Widespread drying of European peatlands in recent centuries

This is the author accepted manuscript. The final version is available from Nature Research via the DOI in this record Climate warming and human impacts are thought to be causing peatlands to dry,potentially converting them from sinks to sources of carbon. However, it is unclear whether the hydrological status of peatlands has moved beyond their natural envelope. Here we show that European peatlands have undergone substantial, widespread drying during the last ~300 years. We analyse testate amoeba-derived hydrological reconstructions from 31 peatlands across Britain, Ireland, Scandinavia and continental Europe to examine changes in peatland surface wetness during the last 2000 years. 60% of our study sites were drier during the period CE 1800-2000 than they have been for the last 600 years; 40% of sites were drier than they have been for 1000 years; and 24% of sites were drier than they have been for 2000 years. This marked recent transition in the hydrology of European peatlands is concurrent with compound pressures including climatic drying, warming and direct human impacts on peatlands, although these factors vary between regions and individual sites. Our results suggest that the wetness of many European peatlands may now be moving away from natural baselines. Our findings highlight the need for effective management and restoration of European peatlands.Natural Environment Research Council (NERC

Detecting the provenance of Galapagos non-native pollen: The role of humans and air currents as transport mechanisms

The influence of non-native pollen, both long-distance transported and from introduced taxa, on reconstruction of past vegetation is not often well quantified in palynological investigations. We examined both fossil and modern samples from the Galápagos Islands, a remote archipelago lying 1000 km from the nearest continent. These islands are particularly well-suited for such an assessment, as (1) the native flora is limited and well-known, enabling increased taxonomic resolution within the palynological record, and (2) human impact in the Galápagos started after discovery by Europeans in 1535, allowing clear distinctions to be made between native and introduced taxa. Pollen samples were collected from five profiles in the Galápagos and grouped in (a) a pre-human-impact period, (b) an early human-impact period after c. 1535, and (c) a late human-impact period after c. 1973 when the introduced Cinchona pubescens tree started to expand. Introduced taxa accounted for approximately 10% of total pollen (excluding Cyperaceae) throughout the human-impact periods and long-distance transported pollen for approximately 5%. Twenty pollen taxa of introduced plants were found. Cinchona, which grows abundantly near the study sites, accounted for most of the introduced pollen, but an appreciable part also came from introduced plants growing in low numbers and at more distant locations within the archipelago. Total long-distance transported pollen (35 taxa) increased from 3% of total pollen in the pre-human-impact period to 5% in the human-impact periods, probably due to destruction of native vegetation through fire and thus reduction of local pollen production. These phenomena might lead to erroneous interpretation of local plant occurrence when the native/non-native or local/extra-local status of plants is not known. © The Author(s) 2012

Holocene environmental and climatic changes at Gorgo Basso, a coastal lake in southern Sicily, Italy

We used a new sedimentary record to reconstruct the Holocene vegetation and fire history of Gorgo Basso, a coastal lake in south-western Sicily (Italy). Pollen and charcoal data suggest a fire-prone open grassland near the site until ca 10,000 cal yr BP (8050 cal BC), when Pistacia shrubland expanded and fire activity declined, probably in response to increased moisture availability. Evergreen Olea europaea woods expanded ca 8400 to decline abruptly at 8200 cal yr BP, when climatic conditions became drier at other sites in the Mediterranean region. Around 7000 cal yr BP evergreen broadleaved forests (Quercus ilex, Quercus suber and O. europaea) expanded at the cost of open communities. The expansion of evergreen broadleaved forests was associated with a decline of fire and of local Neolithic (Ficus carica–Cerealia based) agriculture that had initiated ca 500 years earlier. Vegetational, fire and land-use changes ca 7000 cal yr BP were probably caused by increased precipitation that resulted from (insolation-forced) weakening of the monsoon and Hadley circulation ca 8000–6000 cal yr BP. Low fire activity and dense coastal evergreen forests persisted until renewed human activity (probably Greek, respectively Roman colonists) disrupted the forest ca 2700 cal yr BP (750 BC) and 2100 cal yr BP (150 BC) to gain open land for agriculture. The intense use of fire for this purpose induced the expansion of open maquis, garrigue, and grassland-prairie environments (with an increasing abundance of the native palm Chamaerops humilis). Prehistoric land-use phases after the Bronze Age seem synchronous with those at other sites in southern and central Europe, possibly as a result of climatic forcing. Considering the response of vegetation to Holocene climatic variability as well as human impact we conclude that under (semi-)natural conditions evergreen broadleaved Q. ilex–O. europaea (s.l.) forests would still dominate near Gorgo Basso. However, forecasted climate change and aridification may lead to a situation similar to that before 7000 cal yr BP and thus trigger a rapid collapse of the few relict evergreen broadleaved woodlands in coastal Sicily and elsewhere in the southern Mediterranean region