In July 2018, theInternational Union of Geological Sciences split the Holocene Epoch into three distinctages based on the climate,Greenlandian (11,700 years ago to 8,200 years ago),Northgrippian (8,200 years ago to 4,200 years ago) andMeghalayan (4,200 years ago to the present), as proposed by theInternational Commission on Stratigraphy.[7] The oldest age, the Greenlandian, was characterized by a warming following the preceding ice age. The Northgrippian Age is known for vast cooling due to a disruption in ocean circulations that was caused by the melting of glaciers. The most recent age of the Holocene is the present Meghalayan, which began with extreme drought that lasted around 200 years.[7]
The word "Holocene" comes fromAncient Greekὅλος (hólos), meaning "whole", andκαινός (kainós), meaning "new, recent", referring that this epoch is "entirely new".[8][9][10] The suffix '-cene' is used for all the seven epochs of theCenozoic Era.
TheInternational Commission on Stratigraphy has defined the Holocene as starting approximately 11,700 years before 2000CE (11,650cal yearsBP, or 9,700 BCE).[5] The Subcommission on Quaternary Stratigraphy (SQS) regards the term 'recent' as an incorrect way of referring to the Holocene, preferring the term 'modern' instead to describe current processes. It also observes that the term 'Flandrian' may be used as a synonym for Holocene, although it is becoming outdated.[11] The International Commission on Stratigraphy, however, considers the Holocene to be an epoch following thePleistocene and specifically following thelast glacial period. Local names for thelast glacial period include theWisconsinan inNorth America,[12] theWeichselian in Europe,[13] the Devensian in Britain,[14] theLlanquihue in Chile[15] and the Otiran in New Zealand.[16]
The Holocene can be subdivided into five time intervals, orchronozones, based on climatic fluctuations:[17][needs update?]
Note: "ka BP" means "kilo-annumBefore Present", i.e. 1,000 years before 1950 (non-calibratedC14 dates)
Geologists working in different regions are studying sea levels, peat bogs, andice-core samples, using a variety of methods, with a view toward further verifying and refining theBlytt–Sernander sequence. This is a classification of climatic periods initially defined by plant remains inpeat mosses.[18] Though the method was once thought to be of little interest, based on14C dating of peats that was inconsistent with the claimed chronozones,[19] investigators have found a general correspondence acrossEurasia andNorth America. The scheme was defined forNorthern Europe, but theclimate changes were claimed to occur more widely. The periods of the scheme include a few of the final pre-Holocene oscillations of the last glacial period and then classify climates of more recentprehistory.[20]
Paleontologists have not defined anyfaunal stages for the Holocene. If subdivision is necessary, periods of human technological development, such as theMesolithic,Neolithic, andBronze Age, are usually used. However, the time periods referenced by these terms vary with the emergence of those technologies in different parts of the world.[21]
Some scholars have argued that a third epoch of the Quaternary, theAnthropocene, has now begun.[22] This term has been used to denote the present time-interval in which many geologically significant conditions and processes have been profoundly altered by human activities. The 'Anthropocene' (a term coined byPaul J. Crutzen andEugene Stoermer in 2000) was never a formally defined geological unit. The Subcommission on Quaternary Stratigraphy (SQS) of theInternational Commission on Stratigraphy (ICS) had a working group to determine whether it should be. In May 2019, members of the working group voted in favour of recognizing the Anthropocene as formal chrono-stratigraphic unit, with stratigraphic signals around the mid-twentieth century CE as its base. The exact criteria were still to be determined, after which the recommendation also had to be approved by the working group's parent bodies (ultimately theInternational Union of Geological Sciences).[23] In March 2024, after 15 years of deliberation, the Anthropocene Epoch proposal of the working group was voted down by a wide margin by the SQS, owing largely to its shallow sedimentary record and extremely recent proposed start date.[24][25] The ICS and the International Union of Geological Sciences later formally confirmed, by a near unanimous vote, the rejection of the working group's Anthropocene Epoch proposal for inclusion in the Geologic Time Scale.[26][27][28]
The Holocene is a geologic epoch that follows directly after the Pleistocene. Continental motions due toplate tectonics are less than a kilometre over a span of only 10,000 years. However, ice melt caused worldsea levels to rise about 35 m (115 ft) in the early part of the Holocene and another 30 m in the later part of the Holocene. In addition, many areas above about40 degrees north latitude had been depressed by the weight of the Pleistocene glaciers and rose as much as 180 m (590 ft) due topost-glacial rebound over the late Pleistocene and Holocene, and are still rising today.[29]
The sea-level rise and temporaryland depression allowed temporary marine incursions into areas that are now far from the sea. For example, marine fossils from the Holocene epoch have been found in locations such asVermont andMichigan. Other than higher-latitude temporary marine incursions associated with glacial depression, Holocene fossils are found primarily in lakebed,floodplain, andcave deposits. Holocene marine deposits along low-latitude coastlines are rare because the rise in sea levels during the period exceeds any likelytectonic uplift of non-glacial origin.[citation needed]
Post-glacial rebound in theScandinavia region resulted in a shrinkingBaltic Sea. The region continues to rise, still causing weakearthquakes across Northern Europe. An equivalent event in North America was the rebound ofHudson Bay, as it shrank from its larger, immediate post-glacialTyrrell Sea phase, to its present boundaries.[30]
Vegetation and water bodies in northern and central Africa in theEemian (bottom) and Holocene (top)
The climate throughout the Holocene has shown significant variability despite ice core records from Greenland suggesting a more stable climate following the preceding ice age. Marine chemical fluxes during the Holocene were lower than during the Younger Dryas, but were still considerable enough to imply notable changes in the climate.
The temporal and spatial extent of climate change during the Holocene is an area of considerable uncertainty, withradiative forcing recently proposed to be the origin of cycles identified in the North Atlantic region. Climate cyclicity through the Holocene (Bond events) has been observed in or near marine settings and is strongly controlled by glacial input to the North Atlantic.[31][32] Periodicities of ≈2500, ≈1500, and ≈1000 years are generally observed in the North Atlantic.[33][34][35] At the same time spectral analyses of the continental record, which is remote from oceanic influence, reveal persistent periodicities of 1,000 and 500 years that may correspond to solar activity variations during the Holocene Epoch.[36] A 1,500-year cycle corresponding to the North Atlantic oceanic circulation may have had widespread global distribution in the Late Holocene.[36] From 8,500 BP to 6,700 BP, North Atlantic climate oscillations were highly irregular and erratic because of perturbations from substantial ice discharge into the ocean from the collapsing Laurentide Ice Sheet.[37] The Greenland ice core records indicate that climate changes became more regional and had a larger effect on the mid-to-low latitudes and mid-to-high latitudes after ~5600 B.P.[38]
Human activity through land use changes already by the Mesolithic had major ecological impacts;[39] it was an important influence on Holocene climatic changes, and is believed to be why the Holocene is an atypical interglacial that has not experienced significant cooling over its course.[40] From the start of theIndustrial Revolution onwards, large-scale anthropogenic greenhouse gas emissions caused the Earth to warm.[41] Likewise, climatic changes have induced substantial changes in human civilisation over the course of the Holocene.[42][43]
During the transition from the last glacial to the Holocene, theHuelmo–Mascardi Cold Reversal in theSouthern Hemisphere began before the Younger Dryas, and the maximum warmth flowed south to north from 11,000 to 7,000 years ago. It appears that this was influenced by the residual glacial ice remaining in theNorthern Hemisphere until the later date.[citation needed] The first major phase of Holocene climate was thePreboreal.[44] At the start of the Preboreal occurred thePreboreal Oscillation (PBO).[45] TheHolocene Climatic Optimum (HCO) was a period of warming throughout the globe but was not globally synchronous and uniform.[46] Following the HCO, the global climate entered a broad trend of very gradual cooling known asNeoglaciation, which lasted from the end of the HCO to before theIndustrial Revolution.[44] From the 10th-14th century, the climate was similar to that of modern times during a period known as theMediaeval Warm Period (MWP), also known as the Mediaeval Climatic Optimum (MCO). It was found that the warming that is taking place in current years is both more frequent and more spatially homogeneous than what was experienced during the MWP. A warming of +1 degree Celsius occurs 5–40 times more frequently in modern years than during the MWP. The major forcing during the MWP was due to greater solar activity, which led to heterogeneity compared to the greenhouse gas forcing of modern years that leads to more homogeneous warming. This was followed by theLittle Ice Age (LIA) from the 13th or 14th century to the mid-19th century.[47] The LIA was the coldest interval of time of the past two millennia.[48] Following the Industrial Revolution, warm decadal intervals became more common relative to before as a consequence of anthropogenic greenhouse gases, resulting in progressive global warming.[41] In the late 20th century, anthropogenic forcing superseded variations in solar activity as the dominant driver of climate change,[49] though solar activity has continued to play a role.[50][51]
European coastline: modern (left), during the early Holocene (center) and during theLast Glacial Maximum (right)
Drangajökull, Iceland's northernmost glacier, melted shortly after 9,200 BP.[52] InNorthern Germany, the Middle Holocene saw a drastic increase in the amount of raised bogs, most likely related to sea level rise. Although human activity affected geomorphology and landscape evolution in Northern Germany throughout the Holocene, it only became a dominant influence in the last four centuries.[53] In theFrench Alps, geochemistry and lithium isotope signatures in lake sediments have suggested gradual soil formation from theLast Glacial Period to theHolocene climatic optimum, and this soil development was altered by the settlement of human societies. Early anthropogenic activities such as deforestation and agriculture reinforced soil erosion, which peaked in theMiddle Ages at an unprecedented level, marking human forcing as the most powerful factor affecting surface processes.[54] The sedimentary record fromAitoliko Lagoon indicates that wet winters locally predominated from 210 to 160 BP, followed by dry winter dominance from 160 to 20 BP.[55]
North Africa, dominated by theSahara Desert in the present, was instead a savanna dotted with large lakes during the Early and Middle Holocene,[56] regionally known as theAfrican Humid Period (AHP).[57] The northward migration of theIntertropical Convergence Zone (ITCZ) produced increased monsoon rainfall over North Africa.[58] The lush vegetation of the Sahara brought an increase inpastoralism.[59] The AHP ended around 5,500 BP, after which the Sahara began to dry and become the desert it is today.[60]
A stronger East African Monsoon during the Middle Holocene increased precipitation in East Africa and raised lake levels.[61] Around 800 AD, or 1,150 BP, a marine transgression occurred in southeastern Africa; in the Lake Lungué basin, this sea level highstand occurred from 740 to 910 AD, or from 1,210 to 1,040 BP, as evidenced by the lake's connection to the Indian Ocean at this time. This transgression was followed by a period of transition that lasted until 590 BP, when the region experienced significant aridification and began to be extensively used by humans for livestock herding.[62]
In theKalahari Desert, Holocene climate was overall very stable and environmental change was of low amplitude. Relatively cool conditions have prevailed since 4,000 BP.[63]
In theMiddle East, the Holocene brought a warmer and wetter climate, in contrast to the preceding cold, dryYounger Dryas. The Early Holocene saw the advent and spread of agriculture in theFertile Crescent—sheep,goat,cattle, and laterpig were domesticated, as well as cereals, likewheat andbarley, andlegumes—which would laterdisperse into much of the world. This 'Neolithic Revolution', likely influenced by Holocene climatic changes, included an increase insedentism and population, eventually resulting in the world's first large-scale state societies inMesopotamia andEgypt.[64]
During the Middle Holocene, theIntertropical Convergence Zone, which governs the incursion of monsoon precipitation through theArabian Peninsula, shifted southwards, resulting in increased aridity.[65] In the Middle to Late Holocene, the coastline of theLevant andPersian Gulf receded, prompting a shift in human settlement patterns following this marine regression.[66]
Central Asia experienced glacial-like temperatures until about 8,000 BP, when the Laurentide Ice Sheet collapsed.[67] InXinjiang, long-term Holocene warming increased meltwater supply during summers, creating large lakes and oases at low altitudes and inducing enhanced moisture recycling.[68] In theTien Shan, sedimentological evidence from Swan Lake suggests the period between 8,500 and 6,900 BP was relatively warm, with steppe meadow vegetation being predominant. An increase inCyperaceae from 6,900 to 2,600 BP indicates cooling and humidification of the Tian Shan climate that was interrupted by a warm period between 5,500 and 4,500 BP. After 2,600 BP, an alpine steppe climate prevailed across the region.[69] Sand dune evolution in the Bayanbulak Basin shows that the region was very dry from the Holocene's beginning until around 6,500 BP, when a wet interval began.[70] In theTibetan Plateau, the moisture optimum spanned from around 7,500 to 5,500 BP.[71] TheTarim Basin records the onset of significant aridification around 3,000-2,000 BP.[72]
After 11,800 BP, and especially between 10,800 and 9,200 BP,Ladakh experienced tremendous moisture increase most likely related to the strengthening of the Indian Summer Monsoon (ISM). From 9,200 to 6,900 BP, relative aridity persisted in Ladakh. A second major humid phase occurred in Ladakh from 6,900 to 4,800 BP, after which the region was again arid.[73]
From 900 to 1,200 AD, during the MWP, the ISM was again strong as evidenced by low δ18O values from the Ganga Plain.[74]
The sediments ofLonar Lake inMaharashtra record dry conditions around 11,400 BP that transitioned into a much wetter climate from 11,400 to 11,100 BP due to intensification of the ISM. Over the Early Holocene, the region was very wet, but during the Middle Holocene from 6,200 to 3,900 BP, aridification occurred, with the subsequent Late Holocene being relatively arid as a whole.[75]
Coastal southwestern India experienced a stronger ISM from 9,690 to 7,560 BP, during the HCO. From 3,510 to 2,550 BP, during the Late Holocene, the ISM became weaker, although this weakening was interrupted by an interval of unusually high ISM strength from 3,400 to 3,200 BP.[76]
Southwestern China experienced long-term warming during the Early Holocene up until ~7,000 BP.[77] Northern China experienced an abrupt aridification event approximately 4,000 BP.[78] From around 3,500 to 3,000 BP, northeastern China underwent a prolonged cooling, manifesting itself with the disruption of Bronze Age civilisations in the region.[79] Eastern and southern China, the monsoonal regions of China, were wetter than present in the Early and Middle Holocene.[80] Lake Huguangyan's TOC, δ13Cwax, δ13Corg, δ15N values suggest the period of peak moisture lasted from 9,200 to 1,800 BP and was attributable to a strong East Asian Summer Monsoon (EASM).[81] Late Holocene cooling events in the region were dominantly influenced by solar forcing, with many individual cold snaps linked to solar minima such as the Oort,Wolf,Spörer, andMaunder Minima.[82] A notable cooling event in southeastern China occurred 3,200 BP.[83] Strengthening of the winter monsoon occurred around 5,500, 4,000, and 2,500 BP.[84] Monsoonal regions of China became more arid in the Late Holocene.[80]
In the Sea of Japan, the Middle Holocene was notable for its warmth, with rhythmic temperature fluctuations every 400–500 and 1,000 years.[85]
Before 7,500 BP, theGulf of Thailand was exposed above sea level and was very arid. A marine transgression occurred from 7,500 to 6,200 BP amidst global warming.[86]
During the Middle Holocene, western North America was drier than present, with wetter winters and drier summers.[87] After the end of the thermal maximum of the HCO around 4,500 BP, theEast Greenland Current underwent strengthening.[88] A massive megadrought occurred from 2,800 to 1,850 BP in theGreat Basin.[89]
Eastern North America underwent abrupt warming and humidification around 10,500 BP and then declined from 9,300 to 9,100 BP. The region has undergone a long term wettening since 5,500 BP occasionally interrupted by intervals of high aridity. A major cool event lasting from 5,500 to 4,700 BP was coeval with a major humidification before being terminated by a major drought and warming at the end of that interval.[90]
During the Early Holocene, relative sea level rose in theBahia region, causing a landward expansion of mangroves. During the Late Holocene, the mangroves declined as sea level dropped and freshwater supply increased.[91] In theSanta Catarina region, the maximum sea level highstand was around 2.1 metres above present and occurred about 5,800 to 5,000 BP.[92] Sea levels atRocas Atoll were likewise higher than present for much of the Late Holocene.[93]
The Northwest Australian Summer Monsoon was in a strong phase from 8,500 to 6,400 BP, from 5,000 to 4,000 BP (possibly until 3,000 BP), and from 1,300 to 900 BP, with weak phases in between and the current weak phase beginning around 900 BP after the end of the last strong phase.[94]
Ice core measurements imply that thesea surface temperature (SST) gradient east of New Zealand, across the subtropical front (STF), was around 2 degrees Celsius during the HCO. This temperature gradient is significantly less than modern times, which is around 6 degrees Celsius. A study utilizing five SST proxies from 37°S to 60°S latitude confirmed that the strong temperature gradient was confined to the area immediately south of the STF, and is correlated with reduced westerly winds near New Zealand.[95] Since 7,100 BP, New Zealand experienced 53 cyclones similar in magnitude toCyclone Bola.[96]
Evidence from theGalápagos Islands shows that theEl Niño–Southern Oscillation (ENSO) was significantly weaker during the Middle Holocene, but that the strength of ENSO became moderate to high over the Late Holocene.[97]
The decimation of terrestrialmegafauna species outside of Africa during the preceding 40,000 years (theLate Pleistocene megafauna extinctions), likely as a result of climate change, human hunting, or a combination of both, including in the extinction of over half of all megafauna species, left Holocene ecosystems highly altered and depauperate at their highest trophic levels compared to those in the preceding Pleistocene.[98] Megafauna losses continued during the early-mid Holocene, with theIrish elk (Megaloceros giganteus, also known as the giant deer) surviving until around 7,700 years ago in western Russia,[99] withwoolly mammoths (Mammuthus primigenius) surviving in mainland Siberia until around 10,000 years ago,[100] with a small population onWrangel Island surviving until around 4,000 years ago.[101]
Throughout the world, ecosystems in cooler climates that were previously regional have been isolated in higher altitude ecological "islands".[102]
The8.2-ka event, an abrupt cold spell recorded as a negative excursion in theδ18O record lasting 400 years, is the most prominent climatic event occurring in the Holocene Epoch, and may have marked a resurgence of ice cover. It has been suggested that this event was caused by the final drainage ofLake Agassiz, which had been confined by the glaciers, disrupting thethermohaline circulation of theAtlantic.[103] This disruption was the result of an ice dam overHudson Bay collapsing sending coldlake Agassiz water into theNorth Atlantic ocean.[104] Furthermore, studies show that the melting ofLake Agassiz led to sea-level rise which flooded the North American coastal landscape. The basal peat plant was then used to determine the resulting local sea-level rise of 0.20-0.56m in theMississippi Delta.[104] Subsequent research, however, suggested that the discharge was probably superimposed upon a longer episode of cooler climate lasting up to 600 years and observed that the extent of the area affected was unclear.[105]
The preceding period of the Late Pleistocene had already brought advancements such as thebow and arrow, creating more efficient forms of hunting and replacingspear throwers. In the Holocene, however, thedomestication of plants and animals allowed humans to develop villages and towns in centralized locations. Archaeological data shows that between 10,000 and 7,000BP rapid domestication of plants and animals took place in tropical and subtropical parts ofAsia,Africa, andCentral America.[108] The development of farming allowed humans to transition away fromhunter-gatherer nomadic cultures, which did not establish permanent settlements, to a more sustainablesedentary lifestyle. This form of lifestyle change allowed humans to develop towns and villages in centralized locations, which gave rise to the world known today. It is believed that the domestication of plants and animals began in the early part of the Holocene in the tropical areas of the planet.[108] Because these areas had warm, moist temperatures, the climate was perfect for effective farming. Culture development and human population change, specifically in South America, has also been linked to spikes in hydroclimate resulting in climate variability in the mid-Holocene (8.2–4.2 k cal BP).[109] Climate change on seasonality and available moisture also allowed for favorable agricultural conditions which promoted human development for Maya and Tiwanaku regions.[110] In theKorean Peninsula, climatic changes fostered a population boom during theMiddle Chulmun period from 5,500 to 5,000 BP, but contributed to a subsequent bust during the Late and Final Chulmun periods, from 5,000 to 4,000 BP and from 4,000 to 3,500 BP respectively.[111]
Combination of temperature indicators ("proxies") for north-western Europe from Greenland icecores and Alpine glacier extensions, with subdivisions from three disciplines
^The name "Holocene" was proposed in 1850 by the French palaeontologist and entomologistPaul Gervais (1816–1879):Gervais, Paul (1850)."Sur la répartition des mammifères fossiles entre les différents étages tertiaires qui concourent à former le sol de la France" [On the distribution of mammalian fossils among the different tertiary stages which help to form the ground of France].Académie des Sciences et Lettres de Montpellier. Section des Sciences (in French).1:399–413.Archived from the original on 2020-05-22. Retrieved2018-07-15.From p. 413:Archived 2020-05-22 at theWayback Machine"On pourrait aussi appelerHolocènes, ceux de l'époque historique, ou dont le dépôt n'est pas antérieur à la présence de l'homme; … " (One could also call "Holocene" those [deposits] of the historic era, or the deposit of which is not prior to the presence of man; … )
^Gibbard, P. L.; Head, M. J. (2020-01-01), Gradstein, Felix M.; Ogg, James G.; Schmitz, Mark D.; Ogg, Gabi M. (eds.),"Chapter 30 – The Quaternary Period",Geologic Time Scale 2020, Elsevier, pp. 1217–1255,ISBN978-0-12-824360-2, retrieved2022-04-21.
^Schrøder, N.; Højlund Pedersen, L.; Juel Bitsch, R. (2004). "10,000 years of climate change and human impact on the environment in the area surrounding Lejre".The Journal of Transdisciplinary Environmental Studies.3 (1):1–27.
^abKravchinsky, V.A.; Langereis, C.G.; Walker, S.D.; Dlusskiy, K.G.; White, D. (2013). "Discovery of Holocene millennial climate cycles in the Asian continental interior: Has the sun been governing the continental climate?".Global and Planetary Change.110:386–396.Bibcode:2013GPC...110..386K.doi:10.1016/j.gloplacha.2013.02.011.
^abGupta, Anil K. (10 July 2004). "Origin of agriculture and domestication of plants and animals linked to early Holocene climate amelioration".Current Science.87 (1):54–59.ISSN0011-3891.JSTOR24107979.
^Ripple WJ, Wolf C, Newsome TM, Galetti M, Alamgir M, Crist E, Mahmoud MI, Laurance WF (13 November 2017)."World Scientists' Warning to Humanity: A Second Notice"(PDF).BioScience.67 (12):1026–1028.doi:10.1093/biosci/bix125. Archived fromthe original(PDF) on 15 December 2019. Retrieved4 October 2022.Moreover, we have unleashed a mass extinction event, the sixth in roughly 540 million years, wherein many current life forms could be annihilated or at least committed to extinction by the end of this century.
^Hollingsworth, Julia (June 11, 2019)."Almost 600 plant species have become extinct in the last 250 years". CNN. RetrievedJanuary 14, 2020.The research – published Monday in Nature, Ecology & Evolution journal – found that 571 plant species have disappeared from the wild worldwide, and that plant extinction is occurring up to 500 times faster than the rate it would without human intervention.
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