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1. Priority question exercises are becoming an increasingly common tool to frame future agendas in conservation and ecological science. They are an effective way to identify research foci that advance the field and that also have high policy and conservation relevance. 2. To date, there has been no coherent synthesis of key questions and priority research areas for palaeoecology, which combines biological, geochemical and molecular techniques in order to reconstruct past ecological and environmental systems on time-scales from decades to millions of years. 3. We adapted a well-established methodology to identify 50 priority research questions in palaeoecology. Using a set of criteria designed to identify realistic and achievable research goals, we selected questions from a pool submitted by the international palaeoecology research community and relevant policy practitioners. 4. The integration of online participation, both before and during the workshop, increased international engagement in question selection. 5. The questions selected are structured around six themes: human–environment interactions in the Anthropocene; biodiversity, conservation and novel ecosystems; biodiversity over long time-scales; ecosystem processes and biogeochemical cycling; comparing, combining and synthesizing information from multiple records; and new developments in palaeoecology. 6. Future opportunities in palaeoecology are related to improved incorporation of uncertainty into reconstructions, an enhanced understanding of ecological and evolutionary dynamics and processes and the continued application of long-term data for better-informed landscape management. 7. Synthesis. Palaeoecology is a vibrant and thriving discipline, and these 50 priority questions highlight its potential for addressing both pure (e.g. ecological and evolutionary, methodological) and applied (e.g. environmental and conservation) issues related to ecological science and global change.

1. Tropical peatlands, which provide important functions such as biodiversity provisioning and carbon (C) storage, are currently threatened by land-use conversions. Thus, conservation and restoration efforts are needed to maintain their functions. Conservation concepts aiming to separate human from ecosystems are no longer conceivable. Therefore, understanding peatland resilience to human disturbance, that is the ability of peatland ecosystems to maintain their structure and function despite perturbations and to return to their predisturbance states, can assist with integrating human needs into conservation strategies and improving restoration effectiveness. 2. Understanding ecosystem resilience is often impeded by a lack of long-term data, which can be obtained from palaeoecological studies. Located close to the archaeological remains of the Malayu Empire, the Sungai Buluh peatland in Sumatra, Indonesia provides an opportunity to study the resilience of a tropical peatland to past human disturbance. We subjected a 250-cm-long peat core to palynological, charcoal and C content analyses to delineate the anthropogenic impact on the peatland and the ecosystem's response. 3. The results revealed that extensive human activities in Sungai Buluh such as logging, grazing/cut-and-carry, and wild-harvesting started soon after humans occupied the vicinity of the peatland c. 1,000 cal yr BP. Even without fire use and cultivation, these activities were able to alter vegetation composition and decrease the peatland's C sequestration capacity. 4. Following site abandonment after the demise of the Malayu Empire at c. 600 cal yr BP, the palaeoecological record suggests that the Sungai Buluh peatland recovered in terms of both floristic composition and C sink function, with the latter recovering faster (c. 60 years) than the former (c. 170 years). 5. Synthesis. The palaeoecological record from Sungai Buluh provides the first evidence of tropical peatland recovery following human disturbance, which can help improve present peatland conservation/restoration strategies. The design of peatland wise-use strategies can mimic the \"resilience-friendly\" human activities identified in this study. Consideration should also be given to selecting rapidly regenerating taxa for cost-and-effort-efficient restoration strategies. Additionally, the 170-year recovery time of the Sungai Buluh peatland suggests that the 60 year timeframe currently allocated in most tropical peatland restoration projects may be insufficient.

1. This paper addresses the origin and development of the oldest prehistoric pasture in the timberline ecotone known so far in the Alps and its relation to anthropogenic pressure and natural climate change. 2. Palaeoecological and geochemical techniques were applied on the Crotte Basse mire stratigraphy (2365 m a.s.1, northwestern Italy) to describe changes in vegetation composition, forest biomass, land use and fertilization between c. 6400–1800 cal years BP. 3. Subalpine forests dominated by Pinus cembra occurred at very high-altitude up to c. 5600 cal years BP, when a sharp contraction of woody vegetation took place. This major vegetation shift is matched by increasing charcoal input and markers of pastoral/grazing activities (pollen, dung spores and forms of phosphorus) in the sediment sequence in this small basin. 4. Major phases of landscape change detected in our multiproxy record chronologically match intervals of cumulative probability density of ¹⁴C ages from nearby archaeological sites, suggesting that human activity was the factor leading to massive landscape change from the onset of the Copper Age (c. 5600 cal years BP). The change may have been reinforced by climate variability in the period 5700–5300 cal years BP. 5. Sensitivity of woody species to fires was statistically explored (Appendix S1, Supporting Information), revealing negative reactions of P. cembra and Betula to frequent fire episodes and positive reactions of Alnus viridis and Juniperus. Fire episodes do not affect Larix dynamics. 6. Synthesis. Mt. Fallère provides some of the oldest and consistent evidence so far available in the Alps for major anthropogenic pressure at the upper forest limit. As far back as 5600 cal years BP, high-elevation forest ecosystems were permanently disrupted and the alpine pastures were created. Palaeoecological data enable a clear distinction between a random and sporadic use of the alpine space, typical for Mesolithic and Neolithic societies, and an organized seasonal exploitation of natural resources, starting from the Copper Age onwards. The chronological comparison of independent climate proxies, palaeoecological information and pollen-based temperature reconstructions sheds light on the relationships between climate and humans since prehistoric times.

1. Natural succession trajectories of Central European forest ecosystems are poorly understood due to the absence of long-term observations and the pervasive effects of past human impacts on today's vegetation communities. This knowledge gap is significant given that currently forest ecosystems are expanding in Europe as a consequence of global change. 2. Annually laminated sediments were extracted from two small lowland lakes (Moossee 521 m a.s.l.; Burgäschisee 465 m a.s.l.) on the Swiss Plateau. We combine high-resolution palaeoecological and quantitative analyses to assess changes in vegetation during the Neolithic. We test for regionally synchronous land-use phases and plant successional patterns that may originate from complex interactions between human and climatic impacts. 3. Mixed Fagus sylvatica forests dominated the Swiss Plateau vegetation over millennia. During the period 6,500-4,200 cal year BP, pronounced forest disruptions accompanied by increased fire and agricultural activities occurred at c. 6,400-6,000 cal year BP, 5,750-5,550 cal year BP, around 5,400 cal year BP and at 5,100-4,600 cal year BP. Biodiversity increased during these land-use phases, likely in response to the creation of new open habitats. After decades to centuries of land-use, arboreal vegetation re-expanded. In a first succession stage, heliophilous Corylus avellana shrubs were replaced by pioneer Betula trees. These open arboreal communities were out-competed within 150-200 years by late-successional F. sylvatica and Abies alba forests. Most strikingly, cross-correlations show that these successions occurred synchronously (±11 years) and repeatedly over large areas (>1,000 km²) and millennia. 4. Synthesis. First notable human impact shaped the primeval mixed Fagus sylvatic forests in Central Europe from c. 6,800-6,500 cal year BP on. Agrarian societies were susceptible to climate changes and we hypothesize that climate-induced, simultaneous agricultural expansion and contraction phases resulted in synchronous regional forest successions. Currently, forests are expanding in Central Europe as a result of land abandonment in marginal areas. Our results imply that mixed Fagus sylvatica forests with Abies alba and Quercus may re-expand rapidly in these areas, if climate conditions will remain within the range of the mid-Holocene climatic variability (with summers c. +1-2°C warmer than today).

1. The Mediterranean seagrass Posidonia oceanica maintains a biodiverse ecosystem and it is a world-wide important carbon sink. It grows for millennia, accumulating organic-rich soils (mats) beneath the meadows. This marine habitat is protected by the European Union; however, it is declining rapidly due to coastal development. Understanding its response to disturbances could inform habitat restoration, but many environmental impacts predate monitoring programs (<50 years). 2. This research explores the palaeoecological potential of Posidonia mats to reconstruct six thousand years of environmental change that could have affected Posidonia meadows and, in turn, left an imprint on the mats. 3. Palynological, microcharcoal, magnetic susceptibility and glomalin-related soil protein (GRSP) analyses on Posidonia mats enabled us to detect climate- and human-induced environmental processes impacting on the seagrass during the Late Holocene. 4. The pollen and microcharcoal records reconstructed anthropogenic disturbances attributed to agriculture. The record of GRSP shows that agrarian activities affected continental soil quality. Changes in magnetic susceptibility reveal that enhanced soil erosion was caused by both climate (major flooding events in the NW Mediterranean) and humans (cultivation) which impacted on the Posidonia mat. Finally, increased human impact is linked to eutrophication of coastal waters since RomanMedieval times. 5. Synthesis. This study shows that climate and land-use changes in the western Mediterranean resulted in enhanced loadings of terrigenous material to the coastal zone since the Late Holocene, likely disturbing the Posidonia meadows and their mat carbon accumulation dynamics. Under the current global change scenario in which CO₂ emissions are projected to increase, restoring carbon sinks is a priority. Seagrass habitat restoration should consider not only the coastal perturbations, but also the continental ones at a catchment scale to preserve the socio-economic ecosystem services provided by seagrasses.

1. Tree lines are supposed to react sensitively to the current global change. However, the lack of a long-term (millennial) perspective on tree line shifts in the Pyrenees prevents understanding the underlying ecosystem dynamics and processes. 2. We combine multiproxy palaeoecological analyses (fossil pollen, spores, conifer stomata, plant macrofossils, and ordination) from an outstanding ice cave deposit located in the alpine belt 200 m above current tree line (Armeña-A294 Ice Cave, 2,238 m a.s.l.), to assess for the first time in the Pyrenees, tree line dynamics, and ecosystem resilience to climate changes 5,700-2,200 (cal.) years ago. 3. The tree line ecotone was located at the cave altitude from 5,700 to 4,650 cal year BP, when vegetation consisted of open Pinus uncinata Ramond ex DC and Betuia spp. Woodlands and timberline were very close to the site. Subsequently, tree line slightly raised and timberline reached the ice cave altitude, exceeding its today's uppermost limit by 300-400 m during more than four centuries (4,650 and 4,200 cal year BP) at the end of the Holocene Thermal Maximum. After 4,200 cal year BP, alpine tundra communities dominated by Dryas octopetala L. expanded while tree line descended, most likely as a consequence of the Neoglacial cooling. Prehistoric livestock raising likely reinforced climate cooling impacts at 3,4503,250 cal year BP. Finally, a tree line ecotone developed around the cave that was on its turn replaced by alpine communities during the past 2,000 years. 4. Synthesis. The long-term Pyrenean tree line ecotone sensitivity suggests that rising temperatures will trigger future P. uncinata and Betuia expansions to higher elevations, replacing arctic-alpine plant species. Climate change is causing the rapid melting of the cave ice; rescue investigations would be urgently needed to exploit its unique ecological information.

During the Pleistocene the Great Basin was filled by endorheic lakes that receded greatly during the Holocene. Several proxy records provide extensive evidence that the basin has gone through periods of amelioration from low precipitation followed by a return to dry conditions through the Holocene. Relative to the Pleistocene/Holocene transition and middle Holocene, aside from the Medieval Climate Anomaly, study of the late Holocene has received less attention. In recent years evidence has emerged for a ca. millennial length drought termed the Late Holocene Dry Period (LHDP), between about 2800 and 1800 years ago. The LHDP has been proposed to follow a dipole climatic pattern associated with changes in precipitation linked to the Southern Oscillation Index (SOI) and described as a dry southwest and wet northwest in the United States. Here I present a 4000-year pollen record from northwestern Nevada, investigating the potential for the Late Holocene Dry Period to conform to the modeled dipole pattern in this part of the region. This site is located near a zone of ambiguity between wet and dry conditions in order to identify more definitively where the modeled dipole pattern is centered.

1. Alexander von Humboldt is a key figure in the history of ecology and biogeography who contributed to shape what is today ecology, as well as the environmentalist movement. His observation that the world's vegetation varies systematically with climate was one of his many contributions to science. 2. Here, we question to what extent Humboldt's view biased our vision of nature. The current emphasis on the role of climate and soils in ecological and evolutionary studies, and the emphasis on forests as the potential and most important vegetation, suggests that we still view nature through the eyes of Humboldt. 3. Over the last 20 years, diverse studies have shown that many open non-forested ecosystems (savannas, grasslands, and shrublands) cannot be predicted by climate and are ancient and diverse systems maintained by fire and/or vertebrate herbivory. Paleoecological and phylogenetic studies have shown the key role of these plant consumers at geological time scales. This has major implications for how we understand and manage our ecosystems. 4. Synthesis. We need to consciously probe the long-standing idea that climate and soils are the only major factors shaping broad-scale patterns in nature. We propose to move beyond the legacy of Humboldt by embracing fire and large mammal herbivory as additional key factors in explaining the ecology and evolution of world vegetation.

1. Past changes in plant and landscape diversity can be evaluated through pollen analysis, however, pollen-based diversity indexes are potentially biased by differential pollen production and deposition. Studies examining the relationship between pollen and landscape diversity are therefore needed. The aim of this study was to evaluate how different pollen-based indexes capture aspects of landscape diversity. 2. Pollen counts were obtained from surface samples of 50 small- to medium-sized lakes in Brandenburg (north-east Germany) and compiled into two sets, with one containing all pollen counts from terrestrial plants and the second restricted to wind-pollinated taxa. Both sets were adjusted for the pollen production/dispersal bias using the REVEALS model. A high-resolution biotope map was used to extract the density of total biotopes and different biotopes per area as parameters describing landscape diversity. In addition, tree species diversity was obtained from forest inventory data. 3. The Shannon index and the number of taxa in a sample of 10 pollen grains are highly correlated and provide a useful measure of pollen type diversity which corresponds best to landscape diversity within one km of the lake and the proportion of non-forested area within seven km. Adjustments of the pollen production/dispersal bias only slightly improve the relationships between pollen diversity and landscape diversity for the restricted data set as well as for the forest inventory data and corresponding pollen types. 4. Using rarefaction analysis, we propose the following convention: pollen type diversity is represented by the number of types in a small sample (low count e.g. 10), pollen type richness is the number of types in a large sample (high count e.g. 500), and pollen sample evenness is characterized by the ratio of the two. 5. Synthesis. Pollen type diversity is a robust index that captures vegetation structure and landscape diversity. It is ideally suited for between site comparisons as it does not require high pollen counts. In concert with pollen type richness and evenness, it helps evaluating the effect of climate change and human land use on vegetation structure on long timescales.