Misplaced Pages

#499500

58-455: These regions are further subdivided into a variety of ecoregions . Many ecosystems and the animal and plant communities that depend on them extend across a number of continents and cover large portions of the Holarctic realm. This continuity is the result of those regions’ shared glacial history. Within the Holarctic realm, there are a variety of ecosystems. The type of ecosystem found in

116-488: A given area depends on its latitude and the local geography. In the far north, a band of Arctic tundra encircles the shore of the Arctic Ocean . The ground beneath this land is permafrost (frozen year-round). In these difficult growing conditions, few plants can survive. South of the tundra, the boreal forest stretches across North America and Eurasia. This land is characterized by coniferous trees . Further south,

174-415: A given ecoregion are more similar to each other than to those of surrounding ecoregions and together form a conservation unit. Freshwater systems include rivers , streams , lakes , and wetlands . Freshwater ecoregions are distinct from terrestrial ecoregions, which identify biotic communities of the land, and marine ecoregions, which are biotic communities of the oceans. A map of Freshwater Ecoregions of

232-427: A greater problem throughout the northern parts of the Holarctic. Another potential effect of global warming to northern ecosystems is the melting of permafrost . This can have significant effects on the plant communities that are adapted to the frozen soil, and may also have implications for further climate change. As permafrost melts, any trees growing above it may die, and the land shifts from forest to peatland . In

290-469: A holistic, "weight-of-evidence" approach where the importance of various factors may vary. An example of the algorithmic approach is Robert Bailey 's work for the U.S. Forest Service, which uses a hierarchical classification that first divides land areas into very large regions based on climatic factors, and subdivides these regions, based first on dominant potential vegetation, and then by geomorphology and soil characteristics. The weight-of-evidence approach

348-405: A more immediate threat to those found in cold climates. The communities of species found at these latitudes are adapted to the cold, so any significant warming can upset the balance. For instance, insects struggle to survive the cold winters typical of the boreal forest. Many do not make it, especially in harsh winters. However, recently the winters have grown milder, which has had a drastic effect on

406-407: A result of climate change. Warming temperatures may also allow pest species to enlarge their range, moving into habitats that were previously unsuitable. Studies of potential areas for outbreaks of bark beetles indicate that as the climate shifts, these beetles will expand to the north and to higher elevations than they have previously affected. With warmer temperatures, insect infestation will become

464-517: A set of ecoregions identified by WWF whose conservation would achieve the goal of saving a broad diversity of the Earth's ecosystems, includes a number of areas highlighted for their freshwater biodiversity values. The Global 200 preceded Freshwater Ecoregions of the World and incorporated information from regional freshwater ecoregional assessments that had been completed at that time. Sources related to

522-407: A web application developed by Resolve and Google Earth Engine. An ecoregion is a "recurring pattern of ecosystems associated with characteristic combinations of soil and landform that characterise that region". Omernik (2004) elaborates on this by defining ecoregions as: "areas within which there is spatial coincidence in characteristics of geographical phenomena associated with differences in

580-472: A wide variety of habitats throughout the world, and the Holarctic is no exception. Fragmentation has a variety of negative effects on populations. As populations become cut off, their genetic diversity suffers and they become susceptible to sudden disasters and extinction. While the northern parts of the Holarctic represent some of the largest areas of wilderness left on Earth, the southern parts are in some places extensively developed. This realm contains most of

638-488: Is a species of orb-weaving spider with a Holarctic distribution, mostly inhabiting urban and suburban regions of Europe and parts of North America. Hemerobius humulinus is a species of brown lacewing in the family Hemerobiidae. It is found in Europe and Northern Asia (excluding China), North America, and Southern Asia. The continuity of the northern parts of the Holarctic results from their shared glacial history. During

SECTION 10

#1732765710500

696-547: Is an ecologically and geographically defined area that is smaller than a bioregion , which in turn is smaller than a biogeographic realm . Ecoregions cover relatively large areas of land or water, and contain characteristic, geographically distinct assemblages of natural communities and species . The biodiversity of flora , fauna and ecosystems that characterise an ecoregion tends to be distinct from that of other ecoregions. In theory, biodiversity or conservation ecoregions are relatively large areas of land or water where

754-426: Is analogous to that used for terrestrial ecoregions. Major habitat types are identified: polar, temperate shelves and seas, temperate upwelling, tropical upwelling, tropical coral, pelagic (trades and westerlies), abyssal, and hadal (ocean trench). These correspond to the terrestrial biomes . The Global 200 classification of marine ecoregions is not developed to the same level of detail and comprehensiveness as that of

812-426: Is distributed throughout the majority of the Holarctic, but it has avoided extirpation. The wolverine ( Gulo gulo ) is a large member of the weasel family found primarily in the arctic and in boreal forests, ranging south in mountainous regions. It is distributed in such areas throughout Eurasia and North America. The moose ( Alces alces ) is the largest member of the deer family. It is found throughout most of

870-622: Is exemplified by James Omernik's work for the United States Environmental Protection Agency , subsequently adopted (with modification) for North America by the Commission for Environmental Cooperation . The intended purpose of ecoregion delineation may affect the method used. For example, the WWF ecoregions were developed to aid in biodiversity conservation planning, and place a greater emphasis than

928-398: Is found in a variety of habitats, but primarily wooded northern areas. It has been known to adapt well to areas of human activity. Their distribution also makes up most of the Holarctic realm. Leptothorax acervorum is a small red Holarctic ant widely distributed across Eurasia, ranging from central Spain and Italy to the northernmost parts of Scandinavia and Siberia. Zygiella x-notata

986-440: Is found in mountainous and semi-open areas distributed throughout the Holarctic. It once occupied much larger areas, but has been driven out by human development and the resulting habitat fragmentation . Today it is only found in remaining wilderness areas. The grey wolf ( Canis lupus ) is found in a wide variety of habitats from tundra to desert, with different populations adapted for each. Its historical distribution encompasses

1044-483: Is one of the best-known birds of prey in the Northern Hemisphere. It is the most widely distributed species of eagle. Golden eagles use their agility and speed combined with powerful feet and massive, sharp talons to snatch up a variety of prey (mainly hares, rabbits, marmots and other ground squirrels). The common raven ( Corvus corax ) is the most widespread of the corvids , and one of the largest. It

1102-526: Is optimal for all taxa. Ecoregions reflect the best compromise for as many taxa as possible. Secondly, ecoregion boundaries rarely form abrupt edges; rather, ecotones and mosaic habitats bound them. Thirdly, most ecoregions contain habitats that differ from their assigned biome . Biogeographic provinces may originate due to various barriers, including physical (plate tectonics, topographic highs), climatic (latitudinal variation, seasonal range) and ocean chemical related (salinity, oxygen levels). The history of

1160-399: Is subject to environmental problems of international scale. The primary threats throughout the region result from global warming and habitat fragmentation . The former is of particular concern in the north, as these ecosystems are adapted to cold. The latter is more of a concern in the south, where development is prevalent. Global warming is a threat to all the Earth's ecosystems, but it is

1218-608: The Himalayas and the Sahara . The boundaries of ecoregions are often not as decisive or well recognized, and are subject to greater disagreement. Ecoregions are classified by biome type, which are the major global plant communities determined by rainfall and climate. Forests, grasslands (including savanna and shrubland), and deserts (including xeric shrublands ) are distinguished by climate ( tropical and subtropical vs. temperate and boreal climates) and, for forests, by whether

SECTION 20

#1732765710500

1276-487: The Pleistocene (Ice Age), these areas were subjected to repeated glaciations. Icecaps expanded, scouring the land of life and reshaping its topography. During glacial periods, species survived in refugia , small areas that maintained a suitable climate due to local geography. These areas are believed to have been primarily in southern regions, but some genetic and paleontological evidence points to additional refugia in

1334-450: The "ecoregion" as a unit of analysis. The " Global 200 " is the list of ecoregions identified by WWF as priorities for conservation . Terrestrial ecoregions are land ecoregions, as distinct from freshwater and marine ecoregions. In this context, terrestrial is used to mean "of land" (soil and rock), rather than the more general sense "of Earth " (which includes land and oceans). WWF (World Wildlife Fund) ecologists currently divide

1392-558: The Earth. The use of the term ecoregion is an outgrowth of a surge of interest in ecosystems and their functioning. In particular, there is awareness of issues relating to spatial scale in the study and management of landscapes . It is widely recognized that interlinked ecosystems combine to form a whole that is "greater than the sum of its parts". There are many attempts to respond to ecosystems in an integrated way to achieve "multi-functional" landscapes, and various interest groups from agricultural researchers to conservationists are using

1450-475: The Holarctic. Each country is given a target for emission levels, and they may trade emissions credits in a market-based system that includes developing countries as well. Once this period is ended, a new agreement will be written to further mitigate the effects of climate change . The process of drafting a new agreement has already begun. In late 2007, an international meeting in Bali was held to begin planning for

1508-480: The Holarctic. Some efforts are limited to a local scale of protection, while others are regional in scope. Local efforts include creating reserves and establishing safe routes for animals to cross roads and other human-made barriers. Regional efforts to combat habitat fragmentation take a broader scope. One major such effort in the Holarctic is the Yellowstone to Yukon Conservation Initiative . This organization

1566-552: The Omernik or Bailey systems on floral and faunal differences between regions. The WWF classification defines an ecoregion as: A large area of land or water that contains a geographically distinct assemblage of natural communities that: According to WWF, the boundaries of an ecoregion approximate the original extent of the natural communities prior to any major recent disruptions or changes. WWF has identified 867 terrestrial ecoregions, and approximately 450 freshwater ecoregions across

1624-571: The WWF concept prioritizes biogeography, that is, the distribution of distinct species assemblages. In 2017, an updated terrestrial ecoregions dataset was released in the paper "An Ecoregion-Based Approach to Protecting Half the Terrestrial Realm" led by E. Dinerstein with 48 co-authors. Using recent advances in satellite imagery the ecoregion perimeters were refined and the total number reduced to 846 (and later 844), which can be explored on

1682-523: The World (TEOW), led by D. Olsen, E. Dinerstein, E. Wikramanayake, and N. Burgess. While the two approaches are related, the Bailey ecoregions (nested in four levels) give more importance to ecological criteria and climate zones, while the WWF ecoregions give more importance to biogeography, that is, the distribution of distinct species assemblages. The TEOW framework originally delineated 867 terrestrial ecoregions nested into 14 major biomes, contained with

1740-783: The World, released in 2008, has 426 ecoregions covering virtually the entire non-marine surface of the earth. World Wildlife Fund (WWF) identifies twelve major habitat types of freshwater ecoregions: Large lakes, large river deltas, polar freshwaters, montane freshwaters, temperate coastal rivers, temperate floodplain rivers and wetlands, temperate upland rivers, tropical and subtropical coastal rivers, tropical and subtropical floodplain rivers and wetlands, tropical and subtropical upland rivers, xeric freshwaters and endorheic basins, and oceanic islands. The freshwater major habitat types reflect groupings of ecoregions with similar biological, chemical, and physical characteristics and are roughly equivalent to biomes for terrestrial systems. The Global 200 ,

1798-406: The ability of animals, especially large ones, to migrate from place to place. Large carnivores are particularly affected by habitat fragmentation. These mammals, such as brown bears and wolves, require large areas of land with relatively intact habitat to survive as individuals. Much larger areas are required to maintain a sustainable population. They may also serve as keystone species , regulating

Holarctic realm - Misplaced Pages Continue

1856-480: The authors was to support global biodiversity conservation by providing a "fourfold increase in resolution over that of the 198 biotic provinces of Dasmann (1974) and the 193 units of Udvardy (1975)." In 2007, a comparable set of Marine Ecoregions of the World (MEOW) was published, led by M. Spalding, and in 2008 a set of Freshwater Ecoregions of the World (FEOW) was published, led by R. Abell. Bailey's ecoregion concept prioritizes ecological criteria and climate, while

1914-514: The boreal forest through continental Eurasia into Scandinavia, eastern North America, and boreal and montane regions of western North America. In some areas it ranges south into the deciduous forest. The caribou, or reindeer ( Rangifer tarandus ) is found in boreal forest and tundra in the northern parts of the Holarctic. In Eurasia, it has been domesticated. It is divided into several subspecies, which are adapted to different habitats and geographic areas. The golden eagle ( Aquila chrysaetos )

1972-677: The broad latitudinal divisions of polar, temperate, and tropical seas, with subdivisions based on ocean basins (except for the southern hemisphere temperate oceans, which are based on continents). Major marine biogeographic realms, analogous to the eight terrestrial biogeographic realms , represent large regions of the ocean basins: Arctic , Temperate Northern Atlantic , Temperate Northern Pacific , Tropical Atlantic , Western Indo-Pacific , Central Indo-Pacific , Eastern Indo-Pacific , Tropical Eastern Pacific , Temperate South America , Temperate Southern Africa , Temperate Australasia , and Southern Ocean . A similar system of identifying areas of

2030-401: The delineation of ecoregions an imperfect science. Another complication is that environmental conditions across an ecoregion boundary may change very gradually, e.g. the prairie-forest transition in the midwestern United States, making it difficult to identify an exact dividing boundary. Such transition zones are called ecotones . Ecoregions can be categorized using an algorithmic approach or

2088-405: The early 1970s, the term 'ecoregion' was introduced (short for ecological region), and R.G. Bailey published the first comprehensive map of U.S. ecoregions in 1976. The term was used widely in scholarly literature in the 1980s and 1990s, and in 2001 scientists at the U.S. conservation organization World Wildlife Fund (WWF) codified and published the first global-scale map of Terrestrial Ecoregions of

2146-527: The ecosystems become more diverse. Some areas are temperate grassland , while others are temperate forests dominated by deciduous trees . Many of the southernmost parts of the Holarctic are deserts , which are dominated by plants and animals adapted to the dry conditions. A variety of animal species are distributed across continents, throughout much of the Holarctic realm. These include the brown bear, grey wolf, red fox, wolverine, moose, caribou, golden eagle and common raven. The brown bear ( Ursus arctos )

2204-514: The far north, shrubs may later take over what was formerly tundra. The precise effect depends on whether the water that was locked up is able to drain off. In either case, the habitat will undergo a shift. Melting permafrost may also accelerate climate change in the future. Within the permafrost, vast quantities of carbon are locked up. If this soil melts, the carbon may be released into the air as either carbon dioxide or methane . Both of these are greenhouse gases . Habitat fragmentation threatens

2262-499: The forest. Winter mortality of some insect species drastically decreased, allowing the population to build on itself in subsequent years. In some areas the effects have been severe. Spruce beetle outbreaks have wiped out up to ninety percent of the Kenai Peninsula 's spruce trees; this is blamed primarily on a series of unusually warm years since 1987. In this case a native species has caused massive disturbance of habitat as

2320-629: The hope of preserving the biodiversity of the region. International agreements to combat global warming may help to lessen the effects of climate change on this region. Efforts are also underway to fight habitat fragmentation, both on local and regional scales. The most comprehensive effort to combat global warming to date is the Kyoto Protocol . Developed countries who sign this protocol agree to cut their collective greenhouse gas emissions by five percent since 1990 by sometime between 2008 and 2012. The vast majority of these nations are found within

2378-579: The ice caps. The communities found in the Palearctic and the Nearctic are different, but have many species in common. This is the result of several faunal interchanges that took place across the Bering land bridge. However, these migrations were mostly limited to large, cold-tolerant species. Today it is mainly these species which are found throughout the realm. As the Holarctic is an enormous area, it

Holarctic realm - Misplaced Pages Continue

2436-501: The land surface of the Earth into eight biogeographical realms containing 867 smaller terrestrial ecoregions (see list ). The WWF effort is a synthesis of many previous efforts to define and classify ecoregions. The eight realms follow the major floral and faunal boundaries, identified by botanists and zoologists, that separate the world's major plant and animal communities. Realm boundaries generally follow continental boundaries, or major barriers to plant and animal distribution, like

2494-476: The many existing protected areas in this region, with a focus on integrating existing and future human activities into the conservation plan rather than seeking to exclude them (Yellowstone to Yukon). If these efforts are successful, they will be especially beneficial to wide-ranging species such as grizzly bears . If these species can survive, other members of the communities they live in will survive as well. Ecoregions An ecoregion ( ecological region )

2552-472: The oceans for conservation purposes is the system of large marine ecosystems (LMEs), developed by the US National Oceanic and Atmospheric Administration (NOAA). A freshwater ecoregion is a large area encompassing one or more freshwater systems that contains a distinct assemblage of natural freshwater communities and species. The freshwater species, dynamics, and environmental conditions within

2610-575: The other hand, shifted their ranges with the climate, maintaining consistency in species for the most part throughout the period. Their high degree of mobility allowed them to move as the glaciers advanced or retreated, maintaining a constant habitat despite the climatic oscillations . Despite their apparent lack of mobility, plants managed to colonize new areas rapidly as well. Studies of fossil pollen indicate that trees recolonized these lands at an exponential rate. Mammals recolonized at varying rates. Brown bears, for instance, moved quickly from refugia with

2668-473: The populations of the species they prey on. Thus, their conservation has direct implications for a wide range of species, and is difficult to accomplish politically due to the large size of the areas they need. With increasing development, these species in particular are at risk, which could have effects that carry down throughout the ecosystem. The threats to the Holarctic realm are not going unrecognized. Many efforts are being made to mitigate these threats, with

2726-430: The probability of encountering different species and communities at any given point remains relatively constant, within an acceptable range of variation (largely undefined at this point). Ecoregions are also known as "ecozones" ("ecological zones"), although that term may also refer to biogeographic realms . Three caveats are appropriate for all bio-geographic mapping approaches. Firstly, no single bio-geographic framework

2784-415: The quality, health, and integrity of ecosystems ". "Characteristics of geographical phenomena" may include geology , physiography , vegetation, climate, hydrology , terrestrial and aquatic fauna , and soils, and may or may not include the impacts of human activity (e.g. land use patterns, vegetation changes). There is significant, but not absolute, spatial correlation among these characteristics, making

2842-462: The receding glaciers, becoming one of the first large mammals to recolonize the land. The Last Glacial Period ended about 10,000 years ago, resulting in the present distribution of ecoregions. Another factor contributing to the continuity of Holarctic ecosystems is the movement between continents allowed by the Bering land bridge , which was exposed by the lowering of sea level due to the expansion of

2900-464: The sheltered areas of the north. Wherever these areas were found, they became source populations during interglacial periods . When the glaciers receded, plants and animals spread rapidly into the newly opened areas. Different taxa responded to these rapidly changing conditions in different ways. Tree species spread outward from refugia during interglacial periods, but in varied patterns, with different trees dominating in different periods. Insects , on

2958-486: The successor to the Kyoto Protocol. This agreement will aim to build on the successes and failures of Kyoto to produce a more effective method of cutting greenhouse gas emissions ( UNFCCC ). If these efforts are successful, the biodiversity of the Holarctic and the rest of the world will see fewer effects of climate change. Fighting habitat fragmentation is a major challenge in conserving the wide-ranging species of

SECTION 50

#1732765710500

3016-408: The term is somewhat vague. It has been used in many contexts: forest classifications (Loucks, 1962), biome classifications (Bailey, 1976, 2014), biogeographic classifications ( WWF / Global 200 scheme of Olson & Dinerstein, 1998), etc. The phrase "ecological region" was widely used throughout the 20th century by biologists and zoologists to define specific geographic areas in research. In

3074-454: The terrestrial ecoregions; only the priority conservation areas are listed. See Global 200 Marine ecoregions for a full list of marine ecoregions. In 2007, TNC and WWF refined and expanded this scheme to provide a system of comprehensive near shore (to 200 meters depth) Marine Ecoregions of the World (MEOW). The 232 individual marine ecoregions are grouped into 62 marine provinces , which in turn group into 12 marine realms , which represent

3132-913: The trees are predominantly conifers ( gymnosperms ), or whether they are predominantly broadleaf ( Angiosperms ) and mixed (broadleaf and conifer). Biome types like Mediterranean forests, woodlands, and scrub ; tundra ; and mangroves host very distinct ecological communities, and are recognized as distinct biome types as well. Marine ecoregions are: "Areas of relatively homogeneous species composition , clearly distinct from adjacent systems….In ecological terms, these are strongly cohesive units, sufficiently large to encompass ecological or life history processes for most sedentary species." They have been defined by The Nature Conservancy (TNC) and World Wildlife Fund (WWF) to aid in conservation activities for marine ecosystems . Forty-three priority marine ecoregions were delineated as part of WWF's Global 200 efforts. The scheme used to designate and classify marine ecoregions

3190-400: The vast majority of the Holarctic realm, though human activities such as development and active extermination have extirpated the species from much of this range. The red fox ( Vulpes vulpes ) is a highly adaptable predator. It has the widest distribution of any terrestrial carnivore, and is adapted to a wide range of habitats, including areas of intense human development. Like the wolf, it

3248-563: The world's developed countries , including the United States and the nations of Western Europe. Temperate forests were the primary ecosystem in many of the most developed areas today. These lands are now used for intensive agriculture or have become urbanized. As lands have been developed for agricultural uses and human occupation, natural habitat has for the most part become limited to areas considered unsuitable for human use, such as slopes or rocky areas. This pattern of development limits

3306-491: The world's 8 major biogeographical realms. Subsequent regional papers by the co-authors covering Africa, Indo-Pacific, and Latin America differentiate between ecoregions and bioregions, referring to the latter as "geographic clusters of ecoregions that may span several habitat types, but have strong biogeographic affinities, particularly at taxonomic levels higher than the species level (genus, family)". The specific goal of

3364-468: Was started in 1997 to help establish a contiguous network of protection for the northern Rocky Mountains , from mid Wyoming to the border between Alaska and Canada's Yukon . It brings together a wide variety of environmental organizations for a shared purpose. The goal of the Initiative is to create a core of protected areas, connected by corridors and surrounded by buffer zones. This will build on

#499500