The Nexus Land-Use model, approach articulating biophysical potentials and economic dynamics to model competition for land-use

International audienceInteractions between food demand, biomass energy and forest preservation are driving both food prices and land-use changes. This study presents a new model called Nexus Land-Use which describes these interactions through a representation of agricultural intensification. The model combine biophysics and economics to calculate crop yields, food prices, and resulting pasture and cropland areas within 12 inter-connected regions. The representation of cropland production systems relies on a biomass production function derived from the crop yield response function to inputs and a spatially explicit distribution of potential crop yields prescribed from the Lund-Postdam-Jena global vegetation model for managed Land (LPJmL). The economic principles governing decisions about land-use and intensification are adapted from the Ricardian rent theory, assuming cost minimisation. The land-use modelling approach described in this paper makes it possible to explore interactions among different types of demand for biomass, including indirect effects on land-use change resulting from international trade. Yield variations induced by the possible expansion of croplands on less suitable lands are modelled by using regional land area distributions of potential yields, and a boundary between intensive and extensive production. Idealized scenarios exploring the impact of forest preservation policies or rising energy price on agricultural intensification are presented

Impacts of urbanization around Mediterranean cities : changes in ecosystem service supply

Unidad de excelencia María de Maeztu MdM-2015-0552Urbanization is an important driver of changes in land cover in the Mediterranean Basin and it is likely to impact the supply and demand of ecosystem services (ES). The most significant land cover changes occur in the peri-urban zone, but little is known about how these changes affect the ES supply. For eight European and four North African cities, we have quantified changes in peri-urban land cover, for periods of sixteen years (1990-2006) in the Northern African, and twenty-two years (1990-2012) in the European cities, respectively. Using an expert-based method, we derived quantitative estimates of the dynamics in the supply of twenty-seven ES. The nature of land cover changes slightly differed between European and North African Mediterranean cities, but overall it increased in urban areas and decreased in agricultural land. The capacity of the peri-urban areas of Mediterranean cities to supply ES generally reduced over the last 20-30 years. For nine ES the potential supply actually increased for all four North African cities and three out of the eight European cities. Across all cities, the ES timber, wood fuel and religious and spiritual experience increased. Given the expected increase of urban population in the Mediterranean Basin and the current knowledge of ES deficits in urban areas, the overall decrease in ES supply capacity of peri-urban areas is a risk for human well-being in the Mediterranean and poses a serious challenge for the Sustainable Development Goals in the Mediterranean basin

Multiple cropping systems of the world and the potential for increasing cropping intensity

Multiple cropping, defined as harvesting more than once a year, is a widespread land management strategy in tropical and subtropical agriculture. It is a way of intensifying agricultural production and diversifying the crop mix for economic and environmental benefits. Here we present the first global gridded data set of multiple cropping systems and quantify the physical area of more than 200 systems, the global multiple cropping area and the potential for increasing cropping intensity. We use national and sub-national data on monthly crop-specific growing areas around the year 2000 (1998–2002) for 26 crop groups, global cropland extent and crop harvested areas to identify sequential cropping systems of two or three crops with non-overlapping growing seasons. We find multiple cropping systems on 135 million hectares (12% of global cropland) with 85 million hectares in irrigated agriculture. 34%, 13% and 10% of the rice, wheat and maize area, respectively are under multiple cropping, demonstrating the importance of such cropping systems for cereal production. Harvesting currently single cropped areas a second time could increase global harvested areas by 87–395 million hectares, which is about 45% lower than previous estimates. Some scenarios of intensification indicate that it could be enough land to avoid expanding physical cropland into other land uses but attainable intensification will depend on the local context and the crop yields attainable in the second cycle and its related environmental costs. © 2020 The Author(s

Analyzing the causes and spatial pattern of the European 2003 carbon flux anomaly in Europe using seven models

International audienceGlobally, the year 2003 is associated with one of the largest atmospheric CO2 rises on record. In the same year, Europe experienced an anomalously strong flux of CO2 from the land to the atmosphere associated with an exceptionally dry and hot summer in Western and Central Europe. In this study we analyze the magnitude of this carbon flux anomaly and key driving ecosystem processes using simulations of seven terrestrial ecosystem models of different complexity and types (process-oriented and diagnostic). We address the following questions: (1) how large were deviations in the net European carbon flux in 2003 relative to a short-term baseline (1998–2002) and to longer-term variations in annual fluxes (1980 to 2005), (2) which regions exhibited the largest shift in carbon fluxes during the growing season 2003, and (3) which processes controlled the carbon balance anomaly . In Western and Central Europe, the anomaly in net ecosystem productivity (NEP) over growing season 2003 was outside the 1s bound of the carbon flux anomalies for 1980–2005. The estimated growing season anomaly ranged between –29 and –196 Tg C for Western Europe and between 13 and –94 Tg C for Central Europe depending on the model used. All models responded to a dipole pattern of the climate anomaly in 2003. In Western and Central Europe NEP was reduced due to heat and drought. Over Western Russia NEP was decreased in response to lower than normal temperatures and high precipitation. While models agree on changes in simulated NEP and gross primary productivity anomalies in 2003 over Western and Central Europe, models diverge in the estimates of anomalies in ecosystem respiration. Except for two process models which simulate respiration increase, most models simulated a decrease in ecosystem respiration in 2003. The diagnostic models showed a weaker decrease in ecosystem respiration than the process-oriented models. Based on the multi-model simulations we estimated the total carbon flux anomaly over the 2003 growing season in Europe to range between –0.02 and –0.27 Pg C relative to the net flux in 1998–2002

Global change pressures on soils from land use and management

Soils are subject to varying degrees of direct or indirect human disturbance, constituting a major global change driver. Factoring out natural from direct and indirect human influence is not always straightforward, but some human activities have clear impacts. These include land-use change, land management and land degradation (erosion, compaction, sealing and salinization). The intensity of land use also exerts a great impact on soils, and soils are also subject to indirect impacts arising from human activity, such as acid deposition (sulphur and nitrogen) and heavy metal pollution. In this critical review, we report the state-of-the-art understanding of these global change pressures on soils, identify knowledge gaps and research challenges and highlight actions and policies to minimize adverse environmental impacts arising from these global change drivers. Soils are central to considerations of what constitutes sustainable intensification. Therefore, ensuring that vulnerable and high environmental value soils are considered when protecting important habitats and ecosystems, will help to reduce the pressure on land from global change drivers. To ensure that soils are protected as part of wider environmental efforts, a global soil resilience programme should be considered, to monitor, recover or sustain soil fertility and function, and to enhance the ecosystem services provided by soils. Soils cannot, and should not, be considered in isolation of the ecosystems that they underpin and vice versa. The role of soils in supporting ecosystems and natural capital needs greater recognition. The lasting legacy of the International Year of Soils in 2015 should be to put soils at the centre of policy supporting environmental protection and sustainable development

Climatic risks and impacts in South Asia: extremes of water scarcity and excess

This paper reviews the current knowledge of climatic risks and impacts in South Asia associated with anthropogenic warming levels of 1.5°C to 4°C above pre-industrial values in the 21st century. It is based on the World Bank Report “Turn Down the Heat, Climate Extremes, Regional Impacts and the Case for Resilience” (2013). Many of the climate change impacts in the region, which appear quite severe even with relatively modest warming of 1.5–2°C, pose significant hazards to development. For example, increased monsoon variability and loss or glacial meltwater will likely confront populations with ongoing and multiple challenges. The result is a significant risk to stable and reliable water resources for the region, with increases in peak flows potentially causing floods and dry season flow reductions threatening agriculture. Irrespective of the anticipated economic development and growth, climate projections indicate that large parts of South Asia’s growing population and especially the poor are likely to remain highly vulnerable to climate change

Mesure par pénétrométrie de viscosités élevées (104-1011 Pl) à basse température (77-300 K)

On a réalisé un pénétromètre à cylindres destiné à la mesure des viscosités de cisaillement des liquides newtoniens comprises entre 104 et 1011 Pl dans l'intervalle de température 77-300 K. L'évolution temporelle de la profondeur d'enfoncement h(t) mesurée par un capteur électromagnétique de déplacement est enregistrée sur mémoire magnétique et traitée par un calculateur de table. Les variations de h2(t) sont linéaires conformément à la théorie. Les valeurs de la viscosité du phényle salicylate mesurées avec ce dispositif sont en bon accord avec celles de Laughlin et Uhlmann obtenues par flexion d'une éprouvette

7. Modélisation globale

Les différentes composantes du système Terre sont désormais reconnues pour leurs comportements fortement non-linéaires, face aux grands forçages* (économiques, climatiques, sociétaux…) observés pendant les dernières décennies – et l’avenir nous conduira sans aucun doute à des situations totalement nouvelles. La modélisation, comprise comme toute méthode scientifique de représentation mathématique du comportement d’un système, est donc devenue une technique incontournable pour la compréhension..

Combining agricultural crop models and satellite observations: From field to regional scales

International audienc