Late Holocene Climate Change Research Articles

Long-Term Steady-State Dry Boreal Forest in the Face of Disturbance

We used bioproxies from paleosoils buried within two aeolian dunes to test hypotheses concerning the origin of dry sandy boreal forests in Canada. These forests are dominated today by Pinus banksiana Lamb. One hypothesis is that too frequent Holocene stand-replacing fires would have transformed the original vegetation through extirpation of susceptible species to fire in water stress habitat. Alternatively, the ecosystem would have not changed since the dunes stabilized enough to support forest establishment. The vegetation composition and richness were determined by identification of charcoal and macroremains and radiocarbon dating for the chronology. Both sites revealed a similar history covering 6400 years. Half of the charcoal layers were less than 2500 years old in both sites, indicating that they had been subjected to the same fire history. Data indicated a stable plant composition and richness, although the percentage of Pinus decreased slightly over 4000 years (decreasing rate 1% per century). The fungus Cenococcum geophilum was consistently present, with a stochastic abundance. The vegetation grew under natural fire conditions and soil dryness since 6000 years. The ecosystem was probably not stressed by late-Holocene fires or climate changes, as the multi-millennial steady state reveals a resistant and resilient ecosystem.

Use of the magnetic, geochemical, and sedimentary records in establishing paleoclimate change in the environment of Sebkha: Case of the Sebkha Mhabeul in southeastern Tunisia

In this study, we explored the evidence of late Holocene climate changes in southern Tunisia, examining extreme events of flood and sandstorm sedimentary succession records, in Sebkha Mhabeul. A sediment-derived climatic proxy was inferred from a 93.5-cm-deep core (Mh1), whose dating by tephrochronology has already been achieved in previous works. Multiple geochemical, sedimentological, magnetic susceptibility, and quartz grain microtexture proxies were used to determine the shifts in regional climatic conditions. The Sebkha core captured sensitive changes in the precipitation/evaporation (P/E) balance by adjustments in salinity, and is especially valuable for reconstructing variability over centennial timescales. The Sebkha Mhabeul area showed higher salinity during the Roman Warm Period (RWP: 2100–1400 cal yr BP), the Medieval Warm Period (MWP: 1000–600 cal yr BP) and the present era, and generally lower salinity during the Dark Ages (DA: 1400-1000 cal yr BP) and the Little Ice Age (LIA: 600-200 cal yr BP).In southeastern Tunisia, the hydrological behavior was sometimes consistent with the flood activities in the eastern Mediterranean, and sometimes contemporaneous with the flood pulsations of the western Mediterranean.

Проявление климатических изменений и природных катастроф в позднем голоцене на юге о. Уруп (Курильские острова)

Проявление климатических изменений и природных катастроф в позднем голоцене на юге о. Уруп (Курильские острова)

Chinook Salmon, Late Holocene Climate Change, and the Occupational History of Kettle Falls, a Columbia River Fishing Station

ABSTRACT Kettle Falls, located 1125 km from the mouth of the Columbia River in present-day Washington State (USA), was the second-most important salmon fishing and trading locus on that river in the early historic era. We encapsulate the late Holocene history of the fishery by deriving a summed probability distribution function (SPDF) from 50 radiocarbon ages from 13 archaeological sites within 2 km of the falls. When compared to an SPDF from 307 sites from elsewhere on the Columbia Plateau, and a null model, the Kettle Falls SPDF exhibits two phases of elevated activity at 1700–1300 cal BP and 800–500 cal BP, and an intervening lull. These phases are not related to the excavation history or differential exposure of sites to taphonomic processes, but they are concordant with episodes of glacial advance in the local mountains, which reflect hemispheric-scale changes in climate. Modern returns of summer-run Chinook salmon to the Columbia River are inversely correlated with sea-surface temperature regimes in the northeast Pacific Ocean, and we propose that the occupational history of the Kettle Falls fishery echoes long-term variations in the returns of salmon to the upper Columbia River linked to climate change.

A sub-centennial, Little Ice Age climate reconstruction using beetle subfossil data from Nunalleq, southwestern Alaska

There is myriad evidence that global warming is exerting a profoundly disruptive influence on the lifeways of modern native (Yup'ik) communities living in the Yukon-Kuskokwim (Y-K) delta of southwestern Alaska. Yup'ik subsistence is intimately tied to seasonal change and the ability to accurately predict the availability of plant and animal resources. It therefore seems reasonable to suggest that periods of climatic instability such as the Little Ice Age (LIA) may have had a deleterious effect on Yup'ik communities in the past. However, at present there are no palaeotemperature records that document the localised climatic changes of the last millennium in the Y-K Delta region. This lack of data hinders our understanding of the archaeological record from the site of Nunalleq, which is situated at the heart of the delta and was occupied during the LIA. To address this oversight, this paper presents the results of a Coleoptera (beetle) based climate reconstruction from a peat profile in the vicinity of Nunalleq to investigate the magnitude of Late Holocene climatic changes. Using the Mutual Climatic Range (MCR) method, we reconstruct mean summer and winter temperatures from the mid-15th to late-19th centuries. The results indicate that the past environments of Nunalleq were characterised by a climate significantly cooler than the present. The earliest definitive evidence for Little Ice Age cooling dates from the late 16th century, when mean summer temperatures were at least 1.2ᵒC below the modern mean. Temperatures appear to have remained lower than modern until the early 19th century. The coolest Nunalleq record – 1.3ᵒC below the modern mean summer temperatures – is centred on AD 1815, after which there is evidence for climatic amelioration. These data present differences with observations from other regions of Alaska and underline the importance of more local palaeoclimate reconstructions, particularly when interrogating the relationships between past climatic and social change.

Multiproxy record of late Holocene climatic changes and natural hazards from paleolake deposits of Urup Island (Kuril Islands, North-Western Pacific)

The evolution of the late Holocene environments has been reconstructed on the basis of multiproxy studies of peat sequences. The vegetation response to short-period climate fluctuations has been traced. Early in the late Holocene there were birch forests with oak and other broadleaf trees; vast areas were occupied by forb meadows. Under cooling (3250 yr BP) the shrub pine (Pinus pumila) became the landscape-forming species, and since 2490 yr BP Selaginella selaginoides appeared in abundance. The Little Ice Age was marked by the disappearance of broadleaf trees and widely spread heath land communities. The higher stands of the lake level were related to warmings (3660–3590; 3450–3180; 2960–2840; 2410–2260 cal yr BP). Shallowing coincided with short-term coolings (3590–3450; 3180–2960; 2840–2410; 2260–2150 cal yr BP) marked by reduced precipitations. The dune ridge formation began during the longest cooling accompanied by a minor regression. The dunes were stabilized and a paleosol developed ~2340–2260 yr BP. A younger generation of eolian sands developed during the Little Ice Age. An ecological effect of volcanic ashfalls has been estimated. The local biotic components seem to have been most afflicted by the eruption in the north of Iturup in ~2100–2300 cal yr BP, when CKr tephra up to 30 cm thick was deposited. The ages of 4 strongest tsunamis that occurred over the last 3660 years were determined. They appeared to be related to the earthquakes with focuses close to Urup Island or south of it. The lake microflora shows ecological effect of the marine water invasions.

Soil Parameters for Quantitative Estimation of Late Holocene Climate Changes in the Southern East European Plain

The results of studies of the regularities of evolution of soils and the environment in the steppe zone of the East European Plain are presented. Different culture-based chronological stages of the Bronze Age, Iron Age, and Middle Ages (3rd millennium BC–2nd millennium AD) are considered on the basis of buried soils at archeological monuments (burial mounds).

Climate changes in the Eastern Mediterranean over the last 5000 years and their links to the high-latitude atmospheric patterns and Asian monsoons

Abstract This research aims to improve the knowledge of the mid to late Holocene climate changes and the underlying drivers in the eastern Mediterranean. We focus on the Peloponnese peninsula, SW Greece, characterized by a W-E rainfall/temperature gradient and a strong climate-sensitivity to shifts in the large-scale atmospheric patterns. A radiocarbon-dated sediment core, taken from the ancient Lake Lerna, a former lake in NE Peloponnese, was analyzed for distribution and hydrogen isotope (δD) composition of n-alkanes and bulk organic geochemistry (δ13C, TOC). The predominantly macrophyte (submerged/floating)-derived δD23 profile exhibits the largest long-term fluctuation in the record and co-varies with δD of long-chain n-alkanes providing evidence for precipitation and temperature changes over the last 5000 years. The Lerna δD23 signal is sometimes in agreement with other n-alkane δD records from SW Peloponnese indicating wetter conditions in the peninsula at ca 5000–4600, ca 4500–4100, ca 3000–2600 (more unstable in SW) and after ca 700 cal BP with drier periods at ca 4100–3900 and ca 1000–700 cal BP. Conversely, a NE-SW climate see-saw is revealed at ca 4600–4500, ca 3200, ca 2600–1800, and ca 1200–1000 cal BP when the δD23 Lerna exhibits more positive trends (drier in NE) with a reversal at ca 3900–3300, ca 3200–3000 and ca 1800–1300 cal BP. These opposing and sometimes similar signals between NE and SW Peloponnese can be explained by the relative dominance of high-latitude atmospheric patterns over the peninsula. A similar signal would be expected when the North Atlantic Oscillation (NAO) exerts the main control with NAO (+) creating conditions of reduced moisture. The dipole pattern is likely driven by shifts in North Sea–Caspian Atmospheric pattern (NCP), which account for the present-day regional climate variability with NCP (+) leading to wetter and colder conditions in NE Peloponnese. The Asian monsoonal system likely has an additional impact on the δD variabilities through influencing the summer temperatures. There is a consistency between the Peloponnesian δD signals and monsoonal records after ca 4000 cal BP confirming the actualistic models. Strong monsoonal periods coincide with cooler summers (lower δD values) in Lerna, due to the northerly winds, the Etesians. On the contrary, SW Peloponnese is dominated by warmer conditions during the same periods as the area is located on the lee side of the mountain and highly influenced by the adiabatic warming associated with the subsidence over the Eastern Mediterranean.

A First Millennium A.D. Vegetation History from the Crystal River Site (8CI1), Florida

While seldom integrated within coastal archaeological research in Southeastern North America, vegetation histories derived from palynological data offer valuable records of ancient landscape transformations driven by climatic flux, sea-level oscillations, and anthropogenic modifications. In this paper, we develop a paleo-historical-ecological reconstruction from preliminary analyses on fossil pollen assemblages preserved within marsh, hammock, and shell-midden soils at the Crystal River site (8CI1), a mound center on Florida’s west-central coast occupied throughout the first millennium AD. When contextualized alongside paleoenvironmental records from western Florida and farther afield, our analysis suggests that the nature and timing of late-Holocene climatic changes varied little between different sub-regions of Florida’s Gulf Coast, but also that manifestations of eustatic sea-level flux may have been highly localized.

Late Holocene Climate Change in Central Mexico and the Decline of Teotihuacan

For decades, scientists have been trying to determine the causes that led to the decline of Teotihuacan, and they have suggested several possible factors, including wars, social conflict, and droughts. The causality remains unclear, however, and interest in the topic has hardly subsided. In this study, we assess the plausibility of the drought hypothesis by exploring the drought mechanisms in late Holocene central Mexico. Our δ18O records provide valuable information regarding climate variations in late Holocene central Mexico. For example, El Niño–Southern Oscillation decoupled from the Intertropical Convergence Zone (ITCZ) mainly drove late Holocene climate, particularly between 900 and 1550 CE, causing a dry Medieval Climate Anomaly and a wet early Little Ice Age. Most interesting, our results indicate that the decline of Teotihuacan could be partially attributed to seventh-century droughts induced by a coupling of pronounced El Niño and reduced solar output (i.e., a more southern location of the ITCZ). Also, these droughts seem to have caused a corresponding migration from the west into the Basin of Mexico. Key Words: central Mexico, climate change, late Holocene, Teotihuacan.数十年来，科学家们尝试指认导致特奥蒂瓦坎衰败的原因，并提出若干可能因素，包括战争、社会冲突，以及乾旱。但其原因仍不甚明确，而对此议题的兴趣亦丝毫不见衰退。我们于本研究中，通过探讨墨西哥中部在全新世晚期的乾旱过程，评估乾旱假说的可信度。我们的洞穴沉积 δ18氧同位素的纪录，提供墨西哥中部全新世晚期的气候变异之宝贵信息。例如圣婴南方振盪现象与热带幅合带（ITCZ）脱钩，主导了全新世晚期的气候，特别是在公元九百到一千五百五十年之间，导致了乾燥的中世纪气候异常，以及潮湿的早期小冰期。最有趣的是，我们的研究结果指出，特奥蒂瓦坎的衰败，可能部分是由第七世纪时由显着的圣婴现象和减少的太阳能产出（例如位于更南方的 ITCZ）共同引发的乾旱所导致。此外，这些乾旱似乎导致了从墨西哥西部到盆地地区的相应人口迁徙。 关键词：墨西哥中部，气候变迁，全新世晚期，特奥蒂瓦坎。Durante décadas, los científicos han estado tratando de determinar las causas que condujeron a la declinación de Teotihuacán, respecto de lo cual ellos han sugerido varios factores posibles, que incluyen guerras, conflicto social y sequía. Sin embargo, esa causalidad sigue confusa, y el interés en el tema casi no ha menguado. En el presente estudio, evaluamos la plausibilidad de la hipótesis de la sequía explorando los mecanismos de sequedad prolongada en el México central del Holoceno tardío. Nuestros registros δ18O aportan valiosa información en lo que concierne a las variaciones climáticas del centro de México a finales del Holoceno. Por ejemplo, la escisión de El Niño–Oscilación del Sur de la Zona de Convergencia Intertropical (ITCZ) movió principalmente el clima de finales del Holoceno, en particular entre 900 y 1550 CE, causando una Anomalía Climática Medieval seca y una temprana Pequeña Edad del Hielo húmeda. De singular interés, nuestros resultados indican que la declinación de Teotihuacán podría atribuirse parcialmente a las sequías del siglo VII inducidas por la concurrencia de un El Niño intensificado y una reducida intensidad solar (esto es, una localización más meridional de la ITCZ). También, estas sequías parecen haber causado una correspondiente migración desde el oeste hacia la Cuenca de México. Palabras clave: centro de México, cambio climático, Holoceno tardío, Teotihuacán.

Plant pathogen responses to Late Pleistocene and Holocene climate change in the central Atacama Desert, Chile

Future climate change has the potential to alter the distribution and prevalence of plant pathogens, which may have significant implications for both agricultural crops and natural plant communities. However, there are few long-term datasets against which modelled predictions of pathogen responses to climate change can be tested. Here, we use 18S metabarcoding of 28 rodent middens (solidified deposits of rodent coprolites and nesting material) from the Central Atacama, spanning the last ca. 49 ka, to provide the first long-term late Quaternary record of change in plant pathogen communities in response to changing climate. Plant pathogen richness was significantly greater in middens deposited during the Central Andean Pluvial Event (CAPE); a period of increased precipitation between 17.5–8.5 ka. Moreover, the occurrence frequency of Pucciniaceae (rust fungi) was significantly greater during the CAPE, and the highest relative abundances for five additional potentially pathogenic taxa also occurred during this period. The results demonstrate the promising potential for ancient DNA analysis of late Quaternary samples to reveal insights into how plant pathogens responded to past climatic and environmental change, which could help predict how pathogens may responded to future change.

Landscape Changes during the Pleistocene–Holocene Transition and Range Dynamics of Large Herbivorous Mammals of Northern Asia

This work studies the effect of the reduction of steppe and tundra landscapes in Northern Asia during the Late Pleistocene and Holocene climatic changes on the ranges of large herbivorous mammals. The relationship between a complex of characteristics of herbivore species and their landscape was evaluated. It is found that not only the Mongolian gazelle, saiga, and musk ox, but also the snow sheep, the ancestors of domestic sheep and goats, and probably the Amur goral may reduced their ranges during the late Quaternary landscape changes. The widening of the range of the sika deer, as well as the range of the Siberian musk deer associated exclusively with forest landscapes, can be explained by a reduction of open landscapes. Any significant changes in the ranges of roe deer, red deer, reindeer, elk, wild boar, steppe bison, mammoth, woolly rhinoceros, and ancestral and probably related forms of domestic horse and cattle could not be directly caused by landscape changes 17 000–7000 years ago, even if they coincide chronologically.

A multi-proxy late Holocene climate record from aeolian deposits of the Horqin sandy land, northeast China and its societal implications

Abstract Late Holocene climate change is an important issue in global change research, because of its close relationship with human societal development. The Horqin sandy land is an important area for early dryland agriculture development. However, the role that climatic factors, especially temperature and precipitation, played in regional agriculture development is still unclear. This paper presents a high-resolution multi-proxy palaeomoisture record spanning 4300–1000 cal. yr BP derived from sequential aeolian sediments of the Liuhutun section on the northeastern frontier of the Horqin sandy land, northeast China. The 2.96 m section, with a chronology based on seven radiocarbon dates, was analyzed for sediment grain-size, CaCO3 content, organic matter content and environmental magnetic parameters. The results indicate that 4300–3800 cal. yr BP was a humid period with a drying trend; that 3800–1700 cal. yr BP was generally dry; and that 1700–1000 cal. yr BP was sub-humid. It is clear that the regional climate was responsive to East Asian monsoonal circulation driven by variations in Northern Hemisphere summer insolation. We further investigate the relationship between climate change and regional agriculture development by comparing moisture records with regional temperature and subsistence strategy changes inferred from previous studies. The results suggest that high temperature and moderate precipitation may have facilitated agricultural development during the Lower Xiajiadian period (ca. 4000–3400 yr BP). Owing to the drought-tolerant and thermophilic phenological properties of millets, which are major crops of northeast China, temperature may have played a more important role in regional agriculture than precipitation.

Correction to: Late Holocene climate changes from diatom records in the historical reservoir Gonggeomji, Korea

The original version of this article unfortunately contained a mistake. The authors wish to revise the “Acknowledgements” section of their article.

In Memoriam: Keith R Briffa, 1952–2017

Keith R Briffa was one of the most influential palaeoclimatologists of the last 30 years. His primary research interests lay in Late-Holocene climate change with a geographical emphasis on northern Eurasia. His greatest impact was in the field of dendroclimatology, a field that he helped to shape. His contributions have been seminal to the development of sound methods for tree-ring analysis and in their proper application to allow the interpretation of climate variability from tree rings. This led to the development of many important records that allow us to understand natural climate variability on timescales from years to millennia and to set recent climatic trends in their historical context.

Late Holocene landscape instability in the Breckland (England) drift sands

This research investigates the landscape instability associated with the drift sands, which are widespread across north-western Europe. It focuses on Breckland, UK using new sites along with existing geomorphic, archaeological and historical data. This shows landscape instability of drift sands occurred at 5240 ± 1040 years BCE, 600 ± 100, 1150 ± 50, 1600 and ~1790 CE. Comparison of these phases to climate records show no clear patterns with drifting occurring during dry/wet as well as cold/warm periods. Additionally, similar climatic shifts lead to diverging reactions of landscapes in different regions throughout Europe. At the regional scale, land usage and population pressures also may not be the direct cause of sand drifting, suggesting that complex responses or different triggers at different times were responsible. Within this, society's unawareness of the inherent landscape instability and the threat posed by the sand hazard may have been important as it affected whether mitigation measures were or could be implemented. In Breckland, initial instability may have been due to the establishment of the open field system on virgin soil. Later changes in land ownership and associated power within the society, led to an inability of communities to implement mitigation measures and large land owners abstaining from tackling the sand hazard. Whilst the widespread coversands and climatic extremes provide the underlying susceptibility to sand drifting, it would appear that drift sands of the last 2000 years may provide less of a sedimentary archive of Late Holocene climatic changes and more a record of land management changes.

Late glacial and early Holocene climate and environmental changes in the eastern Baltic area inferred from sediment C/N ratio

We assessed the utility of using the sediment total organic carbon/total nitrogen (C/N) ratio as an indicator of paleoclimate changes in the eastern Baltic area during the late glacial and early Holocene. The C/N ratio in sediments from Lake Lielais Svētiņu, eastern Latvia, was compared with other sediment variables that are used as proxies of past climate and environment. Analysis revealed that although the organic matter (OM) content in late glacial sediments was extremely low, the C/N ratio captured information about OM origin, and fluctuations in the ratio tracked climate oscillations. The C/N ratio was significantly positively correlated with pollen-inferred mean summer temperature. Therefore, C/N ratio was lower under colder conditions, indicating a predominantly phytoplankton origin of OM, and was higher during warmer conditions, when there was more vegetation around the lake. A strong positive correlation between C/N ratio and the paleopigment beta carotene suggested that elevated phytoplankton production resulted from higher nutrient availability that was controlled largely by the input of terrestrial OM to the lake during warmer climate episodes. Thus, C/N ratio was a good indicator of paleoclimate changes, at least for the late glacial period, when generally cold conditions prevailed. This study also demonstrates the power of multi-proxy paleolimnological analyses for investigating past environmental changes in lakes and their watersheds.

Late Holocene climate changes from diatom records in the historical Reservoir Gonggeomji, Korea

The paleoenvironmental history of the artificial Reservoir Gonggeomji in Sangju City, Korea, was reconstructed using fossil diatom analysis of four sediment cores: GG01, 02, 03, and 04. Accelerator mass spectrometer (AMS) radiocarbon dating results suggest that Reservoir Gonggeomji was maintained from ca. 1350 to 150 cal year BP, and the diatom record in core sediment samples revealed well-defined hydrological changes and paleoenvironmental conditions during this period. The fossil diatom assemblages were predominantly benthic freshwater diatoms. The highest diatom concentrations in all cores were in diatom zone II, in which species richness and diversity were also very high. Cymbella, Eunotia, Gomphonema, Gyrosigma, Navicula, and Pinnularia were the dominant genera in all core sediments. The long-term trend in diatom species abundance and species diversity showed a stronger relationship to temperature anomalies in the northern hemisphere during the past 2000 years with changes in precipitation. These diatom changes could have been controlled by natural climate change, despite anthropogenic activities linked to construction of the dyke in the artificial reservoir.

Decoupled geomorphic and sedimentary response of Po River and its Alpine tributaries during the last glacial/post-glacial episode

The complex geomorphic and sedimentary evolution of the central Po Plain (northern Italy) during the last 30 ky was reconstructed through the integration of stratigraphic, geomorphological, geochemical and radiocarbon data. A key element of the Late Pleistocene stratigraphy is a 20 km-wide channel-belt sand body, with its top at a depth of ~13 m, fed by the Po River. Whereas the southern boundary of the Po fluvial channel belt coincides with a sharp lithological contact with floodplain muds, its northern boundary is an erosional (sand-on-sand) surface that was traced tentatively in the subsurface with the aid of sediment provenance (Po versus Alpine) proxies and radiocarbon data. Stratigraphic and geomorphological features testify to a decoupled sedimentary and geomorphic response of the Alpine and Po River systems to climate change in the last 30 ky. Contemporaneous Po River incision and Alpine rivers aggradation occurred at the onset of the Last Glacial Maximum (LGM). In contrast, Po River aggradation and Alpine rivers entrenchment took place during early deglaciation. The Holocene stratigraphy records the overall aggradation and northward migration of the Po River, with the consequent erosion of distal Alpine LGM deposits and formation of a fluvial scarp parallel to the Po River course. Late Pleistocene and Holocene climate change influenced river dynamics controlling (i) the balance between sediment supply and water discharge, through glacier and vegetation dynamics, and (ii) the rate of sea-level fall/rise. Apennine, Alpine and Po river systems responded in distinct ways to climate forcing due to the influence of local factors. Lithology, drainage area and mean elevation of river catchments, as well as river and valley gradients, determined the type of sedimentary response (e.g., aggradation versus degradation). This study shows that a combined geomorphic and stratigraphic approach focusing on the geometric relations between exposed and buried features can provide valuable information about the evolution of a fluvial system and its controlling factors.

Two-step human–environmental impact history for northern New Zealand linked to late-Holocene climate change

Following resolution of a long-standing debate over the timing of the initial settlement of New Zealand from Polynesia (late 13th century), a prevailing paradigm has developed that invokes rapid transformation of the landscape, principally by fire, within a few decades of the first arrivals. This model has been constructed from evidence mostly from southern and eastern regions of New Zealand, but a more complicated pattern may apply in the more humid western and northern regions where forests are more resilient to burning. We present a new pollen record from Lake Pupuke, Auckland, northern New Zealand, that charts the changing vegetation cover over the last 1000 years, before and after the arrival of people. Previous results from this site concurred with the rapid transformation model, although sampling resolution, chronology and sediment disturbance make that interpretation equivocal. Our new record is dated principally by tephrochronology together with radiocarbon dating and includes a cryptotephra deposit identified as Kaharoa tephra, a key marker for first settlement in northern New Zealand. Its discovery and stratigraphic position below two Rangitoto-derived tephras enables a clearer picture of environmental change to be drawn. The new pollen record shows an early phase (step 1) of minor, localised forest clearance around the time of Kaharoa tephra ( c. 1314 AD) followed by a later, more extensive deforestation phase (step 2) commencing at around the time of deposition of the Rangitoto tephras ( c. 1400–1450 AD). This pattern, which needs to be corroborated from other well-resolved records from northern New Zealand, concurs with an emerging hypothesis that the ‘Little Ice Age’ had a significant impact on pre-European Māori with the onset of harsher conditions causing a consolidation of populations and later environmental impact in northern New Zealand.