The mammoth steppe, also known as steppe-tundra, was once the Earth's most extensive biome. During glacial periods in the later Pleistocene it stretched east-to-west, from the Iberian Peninsula in the west of Europe, across Eurasia to North America, through Beringia (the region including the far northwest of Siberia and Alaska and the now submerged land between them) and northwest Canada; from north-to-south, the steppe reached from the Arctic southward to southern Europe, Central Asia and northern China. [2] [3] [4] [5] [6] The mammoth steppe was cold and dry, and relatively featureless, though climate, topography, and geography varied considerably throughout. Certain areas of the biome—such as coastal areas—had wetter and milder climates than others. Some areas featured rivers which, through erosion, naturally created gorges, gulleys, or small glens. The continual glacial recession and advancement over millennia contributed more to the formation of larger valleys and different geographical features. Overall, however, the steppe is known to be flat and expansive grassland. [7] [6] The vegetation was dominated by palatable, high-productivity grasses, herbs and willow shrubs. [3] [6] [8]
The animal biomass was dominated by species such as reindeer, muskox, saiga antelope, steppe bison, horses, woolly rhinoceros and woolly mammoth. [7] [9] These herbivores, in turn, were followed and preyed upon by various carnivores, such as wolves, brown bears, Panthera spelaea (the cave or steppe-lion), cave hyenas, wolverines, among others, as well as scimitar-toothed cats and giant short-faced bears in east Beringia (with scimitar-toothed cats also having rare records from the mammoth steppe in Eurasia). This ecosystem covered wide areas of the northern part of the globe, and thrived for approximately 100,000 years without major changes, but then diminished to small regions around 12,000 years ago. [7]
Although it was primarily a Eurasian and Beringian biome, an analog of the mammoth steppe existed on the southern edge of the Laurentide sheet in North America as well, and contained many of the same animals such as woolly mammoths, muskoxen, scimitar cats, and caribou. [10]
Modern humans began to inhabit the biome following their expansion out of Africa, reaching the Siberian Arctic by around 45,000 years ago. [11]
At the end of the 19th century, Alfred Nehring (1890) [12] and Jan Czerski (Iwan Dementjewitsch Chersky, 1891) [13] proposed that during the last glacial period a major part of northern Europe had been populated by large herbivores and that a steppe climate had prevailed there. [14] In 1982, the scientist R. Dale Guthrie coined the term "mammoth steppe" for this paleoregion. [15] [14]
The steppe-tundra biome first emerged during the glacial period of Marine Isotope Stage 12, around 460,000 years ago, during the Middle Pleistocene, uniting animals that previously inhabited the previously disparate northern tundra and Central Asian steppe biomes. The size of the steppe-tundra biome would repeatedly expand and contract as a result of subsequent glacial cycles. [9]
The last glacial period, commonly referred to as the 'Ice Age', spanned from 126,000 YBP–11,700 YBP [16] and was the most recent glacial period within the current ice age which occurred during the last years of the Pleistocene epoch. [17] This arctic environment was very cold and dry and probably dusty, resembling mountaintop environments (alpine tundra), and was very different from today's swampy tundra. [18] It reached its peak during the last glacial maximum, when ice sheets commenced advancing from 33,000 years BP and reached their maximum positions 26,500 years BP. Deglaciation commenced in the Northern Hemisphere approximately 19,000 years BP, and in Antarctica approximately 14,500 years BP, which is consistent with evidence that it was the primary source for an abrupt rise in the sea level at that time. [19]
During the peak of the last glacial maximum, a vast mammoth steppe stretched from the Iberian Peninsula across Eurasia and over the Bering land bridge into Alaska and the Yukon where it was stopped by the Wisconsin glaciation. This land bridge existed because more of the planet's water was locked up in ice than now, hence sea levels were lower. When the sea levels began to rise this bridge was inundated around 11,000 years BP. [20]
During glacial periods, there is clear evidence for intense aridity due to water being held in glaciers and their associated effects on climate. [21] [22] [7] The mammoth steppe was like a huge 'inner court' that was surrounded on all sides by moisture-blocking features: massive continental glaciers, high mountains, and frozen seas. These kept rainfall low and created more days with clear skies than are seen today, which increased evaporation in the summer leading to aridity, and radiation of warmth from the ground into the night sky in winter leading to cold. [7] This is thought to have been caused by seven factors:
These physical barriers to moisture flow created a vast arid basin spanning three continents. [7]
Animal biomass and plant productivity of the mammoth steppe were similar to today's African savanna. [6] There is no comparison to it today. [7] [6]
The paleo-environment changed across time, [24] a proposal that is supported from mammoth dung samples found in northern Yakutia. [25] During Pleniglacial interstadials, alder, birch, and pine trees survived in northern Siberia, however during the Last Glacial Maximum only a treeless steppe vegetation existed. At the onset of the Late Glacial Interstadial (15,000–11,000 BP), global warming resulted in shrub and dwarf birch in northeastern Siberia, which was then colonized by open woodland with birch and spruce during the Younger Dryas (12,900–11,700 YBP). By the Holocene (10,000 YBP), patches of closed larch and pine forests developed. [25] Researchers had previously concluded that the mammoth steppe must have been very unproductive because they assumed that its soils had a very low carbon content; however, these soils (yedoma) were preserved in the permafrost of Siberia and Alaska and are the largest reservoir of organic carbon known. It was a highly productive environment. [6] [26] The vegetation was dominated by palatable high-productivity grasses, herbs and willow shrubs. [3] [6] [8] The herbaceous flora included graminoids such as wild rye, bluegrass, junegrass, fescue, and sedge, and also diverse forbs such as fringed sagebrush, campion, rock-jasmine, cinquefoil, goosefoot, buttercup, and plantain. [27] [14] Herbs were far more widespread than they are today, and were the main food source of the large plant eating mammals. [28]
Varying slightly by geographical location, the mammoth steppe was dominated (in biomass) primarily by giant deer, caribou, steppe bison, horses, woolly mammoth and yak, among other mammals, and was the center for the evolution of the Pleistocene “woolly” fauna. [7] Woolly rhinoceros, moose, saiga antelope and musk ox also lived in different regions of the steppe. In what-is-today Siberia were the relatives of extant animals like the argali, snow sheep, Siberian roe deer, and the Mongolian gazelle. Not long before the last glacial maximum (roughly 40,000 years ago), an extinct paleospecies of argali (Ovis argaloides) also lived in Europe. [30] Notable carnivores found across the whole range of the mammoth steppe included the cave lion ( Panthera spelaea ), the wolverine ( Gulo gulo ), wolves (Canis lupus) and the brown bear (Ursus arctos). While the cave hyena was a part of the mammoth steppe fauna in Europe, it did not range into the core high-latitude, northern Eurasian-Siberian reaches of the biome. [31] The short faced bear (Arctodus simus) was found across the tundra of North America, but never crossed over into Asia. Bird remains are rare because of their fragile structure, but there is some evidence for the snowy owl, willow ptarmigan, gyrfalcon, common raven and great bustard. Other bird species included the white-tailed and golden eagles. Vultures, like the griffon and cinereous vulture, are not known but they were likely common scavengers on the mammoth steppe, following the large herds and scavenging on predated or deceased animals. On Wrangel Island, the remains of woolly mammoth, woolly rhinoceros, horse, bison and musk ox have been found. Reindeer (caribou) and smaller animal remains do not preserve well, but reindeer excrement has been found in sediment. [6] However, small animals on the mammoth steppe included, for example, steppe pika, ground squirrels and alpine marmot. In the most arid regions of the mammoth steppe (that were to the south of Central Siberia and Mongolia), woolly rhinoceroses were common, [32] [6] while woolly mammoths were rare. [33] [6] Reindeer still live in the far north of Mongolia today and, historically, their southern boundary passed through Germany and along the steppes of eastern Europe, [34] [6] indicating they once covered much of the mammoth steppe. [6]
Mammoths survived on the Taimyr Peninsula until the Holocene. [8] [6] A small population of mammoths survived on St. Paul Island, Alaska, up until 3750 BC, [35] [36] and the small mammoths [37] of Wrangel Island survived until 1650 BC. [38] [39] Bison in Alaska and the Yukon, and horses and muskox in northern Siberia, have survived the loss of the mammoth steppe. [6] One study has proposed that a change of suitable climate caused a significant drop in the mammoth population size, which made them vulnerable to hunting from expanding human populations. The coincidence of both of these impacts in the Holocene most likely set the place and time for the extinction of the woolly mammoth. [23]
The mammoth steppe had a cold, dry climate. [7] [6] During the past interglacial warmings, forests of trees and shrubs expanded northward into the mammoth steppe, when northern Siberia, Alaska and the Yukon (Beringia) would have formed a mammoth steppe refugium. When the planet grew colder again, the mammoth steppe expanded. [6] This ecosystem covered wide areas of the northern part of the globe, thrived for approximately 100,000 years without major changes, but then diminished to small regions around 12,000 years ago. [7]
There are two theories about the decline of the mammoth steppe.
The Climatic Hypothesis assumes that the vast mammoth ecosystem could have only existed within a certain range of climatic parameters. At the beginning of the Holocene 10,000 years ago, mossy forests, tundra, lakes and wetlands displaced mammoth steppe. It has been assumed that in contrast to other previous interglacials the cold dry climate switched to a warmer wetter climate that, in turn, caused the disappearance of the grasslands and their dependent megafauna. [3]
The extinct steppe bison (Bison priscus) survived across the northern region of central eastern Siberia until 8000 years ago. A study of the frozen mummy of a steppe bison found in northern Yakutia indicated that it was a pasture grazer in a habitat that was becoming dominated by shrub and tundra vegetation. Higher temperature and rainfall led to a decrease in its previous habitat during the early Holocene, and this led to population fragmentation followed by extinction. [40]
The mammoth steppe was covered all winter with snow, which reflected sunlight into space and thus delayed the spring warming. With no more mammoths left to push trees down to get at their leaves to eat, the area became covered in tall forest sticking up above the snow all winter and catching the early sunlight and thus causing an early spring warming.
In 2017 a study looked at the environmental conditions across Europe, Siberia and the Americas from 25,000 to 10,000 YBP. The study found that prolonged warming events leading to deglaciation and maximum rainfall occurred just before the transformation of the rangelands that supported megaherbivores into widespread wetlands that supported herbivore-resistant plants. The study proposes that moisture-driven environmental change led to the megafaunal extinctions, and that Africa's trans-equatorial position allowed rangeland to continue to exist between the deserts and the central forests; therefore fewer megafauna species became extinct there. [41]
The Ecosystem Hypothesis assumes that the vast mammoth ecosystem extended over a range of many regional climates and was not affected by climate fluctuations. Its highly productive grasslands were maintained by animals trampling any mosses and shrubs, and actively transpiring grasses and herbs dominated. At the beginning of the Holocene the rise in precipitation was accompanied by increased temperature, and so its climatic aridity did not change substantially. As a result of human hunting, the decreasing density of the mammoth ecosystem animals was not enough to stop forest from spreading over the grasslands, leading to an increase in forests, shrubs and mosses with further animal reduction due to loss of feed. The mammoth continued to exist on isolated Wrangel Island until a few thousand years ago, and some of the other megafauna from that time still exist today, which indicates that something other than climate change was responsible for megafaunal extinctions. [6]
Remains of mammoth that had been hunted by humans 45,000 YBP have been found at Yenisei Bay in the central Siberian Arctic. [43] Two other sites in the Maksunuokha River valley to the south of the Shirokostan Peninsula, northeast Siberia, dated between 14,900 and 13,600 years ago showed the remains of mammoth hunting and the production of micro-blades similar to those found in northwest North America, suggesting a cultural connection. [44]
During the Holocene, the arid-adapted species became extinct or were reduced to minor habitats. [7] Cold and dry conditions similar to the last glacial period are found today in the eastern Altai-Sayan mountains of Central Eurasia, [45] [1] with no significant changes occurring between the cold phase of the Pleistocene and the Holocene. [46] [1] Recent paleo-biome reconstruction [47] [48] [49] and pollen analysis [50] [51] [52] suggest that some present-day Altai-Sayan areas could be considered the closest analogue to the mammoth steppe environment. [1] The environment of this region is thought to have been stable for the past 40,000 years. The Eastern part of the Altai-Sayan region forms a Last Glacial refugium. In both the Last Glacial and modern times, the eastern Altai-Sayan region has supported large herbivore and predator species adapted to the steppe, desert and alpine biomes where these biomes have not been separated by forest belts. None of the surviving Pleistocene mammals live in temperate forest, taiga, or tundra biomes. The areas of Ukok-Sailiugem in the southern Altai Republic and Khar Us Nuur and Uvs Nuur (Ubsunur Hollow) in western Mongolia have supported reindeer and saiga antelope since the glacial period. [1]
A mammoth is any species of the extinct elephantid genus Mammuthus. They lived from the late Miocene epoch into the Holocene until about 4,000 years ago, with mammoth species at various times inhabiting Africa, Asia, Europe, and North America. Mammoths are distinguished from living elephants by their spirally twisted tusks and in at least some later species, the development of numerous adaptions to living in cold environments, including a thick layer of fur.
Beringia is defined today as the land and maritime area bounded on the west by the Lena River in Russia; on the east by the Mackenzie River in Canada; on the north by 72° north latitude in the Chukchi Sea; and on the south by the tip of the Kamchatka Peninsula. It includes the Chukchi Sea, the Bering Sea, the Bering Strait, the Chukchi and Kamchatka Peninsulas in Russia as well as Alaska in the United States and the Yukon in Canada.
The muskox is a hoofed mammal of the family Bovidae. Native to the Arctic, it is noted for its thick coat and for the strong odor emitted by males during the seasonal rut, from which its name derives. This musky odor has the effect of attracting females during mating season. Its Inuktitut name "umingmak" translates to "the bearded one".
The woolly rhinoceros is an extinct species of rhinoceros that inhabited northern Eurasia during the Pleistocene epoch. The woolly rhinoceros was a member of the Pleistocene megafauna. The woolly rhinoceros was covered with long, thick hair that allowed it to survive in the extremely cold, harsh mammoth steppe. It had a massive hump reaching from its shoulder and fed mainly on herbaceous plants that grew in the steppe. Mummified carcasses preserved in permafrost and many bone remains of woolly rhinoceroses have been found. Images of woolly rhinoceroses are found among cave paintings in Europe and Asia. The range of the woolly rhinoceros contracted towards Siberia beginning around 17,000 years ago, with the youngest known records being around 14,000 years old in northeast Siberia, coinciding with the Bølling–Allerød warming, which likely disrupted its habitat, with environmental DNA records possibly extending the range of the species around 9,800 years ago. Its closest living relative is the Sumatran rhinoceros.
The steppe bison or steppe wisent is an extinct species of bison. It was widely distributed across the mammoth steppe, ranging from Western Europe to eastern Beringia in North America during the Late Pleistocene. It is ancestral to all North American bison, including ultimately modern American bison. Three chronological subspecies, Bison priscus priscus, Bison priscus mediator, and Bison priscus gigas, have been suggested.
Panthera spelaea, commonly known as the cave lion, is an extinct Panthera species that was native to Eurasia and northwest North America during the Pleistocene epoch. Genetic analysis of ancient DNA has revealed that while closely related, it was a distinct species genetically isolated from the modern lion, with the genetic divergence between the two species estimated at around 500,000 years ago. The earliest fossils of the P. spelaea lineage in Eurasia date to around 700,000 years ago. It is closely related and probably ancestral to the American lion. The species ranged from Western Europe to eastern Beringia in North America, and was a prominent member of the mammoth steppe fauna, and an important apex predator across its range. It became extinct about 13,000 years ago. It closely resembled living lions with a coat of yellowish-grey fur though unlike extant lions, males appear to have lacked manes.
The Late Pleistocene is an unofficial age in the international geologic timescale in chronostratigraphy, also known as the Upper Pleistocene from a stratigraphic perspective. It is intended to be the fourth division of the Pleistocene Epoch within the ongoing Quaternary Period. It is currently defined as the time between c. 129,000 and c. 11,700 years ago. The late Pleistocene equates to the proposed Tarantian Age of the geologic time scale, preceded by the officially ratified Chibanian. The beginning of the Late Pleistocene is the transition between the end of the Penultimate Glacial Period and the beginning of the Last Interglacial around 130,000 years ago. The Late Pleistocene ends with the termination of the Younger Dryas, some 11,700 years ago when the Holocene Epoch began.
The Older Dryas was a stadial (cold) period between the Bølling and Allerød interstadials, about 14,000 years Before Present, towards the end of the Pleistocene. Its date range is not well defined, with estimates varying by 400 years, but its duration is agreed to have been around two centuries.
Mammuthus trogontherii, sometimes called the steppe mammoth, is an extinct species of mammoth that ranged over most of northern Eurasia during the Early and Middle Pleistocene, approximately 1.7 million to 200,000 years ago. The evolution of the steppe mammoth marked the initial adaptation of the mammoth lineage towards cold environments, with the species probably being covered in a layer of fur. One of the largest mammoth species, it evolved in East Asia during the Early Pleistocene, around 1.8 million years ago, before migrating into North America around 1.3 million years ago, and into Europe during the Early/Middle Pleistocene transition, around 1 to 0.7 million years ago. It was the ancestor of the woolly mammoth and Columbian mammoth of the later Pleistocene.
Yedoma is an organic-rich Pleistocene-age permafrost with ice content of 50–90% by volume. Yedoma are abundant in the cold regions of eastern Siberia, such as northern Yakutia, as well as in Alaska and the Yukon.
Pleistocene rewilding is the advocacy of the reintroduction of extant Pleistocene megafauna, or the close ecological equivalents of extinct megafauna. It is an extension of the conservation practice of rewilding, which aims to restore functioning, self-sustaining ecosystems through practices that may include species reintroductions.
The woolly mammoth is an extinct species of mammoth that lived from the Middle Pleistocene until its extinction in the Holocene epoch. It was one of the last in a line of mammoth species, beginning with the African Mammuthus subplanifrons in the early Pliocene. The woolly mammoth began to diverge from the steppe mammoth about 800,000 years ago in Siberia. Its closest extant relative is the Asian elephant. The Columbian mammoth lived alongside the woolly mammoth in North America, and DNA studies show that the two hybridised with each other. Mammoth remains had long been known in Asia before they became known to Europeans. The origin of these remains was long a matter of debate and often explained as being remains of legendary creatures. The mammoth was identified as an extinct species of elephant by Georges Cuvier in 1796.
The Late Pleistocene to the beginning of the Holocene saw the extinction of the majority of the world's megafauna, which resulted in a collapse in faunal density and diversity across the globe. The extinctions during the Late Pleistocene are differentiated from previous extinctions by its extreme size bias towards large animals, and widespread absence of ecological succession to replace these extinct megafaunal species, and the regime shift of previously established faunal relationships and habitats as a consequence. The timing and severity of the extinctions varied by region and are thought to have been driven by varying combinations of human and climatic factors. Human impact on megafauna populations is thought to have been driven by hunting ("overkill"), as well as possibly environmental alteration. The relative importance of human vs climatic factors in the extinctions has been the subject of long-running controversy.
Pleistocene Park is a nature reserve on the Kolyma River south of Chersky in the Sakha Republic, Russia, in northeastern Siberia, where an attempt is being made to re-create the northern subarctic steppe grassland ecosystem that flourished in the area during the last glacial period.
Silene stenophylla is a species of flowering plant in the family Caryophyllaceae. Commonly called narrow-leafed campion, it is a species in the genus Silene. It grows in the Arctic tundra of far eastern Siberia and the mountains of northern Japan. Frozen samples, estimated via radiocarbon dating to be around 32,000 years old, were discovered in the same area as current living specimens, and in 2012, a team of scientists successfully regenerated a plant from the samples.
The Beringian wolf is an extinct population of wolf that lived during the Ice Age. It inhabited what is now modern-day Alaska, Yukon, and northern British Columbia. Some of these wolves survived well into the Holocene. The Beringian wolf is an ecomorph of the gray wolf and has been comprehensively studied using a range of scientific techniques, yielding new information on their prey species and feeding behaviors. It has been determined that these wolves are morphologically distinct from modern North American wolves and genetically basal to most modern and extinct wolves. The Beringian wolf has not been assigned a subspecies classification and its relationship with the extinct European cave wolf is not clear.
During the Pleistocene, wolves were widely distributed across the Northern Hemisphere. Some Pleistocene wolves, such as Beringian wolves and those from Japan, exhibited large body size in comparison to modern gray wolf populations. Genetic analysis of the remains of Late Pleistocene wolves suggest that across their range populations of wolves maintained considerable gene flow between each other and thus there was limited genetic divergence between them. Modern wolves mostly draw their ancestry from some Siberian populations of Late Pleistocene gray wolves, which largely replaced other gray wolf populations after the Last Glacial Maximum.
The cave wolf is an extinct glacial mammoth steppe-adapted white wolf that lived during the Middle Pleistocene to the Late Pleistocene. It inhabited Europe, where its remains have been found in many caves. Its habitat included the mammoth steppe grasslands and boreal needle forests. This large wolf was short-legged compared to its body size, yet its leg size is comparable with that of the Arctic wolf C. l. arctos. Genetic evidence suggests that Late Pleistocene European wolves shared high genetic connectivity with contemporary wolves from Siberia, with continual gene flow from Siberian wolves into European wolves over the course of the Late Pleistocene. Modern European wolves derive most of their ancestry from Siberian wolf populations that expanded into Europe during and after the Last Glacial Maximum, but retain a minor fraction of their ancestry from earlier Late Pleistocene European wolves.
Changing climate conditions are amplified in polar regions and northern high-latitude areas are projected to warm at twice the rate of the global average. These modifications result in ecosystem interactions and feedbacks that can augment or mitigate climatic changes. These interactions may have been important through the large climate fluctuations since the glacial period. Therefore it is useful to review the past dynamics of vegetation and climate to place recent observed changes in the Arctic into context. This article focuses on northern Alaska where there has been much research on this theme.
{{cite journal}}
: CS1 maint: multiple names: authors list (link)