Main Environmental Changes Research Articles

New Fetch- and Depth-Limited Forecasting Curves Depending on Bed Roughness

ABSTRACT Predicting wind waves within confined and shallow basins is very important, given the decisive role they play in the resuspension mechanisms of sediments and nutrients from the bottom, on which the main morphological and environmental changes depend. Pascolo, Petti, and Bosa (2019) proposed a set of wave forecasting curves for fully developed conditions in finite depth, which consider the bottom roughness as an additional variable, since it plays a fundamental role in the wave energy dissipation during the generation process. The present study incorporates and integrates the results previously obtained by Pascolo, Petti, and Bosa (2019) and provides the growth curves in the complete form, taking into account also the limitation on fetch. A numerical approach on a simplified domain has been adopted and statistical analyses on the fit of the curves to numerical results have been performed. The new set of equations confirms the variability of the wave heights and periods as a function of the bottom conditions, which can change due to the presence of bedforms, vegetation, or particle size differences. Applications at different conditions of depth, fetch, and roughness have been analyzed, in order to confirm the validity of the new growth curves.

Holocene environmental changes inferred from an oxbow lake in a Mauritia palm swamp (aguajal) in the Madre de Dios region, southeastern Peru

Mauritia peatland palm swamps (locally called aguajales) are typical ecosystems in Madre de Dios River floodplains in southeastern Peru. We investigated a sediment core from an oxbow lake in Los Amigos Aguajal to reconstruct paleoclimatic changes, vegetation dynamics on a regional scale, and human impact using multi-proxy analysis. The results show that the oxbow lake was part of Madre de Dios River's active meandering system and cut off at ca. 1760 cal yr BP. X-Ray Fluorescence results combined with stratigraphy suggest that since the cutting off, the recorded climate was humid until 540 cal yr BP excepting a shortly drier period of 640–610 cal yr BP, but after 540 cal yr BP the climate became less wet until the present. Pollen results show a stable terra firme forest composed primarily by Moraceae/Urticaceae throughout the record. The dense aguajal surrounding the oxbow lake developed from 1240 cal yr BP until the present, but canopy was more open during 780–180 cal yr BP. Hedyosmum became consecutively abundant since 270 cal yr BP until the present. Charcoal analysis indicated almost no human activity in the study area throughout the record. Comparison of the oxbow lake record and the previously studied palm swamp record both from Los Amigos Aguajal shows that: (1) main environmental changes in the palm swamp may correspond to moisture changes; (2) vegetation composition and dynamics on local aguajal and more regional scales are similar, except for the missing period of marsh in the oxbow lake. Furthermore, the oxbow lake record shows less wet conditions during the Little Ice Age and relatively wet in the Medieval Climate Anomaly, which is contrary to many records from the Peruvian Andes. This might be related to elevational differences (lowland vs. mountain) and/or non-climate factors and will need further investigation.

Paleoenvironmental evolution during the Holocene of the coastal plain of Maricá, Rio de Janeiro, Brazil, through silica biomineralizations

Climate change and mean sea level fluctuations were determining factors in the Quaternary evolution of the Maricá coastal plain (Rio de Janeiro, Brazil). In this context, this study aims to contribute to the knowledge on the paleoenvironmental conditions of the Maricá coast in the Holocene, with the aim of identifying the main environmental changes that occurred to understand the evolution of this coastal plain. Three geological boreholes were carried out, reaching depths of up to 12 m, in which silica biomineralizations (sponge spicules, diatom frustules, and phytoliths) were analyzed along with the granulometry, organic matter content, and age (14C-AMS dating) of the sediments. The analysis of the bioindicators present in the sediments enabled the identification of three phases with distinct paleoenvironmental conditions related to the evolution of the Maricá coastal plain: (1) between 8500 and 6500 cal years BP, there was a wetter period with a predominance of very dense shrub/tree vegetation, occupying the slopes and the coastal plain; marine bioindicators (sponge spicules, diatoms frustules, and bivalves) indicate the existence of an ancient shallow-water lagoon, sporadically connected to the sea; (2) between 6500 and 3000 cal years BP, a less humid period predominated, with herbaceous vegetation dominating and increasing hydrodynamic energy, possibly caused by events of wave transposition over the barrier; concomitant with the process of colmation; and (3) the third phase, starting at 3000 cal years BP, is characterized as a new period of higher humidity with the return of shrub/tree vegetation, albeit less dense than in the first phase, again corresponding to an environment with low hydrodynamic energy. The decrease in the amount of sponge spicules evidences the reduction of the paleolagoon water depth and its colmation in this period.

Abrupt diatom responses to recent climate and land use changes in the Cantabrian Mountains (NW Spain)

The multi-proxy study of sediment cores from Lake Isoba (43° 02′ N, 5° 18′ W; 1400 m a.s.l.) allows a detailed assessment of the past hydrological and environmental dynamics in north-western Iberia resulting from the interplay between climate variability and anthropogenic impact. The combination of diatom stratigraphy, sedimentology and high-resolution elemental geochemistry along with a robust chronological framework (established by 210Pb, 137Cs and 14C dating) provides a detailed environmental reconstruction for the past ~ 500 years. Abrupt changes in the fossil diatom assemblages indicate a high sensitivity of this small lake to past environmental change and allow identifying four major stages related to the main climate fluctuations of the Little Ice Age (LIA) and recent warming. High lake levels, enhanced runoff and higher productivity characterised the middle phase of the LIA (~ 1550 to 1630 CE), indicating an overall wet climate. Conversely, shallow lake levels, decreased runoff and relatively low productivity prevailed during the last phase of the LIA and the onset of the Industrial Era (~ 1630 to 1925 CE), likely due to colder and drier conditions. High lake levels and higher carbonate input occurred after ~ 1925 CE until the 1980s CE, when our data show an abrupt drop in lake levels probably caused by a regional negative rainfall anomaly related to climate warming during the past decades. Finally, since ~ 1997 CE a remarkable and abrupt increase in the lake nutrient load and turbidity is detected, probably associated with the replacement of transhumant sheep flocks with staying cattle. The main environmental changes reconstructed at Lake Isoba mostly agree with other palaeoclimatic records from northern Spain. However, the hydrological patterns reconstructed are opposed to those observed on the northern slopes of the Cantabrian Mountains. The recent and strong impact of land-use changes on the lake, causing more ecological disruptions than previous climate changes, is noteworthy and demonstrates the high sensitivity of mountain lakes to human activities in a global change context.

Hydroclimate reconstruction through MIS 3 in the Middle Paleolithic site of Crvena Stijena (Montenegro) based on hydrogen-isotopic composition of sedimentary n-alkanes

This study presents a hydroclimatic reconstruction from Crvena Stijena (Montenegro, Balkan Peninsula), a rock shelter that has yielded evidence for Middle Paleolithic human occupation. The integration of lipid biomarkers, hydrogen (δD) isotopic compositions of n-alkanes, and organic elemental geochemistry in the 7-m deep vertical sedimentary sequence enables reconstruction of the main hydrological and environmental changes during the MIS 3 and their correlation with the presence at the site. We apply agglomerative hierarchical clustering and principal component analysis to the geochemical, molecular, and stable isotopic data to obtain a robust hydrological record. We find evidence of three aridity trends from the studied period, one of them correlated with the Heinrich Event 5, and humid and cold-temperate conditions in archaeology-rich layers. Our dataset also contributes to the knowledge of past hydrological variability in the Balkan Peninsula, a sensitive area to short-lived climatic shifts, and overall, in the Mediterranean region during the last glacial/interglacial cycle.

A Late Pleistocene (MIS4-MIS2) palaeohydrological reconstruction from Lake Chalco, Basin of Mexico

We present a palaeohydrological reconstruction of Lake Chalco from 70 to 11.5 ka BP based on ostracod records consisting of three species: Limnocytherina axalapasco, Candona patzcuaro, and Cypridopsis vidua. Overall, the presence of these species helped investigate Lake Chalco water level fluctuations, and thus water salinity variations. Moreover, this work helped improve our knowledge of L. axalapasco and Candona alchichica, two endemic species of Central Mexico, the latter of which was replaced by C. patzcuaro after the cold and dry MIS4. Five ostracod zones reflect the main environmental changes that occurred during the Late Pleistocene. During 70–62 ka BP (Zone 5), shallow and very variable salinity conditions were inferred with a possible occupancy of submerged macrophytes. The Lake Chalco water level increased from 62 to 49 ka BP (Zone 4) and relatively less saline conditions were inferred. The warmer period from of 49–39 ka BP (Zone 3) was characterised by lower lake levels and a gradually increasing salinity. The evaporation rates continued to increase during 39–27 ka BP (Zone 2). However, a higher runoff input helped maintain a relatively high lake level. Later on, cold and dry conditions from 27 to 11.5 ka BP (Zone 1) inhibited the ostracod occupancy in Lake Chalco.

Late Pleistocene and Holocene palaeoecological reconstruction of Lake Texcoco (Basin of Mexico) based on its ostracod record

AbstractWe present a palaeohydrological reconstruction of Lake Texcoco over the last 32.7 cal ka based on ostracod records consisting of two species, Candona patzcuaro and Limnocytherina axalapasco. Overall, the presence of these species suggests that Lake Texcoco was highly saline and experienced occasional desiccation periods. Moreover, this work helps improve our knowledge of L. axalapasco, an endemic species of central Mexico; their eggs could remain dormant‐resting to survive long dry periods. Four ostracod zones reflect the main environmental changes that occurred during the Late Pleistocene and Holocene. From 32.7 to 30 cal ka bp (Zone 4), Lake Texcoco's water levels were stable and alkaline with saline conditions. Zone 3, representing the period from 30 to 18 cal ka bp, includes a period of enhanced precipitation (greatest abundance of C. patzcuaro) from 30 to 26 cal ka bp. From 26 to 18 cal ka bp, an abundance of L. axalapasco reflects shallower and more saline conditions. The Last Glacial Maximum was characterised by cold and humid conditions with enhanced runoff, especially at 25.3, 21.9, and 20.7 cal ka bp. Zone 2 (18–7 cal ka bp) represents the driest period on record. Finally, shallow and saline lake conditions have prevailed over the last 7 cal ka (Zone 1).

Evolutionary dynamics of climatic niche influenced the current geographical distribution of Viperidae (Reptilia: Squamata) worldwide

Abstract An understanding of patterns of climatic niche evolution has important implications for ecological and evolutionary theory and conservation planning. However, despite considerable testing, niche evolution studies continue to focus on clade-wide, homogeneous patterns, without considering the potentially complex dynamics (i.e. phylogenetic non-stationarity) along the evolutionary history of a clade. Here, we examine the dynamics of climatic niche evolution in vipers and discuss its implication for their current patterns of diversity and distribution. We use comparative phylogenetic methods and global-scale datasets, including 210 viper species with phylogenetic and climatic data. We find that climatic niche evolution in Viperidae shows an overall pattern of phylogenetic conservatism, but with different dynamics depending on the niche feature (niche breadth or niche position) and the evolutionary history of particular lineages within the family, thus resulting in phylogenetic non-stationarity. Indeed, we find several shifts in niche breadth evolution that were probably influenced by the main geological and environmental changes experienced during the evolutionary history of the family. These results highlight the importance of considering complex patterns of climatic niche evolution and their role in shaping patterns of diversity and distribution.

Fish Assemblages of a Sub-Arctic Fjord Show Early Signals of Climate Change Response Contrary to the Benthic Assemblages

Arctic benthic ecosystems are facing high-speed environmental changes, such as decreased sea ice coverage, increased temperature and precipitations, as well as the invasion by non-indigenous species. Few sub-arctic fjords have the particularity to have an inner-most part forming a basin in which water remains very cold. Those fjords may offer a refugee for cold-water arctic species as well as a small-scale “laboratory” of the changes that arctic assemblages located at higher latitudes might face soon. The Porsangerfjord in Northern Norway is a sub-arctic fjord with an inner arctic part and face red king crabs Paralithodes camtchasticus invasion since the end of the 1990s. It offers a case study of the dynamics of arctic ecosystems facing multiple stressors, i.e., climate change and invasive species. Based on a time series of megabenthic invertebrates and bentho-demersal fishes over 2007–2019, a complex multivariate analysis (STATICO) was used to identify the trends in the relationship between taxa and the environment. We showed the main environmental changes in the fjord were the freshening of the water, the increase of the seabed current, and the decrease of the maximum sea ice extent. A strong along-fjord gradient was visible for both benthic and fish assemblages. Species richness and Shannon diversity of fishes significantly increased into the fjord, due to the arrival of warm-water species over time that overlapped with cold-water species that have seen their biomass significantly reduced. No significant decrease in the biomass of the cold-water benthic species was visible, which could indicate an efficient refugee effect of the inner fjord. Yet, this refugee effect could be unbalanced by the red king crab invasion as it is a predator of several arctic species. In the Porsangerfjord, fish species thus respond to climate change while megabenthic assemblages are more threatened by invasive species.

Land-sea ecological connectivity during a Jurassic warming event

Knowledge on how climate change affects land-sea ecological connectivity in deep time is scarce. To fill this knowledge gap we have assembled a unique dataset through a Jurassic (early Toarcian) warming event that includes quantitative abundance data from pollen and spores, organic-walled marine plankton and benthic macro-invertebrates, in association with geochemical data derived from the same sampled horizons, from the Cleveland Basin, UK. Using this dataset we: (i) reconstruct the timing of degradation and recovery of land-plants, marine primary producers and benthic fauna in response to this event, and (ii) test for connectivity between changes in land and marine ecosystems. We find a discrepancy between the timing of the response of land-plant and marine ecosystems to the event. Land-plants were the first to be affected by initial warming, but also recovered relatively quickly after the peak of warmth to return to pre-event levels of richness and diversity. Plankton and benthic fauna instead experienced a delayed response to initial warming, but as warming peaked, they suffered a rapid and extreme turnover. Recovery in the shelf sea was also delayed (particularly for the benthos) compared to the vegetation. Ecological connectivity analyses show a strong link between changes in terrestrial and marine ecosystems. The loss of large trees on land contributed to changes in marine plankton, from dinoflagellate- to prasinophyte algal-dominated communities, by enhancing erosion, runoff and nutrient-supply into shallow seas. Eutrophication and changes in primary productivity contributed to the decrease of dissolved oxygen in the water column and in bottom waters, which in turn affected benthic communities. Such cause-effect mechanisms observed in the Cleveland Basin are likely to have occurred in other basins of the Boreal Realm, and in part also in basins of the Sub-Boreal and Tethyan realms. Although palaeolatitudinal and palaeoceanographic gradients may have controlled local and regional changes in land-plants and marine ecosystems during the Early Jurassic, the main climatic and environmental changes linked to rapid global warming, enhanced weathering and high primary productivity, are shared among all the examined realms.

The timing of the postglacial marine transgression in the Ría de Ferrol (NW Iberia): A new multiproxy approach from its sedimentary infill

The Ría de Ferrol is a confined tide-dominated incised valley in the mesotidal passive Atlantic margin of NW Iberia. A new multidisciplinary approach enables a high-resolution reconstruction of the main environmental changes affecting this area during the Lateglacial and the Holocene. We defined the main seismic and sedimentary facies in the infill and selected different key points to be cored. A number of multiproxy analyses were performed on four sections of sediment (sedimentology, X-ray fluorescence, radiocarbon dating and palynological analyses). Physiography exerted a strong control on the evolution of the basin, as a rock-bounded narrow channel in the middle of the basin influenced the flooding of the ria during the postglacial marine transgression. Depositional environments shifted towards the east as the sea level rose and fluvial facies at the base were covered by facies from a tide-dominated estuary, which were predominant during most of the Holocene. Several layers of sediments from stagnant freshwater areas dominated by Juncus sp. were recovered at ca. −20.5 to −21, ca. −13.1 to −13.5, −12.5 to −12.8 and −12.1 to −13.5 m NMMA along the central axis of the embayment, and dated to be older than 10190–10290; 10790–10970; 7510–8220 and 7130–7830 cal yr BP. They may respectively represent a local stage of lowering sea-level dated at the end of the Lateglacial (i.e. the Younger Dryas), and different episodes of deceleration/stabilization of sea-level rise occurred during the early Holocene (i.e. the 11.4, 10.5, 9.3, 8.2 kyr Henrich events). Thus, for the first time in this region, we were able to generate a high-resolution spatial–temporal interpretation of environmental changes linked to the relative sea-level variations using subtidal sediments from the same sub-basin (and thus free of substantial/differential post-depositional deformations) that describes in detail the flooding of the ancient coastal plains of this region at the beginning of the Holocene.

Shoreline Evolution and Environmental Changes at the NW Area of the Gulf of Gela (Sicily, Italy)

Coastal areas are among the most biologically productive, dynamic and valued ecosystems on Earth. They are subject to changes that greatly vary in scale, time and duration and to additional pressures resulting from anthropogenic activities. The aim of this work was to investigate the shoreline evolution and the main environmental changes of the coastal stretch between the towns of Licata and Gela (in the Gulf of Gela, Sicily, Italy). The methodology used in this work included the analysis of: (i) shoreline changes over the long- and medium-term periods (1955–2019 and 1989–2019, respectively), (ii) dune system fragmentation and (iii) the impact of coastal structures (harbours and breakwaters) on coastal evolution. The shoreline change analysis mainly showed a negative trend both over the long- and medium-term periods, with a maximum retreat of 3.87 m/year detected over the medium-term period down-drift of the Licata harbour. However, a few kilometres eastward from the harbour, significant accretion was registered where a set of breakwaters was emplaced. The Shoreline Change Envelope (SCE) showed that the main depositional phenomena occurred during the decade between 1955 and 1966, whereas progressive and constant erosion was observed between 1966 and 1989 in response to the increasing coastal armouring.

Environmental evolution and anthropogenic forcing in the Garigliano coastal plain (Italy) during the Holocene

The Garigliano alluvial-coastal plain, at the Latium-Campania border (Italy), witnessed a long-lasting history of human-environment interactions, as demonstrated by the rich archaeological knowledge. With the aim of reconstructing the evolution of the landscape and its interaction with human activity during the last millennia, new pollen results from the coastal sector of the Garigliano Plain were compared with the available pollen data from other nearby sites. The use of pollen data from both the coastal and marine environment allowed integrating the local vegetation dynamics within a wider regional context spanning the last 8000 years. The new pollen data presented in this study derive from the analysis of a core, drilled in the coastal sector, which intercepted the lagoon-marshy environments that occurred in the plain as a response to the Holocene transgression and subsequent coastal progradation. Three radiocarbon ages indicate that the chronology of the analyzed core interval ranges from c. 7200 to c. 2000 cal yr BP. The whole data indicate that a dense forest cover characterized the landscape all along the Prehistoric period, when a few signs of human activity are recorded in the spectra, such as cereal crops, pasture activity and fires. The main environmental changes, forced by natural processes (coastal progradation) but probably enhanced by reclamation works, started from the Graeco-Roman period and led to the reduction of swampy areas that favoured the colonisation of the outer plain.

Anthropogenic amplification of geomorphic processes along the Mediterranean coasts: A case-study from the Graeco-Roman town of Elea-Velia (Campania, Italy)

Coastal areas are very dynamic environments where natural and man-induced modifications often interact. This is the case of the Graeco-Roman town of Elea-Velia, along the Cilento coast of southern Italy. The town was founded in the 6th century BCE on a hilly promontory bounded by two profound gulfs and assumed a prominent role in maritime commercial routes in the Graeco-Roman period. It declined in the Late Antiquity and was abandoned in the Middle Ages also due to serious landscape changes. In this study, the integration of geomorphology, borehole stratigraphy and analysis of archaeo-stratigraphical trenches was used to detail the relationship between geological and archaeological evidence. The huge amount of collected data allowed providing chronological constraints to the landscape modification occurred before and after the town foundation. The main environmental changes consisted in enhanced coastal progradation and alluvial fan deposition that mainly affected the lower quarters of the town. The results of this study suggest that alluvial flooding was one of the main causes of the Elea-Velia decline and subsequent abandonment. The increasing disruption of slope stability was driven by the neglect in the management of the hillslopes behind the town during periods of social-economic crisis, but a concomitant climate forcing cannot be excluded. To the final abandonment also contributed the declining of harbour activities and the consequent decreased relevance of Elea-Velia as a maritime centre.

Polygenesis of loamy soils in North-West Siberia in the context of environmental history of the Eurasian Artic region during the Late Quaternary

This research provided a model of genesis of soils in North-West Siberia connecting the stages of their development to the main environmental changes over the Late Pleistocene and the Holocene. The “soil memory” showed that the studied soils had a complex polygenetic origin. A gleyed paleosol with signs of solifluction found at a depth of 2 m was most probably formed during the Marine Isotope Stage (MIS) 3 that is the Karginsky interstadial. The following stage, i.e., MIS2 – the Sartanian cryochron was characterized by the eolian sedimentation of silty material. In the Late Sartanian, new soil formation began in the silty parent material, with a strong platy cryogenic aggregation and grain size sorting. The warmer and more humid climate in the early Holocene induced clay illuviation and allowed for the formation of the argic horizon. Finally, the modern climatic conditions have caused ooidal cryogenic aggregation within upper horizons, however recent frost action has not been as strong as it was during the previous cold stage. Additionally, the modern pedogenesis included spodic and stagnic processes as well as clay mineral transformation. We suppose that such a model of soil evolution could be extrapolated to the northern Cis-Ural region, but not to the west in the Baltic region, where the dynamics of pedogenesis were different.

Effect of land-use types on the ecomorphological structure of fish assemblage in distinct mesohabitats of neotropical streams

Abstract The use and occupation of land by human population substantially influence environmental variables and fish assemblage in streams. However, there is little knowledge on how these changes affect the ecomorphological structure of fish assemblage in mesohabitats. Therefore, we aim to assess whether the land-use types affect the ecomorphological structure of fish assemblage in distinct mesohabitats. Environmental and ichthyofaunistic data were collected in three mesohabitats (rifles, runs, and pools) of five rural and five urban streams. Twenty-one ecomorphological indices were obtained from the mean of linear morphological measurements and areas of the fishes. Subsequently, the Euclidean distance was calculated, based on the ecomorphological indices, between each pair of species, to measure the ecomorphological distances for the mesohabitats of the rural and urban streams. The results show that the urban environment is more harmful to streams than the rural one, due to changes in the environmental variables and decrease in species richness. The main environmental changes found in urban streams were the decrease in canopy cover by riparian vegetation and dissolved oxygen, and the increase in electrical conductivity and bed silting. Also, there was a significant decrease in the morphological similarity between fish species in the mesohabitats of urban streams compared to rural ones. Therefore, we can conclude that the urban environment leads to the loss of morphologically similar fish species in the mesohabitats, with only a few functionally distinct species remaining.

Climate and vegetation dynamics of the Northern Apennines (Italy) during the Late Pleistocene and Holocene

This study reconstructs the regional vegetation and climate dynamics between the upper Late Pleistocene and Holocene around Pian del Lago, a coastal mountain marshland located at 831 m asl in western Liguria (NW-Italy), based on the pollen analysis of a 13 m-long sediment core. The record provided a unique opportunity to study a poorly documented period in northern Italy and across many parts of southwestern Europe. We propose an event stratigraphy based upon the identification of seven interstadials (NAI-7 to NAI-1) spanning the upper Late Pleistocene. The correlation with other terrestrial records in Italy, and with Mediterranean marine sequences and the Greenland ice cores, permitted a coherent reconstruction of main environmental changes from >∼43,000 cal. BP. Significantly, the pollen record indicates the persistence of a mesophilous mountain vegetation cover, mainly composed of Quercus (deciduous and evergreen), Abies, Fagus and Alnus over the whole time period recorded. At the Last Glacial Maximum (LGM) and during the Late Würm Lateglacial, despite the presence of steppic vegetation composed of Artemisia, woodlands dominated by Pinus, with Abies, Picea, Fagus, Alnus and Betula are present. This forest composition provides an important insight into the history of Picea in southern Europe and Late Pleistocene refugia for mesophilous species. During the Early Holocene, Pinus is first replaced by Abies and then by deciduous Quercus and mixed temperate species as the dominant forest component. Both arboreal and herbaceous anthropogenic pollen indicators only make their appearance during the Late Holocene, attesting to the increasing importance of human activities.

An integrated sea-land approach for analyzing forms, processes, deposits and the evolution of the urban coastal belt of Cagliari

ABSTRACT Using a comprehensive cartographic product, this paper aims to illustrate the evolution of the urban geomorphological setting of the urban coastal belt of Cagliari (southern Sardinia, Italy, western Mediterranean Sea). The geomorphological map (1:14,000) presented herein summarizes different data (e.g. urban development, anthropogenic features, geomorphological elements, recent deposits, sedimentological distribution, hydrodynamics and ecological components) acquired through an integrated sea-land approach and a multidisciplinary-multitemporal investigation. The main significant environmental changes are linked to urbanization, the development of port infrastructures (embankments along the shoreline and the construction of the canal harbour), remediation work and filling activities, and the hardening of dune and beach systems and cliffs. These man-made interventions have increased the vulnerability of the shore zones to flood hazards and risks, which are linked to sea-level rises and global warming.

Influence of socio-economic stressors on interpretations of climate change on Takuu Atoll, Papua New Guinea

The global media widely reports low-lying South Pacific islands as being rendered imminently uninhabitable by the effects of anthropogenic climate change. The impacts climate change has on these islands must be adequately addressed, yet there is often a stark contrast between what the media reports and what people on the ground perceive occurring. On Takuu Atoll, Papua New Guinea, socio-economic conditions, more than environmental ones, are presently at the forefront of concern and debate. This paper focuses on three main environmental changes observed by local residents, namely increasingly unpredictable weather patterns, shoreline erosion, and salinization of garden plots. It then explores how specific socio-economic conditions, such as high reliance on imported food, increased population mobility and lack of livelihood opportunities influence local interpretations of the information about climate change received from external sources, including increasingly mobile Takuu Islanders. In order to optimize the effectiveness of future climate change adaptation initiatives in the South Pacific, it is imperative to take into account the particularities of local contexts.

Effects of nitrogen addition on biomass allocation of Pinus koraiensis and Fraxinus mandshurica seedlings under water stress.

Nitrogen deposition and climate warming-drying are the main environmental changes in Northeast China. How they affect forest ecosystems has always been studied in ecological research. In this study, we explored the effects of water stress and nitrogen (N) addition on the short-term (in 55 weeks) growth of seedlings of Pinus koraiensis and Fraxinus mandshurica, two key species in broad-leaved and P. koraiensis mixed forests in temperate zone of Northeast China. Results showed that the responses of seedling growth of P. koraiensis and F. mandshurica to nitrogen addition and water stress were significantly different. P. koraiensis was more sensitive to water stress. In the early stage (in 10 weeks) of water stress, leaf biomass of P. koraiensis significantly decreased while the root biomass increased. Nitrogen addition significantly reduced the root and total biomass of P. koraiensis under water stress. F. mandshurica was more sensitive to N addition. Nitrogen addition rapidly increased the stem, root and total biomass of F. mandshurica. Only sustained water stress could significantly affect the stem, root and total biomass of F. mandshurica. Under continuous water stress and N addition, the biomass contribution of leaves and roots to whole seedling, and the ratio of aboveground to underground biomass of both species tended to be constant, indicating strong self-regulation ability of both species. The results suggested that when drought occurred in the future, P. koraiensis would adopt a "positive" adjustment strategy, while F. mandshurica would adopt a "passive" response. The survival rate and adaptability of P. koraiensis would be higher than F. mandshurica. F. mandshurica would benefit more from N deposition than P. koraiensis. Our results are helpful for predicting the changes of community structure in temperate forest in Northeast China.