1,721,177 research outputs found
The Role of Virtual Water Flows in Physical Water Scarcity: The Case of Central Asia
No full textWater scarcity in Central Asia was analyzed by using two water scarcity indices at the scale of sub-basin areas (SBAs): water stress index (consumption-to-availability ratio) and water shortage index (water availability per capita). These indices were calculated for a baseline scenario that included virtual water flows, and again for a scenario where international trade was eliminated, thus assessing the role of virtual water flows in water scarcity. Over 80% of the study area population suffers from water stress and approximately 50% from water shortage as well. Removing virtual water flows considerably decreased water scarcity for approximately half the population. Reducing the exports of water-intensive products could thus be an option, along with other more traditional measures, for alleviating water scarcity in Central Asia
Decoding the drivers of bank erosion on the Mekong River: the roles of the Asian monsoon, tropical storms and snow melt
No full textWe evaluate links between climate and simulated river bank erosion for one of the world's largest rivers, the Mekong. We employ a process-based model to reconstruct multi-decadal time series of bank erosion at study sites within the Mekong's two main hydrological response zones, defining a new parameter, accumulated excess runoff (AER), pertinent to bank erosion. We employ a hydrological model to isolate how snow melt, tropical storms and monsoon precipitation each contribute to AER and thus modelled bank erosion. Our results show that melt (23.9% at the upstream study site, declining to 11.1% downstream) and tropical cyclones (17.5% and 26.4% at the upstream and downstream sites, respectively) both force significant fractions of bank erosion on the Mekong. We also show (i) small, but significant, declines in AER and hence assumed bank erosion during the 20th century, and; (ii) that significant correlations exist between AER and the Indian Ocean Dipole (IOD) and El Niño Southern Oscillation (ENSO). Of these modes of climate variability, we find that IOD events exert a greater control on simulated bank erosion than ENSO events; but the influences of both ENSO and IOD when averaged over several decades are found to be relatively weak. However, importantly, relationships between ENSO, IOD and AER and hence inferred river bank erosion are not time-invariant. Specifically, we show that there is an intense and prolonged epoch of strong coherence between ENSO and AER from the early 1980s to present, such that in recent decades derived Mekong River bank erosion has been more strongly affected by ENSO
Causes and trends of water scarcity in food production
Full text linkThe insufficiency of water resources to meet the needs of food production is a pressing issue that is likely to increase in importance in the future. Improved understanding of historical developments can provide a basis for addressing future challenges. In this study we analyse how hydroclimatic variation, cropland expansion and evolving agricultural practices have influenced the potential for food self-sufficiency within the last century. We consider a food production unit (FPU) to have experienced green-blue water (GBW) scarcity if local renewable green (in soils) and blue water resources (in rivers, lakes, reservoirs, aquifers) were not sufficient for producing a reference food supply of 3000 kcal with 20% animal products for all inhabitants. The number of people living in FPUs affected by GBW scarcity has gone up from 360 million in 1905 (21% of world population at the time) to 2.2 billion (34%) in 2005. During this time, GBW scarcity has spread to large areas and become more frequent in regions where it occurs. Meanwhile, cropland expansion has increased green water availability for agriculture around the world, and advancements in agronomic practices have decreased water requirements of producing food. These efforts have improved food production potential and thus eased GBW scarcity considerably but also made possible the rapid population growth of the last century. The influence of modern agronomic practices is particularly striking: if agronomic practices of the early 1900s were applied today, it would roughly double the population under GBW scarcity worldwide.Peer reviewe
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Climate change threatens crop diversity at low latitudes
No full textAbstract Climate change alters the climatic suitability of croplands, likely shifting the spatial distribution and diversity of global food crop production. Analyses of future potential food crop diversity have been limited to a small number of crops. Here we project geographical shifts in the climatic niches of 30 major food crops under 1.5–4 °C global warming and assess their impact on current crop production and potential food crop diversity across global croplands. We found that in low-latitude regions, 10–31% of current production would shift outside the climatic niche even under 2 °C global warming, increasing to 20–48% under 3 °C warming. Concurrently, potential food crop diversity would decline on 52% (+2 °C) and 56% (+3 °C) of global cropland. However, potential diversity would increase in mid to high latitudes, offering opportunities for climate change adaptation. These results highlight substantial latitudinal differences in the adaptation potential and vulnerability of the global food system under global warming
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Karkeusominaisuudet ja nopeusjakauma kasvittomassa ja kasvillisuuden peittämässä uomassa
No full textViime vuosien suuret tulvat, varsinkin Euroopassa, ovat kasvattaneet mielenkiintoa tulvatasanteiden, jokien ja kosteikkojen ennallistamiseen.
Kasvillisuuden vaikutus virtausolosuhteisiin on merkittävä.
Ennallistamisen kannalta parempaa tietoa taipuvan kasvillisuuden vaikutuksista virtausoloihin tarvitaan.
Työssä tutkittiin virtaavissa vesissä muodostuvaa vertikaalista nopeusprofiilia ja hydraulisen karkeuden määrittämistä sen perusteella.
Tutkimus koostuu kirjallisuustutkimuksesta ja laboratoriokourukokeista, joissa hyödyntäen 3-ulotteista akustista doppler-tekniikkaa kerättiin virtausnopeusaineistoa erilaisissa virtaustilanteissa.
Mittauksissa keskityttiin ainoastaan pohjamateriaalin yläpuolella olevaan nopeusjakaumaan.
Tarkoituksena oli tutkia karkeuskorkeuden ja nopeusprofiilin yhteyttä.
Mittausten jälkeen verifioitiin kirjallisuudesta valittuja menetelmiä omalla datalla ja tutkittiin saatujen tuloksien soveltuvuutta niihin.
Tutkimuksessa vertailtiin myös sorapohjan ja taipuneen ruohovartisen kasvillisuuden aiheuttamaa virtausvastusta, sekä absoluuttista ja laskennallista karkeuskorkeutta.
Karkeuskorkeus saatiin hyvin määritettyä nopeusprofiilien avulla.
Varsinkin ruohovartisen kasvillisuuden peittämässä uomassa saadut tulokset vastasivat hyvin laskettuja arvoja.
Molemmille pohjamateriaaleille määritettiin myös logaritmisen nopeusprofiilin rajat ja ne vastasivat melko hyvin teoreettisia arvoja.
Nopeusprofiilit ruohovartiselle kasvillisuudelle olivat kohtuullisesti sovellettavissa valittuihin teorioihin
Ilmastonvaihteluiden ja -muutoksen vaikutukset maailman viljelykasvien tuotantoon
No full textDefence is held on 25.2.2022 12:00 – 15:00
Zoom; https://aalto.zoom.us/s/66893209461For millennia, humans have grown their food in relatively stable Holocene climatic conditions, which are now perturbed by anthropogenic climate change. Weather is an inseparable part of food production, and floods, droughts, and heatwaves remain a nuisance to farmers around the globe. Approximately, a third of global crop yield variability is caused by climate variations with even higher sensitivities reported for maize and wheat, both highly important global food commodities. Hence, a comprehensive understanding about the impacts of climate variability and change on global crop production is imperative to ensure a sufficient and stable food supply for the growing global population.
Although the threats posed by climate change are widely acknowledged and researched, the extent of global food crop production at risk of experiencing novel climatic conditions due to climate change has not yet been quantified. Climate change is also projected to increase the frequency of extreme weather events. However, it remains unclear how these changes will relate to agriculture. For example, it is not fully understood how co-occurring extremes impact crop yields, and whether there have been any historical changes in their probability. Interannual variations in climatic conditions are also partially driven by climate oscillations. Predictions about their status could potentially provide useful information for preparing against adverse weather. However, this would require more detailed understanding about their relationship with crop productivity.
This dissertation reveals that climate change might push up to a third of global food crop production to unprecedented climatic conditions if nations continue to increase their greenhouse gas emissions. Further, it finds that weather extremes often reduce crop productivity, with co-occurring heat and drought leading to the largest impacts. Alarmingly, the probability of hot and dry weather has increased in recent decades, especially during the wheat growing season for example in Europe and North America. Finally, this dissertation finds that large-scale climate cycles, such as the El Niño Southern-Oscillation, influence agriculture across all continents that produce crops, with strong impacts observed, for example, in many parts of Australia, Africa, and South America.
Climate change has already affected global crop production; future solutions should therefore concentrate on increasing the resilience of farming systems to anomalous weather, in addition to mitigation actions. Development of early warning systems, and agricultural monitoring as well as improving water and soil management with, for example, irrigation and conservation agriculture could provide viable options to manage these increased climatic risks.Vuosituhansien saatossa ihmiskunta on sopeutunut kasvattamaan ruokansa suotuisassa holoseenikauden ilmastossa. Nyt ihmistoiminnan aiheuttama ilmastonmuutos uhkaa muokata ilmastoa niin, että maatalouden sopeutuminen ei pysy perässä. Sää on erottamaton osa ruoantuotantoa: tulvat, kuivuudet ja lämpöaallot ovat piinanneet maanviljelijöitä kautta historian, ja noin kolmasosa maailman viljelykasvien satoisuuden vaihteluista johtuu kasvukauden säästä. Jotta voisimme taata riittävästi ravintoa kasvavalle ihmiskunnalle, on välttämätöntä, että meillä on globaali ymmärrys ilmastonvaihtelun ja -muutoksen vaikutuksista maatalouteen.
Vaikka ilmastonmuutoksen uhat on tunnustettu ja niitä on tutkittu laajalti, on yhä epäselvää, missä määrin ilmastonmuutos uhkaa siirtää ruoantuotantoa ilmasto-olosuhteisiin, joissa ei tällä hetkellä tuoteta ruokaa lainkaan. Ilmastonmuutoksen on myös arvioitu lisäävän ilmaston ääri-ilmiöitä, mutta niiden vaikutuksia ruoantuotantoon ei vielä tunneta hyvin. Esimerkiksi arviot samanaikaisten ääri-ilmiöiden vaikutuksista ruokakasvien satoisuuteen ovat yhä epävarmoja, minkä lisäksi on epäselvää, onko niiden esiintyvyydessä tapahtunut muutoksia. Myös laajat ilmastosyklit vaikuttavat ilmaston ääri-ilmiöiden esiintymiseen ympäri maailman. Ymmärrys niiden yhteyksistä satoisuuteen voisi auttaa varautumaan ilmastonvaihteluista aiheutuviin haittoihin maataloudessa.
Tämä väitöskirja arvioi, että ilmastonmuutos siirtää kolmanneksen maailman viljelykasvien tuotannosta ilmastollisesti ennennäkemättömiin olosuhteisiin, mikäli kasvihuonepäästöt jatkavat kasvuaan. Tämän lisäksi väitöskirja havaitsi, että ilmaston ääri-ilmiöt laskevat satoisuutta yleisesti, samanaikaisten helleaaltojen ja kuivuuksien aiheuttaessa suurimmat satomenetykset. Huolestuttavasti, samanaikaisten helteiden ja kuivuuksien todennäköisyys on kasvanut viimeisten vuosikymmenten aikana erityisesti vehnän kasvukaudella esimerkiksi Euroopassa ja Pohjois-Amerikassa. Lopuksi, tämä väitöskirja havaitsi, että laajat ilmastosyklit, kuten El Niño Southern-Oscillation -ilmiö, vaikuttavat maatalouteen ympäri maailman, erityisesti Australiassa, sekä monissa osissa Afrikkaa ja Etelä-Amerikkaa.
On selvää, että ilmastonmuutos vaikuttaa ruoantuotantoon ympäri maailman; päästövähennysten lisäksi olisikin tärkeää sopeuttaa ruoantuotantoa muuttuviin ilmasto-olosuhteisiin jo nyt. Maatalouden systemaattinen monitorointi ja järjestelmät, jotka mahdollistavat ennenaikaisen varautumisen epäsuotuisiin sääoloihin, sekä esimerkiksi kastelun sekä hiiliviljelyn edistäminen voivat olla vaihtoehtoja kasvattamaan globaalin ruokajärjestelmän resilienssiä lisääntyville ilmastoriskeille
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