through Russian тундра from the Kildin Sami word tūndâr "uplands," "treeless mountain tract." There are three types of tundra: Arctic tundra, alpine...
and boreal forests. The water in this region is generally frozen and evaporation
Evaporation
Evaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid....
rates are very low. Species diversity, nutrient
Nutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...
availability, precipitation, and average temperatures increase as you move from the tundra to boreal forests and then to deciduous
Deciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
temperate
Temperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...
ecosystems, which are found south of these Arctic biomes.
Tundra
Tundra is found from 55 ° to 80° N latitude in North America, Eurasia and Greenland. It can be found at lower latitudes at high elevations as well. The average temperature is -34 °C; during the summer it is less than 10 °C (50 °F). Average precipitation ranges from 10 to 50 cm (3.9 to 19.7 in), and the permafrost is 400–600 m (1,312.3–1,968.5 ft) thick. Plant species supported by tundra have small leaves, are short (74 mm to <5 m), tend to be deciduous, have a high ratio of roots to shoots, and are composed mainly of perennial forbs, dwarf shrubs, grasses, lichens, and mosses.Boreal
In comparison to tundra, boreal forest has a longer and warmer growing seasonGrowing season
In botany, horticulture, and agriculture the growing season is the period of each year when native plants and ornamental plants grow; and when crops can be grown....
and supports larger species diversity
Species diversity
Species diversity is an index that incorporates the number of species in an area and also their relative abundance. It is a more comprehensive value than species richness....
, an increase in canopy height, vegetation density, and biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....
. Boreal conditions can be found across northern North America and Eurasia. The boreal forests in the interior of the continents grow on top of permafrost due to very cold winters (see drunken trees
Drunken trees
Drunken trees, tilted trees, or a drunken forest, is a stand of trees displaced from their normal vertical alignment.This most commonly occurs in northern subarctic taiga forests of Black Spruce under which discontinuous permafrost or ice wedges have melted, causing trees to tilt at various...
), while much of the boreal forest has patchy permafrost or lack permafrost completely. The short (3–4 month) growing season in boreal forests is sustained by greater levels of rainfall (between 30 and 85 cm (11.8 and 33.5 in) per year) than the tundra receives; This biome is dominated by closed canopy forests of evergreen conifers, especially spruces, fir, pine and tamarack with some diffuse-porous hardwoods. Shrubs, herbs, ferns, mosses, and lichens are also important species. Stand-replacing crown fires are very important to this biome, occurring as frequently as every 50–100 years in some parts.
Humans
Humans living in the Arctic region generally rely on warm clothing and buildings to protect them from the elements. AcclimatizationAcclimatization
Acclimatisation or acclimation is the process of an individual organism adjusting to a gradual change in its environment, allowing it to maintain performance across a range of environmental conditions...
, or the adjustment to new conditions, appears to be the most common form of adaptation to cold environments. No genetic advantage has been found when different people groups or races are compared. There is no evidence that fat is grown in response to cold, although its presence is advantageous. Amazingly, most people living in the Arctic region live a lifestyle very connected to the environment, spending significant time outside and depending heavily on hunting and fishing.
Other animals
Animals that are active in the winter have adaptations for surviving the intense cold. A common example is the presence of strikingly large feet in proportion to body weight. These act like snowshoes, and can be found on animals like the snowshoe hareSnowshoe Hare
The Snowshoe Hare , also called the Varying Hare, or Snowshoe Rabbit, is a species of hare found in North America. It has the name "snowshoe" because of the large size of its hind feet and the marks its tail leaves. The animal's feet prevent it from sinking into the snow when it hops and walks...
and caribou. Many of the animals in the Arctic are larger than their temperate counterparts (Bergmann’s rule), taking advantage of the smaller ratio of surface area to volume that comes with increasing size. This increases the ability to conserve heat. Layers of fat, plumage, and fur are also very effective insulators to help retain warmth and are common in Arctic animals including polar bears and marine mammals. Some animals also have digestive adaptations to improve their ability to digest woody plants either with or without the aid of microbial organisms. This is highly advantageous during the winter months when most soft vegetation is beneath the snow pack.
Not all Arctic animals directly face the rigors of winter. Many migrate to warmer climates at lower latitudes, while others avoid the difficulties of winter by hibernating
Hibernation
Hibernation is a state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and lower metabolic rate. Hibernating animals conserve food, especially during winter when food supplies are limited, tapping energy reserves, body fat, at a slow rate...
until spring. Although these options might seem to be easy solutions to the diffictulties of surviving an extreme environment, both are very expensive in terms of energy and risk of predation.
Plants
One of the most serious problems that plants face is ice crystal formation in the cells, which results in tissue death. Plants have two ways to resist freezing: avoid it or tolerate it. If a plant has taken the avoidance route, it has several different ways to evade freezing. It can build up insulation, have its stem close to the ground, use the insulation from snow cover, and supercool. When supercoolingSupercooling
Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid or a gas below its freezing point without it becoming a solid....
, water is able to remain in its liquid state down to -38 °C (compared to its usual 0 °C (32 °F) freezing point). After water reaches -38 °C, it spontaneously freezes and plant tissue is destroyed. This is called the nucleation point. The nucleation point can be lowered if dissolved solute
Solute
Solute may refer to:* Solute, UMIK or UBOOK desolving in a substance,forming INT/INTY* Solute , a group of Paleozoic echinoderms...
s are present.
If a plant has taken the tolerance route, it has several different ways to tolerate freezing. Some plants allow freezing by allowing extracellular
Extracellular
In cell biology, molecular biology and related fields, the word extracellular means "outside the cell". This space is usually taken to be outside the plasma membranes, and occupied by fluid...
, but not intracellular
Intracellular
Not to be confused with intercellular, meaning "between cells".In cell biology, molecular biology and related fields, the word intracellular means "inside the cell".It is used in contrast to extracellular...
freezing. Plants let water freeze in extracellular spaces, which creates a high vapor deficit that pulls water vapor out of the cell. This process dehydrates the cell and allows it to survive temperatures well below -38 °C.
Another problem associated with extreme cold is cavitation. Ring-porous wood is susceptible to cavitation
Cavitation
Cavitation is the formation and then immediate implosion of cavities in a liquidi.e. small liquid-free zones that are the consequence of forces acting upon the liquid...
because the large pores that are used for water transport easily freeze. Cavitation
Cavitation
Cavitation is the formation and then immediate implosion of cavities in a liquidi.e. small liquid-free zones that are the consequence of forces acting upon the liquid...
is much less of problem in trees with ring-diffuse wood. In ring-diffuse wood, there is a reduced risk of cavitation, as transport pores are smaller. The trade-off is that these species are not able to transport water as efficiently.
Conservation and environmental issues
Suspected worldwide anthropogenic climate change has been particularly evident in the Arctic. This is evident by warmer temperatures, melting glaciers, shorter durations of sea ice and changing weather and storm patterns. Scientists are especially concerned about four aspects of the continued projected warming of the Arctic.First, thermohaline circulation
Thermohaline circulation
The term thermohaline circulation refers to a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes....
is a series of underwater oceanic currents fueled by the salinity and temperature of seawater. Melting ice sheets would introduce vast amounts of fresh water into the North Atlantic, causing a change in density which could disrupt the currents. If this circulation slowed or stopped, the climates of northern Europe and North America would be strongly impacted.
Second, the melting of glaciers and sea ice is disrupting the lifestyles of a wide range of species. Polar bear
Polar Bear
The polar bear is a bear native largely within the Arctic Circle encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. It is the world's largest land carnivore and also the largest bear, together with the omnivorous Kodiak Bear, which is approximately the same size...
s live on the sea ice for much of the year and find their food in the surrounding ocean waters. Recent projections suggest that global warming will lead to the disappearance of most summer sea ice within 40 years.
A third practical concern is the melting of permafrost due to climate change. Degradation of this permafrost is leading to major ground surface subsidence and pounding. The ground is literally melting away in many regions of the Arctic. The locations of towns and communities that have been inhabited for centuries are now in jeopardy. A condition known as drunken tree syndrome is being caused by this melting. Ground water and river runoffs are being negatively impacted as well. Although warming conditions might increase CO2 uptake for photosynthetic organisms in some places, scientists are concerned that melting permafrost will also release large amounts of carbon locked in permafrost.
Finally, the impacts of the release of carbon from the permafrost could be amplified by high levels of deforestation
Deforestation
Deforestation is the removal of a forest or stand of trees where the land is thereafter converted to a nonforest use. Examples of deforestation include conversion of forestland to farms, ranches, or urban use....
in the Boreal forests in Eurasia and Canada. This biome currently serves as a large carbon sink, sequestering large amounts of carbon dioxide. However, over half of the original forest has been or in danger of harvesting, largely for export. Carbon Dioxide is a greenhouse gas, which facilitates increased warming of the earth.
Further exploration
In a meta analysis of the published work in aquatic ecosystems since the term biodiversityBiodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...
appeared in the bibliography, the Arctic and Antarctic Polar regions were found to be still unexplored. In addition, the North Pacific Ocean (Pacific Northeast and Pacific Northwest), still has few citations in comparison to its large size. This limits our perception of the world’s aquatic biodiversity. Consequently we do not have sufficient information about biodiversity in most places on earth. Even though biodiversity declines from the equator to the poles in terrestrial ecosystems, this is still a hypothesis to be tested in aquatic and especially marine ecosystems where causes of this phenomenon are unclear. In addition, particularly in marine ecosystems, there are several well stated cases where diversity in higher latitudes actually increases (Moustakas & Karakassis 2005). Therefore, the lack of information on biodiversity of Arctic Regions prevents scientific conclusions on the distribution of the world’s aquatic biodiversity.
See also
- Arctic flora
- Arctic sea ice ecology and history
- Arctic shrinkageArctic shrinkageOngoing changes in the climate of the Arctic include rising temperatures, loss of sea ice, and melting of the Greenland ice sheet. Projections of sea ice loss suggest that the Arctic ocean will likely be free of summer sea ice sometime between 2060 and 2080, while another estimate puts this date at...
External links
- http://www.blueplanetbiomes.org/tundra.htm
- http://www.windows.ucar.edu/tour/link=/earth/polar/polar_north.html&edu=high
- http://www.borealnet.org/overview/index.html
- http://www.theweatherprediction.com/habyhints/89
- http://fairbanks-alaska.com/permafrost.htm
Life in the Cold
- http://apollo.ogis.state.me.us/catalog/
- Moustakas, A. & I. Karakassis. How diverse is aquatic biodiversity research?, Aquatic Ecology, 39, 367-375