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Water footprints have been proposed as sustainability indicators, relating the consumption of goods like food to the amount of water necessary for their production and the impacts of that water use in the source regions. We further developed the existing water footprint methodology, by globally resolving virtual water flows from production to consumption regions for major food crops at 5 arcmin spatial resolution. We distinguished domestic and international flows, and assessed local impacts of export production. Applying this method to three exemplary cities, Berlin, Delhi and Lagos, we find major differences in amounts, composition, and origin of green and blue virtual water imports, due to differences in diets, trade integration and crop water productivities in the source regions. While almost all of Delhi's and Lagos' virtual water imports are of domestic origin, Berlin on average imports from more than 4000 km distance, in particular soy (livestock feed), coffee and cocoa. While 42% of Delhi's virtual water imports are blue water based, the fractions for Berlin and Lagos are 2 and 0.5%, respectively, roughly equal to the water volumes abstracted in these two cities for domestic water use. Some of the external source regions of Berlin's virtual water imports appear to be critically water scarce and/or food insecure. However, for deriving recommendations on sustainable consumption and trade, further analysis of context-specific costs and benefits associated with export production will be required.
In order to achieve climate change mitigation, long-term decisions are required that must be reconciled with other societal goals that draw on the same resources. For example, ensuring food security for a growing population may require an expansion of crop land, thereby reducing natural carbon sinks or the area available for bio-energy production. Here, we show that current impact-model uncertainties pose an important challenge to long-term mitigation planning and propose a new risk-assessment and decision framework that accounts for competing interests.
Based on cross-sectorally consistent simulations generated within the Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP) we discuss potential gains and limitations of additional irrigation and trade-offs of the expansion of agricultural land as two possible response measures to climate change and growing food demand. We describe an illustrative example in which the combination of both measures may close the supply demand gap while leading to a loss of approximately half of all natural carbon sinks.
We highlight current limitations of available simulations and additional steps required for a comprehensive risk assessment.
The prediction of climate on time scales of years to decades is attracting the interest of both climate researchers and stakeholders. The German Ministry for Education and Research (BMBF) has launched a major research programme on decadal climate prediction called MiKlip (Mittelfristige Klimaprognosen, Decadal Climate Prediction) in order to investigate the prediction potential of global and regional climate models (RCMs). In this paper we describe a regional predictive hindcast ensemble, its validation, and the added value of regional downscaling. Global predictions are obtained from an ensemble of simulations by the MPI-ESM-LR model (baseline 0 runs), which were downscaled for Europe using the COSMO-CLM regional model. Decadal hindcasts were produced for the 5 decades starting in 1961 until 2001. Observations were taken from the E-OBS data set. To identify decadal variability and predictability, we removed the long-term mean, as well as the long-term linear trend from the data. We split the resulting anomaly time series into two parts, the first including lead times of 1–5 years, reflecting the skill which originates mainly from the initialisation, and the second including lead times from 6–10 years, which are more related to the representation of low frequency climate variability and the effects of external forcing. We investigated temperature averages and precipitation sums for the summer and winter half-year. Skill assessment was based on correlation coefficient and reliability. We found that regional downscaling preserves, but mostly does not improve the skill and the reliability of the global predictions for summer half-year temperature anomalies. In contrast, regionalisation improves global decadal predictions of half-year precipitation sums in most parts of Europe. The added value results from an increased predictive skill on grid-point basis together with an improvement of the ensemble spread, i.e. the reliability.
The Sahel has been the focus of scientific interest in environmental-human dynamics and interactions. The objective of the present study is to contribute to the recent debate on the re-greening of Sahel. The paper examines the dynamics of barren land in the Sahel of Burkina Faso through analysis of remotely-sensed and rainfall data from 1975–2011. Discussions with farmers and land management staff have helped to understand the anthropogenic efforts toward soil restoration to enable the subsistence farming agriculture. Results showed that area of barren land has been fluctuating during the study period with approximately 10-year cyclicity. Similarly, rainfall, both at national and local levels has followed the same trends. The trends of the area of barren land and rainfall variability suggest that when rainfall increases, the area of barren land decreases and barren land increases when rainfall decreases. This implies that rainfall is one of the main factors driving the change in area of barren land. In addition, humans have contributed positively and negatively to the change by restoring barren lands for agriculture using locally known techniques and by accelerating land degradation through intensive and inappropriate land use practices.
The link between atmospheric radicals and newly formed particles at a spruce forest site in Germany
(2014)
It has been claimed for more than a century that atmospheric new particle formation is primarily influenced by the presence of sulfuric acid. However, the activation process of sulfuric acid related clusters into detectable particles is still an unresolved topic. In this study we focus on the PARADE campaign measurements conducted during August/September 2011 at Mt Kleiner Feldberg in central Germany. During this campaign a set of radicals, organic and inorganic compounds and oxidants and aerosol properties were measured or calculated. We compared a range of organic and inorganic nucleation theories, evaluating their ability to simulate measured particle formation rates at 3 nm in diameter (J3) for a variety of different conditions. Nucleation mechanisms involving only sulfuric acid tentatively captured the observed noon-time daily maximum in J3, but displayed an increasing difference to J3 measurements during the rest of the diurnal cycle. Including large organic radicals, i.e. organic peroxy radicals (RO2) deriving from monoterpenes and their oxidation products, in the nucleation mechanism improved the correlation between observed and simulated J3. This supports a recently proposed empirical relationship for new particle formation that has been used in global models. However, the best match between theory and measurements for the site of interest was found for an activation process based on large organic peroxy radicals and stabilised Criegee intermediates (sCI). This novel laboratory-derived algorithm simulated the daily pattern and intensity of J3 observed in the ambient data. In this algorithm organic derived radicals are involved in activation and growth and link the formation rate of smallest aerosol particles with OH during daytime and NO3 during night-time. Because the RO2 lifetime is controlled by HO2 and NO we conclude that peroxy radicals and NO seem to play an important role for ambient radical chemistry not only with respect to oxidation capacity but also for the activation process of new particle formation. This is supposed to have significant impact of atmospheric radical species on aerosol chemistry and should be taken into account when studying the impact of new particles in climate feedback cycles.
The Late Cretaceous is known to be mostly affected by warm periods interrupted temporarily by a number of cooling events. The reconstruction of the paleoclimatic conditions during a period of high concentration of CO2 in the atmosphere is of great importance for the creation of future climate models. We applied the recently developed method reconstructing the SST from the TEX86 (TetraEther indeX of tetraethers consisting of 86 carbon atoms).
The sample material used for the present study was obtained from the tropical Late Cretaceous southern Tethys upwelling system (Negev/Israel), lasting from the Late Santonian to the Early Maastrichtian (~ 85 to 68 Ma). On the core samples from the Shefela basin, representing the outer belt of the upwelling system and the outcrop profile from the open mine Mishor Rotem (Efe Syncline), representing the inner belt, various bulk geochemical and biomarker studies were performed in this thesis.
Derived from TEX86 data, a significant long-term SST cooling trend from 36.0 to 29.3 °C is recognized during the Late Santonian and the Early Campanian in the southern Tethys margin. This is consistent with the opening and deepening of the Equatorial Atlantic Gateway (EAG) and the intrusion of cooler deep water from the southern Atlantic Ocean influencing the global SSTs and also the Tethys Ocean. Furthermore, the cooler near shore SST usually found in modern upwelling systems could be verified in case of the ancient upwelling system investigated in the present study. The calculated mean SST in the inner belt (27.7 °C) represented in the Efe Syncline was 1.5 °C cooler in comparison to the more seaward located outer belt (Shefela basin).
Moreover, geochemical and biomarker analyses were used to identify both the accumulation of high amounts of phosphate in the PM and good preservation of organic matter (OM) in the lower part of the OSM section. Total organic carbon (TOC) contents are highly variable over the whole profile reaching from 0.6 % in the MM, to 24.5 % in the OSM. Total iron (TFe) varies from 0.1 % in the PM to 3.3 % in the OSM and total sulfur (TS) varies between 0.1 % in the MM and 3.4 % in the OSM. Different correlations of TS, TOC and TFe were used to identify the conditions during the deposition of the different facies types. Natural sulfurization was found to play a key role in the preservation of the OM particularly in the lower part of the OSM. Samples from the OSM and the PM were deposited under dysoxic to anoxic conditions and iron limitation lasted during the deposition of the OSM and the PM, which effected the incorporation of sulfur into OM.
Phosphorus is highly accumulated in the sediments of the PM with a mean proportion of 11.5 % total phosphorus (TP), which is drastically reduced to a mean value of 0.9 % in the OSM and the MM. From the correlation of the bulk geochemical parameters TOC/TOCOR ratio and TP a major contribution of sulfate reducing bacteria to the phosphate deposition is concluded. This interrelation has previously been investigated in recent coastal upwelling systems off Peru, Chile, California and Namibia. This was further supported by the analysis of branched and monounsaturated fatty acids indicating the occurrence of sulfate reducing and sulfide oxidizing bacteria during the deposition.
According to the results from the analysis of n-alkanes and C27- to C29-steranes up to 95 % of the OM was of marine origin.
Organic sulfur compounds (OSC) were a major compound class in the aromatic hydrocarbon fraction and n-Alkyl and isoprenoid thiophenes were the most abundant, with highest amounts found for 2-methyl-5-tridecyl-thiophene (28 µg/g TOC). The relatively high abundance of ββ-C35 hopanoid thiophenes and epithiosteranes is equivalent to an incorporation of sulfur during the early stages of diagenesis.
Moreover, the geochemical parameters δ13Corg, δ15Norg, C/N and the pristane/phytane (Pr/Ph) ratio, were studied for reconstruction of seafloor and water column depositional environments. The high C/N ratio along with relatively low values of δ15Norg (4 ‰ to 6 ‰) and δ13Corg (-29 ‰ to -28 ‰) are consistent with a significant preferential loss of nitrogen-rich organic compounds during diagenesis. Oxygen-depleted conditions lasted during the deposition of the PM and the bottom of the OSM, reflected by the low Pr/Ph ratio of 0.11–0.7. In the upper part of the OSM and the MM the conditions changed from anoxic to dysoxic or oxic conditions. This environmental trend is consistent with co-occurring foraminiferal assemblages in the studied succession and implies that the benthic species in the Negev sequence were adapted to persistent minimum oxygen conditions by performing complete denitrification as recently found in many modern benthic foraminifera.
Furthermore, the anammox process could have influenced the nitrogen composition of the sediments. In this anaerobically process nitrite and ammonia are converted to molecular nitrogen.
Terrestrial climate and ecosystem evolution during ‘Greenhouse Earth’ phases of the early Paleogene remain incompletely known. Particularly, paleobotanical records from high southern latitudes are giving only limited insights into the Paleocene and early Eocene vegetation of the region. Hence, data from continuous well-calibrated sequences are required to make progress with the reconstruction of terrestrial climate and ecosystem dynamics from the southern latitudes during the early Paleogene.
In order to elucidate the terrestrial conditions from the high southern latitudes during the early Paleogene, terrestrial palynology was applied in the present study to two well-dated deep-marine sediment cores located at the Australo-Antarctic region: (i) IODP Site U1356 (Wilkes Land margin, East Antarctica) and (ii) ODP Site 1172 (East Tasman Plateau, southwest Pacific Ocean). The studied sequence from IODP Site U1356 comprises mid-shelfal sediments from the early to middle Eocene (53.9 – 46 million years ago [Ma]). For the ODP Site 1172, the studied succession is characterized by sediments deposited in shallow marine environments of the middle Paleocene to the early Eocene (60.7 – 54.2 Ma).
Based on the obtained pollen and spores (sporomorphs) results from the studied sequences of Site U1356 and Site 1172, this study aims to: (1) decipher the terrestrial climate conditions along the Australo-Antarctic region from the middle Paleocene to the middle Eocene; (2) evaluate the structure, diversity and compositional patterns of forests that throve in the Australo-Antarctic region during the early Paleogene; (3) understand the response of forests from the high southern latitudes to the climate dynamics from the early Paleogene; (4) establish a connection between the generated terrestrial palynomorph data and published Sea Surface Temperatures (SSTs) from the same cores.
To decipher the terrestrial climatic conditions on the Australo-Antarctic region, this study relies on the nearest living relative (NLR) concept that assumes that fossil taxa have similar climate requirements as their modern counterparts. This approach was applied to the sporomorph results of Site U1356 and Site 1172, following mainly the bioclimatic analysis. With regard to the structure and diversity patterns of the vegetation from the same region, the present study presents combined qualitative (i.e., reconstruction of the vegetation based mainly on the habitats of the known living relatives) and quantitative (i.e., application of ordination techniques, rarefaction and diversity indices) analyses of the fossil sporomorphs results.
The overall results from the paleoclimatic and vegetation reconstruction approaches applied in the present study, indicate that temperate and paratropical forests during the early Paleogene throve under different climatic conditions on the Wilkes Land margin and on Tasmania, at paleolatitudes of ∼70°S and ∼65°S, respectively.
Specifically, the sporomorph results from Site U1356, suggest that a highly diverse forest similar to present-day forests from New Caledonia was thriving on Antarctica during the early Eocene (53.9 – 51.9 Ma). These forests were characterized by the presence of termophilous taxa that are restricted today to tropical and subtropical settings, notably Bombacoideae, Strasburgeria, Beauprea, Spathiphyllum, Anacolosa and Lygodium. In combination with MBT/CBT paleotemperature results, they provide strong evidence for near-tropical warmth at least in the coastal lowlands along the Wilkes Land margin. The coeval presence of frost tolerant taxa such as Nothofagus, Araucariaceae and Podocarpaceae during the early Eocene on the same record suggests that paratropical forests were thriving along the Wilkes Land margin. Due to the presence of this kind of vegetation, it is possible to suggest that forests in this region were subject to a climatic gradient related to differences in elevation and/or the proximity to the coastline.
By the middle Eocene, the paratropical forests that characterized the vegetation of the early Eocene on the Wilkes Land margin were replaced by low diversity temperate forests dominated by Nothofagus, and similar to present-day cool-temperate forests from New Zealand. The dominance of these forests and the absence of thermophilous elements together with the lower temperatures suggested by the MBT/CBT and the sporomorph-based temperatures indicate consistently cooler conditions during this time interval.
With regard to the sporomorph results of Site 1172, this study suggests that three vegetation types were thriving on Tasmania from the middle Paleocene to the early Eocene under different climatic conditions. During the middle to late Paleocene, warm-temperate forests dominated by Podocarpaceae and Araucariaceae were the prevailing vegetation on Tasmania. The dominance of these forests was interrupted by the transient predominance of cool-temperate forests dominated by Nothofagus and Araucariaceae across the middle/late Paleocene transition interval (~59.5 to ~59.0 Ma). This cool-temperate forest was characterized by a lack of frost-sensitive elements (i.e., palms and cycads) indicating cooler conditions with harsher winters on Tasmania during this time interval. By the early Eocene, and linked with the Paleocene Eocene Thermal Maximum (PETM), Paleocene temperate forests dominated by gymnosperms were replaced by paratropical rainforests with the remarkable presence of the tropical mangrove palm Nypa during the PETM and the earliest Eocene. The overall results from Site U1356 and Site 1172, provide a new assessment of the terrestrial climatic conditions in the Australo-Antarctic region for validating climate models and understanding the response of high-latitude terrestrial ecosystems to the climate dynamics of the early Paleogene on southern latitudes.
The climatic conditions in the higher latitudes during the early Paleogene were further unravelled by comparing the obtained terrestrial and marine results. The integration of the obtained sporomorph data with previously published TEX86-based SSTs from Site 1172 documents that the vegetation dynamics were closely linked with the temperature evolution from the Australo-Antarctic region. Moreover, the comparison of TEX86-based SSTs and sporomorph-based climatic estimations from Site 1172 suggests a warm-season bias of both calibrations of TEX86 (i.e., TEX86Hand TEX86H), when this proxy is applied to high southern latitudes records of the early Paleogene.
The Tarim River Basin, located in Xinjiang, NW China, is the largest endorheic river basin of China and one of the largest in whole Central Asia. Due to the extremely arid climate with an annual precipitation of less than 100 mm, the water supply along the Aksu and Tarim River solely depends on river water. This applies for anthropogenic activities (e.g. agriculture) as well as for the natural ecosystems so that both compete for water. The on-going increase of water consumption by agriculture and other human activities in this region has been enhancing the competition for water between human needs and nature. Against this background, 11 German and 6 Chinese universities and research institutes formed the consortium SuMaRiO (www.sumario.de), which aims at gaining a holistic picture of the availability of water resources in the Tarim River Basin and the impacts on anthropogenic activities and natural ecosystems caused by the water distribution within the Tarim River Basin. The discharge of the Aksu River, which is the major tributary to the Tarim, has been increasing over the past 6 decades due to enhanced glacier melt. Alone from 1989 to 2011, the area under agriculture more than doubled. Thereby, cotton became the major crop and there was a shift from small-scale farming to large-scale intensive farming. The major natural ecosystems along the Aksu and Tarim River are riparian ecosystems: Riparian (Tugai) forests, shrub vegetation, reed beds, and other grassland. Within the SuMaRiO Cluster the focus was laid on the Tugai forests, with Populus euphratica as dominant tree, because the most productive and species-rich natural ecosystems can be found among those forests. On sites with groundwater distance of less than 7.5 m the annual increments correlated with river runoffs of the previous year. But, the further downstream along the Tarim River, the more the natural river dynamics ceased, which impacts on the recruitment of Populus euphratica. Household surveys revealed that there is a considerable willingness to pay for conservation of those riparian forests with the mitigation of dust and sandstorms considered as the most important ecosystem service. This interdisciplinary project will result in a decision support tool (DST), build on the participation of regional stakeholders and models based on results and field experiments. This DST finally shall assist stakeholders in balancing the water competition acknowledging the major external effects of any water allocation.
Reconstructing the early Paleogene climate dynamics of terrestrial settings in the high southern latitudes is important to assess the role of high-latitude physical and biogeochemical processes in the global climate system. However, whereas a number of high-quality Paleogene climate records has become available for the marine realm of the high southern latitudes over the recent past, the long-term evolution of coeval terrestrial climates and ecosystems is yet poorly known. We here explore the climate and vegetation dynamics on Tasmania from the middle Paleocene to the early Eocene (60.7–54.2 Ma) based on a sporomorph record from Ocean Drilling Program (ODP) Site 1172 on the East Tasman Plateau. Our results show that three distinctly different vegetation types thrived on Tasmania under a high-precipitation regime during the middle Paleocene to early Eocene, with each type representing different temperature conditions: (i) warm-temperate forests dominated by gymnosperms that were dominant during the middle and late Paleocene; (ii) cool-temperate forests dominated by southern beech (Nothofagus) and araucarians across the middle/late Paleocene transition interval (~59.5 to ~59.0 Ma); and (iii) paratropical forests rich in ferns that were established during and in the wake of the Paleocene–Eocene Thermal Maximum (PETM). The transient establishment of cool-temperate forests lacking any frost-sensitive elements (i.e., palms and cycads) across the middle/late Paleocene transition interval indicates markedly cooler conditions, with the occurrence of frosts in winter, on Tasmania during that time. The integration of our sporomorph data with previously published TEX86-based sea-surface temperatures from ODP Site 1172 documents that the vegetation dynamics on Tasmania were closely linked with the temperature evolution in the Tasman sector of the Southwest Pacific region. Moreover, the comparison of our season-specific climate estimates for the sporomorph assemblages from ODP Site 1172 with the TEX86L- and TEX86H-based temperature data suggests a warm-season bias of both calibrations for the early Paleogene of the high southern latitudes.
Global warming, changes in the hydrological cycle and enhanced marine primary productivity all have been invoked to have contributed to the occurrence of widespread ocean anoxia during the Cenomanian-Turonian Oceanic Anoxic Event (OAE2; ~ 94 Ma), but disentangling these factors on a regional scale has remained problematic. We generated palynological and organic geochemical records that allow the separation of these forcing factors in a core spanning the OAE2 from Wunstorf, Lower Saxony Basin (LSB; North Gemany), which exhibits cyclic black shale–marl alternations related to the orbital precession cycle.
Despite the widely varying depositional conditions complicating the interpretation of the obtained records, TEX86H indicates that sea-surface temperature (SST) evolution in the LSB during OAE2 resembles that of previously studied sites throughout the proto-North Atlantic. Cooling during the so-called Plenus Cold Event interrupted black shale deposition during the early stages of OAE2. However, TEX86 does not vary significantly across marl–black shale alternations, suggesting that temperature variations did not force the formation of the cyclic black shale horizons. Relative (i.e., with respect to marine palynomorphs) and absolute abundances of pollen and spores are elevated during phases of black shale deposition, indicative of enhanced precipitation and run-off. High abundances of cysts from inferred heterotrophic and euryhaline dinoflagellates supports high run-off, which likely introduced additional nutrients to the epicontinental shelf resulting in elevated marine primary productivity.
We conclude that orbitally-forced enhanced precipitation and run-off, in tandem with elevated marine primary productivity, were critical in cyclic black shale formation on the northwest European epicontinental shelf and potentially for other OAE2 sections in the proto-Atlantic and Western Interior Seaway at similar latitudes as well.