Scale Climate Change Research Articles

Fine structure of dark layers in the central Japan Sea and their relationship with the abrupt climate and sea level changes over the last 75 ka inferred from lithophysical, geochemical and pollen results

Abstract High resolution of the color lightness, productivity proxies (TOC, chlorin, CaCO 3 , Ba-bio, Mo and U), and lithological description defined alternation of dark layers (DLs) and light layers in sediment core LV53-23 recovered from the central Japan Sea (west Yamato Rise) over the last 75 ka. Age model was constructed by AMS 14C data, tephrochronology, δ 18 O of planktonic foraminifera record, and the correlation of DLs with lightness of Japan Sea core MD01-2407 and with millennial interstadials recorded in the Greenland ice cores and East Asia stalagmites. Regional interstadials were also independently established and dated by vegetation amelioration of the surrounded land, inferred from the pollen results. Correlation of the DLs with millennial scale climate and sea level changes indicate that both interstadial warming and sea level fluctuations influence on its formation providing their individual features. During MIS 3, with sea level above −90 m, DL was formed mostly consistent with the Tada et al. (1999)’s hypotheses. During MIS 2 and 4, when sea level was nearly and below −90 m, sea level descending led to water column stratification, oxygen depletion in bottom water and facilitates the DLs formation. High-resolution lightness and productivity proxies defined the subtle structure of pronounced interstadials 14 and 12.

The influence of rapid, millennial scale climate change on nitrogen isotope dynamics of the Cariaco Basin during marine isotope stage 3

AbstractUnderstanding changes to the marine nitrogen cycle on millennial and shorter time scales can help determine the influence of rapid climate change on the fixed N pool and its sources and sinks. Rapid changes in denitrification have been observed in the eastern tropical North Pacific (ETNP) and Arabian Sea; however, millennial scale δ15N records in regions influenced by N2 fixation are sparse. We present a sedimentary δ15N record from the Cariaco Basin during marine isotope stage (MIS) 3 (~35–55 ka). The δ15N record displays a pattern of millennial scale variability that tracks the Greenland ice core Dansgaard‐Oeschger cycles, with higher values observed during interstadial periods, lower values during stadial periods, and abrupt transitions in between. Conditions during interstadials are similar to those at present in the Cariaco Basin, with the sedimentary δ15N signal reflecting a combination of local processes and an imported regional signal. If interpreted to reflect regional processes, the interstadial δ15N values (average ~5.1‰) support the argument that N2 fixation did not increase in the tropical North Atlantic during the last glacial. The lower δ15N values during stadials, when lower sea level resulted in increased physical isolation of the basin, can be explained primarily by local processes. In spite of the importance of local processes, striking similarity is observed between the Cariaco record and millennial scale δ15N records from the ETNP and Arabian Sea. The apparent synchronicity of changes observed in all three regions suggests an atmospheric teleconnection between the three sites and high‐latitude climate forcing during MIS 3.

South Asian monsoon history over the past 60 kyr recorded by radiogenic isotopes and clay mineral assemblages in the Andaman Sea

AbstractThe Late Quaternary variability of the South Asian (or Indian) monsoon has been linked with glacial‐interglacial and millennial scale climatic changes but past rainfall intensity in the river catchments draining into the Andaman Sea remains poorly constrained. Here we use radiogenic Sr, Nd, and Pb isotope compositions of the detrital clay‐size fraction and clay mineral assemblages obtained from sediment core NGHP Site 17 in the Andaman Sea to reconstruct the variability of the South Asian monsoon during the past 60 kyr. Over this time interval εNd values changed little, generally oscillating between −7.3 and −5.3 and the Pb isotope signatures are essentially invariable, which is in contrast to a record located further northeast in the Andaman Sea. This indicates that the source of the detrital clays did not change significantly during the last glacial and deglaciation suggesting the monsoon was spatially stable. The most likely source region is the Irrawaddy river catchment including the Indo‐Burman Ranges with a possible minor contribution from the Andaman Islands. High smectite/(illite + chlorite) ratios (up to 14), as well as low 87Sr/86Sr ratios (0.711) for the Holocene period indicate enhanced chemical weathering and a stronger South Asian monsoon compared to marine oxygen isotope stages 2 and 3. Short, smectite‐poor intervals exhibit markedly radiogenic Sr isotope compositions and document weakening of the South Asian monsoon, which may have been linked to short‐term northern Atlantic climate variability on millennial time scales.

Projecting yield changes of spring wheat under future climate scenarios on the Canadian Prairies

The potential impact of the rise in atmospheric CO2 concentration and associated climatic change on agricultural productivity needs assessment. Projecting crop yield changes under climate change requires future climate scenarios as in- put to crop yield models. It is widely accepted that downscal- ing ofclimate data isrequiredtobridgethe gap between large- scale global climate models (GCMs) and climate change im- pact models, such as crop growth models. Regional climate models (RCMs) are often used to dynamically downscale GCM simulations to smaller regional scales, while statistical methods, such as regression-based transfer functions and sto- chastic weather generators, are also widely employed to de- velop future climate scenarios for this purpose. The methods usedindeveloping future climate scenarios often contributeto uncertainties in the projected impacts of climate change, in additiontothoseassociatedwithGCMsandforcingscenarios. We employed climate scenarios from the state-of-the-art RCMs in the North American Regional Climate Change As- sessmentProgram(NARCCAP), along with climatescenarios generated by a stochastic weather generator based on climate change simulations performed by their driving GCMs, to drive the CERES-Wheat model in DSSAT to project changes inspringwheatyieldontheCanadianPrairies.Thefuturetime horizon of 2041-2070 and the baseline period of 1971-2000 were considered. The projected changes showed an average increase ranging from 26 to 37 % of the baseline yield when the effects of the elevated CO2 concentration were simulated, but only up to 15 % if the elevated CO2 effect was excluded. In addition to their potential use in climate change impact assessment, the results also demonstrated that the simulated crop yield changes were fairly consistent whether future cli- mate scenarios were derived from RCMs or they were gener- ated by a stochastic weather generator based on the simulated climate change from the GCMs that were used to drive the RCMs, in this case, when they were compared for regional averages.

Interannual Climate Variability of the Past Millennium from Simulations

The interannual variability of global temperature and precipitation during the last millennium is analyzed using the results of ten coupled climate models participating in the Paleoclimate Modelling Intercomparison Project Phase 3. It is found that large temperature(precipitation) variability is most dominant at high latitudes(tropical monsoon regions), and the seasonal magnitudes are greater than the annual mean. Significant multi-decadal-scale changes exist throughout the whole period for the zonal mean of both temperature and precipitation variability, while their long-term trends are indistinctive. The volcanic forcings correlate well with the temperature variability at midlatitudes, indicating possible leading drivers for the interannual time scale climate change.

Using remote sensing to quantify albedo of roofs in seven California cities, Part 1: Methods

Abstract Cool roofs reflect sunlight and therefore can reduce cooling energy use in buildings. Further, since roofs typically cover about 20–25% of a city, widespread deployment of cool roofs could mitigate the urban heat island effect and partially counter urban temperature increases associated with global scale climate change. The magnitude of these potential benefits for a given city depends on the increase in albedo that can be achieved using reflective roofs. Assessing this increase requires knowledge of roof albedo at the city scale, which until now has been hindered by a lack of reflectance data with sufficient spatial coverage, spatial resolution, and spectral detail. In this work we use multiband aerial imagery to derive the albedos of individual roofs in seven California cities: Los Angeles, Long Beach, San Diego, Bakersfield, Sacramento, San Francisco, and San Jose. The radiometrically calibrated, remotely sensed imagery has high spatial resolution (1 m) and four narrowband reflectances: blue, green, red, and near-infrared. First, we locate roof pixels within GIS building outlines. Next, we use laboratory measurements of the solar spectral reflectances of 190 roofing products to empirically relate broadband solar reflectance to reflectances in the four narrow bands; this empirical relationship well predicts solar reflectance, as indicated by a low root-mean-square of the residuals of 0.016. Albedos computed from remotely sensed reflectances are calibrated to ground measurements of roof albedo in each city. The error (accuracy) at 90% confidence interval of the calibrated albedos is found to vary by city, from 0.00–0.01 at low albedo and 0.06–0.14 at high albedo.

Holocene climate variation determined from rubidium and strontium contents and ratios of sediments collected from the BadainJaran Desert, Inner Mongolia, China

Abstract Rubidium (Rb) and strontium (Sr) contents and ratios were analyzed in 197 sediment samples collected from the CGS1 segment of the Chagelebulu Section in the Badain Jaran Desert of China to study millennial scale climate change during the Holocene. The results showed that the Rb and Sr contents and Rb/Sr ratios were low in the samples of dune sands and loess (Mz 5.64Φ) and paleosols, these data displayed 11 changing cycles in alternation of peaks and valleys in the chart. In addition, the Rb contents were positively correlated with Mz (mean particle diameter) and clay contents. While the correlations were weaker, Sr contents also showed a tendency to increase with increases in the Mz and clay contents. Based on a comprehensive analysis of the distribution of Rb and Sr within the CGS1 segment, it appears that the observed Rb and Sr contents and ratios varied in accordance with fluctuations of the East Asian winter and summer monsoons. In terms of timing and climate, low values (C1–C11) resulting from winter monsoons had a strong correlation with cold events in the North Atlantic: the period C1 corresponded to times ranging from 400 a to 1400 a and the periods C2, C3, C4, C7, C9, C10, and C11 corresponded to times of 3000 a, 4000 a, 5900 a, 8200 a, 9400 a, 10,300 a, and 11,000 a, respectively. The cold event C5 (6200 a) was also discovered in the North Atlantic in recent; and C6 (7100 a), C8 (8700 a) were discovered in some other places of China. These cold events indicated by Rb and Sr contents and ratios in the Chagelebulu Section of the Badain Jaran Desert recorded the regional response of global climate change during the Holocene.

Scaling climate change experiments across space and time

Scaling climate change experiments across space and time

Asynchronous Little Ice Age glacier fluctuations in Iceland and European Alps linked to shifts in subpolar North Atlantic circulation

Abstract Records of past glacier fluctuations are an important source of paleoclimate data and provide context for future changes in global ice volume. In the North Atlantic region, glacier chronologies can be used to track the response of terrestrial environments to variations in marine conditions including circulation patterns and sea ice cover. However, the majority of glacier records are discontinuous and temporally restricted, owing in part to the extensive advance of Northern Hemisphere glaciers during the Little Ice Age (LIA), the most recent and severe climate anomaly of the Neoglacial period. Here, we combine an absolutely dated and continuous record of Langjokull ice marginal fluctuations with new reconstructions of sediment flux through the past 1.2 ka using varved sediments from Hvitarvatn, a proglacial lake in Icelandʼs central highlands. Large spatial and temporal variations in sediment flux related to changing ice cap dimensions are reconstructed from six sediment cores and seismic reflection profiles. Sediment data reveal two discrete phases of ice expansion occurring ca. 1400 to 1550 AD and ca. 1680 to 1890 AD. These advances are separated by a persistent interval of ice retreat, suggesting that a substantial period of warming interrupted LIA cold. The pattern of Icelandic glacier activity contrasts with that of European glaciers but shows strong similarities to reconstructed changes in North Atlantic oceanographic conditions, indicating differing regional responses to coupled ocean–atmosphere–sea ice variations. Our data suggest that subpolar North Atlantic circulation dynamics may have led to coherent asynchronous glacier fluctuations during the mid LIA and highlight the importance of circulation variability in triggering and transmitting multidecadal scale climate changes to nearby terrestrial environments.

Is the Last Years Abrupt Warming in the National Observatory of Athens Records a Climate Change Manifestation?

Instrumental data time series show an average global warming of approximately 0.90C over the last century. Eastern Mediterranean air temperature follows the northern hemisphere (NH) secular trend till 1970s, while the NH warming of the last 30 years is not noticeable in the eastern Mediterranean till 1990s. National Observatory of Athens (NOA) meteorological time series start from the last decades of the 19th Century, therefore are at first suitable for detection of long term trends in the region. In this study we investigate whether the abrupt increase of the NOA air temperature time series, which appears during the last few years, is the finger-print of the broader scale climatic change or it is a discontinuity in the record of urban effect or of station’s problems origin. It is shown that NOA air temperature records display a statistically significant discontinuity attributable to change of the station thermometers on 1995 and therefore NOA records must be treated with caution for long term air temperature trends detection.

Plantation forests, climate change and biodiversity

Nearly 4 % of the world’s forests are plantations, established to provide a variety of ecosystem services, principally timber and other wood products. In addition to such services, plantation forests provide direct and indirect benefits to biodiversity via the provision of forest habitat for a wide range of species, and by reducing negative impacts on natural forests by offsetting the need to extract resources. There is compelling evidence that climate change is directly affecting biodiversity in forests throughout the world. These impacts occur as a result of changes in temperature, rainfall, storm frequency and magnitude, fire frequency, and the frequency and magnitude of pest and disease outbreaks. However, in plantation forests it is not only the direct effects of climate change that will impact on biodiversity. Climate change will have strong indirect effects on biodiversity in plantation forests via changes in forest management actions that have been proposed to mitigate the effects of climate change on the productive capacity of plantations. These include changes in species selection (including use of species mixtures), rotation length, thinning, pruning, extraction of bioenergy feedstocks, and large scale climate change driven afforestation, reforestation, and, potentially deforestation. By bringing together the potential direct and indirect impacts of climate change we conclude that in the short to medium term changes in plantation management designed to mitigate or adapt to climate change could have a significantly greater impact on biodiversity in such plantation forests than the direct effects of climate change. Although this hypothesis remains to be formally tested, forest managers worldwide are already considering new approaches to plantation forestry in an effort to create forests that are more resilient to the effects of changing climatic conditions. Such change presents significant risks to existing biodiversity values in plantation forests, however it also provides new opportunities to improve biodiversity values within existing and new plantation forests. We conclude by suggesting future options, such as functional zoning and species mixtures applied at either the stand level or as fine-scale mosaics of single-species stands as options to improve biodiversity whilst increasing resilience to climate change.

The role of Southern Ocean winds, upwelling and CO2 in glacial abrupt climate change

The last glacial period (ca. 110-10 kyr before present, hereafter kyr BP) is characterized by substantial climate instability, manifested as climatic variability on millennial timescales. Two types of events dominate this variability: Dansgaard-Oeschger (DO) events, which involve decadal-scale warming by more than 10K, and Heinrich events, massive iceberg discharges from the Laurentide Ice Sheet at intervals of ca. 10 kyr during peak glacial conditions. Both DO and Heinrich events are associated with widespread centennial to millennial scale climatic changes, including a synchronous temperature response over the North Atlantic and an anti-phase temperature relationship over Antarctica and most of the Southern Ocean, as revealed by a wealth of deep sea sediments and terrestrial record. Recent studies indicate CO2 changes during deglaciation and, possibly, during glacial abrupt climate changes were preceded by significant increases of Southern Ocean upwelling caused by an enhancement and/or a shift of surface winds over that region. The proposed hypothesis is that periods of halted or reduced North Atlantic deep water (NADW) formation resulted in warming of the Southern Ocean through the bipolar see-saw effect leading to a reorganization of Southern Hemisphere (SH) surface winds, and thereby enhanced upwelling and atmospheric CO2 concentrations. Here, the role of SH surface wind and CO2 changes in the Atlantic meridional overturning circulation (MOC) is analyzed in a coupled climate model of intermediate complexity. We investigate whether changes in the former could eventually trigger an intensification of the Atlantic overturning circulation and a northward shift of NADW formation, which would allow to explain glacial abrupt climate changes as the result of an oscillation which involves the MOC, CO2 and the winds.

Centennial scale climate change in NW Sweden during the mid-late Holocene: a reconstruction based on geochemical and chironomid data

Centennial scale climate change in NW Sweden during the mid-late Holocene: a reconstruction based on geochemical and chironomid data

Response of marine diatom communities to Late Quaternary abrupt climate changes

The high temporal resolution of the marine microfossil record makes it possible to explore how microbial communities responded to abrupt climate changes in the past. We analysed changes in species richness and total abundance of marine diatoms in sedimentary records from the Mauritanian upwelling system and the Panama Basin spanning the last 100 000 years. The analysis shows instances of community change and recovery linked to episodes of rapid, sub-millennial scale climate change (e.g. Heinrich events). The probability of sampling a given species during the perturbation increased with the mean abundance of the species in the database, indicating that (i) dominant species were persistent through long periods of time and (ii) rare species, with low population densities, accounted for much of the variability in species richness. To the extent that contemporaneous climate change falls within the range of climate variability analysed here, our results point to important changes in the structure of marine diatom communities, yet these changes will be reversible. These results highlight the importance of integrating fossil data and ecological theories to understand the effect of climate change on the ecological and biogeochemical functioning of marine ecosystems.

Palaeoenvironmental dynamics and underlying climatic changes in southeast Amazonia (Serra Sul dos Carajás, Brazil) during the late Pleistocene and Holocene

Abstract Pollen, fern spore, micro-charcoal, sediment and mineral analyses have been carried out on a 466 cm-long sediment core from the Serra Sul dos Carajas swamp in southeastern Amazonia. Ten AMS radiocarbon dates suggest that the sediment covers at least the last 73,000 years. Shifts between tropical forests and savanna, changes in species composition, as well as changes in fire frequency indicate several wet and dry periods during this time interval. During the assumed early Pleniglacial (73–50 ka), the dominance of savanna vegetation reflects drier conditions, whereas vegetation changes in the mid-Pleniglacial (50–40 ka) suggest alternating wet and dry phases under generally cool conditions. The recorded next period before the Last Glacial Maximum (LGM) shows a transition to wetter and cooler conditions, followed by a cold and dry LGM and Late glacial. At the beginning of the Holocene, between 11.4 and 10.2 cal ka, tropical forest expanded, reflecting stable and very humid conditions. During the early to mid-Holocene an increasingly seasonal, generally warm and dry climate established. Dry seasons were longer than at present during mid-Holocene times with a pronounced dry phase from 9 to 3.4 cal ka. Only after 3.4 cal ka did modern tropical rainforests became established under present-day climatic conditions. Comparison with other palaeoecological studies in the Amazon basin and eastern Andean regions suggests that environmental changes in Serra Sul were strongly coupled with large scale climatic changes and sea surface temperature variability in the tropical Atlantic.

Widespread Climate Change in the Himalayas and Associated Changes in Local Ecosystems

BackgroundClimate change in the Himalayas, a biodiversity hotspot, home of many sacred landscapes, and the source of eight largest rivers of Asia, is likely to impact the well-being of ∼20% of humanity. However, despite the extraordinary environmental, cultural, and socio-economic importance of the Himalayas, and despite their rapidly increasing ecological degradation, not much is known about actual changes in the two most critical climatic variables: temperature and rainfall. Nor do we know how changes in these parameters might impact the ecosystems including vegetation phenology.Methodology/Principal FindingsBy analyzing temperature and rainfall data, and NDVI (Normalized Difference Vegetation Index) values from remotely sensed imagery, we report significant changes in temperature, rainfall, and vegetation phenology across the Himalayas between 1982 and 2006. The average annual mean temperature during the 25 year period has increased by 1.5°C with an average increase of 0.06°C yr−1. The average annual precipitation has increased by 163 mm or 6.52 mmyr−1. Since changes in temperature and precipitation are immediately manifested as changes in phenology of local ecosystems, we examined phenological changes in all major ecoregions. The average start of the growing season (SOS) seems to have advanced by 4.7 days or 0.19 days yr−1 and the length of growing season (LOS) appears to have advanced by 4.7 days or 0.19 days yr−1, but there has been no change in the end of the growing season (EOS). There is considerable spatial and seasonal variation in changes in climate and phenological parameters.Conclusions/SignificanceThis is the first time that large scale climatic and phenological changes at the landscape level have been documented for the Himalayas. The rate of warming in the Himalayas is greater than the global average, confirming that the Himalayas are among the regions most vulnerable to climate change.

The environmental context for the origins of modern human diversity: A synthesis of regional variability in African climate 150,000–30,000 years ago

We synthesize African paleoclimate from 150 to 30 ka (thousand years ago) using 85 diverse datasets at a regional scale, testing for coherence with North Atlantic glacial/interglacial phases and northern and southern hemisphere insolation cycles. Two major determinants of circum-African climate variability over this time period are supported by principal components analysis: North Atlantic sea surface temperature (SST) variations and local insolation maxima. North Atlantic SSTs correlated with the variability found in most circum-African SST records, whereas the variability of the majority of terrestrial temperature and precipitation records is explained by local insolation maxima, particularly at times when solar radiation was intense and highly variable (e.g., 150-75 ka). We demonstrate that climates varied with latitude, such that periods of relatively increased aridity or humidity were asynchronous across the northern, eastern, tropical and southern portions of Africa. Comparisons of the archaeological, fossil, or genetic records with generalized patterns of environmental change based solely on northern hemisphere glacial/interglacial cycles are therefore imprecise. We compare our refined climatic framework to a database of 64 radiometrically-dated paleoanthropological sites to test hypotheses of demographic response to climatic change among African hominin populations during the 150-30 ka interval. We argue that at a continental scale, population and climate changes were asynchronous and likely occurred under different regimes of climate forcing, creating alternating opportunities for migration into adjacent regions. Our results suggest little relation between large scale demographic and climate change in southern Africa during this time span, but strongly support the hypothesis of hominin occupation of the Sahara during discrete humid intervals ~135-115 ka and 105-75 ka. Hominin populations in equatorial and eastern Africa may have been buffered from the extremes of climate change by locally steep altitudinal and rainfall gradients and the complex and variable effects of increased aridity on human habitat suitability in the tropics. Our data are consistent with hominin migrations out of Africa through varying exit points from ~140-80 ka.

Financing the resilient city

This paper presents a strategy for scaling climate change adaptation within urban areas. The strategy specifically focuses on the requirements for mobilizing large amounts of capital for adaptation and other urban risk reduction above and beyond the amounts that will likely be mobilized through new international adaptation funds. The paper, based on a report published by ICLEI–Local Governments for Sustainability,( 1 ) proposes a re-framing of the urban adaptation and disaster reduction challenge. The approach shifts the adaptation focus from risk reduction as a primary end in itself to a broader development focus on financing the performance of urban assets, areas and/or systems. This emphasis is elaborated through the concept of “resilience”, an urban design and investment metric that measures the ability of urban areas and their individual assets to perform for users and their investors under a wide range of conditions. The paper argues that such a performance-oriented approach provides a business logic that can attract conventional, private investment flows to climate and disaster risk reduction measures and thereby “mainstream” them.

Hydroclimate variability in the low-elevation Atacama Desert over the last 2500 yr

Abstract. Paleoclimate reconstructions reveal that Earth system has experienced sub-millennial scale climate changes over the past two millennia in response to internal/external forcing. Although sub-millennial hydroclimate fluctuations have been detected in the central Andes during this interval, the timing, magnitude, extent and direction of change of these events remain poorly defined. Here, we present a reconstruction of hydroclimate variations on the Pacific slope of the central Andes based on exceptionally well-preserved plant macrofossils and associated archaeological remains from a hyperarid drainage (Quebrada Maní, ∼21° S, 1000 m a.s.l.) in the Atacama Desert. During the late Holocene, riparian ecosystems and farming social groups flourished in the hyperarid Atacama core as surface water availability increased throughout this presently sterile landscape. Twenty-six radiocarbon dates indicate that these events occurred between 1050–680, 1615–1350 and 2500–2040 cal yr BP. Regional comparisons with rodent middens and other records suggest that these events were synchronous with pluvial stages detected at higher-elevations in the central Andes over the last 2500 yr. These hydroclimate changes also coincide with periods of pronounced SST gradients in the Tropical Pacific (La Niña-like mode), conditions that are conducive to significantly increased rainfall in the central Andean highlands and flood events in the low-elevation watersheds at inter-annual timescales. Our findings indicate that the positive anomalies in the hyperarid Atacama over the past 2500 yr represent a regional response of the central Andean climate system to changes in the global hydrological cycle at centennial timescales. Furthermore, our results provide support for the role of tropical Pacific sea surface temperature gradient changes as the primary mechanism responsible for climate fluctuations in the central Andes. Finally, our results constitute independent evidence for comprehending the major trends in cultural evolution of prehistoric peoples that inhabited the region.

Modelling and observation of hedgerow transpiration effect on water balance components at the hillslope scale in Brittany

AbstractVegetation has a major influence on the water and energy balance of the earth's surface. In the last century, human activities have modified land use, inducing a consequent change in albedo and potential evapotranspiration. Linear vegetation structures (hedgerows, shelterbelts, open woodland, etc) were particularly abundant but have declined considerably over the past several decades. In this context, it is important to quantify their effect on water and energy balance both on a global scale (climate change and weather prediction) and on a local scale (soil column, hillslope and watershed). The main objective of this study was to quantify the effect of hedgerows on the water cycle by evaluating spatial and temporal variations of water balance components of a hillslope crossed by a hedgerow. Water flow simulation was performed using Hydrus‐2D to emphasize the importance of transpiration in the water balance and to evaluate water extraction from groundwater. Model validation was performed by comparing simulated and observed soil matrix potentials and groundwater levels. Hedgerow transpiration was calculated from sap flow measurements of four trees. Water balance components calculated with a one‐dimensional water balance equation were compared with simulations. Simulation runs with and without tree root uptake underlined the effect of hedgerow transpiration, increasing capillary rise and decreasing drainage. Results demonstrated that the spatial and temporal variability of water balance components was related to the hedgerow presence as well as to the meteorological context. The relations between transpiration, groundwater proximity and soil‐water availability determined the way in which water balance components were affected. Increased capillary rise and decreased drainage near hedges were related to the high transpiration of trees identified in this study. Transpiration reached twice the potential evapotranspiration when groundwater level and precipitation amounts were high. Water balance analysis showed that transpiration was a substantial component, representing 40% of total water output. These results may offer support for improving hydrological models by including the effect of land use and land cover on hydrological processes. Copyright © 2012 John Wiley & Sons, Ltd.