Research Results (CCW) / Résultats de recherches (CCE)

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    How can a secondary coastal city in Cambodia be better prepared for climate change and natural disaster risks?
    (2018) Yin, Soriya; Ngin, Chanrith; Heng, Naret
    This policy brief discusses the readiness of Khemarak Phumin city in Koh Kong province (Cambodia) to cope with impacts of climate change and natural disasters. It provides policy recommendations derived from study findings. Climate vulnerability is due to the absence of an early warning system, the lack of a responsible specialized agency at the city level, no designated evacuation route or safe areas during emergencies, and no reserve emergency fund. These are critical mechanisms in which to invest. Cambodia is prone to both natural and human-made disasters such as flooding, droughts, storms, fire, riverbank collapses, and pest epidemics.
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    Mudanças climáticas no estuário Amazônico
    (NAEA Editora, 2015) Zeidemann, Vivian; Almeida, Oriana; Rivero, Sergio; Thomas, Shaji
    O efeito da variabilidade e das mudanças climáticas sobre as populações costeiras estuarinas amazônicas é um fato que vem sendo estudado e observado por uma equipe de pesquisadores da Universidade Federal do Pará, no Brasil, da Universidade de Waterloo, no Canadá, e das Universidades de Colúmbia e Indiana, nos EUA. No caso das populações estuarinas amazônicas, tais impactos já foram percebidos pelas comunidades caboclas, que observaram o aumento das temperaturas e das precipitações nos últimos 20 anos. Como consequência, já são percebidos os efeitos do aumento da temperatura na produção de açaí, uma das principais fontes de renda na região. Estas constatações são evidenciadas em um contexto global de amplo consenso que indica que o aquecimento global é um fato indiscutível, em que tampouco se questiona a responsabilidade da humanidade por tais efeitos. Não só a comunidade científica reconhece os impactos do aquecimento global, mas também os governos. Sendo assim, as alterações climáticas são consideradas um dos piores desafios enfrentados pela humanidade.
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    Arrastrando la montaña hacia el mar : hacia dónde van nuestros océanos
    (Agenda del Mar, Colombia, 2017) Restrepo, Juan Dario
    Colombia, país de dos mares, el segundo más biodiverso del planeta y en el top 10 de los más ricos en agua dulce. No obstante, esa riqueza en recursos naturales pareciera escurrirse de las manos debido a las malas prácticas ambientales en todo el territorio, que van desde una preocupante tasa de deforestación en las montañas hasta unos alarmantes niveles de contaminación en los cuerpos de agua, como el río Magdalena y la bahía de Cartagena.
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    Role of social capital in climate adaptation of fish-pond farmers in northern region of Thailand
    (Chiang Mai University, Chiang Mai, Thailand, 2014-10) Kengkaj, Weerakan
    This in-depth study explores (1) the vulnerability of fish farming households to climate-related and socio-economic risks (2) their adaptive capacities in coping with risks, and (3) the role of social capital. It argues that kinship and community are constructed through bridging capital in fish farmer cooperatives and groups. In this way, social capital is mobilized through trust, exchange, regulation and collective action. Large operators can invest in high quality inputs such as fingerlings, feeds and more advanced technologies and are better able to prevent stress to fish and productivity. Smaller operators with less resources must rely on poor quality water in the canals resulting in low fish production.
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    Mobility of fish cage farmers as a response to climate-related and socio-economic risks
    (Chiang Mai University, Chiang Mai, Thailand, 2014-09) Sin-ampol, Phaothai
    Most households in upstream and downstream villages are affected by moderate to high risks, while midstream villages encounter moderate-low risks. Data was collected in the summer period, the first rainy peak, second rainy peak and winter of 2013-2014 from 42 fish cage farming households from four villages in upstream, midstream, and downstream sections. The thesis studies mobility as an adaptation to risk in the Ping River Basin, Thailand. Climate-related risks, especially drought, were affected by irregular low level of water storage and runoff, extreme events in rainfall amount and temperatures from regional to local level, as well as cage location.
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    Impact of land use and vegetation cover on risks of erosion in the Ourika Watershed (Morocco)
    (AJER, 2016) Modeste, Meliho; Abdellatif, Khattabi; Nadia, Mhammdi; Zhang, Hongming
    Results of mapping demonstrated significant erosion in the Ourika watershed. Soil loss below the tolerance level (<7 t/ha/year) represented only 4% of the area. The objective was to map the risks of water erosion using the Revised Universal Soil Loss Equation (RUSLE) and GIS, and highlight the role of land use and vegetation cover in regulation for risks of erosion. Dense forests, moderately dense forests and arboriculture not mixed with cereal growing protected the soil against erosion, improved physical and chemical soil characteristics, facilitated the infiltration of water into the soil, and limited runoff and the risk of erosion.
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    Advancing the application of climate and hydrological information and its translation into policy, Panama City, Panama, 6-9 October 2015 : workshop report
    (2015) Waagsaether, Katinka; Cull, Tracy; Vincent, Katharine
    Targeting country teams of modellers, principal investigators (PIs) and policy-makers from International Development Research Centre (IDRC)-funded Climate Change and Water projects in Latin America, the Caribbean and Asia, the aim of the workshop was to strengthen science-society communication pathways by giving participants the opportunity to reflect on challenges and opportunities of applying climate and hydrological information into policy. The critical role of politicians was highlighted, with policy-makers themselves complaining that politicians do not see the value of the bigger picture, and are less open to alternative management strategies and approaches
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    Flooding in the suburbs of Dakar : impacts on the assets and adaptation strategies of households or communities
    (International Institute for Environment and Development (IIED), 2015) Cissé, Oumar; Sèye, Moustapha
    Since 2005, Senegal has experienced severe and recurrent flooding. In Pikine, the most populous suburb of Dakar, the 2009 floods affected a third of the population. The government mobilized major investment for drainage and water retention infrastructure, as well as for development of resettlement sites for affected households. However, little is known about the responses, expectations and solutions of those affected. To address this gap we examine the experiences of people living in the commune of Yeumbeul Nord in the city of Pikine around the flood events of 2005, 2009 and 2012. In response to flood hazard and its impact, local residents developed a set of actions to preserve their housing, workplace, goods, family health and security, and children’s schooling. Household mobilization was focused on flood water management and physical adaptations, including raising septic tanks and toilets. Affected households preferred the strategy of housing upgrading and neighbourhood improvement over the option of resettlement.
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    Ecohydrology of ecosystem transitions : a meta-analysis
    (John Wiley & Sons, 2014) Viglizzo, Ernesto F.; Nosetto, Marcelo D.; Jobbágy, Esteban G.; Ricard, M. Florencia; Frank, Federico C.
    A vast body of literature demonstrated that anthropogenic disturbances such as overgrazing and fire are key drivers of abrupt transition between vegetation types in ecosystems. In this study, we propose that the hydrological context (described in terms of rainfall, evapotranspiration and water yield) is a first-order, primordial determinant of the propensity of ecosystems to undergo transition. This implies that the anthropogenic disturbance is a second-order determinant that is strongly conditioned by the first one. Through the meta-analysis of existing studies, a collection of 685 geo-referenced study cases was organized to study the hydrological characteristics of three climatic regions and three ecosystems that vary in their relation between woody and grassy plants. Thus, humid, sub-humid and dry climatic regions, respectively, receiving >1000, 500–1000 and <500mmyear 1, were studied, and possible transition mechanisms among grasslands/savannas, shrublands and forests were analysed. The results showed that the ecohydrological context determines the probabilities of ecosystems transitions in different climatic regions and the prevalence of alternative transition mechanisms. We showed that transition of forests into other ecosystems is highly improbable in high-precipitation regions, more probable and likely subject to a bi-stable and reversible regime in sub-humid regions, and highly probable and irreversible in dry regions. Factors such as runoff, deep-water drainage, fire, flammable/ nonflammable biomass and overgrazing were considered as hypothetical transition mechanisms. As a novel finding, we demonstrate that ecohydrology, as a determinant of transition, is a factor that operates at a hierarchical level higher than that of the human-driven disturbance. A synthetic graphical model was proposed to characterize resilience (the capacity of ecosystems to withstand transition) in the three study climatic regions.
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    Charcoal production in the Dry Chaco: Where, how and who?
    (Elsevier, 2015) Vanezza Rueda, Carla; Baldi, Germán; Gasparri, Ignacio; Jobbágy, Esteban G.
    Charcoal production has been widespread in the past and is still common where poor societies and dry forests coexist. For the Dry Chaco in South America, one of the largest remaining dry forests of the world, we describe the geographical distribution, type of production systems, environmental and social context and output of charcoal based on remote sensing (charcoal kiln detection); together with existing environmental (forest cover/biomass), social (population density, poverty), and infrastructure (roads) data. While most of the region has low kiln densities (< 1 kiln every 1000 km2), foci of higher production were found in the north of Santiago del Estero and the west of Chaco provinces (> 1 kiln every 5 km2). Individual or small groups (up to three units) prevail over the regions (58.2% of all kilns sites), frequently associated with a forest land cover. Large groups of kilns (≥ 12 units, 15.5% of all kilns) were associated with land cleared for cultivation. For a subset of kiln sites for which forest biomass data was available, we found that typical kiln sites (1-3 kilns) had half of the average biomass of the region within a radius of 125 m. Although charcoal production in the whole region has been stable for 50 years, a strong redistribution from richer to poorer provinces has taken place. At the county level, kiln density and charcoal production records showed a linear association that suggests an average output of 11 tons of charcoal per year per kiln. Comparing counties with high vs. low charcoal production with similarly high forest cover, the first had higher population density and poverty levels. Today small scale charcoal production by poor rural people represents the only significant use of forests products that provides some market incentive for their preservation. However this situation is associated with marginal social conditions, inefficient production, and forest degradation. Developing charcoal production under environmentally and socially virtuous conditions should be seen as a unique opportunity and an urgent challenge in the face of the fast deforestation of dry forests.
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    Higher water-table levels and flooding risk under grain vs. livestock production systems in the subhumid plains of the Pampas
    (2014) Nosetto, M.D.; Paez, R.A.; Ballesteros, S.I.; Jobbagy, E.G.
    Although the strong influence of vegetation shaping the hydrological cycle is increasingly recognized, the effects of land-use changes in very flat regions (i.e. hyperplains, regional slope < 0.1%) are less understood in spite of their potentially large magnitude. In hyperplains with sub-humid climates, long-lasting flooding episodes associated to water-table raises are a distinctive ecohydrological feature and a critical environmental concern. We evaluated the hydrological impacts caused by the replacement of livestock systems, dominated by perennial alfalfa pastures, by grain production systems, dominated by annual crops, that has been taking place in the Pampas (Argentina). For this purpose, we combined remote sensing estimates of vegetation transpiration and surface water coverage with long-term (1970-2009) hydrological modeling (HYDRUS 1D), and water-table depth and soil moisture measurements. The NDVI derived from MODIS imagery was 15% higher in dairy systems than in grain production ones, suggesting higher transpiration capacity in the former (852 vs. 724 mm y-1). Even higher contrasts were found among individual cover types, with perennial pastures having the highest NDVI and transpiration potential rates (0.66 and 1075 mm y-1), followed by double winter/summer crops (0.55 and 778 mm y-1) and single summer crop (0.45 and 679 mm y-1). Significantly deeper long-term average water-table levels in dairy system compared to single and double cropping (4 m, 2.1 m and 1.5 m, respectively) were suggested by the hydrological modeling and confirmed by field observations at nine paired sites (pasture vs. cropland, p<0.05) and two transects. At two additional paired sites, continuous water-table depth monitoring with pressure transducers, provided insights about the mechanisms behind these contrasts, which included enhanced groundwater recharge in the cropland and direct groundwater discharge by the pasture. Soil profiles, being notably drier under pastures (316 vs. 552 mm stored at 0-3 m depth, p<0.05), prevented the recharge episodes experienced by agricultural plots after an extraordinary rainy period. Our study highlights the key role of land-use on the hydrology of subhumid hyperplains, supporting the linkage of groundwater level raises and flood frequency and severity increases with the expansion of grain production systems in the Pampas. Given the spatial connectivity imposed by the hydrologic system and the strong association observed between the plot water balance and regional flooding, it is highly relevant to improve the quantification of the hydrological responsibility and interdependence of land use decision across plots and farms. This further step should support territorial policies that optimize the hydrological services of the region.
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    What does it take to flood the Pampas? : lessons from a decade of strong hydrological fluctuations
    (2015-01) Kuppel, S.; Houspanoussian, J.; Nosetto, M.D.; Jobbágy, E.G.
    While most landscapes respond to extreme rainfalls with increased liquid water outputs, very flat and poorly drained ones have little capacity to do this and their most common responses include (i) increased water storage leading to rising water tables and floods, (ii) increased evaporative water losses and, at high levels of storage, (iii) increased liquid water losses. The relative importance of these pathways were explored in the extensive plains of the Argentine Pampas, where two significant flood episodes (herein FE1 and FE2) occurred in 2000-2003 and 2012-2013. Focusing on two of the most flood-prone areas (Western and Lower Pampa, 60 000 km2 each), it was found that the surface water cover reached 31 and 19% during FE1 in each subregion, while FE2 covered up to 22 and 10%, respectively. From the spatiotemporal heterogeneity of the flood events, we distinguished 1) slow floods lasting several years when the water table is brought near the surface 16 following sustained precipitation excesses in groundwater-connected systems (Western Pampa), and "fast" floods triggered by surface water accumulation over the course of weeks to months, typical of a poor above-/belowground connectivity (Lower Pampa) or more generally when exceptionally-strong rain-falls overwhelm infiltration. Because of these different hydrological responses, precipitation and evapotranspiration were strongly linked in the Lower Pampa only, while the connection between water fluxes and storage was limited to the Western Pampa. In both regions, evapotranspirative losses (pathway (ii)) were strongly linked to flooded conditions as a regulatory feedback, while liquid water losses (pathway (iii)) remained negligible.
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    Rainwater harvesting in Dry Chaco : regional distribution and local water balance
    (Elsevier, 2015) Magliano, Patricio N.; Murray, Francisco; Baldi, Germán; Aurand, Santiago; Páez, Ricardo A.; Harder, Wilbert; Jobbágy, Esteban G.
    Rainwater harvesting (RWH) has been essential for the establishment of human settlements in many dry regions of the world that lacked suitable surface or groundwater resources. A vast fraction of the South American Dry Chaco ecoregion still relies on RWH to support, not only livestock production, but domestic and industrial uses as well. As a result, water capture and storage infrastructure is widely disseminated throughout the region. In this paper we characterized the most typical RWH systems in two contrastingly developed sub-regions of Dry Chaco, ranging from extensive ranching to intensive beef and dairy production (central Argentina and western Paraguay, respectively). In each sub-region, we quantified RWH systems density, spatial distribution and associations with landscape features; furthermore, we illustrated how the daily dynamic of water stock in a typical RWH system contributes to assess their capture and storage efficiency. We found that randomly distributed low sophisticated RWH systems prevailed in central Argentina, while clustered distributed high sophisticated ones were more common in western Paraguay. RWH systems density was ten times higher in western Paraguay (0.94 vs. 0.098 units/km2), showing an exponential association with land cleared fraction and proximity to villages. The daily dynamic of water stock of the RWH impoundment showed that water harvest events were exponentially associated with precipitation magnitude events (R2 ¼ 0.86), while annual water losses were explained by infiltration and evaporation fluxes (59 vs. 41%, respectively). Across both sub-regions, RWH accounts for less than 1% of the annual precipitation, playing a minor role on the regional water balance; however at a local level, they can affect several hydrological fluxes including the onset of groundwater recharge and the mitigation of extreme runoff events.
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    Imprint of crop choice on global nutrient needs
    (IOP Publishing, 2014) Jobbágy, Esteban G.; Sala, Osvaldo E.
    Future changes in crop composition could contribute to more sustainable food systems, optimizing land and fertilizer use. Changes in crop composition strongly affect how much soil nutrients need to be withdrawn per unit of food output. The paper explores three aspects of major global crops and to what extent crop choice offers the potential to increase food outputs at a faster rate than soil nutrient withdrawals and fertilizer use on the same available land. While soil nutrient needs shift in response to basic biological attributes of crops; fertilizer additions are more dependent on the economic context of crop production.
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    Woody plant-cover dynamics in Argentine Savannas from the 1880s to 2000s : the interplay of encroachment and agriculture conversion at varying scales
    (Springer, 2015) González-Roglich, Mariano; Swenson, Jennifer J.; Villarreal, Diego; Jobbágy, Esteban G.; Jackson, Robert B.
    Woody plant-cover dynamics can alter the provisioning of ecosystem services that humans rely on. However, our understanding of such dynamics today is often limited by the availability of reliable and detailed land-cover information in the past, before the onset of remote sensing technologies. In this study, we carefully extracted information from historical maps of the Caldenal savannas of central Argentina in the 1880s to generate a woody cover map that we compared to a 2000s dataset. Over about the last 120 years, woody cover increased across approximately 12,200 km2 (14.2% of the area). During the same period, about 5,000 km2 of the original woody area was converted to croplands and around 7,000 km2 to pastures, about the same total land area as was affected by encroachment. A smaller area, fine-scale analysis between the 1960s and the 2000s revealed that tree cover increased overall by 27%, shifting from open savannas to a mosaic of dense woodlands along with additional agricultural clearings. Statistical models indicate that woody cover dynamics in this region were affected by a combination of environmental and human factors. Over about the last 120 years, increases in woody plant cover have stored significant amounts of C (95.9 TgC), but not enough to compensate for losses from conversions to croplands and pastures (166.7 TgC), generating a regional net loss of 70.9 TgC. C losses could be even larger in the future if, as predicted, energy crops such as switchgrass, would trigger a new land-cover change phase in this region.
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    Interactive effects of water-table depth, rainfall variation, and sowing date on maize production in the Western Pampas
    (Elsevier, 2014) Florio, E.L.; Mercau, J.L.; Jobbágy, E.G.; Nosetto, M.D.
    tShallow water-tables strongly influence agro-ecosystems and pose difficult management challenges tofarmers trying to minimize their negative effects on crops and maximize their benefits. In this paper, weevaluated how the water-table depth interacts with rainfall and sowing date to shape maize performancein the Western Pampas of Argentina. For this purpose, we analyzed the influence of water-table depthon the yields of 44 maize plots sown in early and late dates along eight growing seasons (2004–2012)that we rated as dry or wet. In addition, we characterized the influence of the water-table depth onintercepted radiation and crop water status by analyzing MODIS and Landsat images, respectively. Thefour conditions we evaluated (early sown-dry growing season, early-wet, late-dry, late-wet) showedsimilar yield response curves to water-table depth, with an optimum depth range (1.5–2.5 m) whereyields were highest and stable (∼11.6 Mg ha−1on average). With water-table above this range, yieldsdeclined in all conditions at similar rates (p > 0.1), as well as the crop water status, as suggested bythe Crop Water Stress Index, evidencing the negative effects of waterlogging. Water-tables deeper thanthe optimum range also caused declines of yield, intercepted radiation and crop water status, beingthese declines remarkably higher in early maize during dry seasons, evidencing a greater reliance of thiscondition on groundwater supply. Yield in areas with deep water-tables (>4 m) was significantly reducedto between a quarter and a half of yields observed in areas with optimum water-tables. Rainfall occurredaround flowering had a strong impact on maize yield in areas with deep water-tables, but not in areaswith optimum depth, where yields showed high temporal stability and independence from rainfall in thatperiod. Our study confirmed the strong influence of water-table on rainfed maize and provides severalguidelines to help farmers to take better decisions oriented to minimize hydrological risks and maximizethe benefits of shallow water-tables.
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    Cultivating the dry forests of South America : diversity of land users and imprints on ecosystem functioning
    (Elsevier, 2014) Baldi, Germán; Houspanossian, Javier; Murray, Francisco; Rosales, Adriel A.; Rueda, Carla V.; Jobbágy, Esteban G.
    In the South American dry forest of the Dry Chaco and Chiquitania, the area under cultivation rose from 10% to 19% over the last 10 years, and little biophysical, economical, or political constrains seem to prevent further expansion. Although typically associated to a homogeneous agribusiness system, agriculture and its expansion in this territory involve a diverse array of land users. Here we (i) identified and mapped the most conspicuous groups of land users based on existing scientific literature and technical reports, and (ii) described their associated landscape pattern and (iii) vegetation functioning based on different remote sensing tools applied to a set of 218 sample points. We recognized 14 groups of land users of local or foreign origin, composed by individuals or corporative organizations, and dedicated either to pasture or crop production, or its combination. These groups displayed a wide variation in the scale of their operations as suggested by a 60-fold difference in paddock sizes. Twelve years of MODISNDVI data showed small and non-significant differences in the magnitude of primary productivity (1.2- fold difference) but strong contrasts in its seasonality and long-term variability, including shifts in the rates of vegetation greening and browning (up to 4-fold differences), growing period length (193 to 278 days y 1), number of cultivation seasons per year (1e1.75), and inter-annual coefficient of variation (up to 0.13). Agriculture under capitalized groups was characterized by very large paddocks, less stable productivity patterns, and more divergent seasonality. Instead, all smallholders showed more stable productivities both seasonally and inter-annually. Deforestation and cultivation in these dry regions does not have a single imprint on landscapes configuration and primary production dynamics, but one that shifts depending on the human and productive context under which they take place.
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    Balancing agricultural and hydrologic risk in farming systems of the Chaco plains
    (Elsevier, 2014) Giménez, Raúl; Mercau, Jorge L.; Houspanossian, Javier; Jobbágy, Esteban G.
    Like in other semiarid areas of the world, farming systems in semiarid Chaco tend to use water-conservative crop systems to minimize production risks associated to water stress. While this strategy aims to stabilize crop yields and farmers income, the underutilization of water resources in wet years may result in heavy deep drainage water losses which could potentially lead to the development of dryland salinity. Conversely, more intensive crop systems that consume water exhaustively present lower drainage rates but are more prone to crop failure. We employed a monthly soil water balance approach to analyze the productive and ecohydrologic effects of five different farming systems across the region (winter, spring, summer, late-summer and a winter-summer double crop system) and to assess the possibility of minimizing emerging trade-offs between them through flexible water-informed cropping sequences. Our results indicate that water stress diminishes as crop systems are delayed towards the rainy season (winter > spring > summer > late-summer), but the productively safer late-summer strategy, is the one with highest drainage rates. In most of the region, the relatively high production risk and insignificant drainage probability generally determine the convenience of conservative late-summer systems. However, in areas (or years) with higher amount and/or seasonality of rainfall, more intensive double-crop systems are necessary to minimize the likely high drainage fluxes. As rainfall is highly variable from one year to the other, the knowledge of soil water content at the onset of the season is useful to predict part of the available water offer and to asses expected production and ecohydrologic risks. In the most drainage-prone areas the implementation of flexible sequences that alternate conservative and intensive crop systems depending on soil water status, significantly reduced mean annual drainage with an acceptable increase in mean water stress index.