Rice availability and stability in Africa under future socio-economic development and climatic change

As Africa is facing multiple challenges related to food security, frameworks integrating production and availability are urgent for policymaking. Attention should be given not only to gradual socio-economic and climatic changes but also to their temporal variability. Here we present an integrated framework that allows one to assess the impacts of socio-economic development, gradual climate change and climate anomalies. We apply this framework to rice production and consumption in Africa whereby we explicitly account for the continent’s dependency on imported rice. We show that socio-economic development dictates rice availability, whereas climate change has only minor effects in the long term and is predicted not to amplify supply shocks. Still, rainfed-dominated or self-producing regions are sensitive to local climatic anomalies, while trade dominates stability in import-dependent regions. Our study suggests that facilitating agricultural development and limiting trade barriers are key in relieving future challenges to rice availability and stability

On the Rice: Climate Change and the (in)stability of rice in Africa

Food stability – or the lack thereof has caused several issues on global food security in the past. Prime examples are the COVID-19 pandemic, the Ukraine-Russian war, and the 2008 African food crisis. Meanwhile, the occurrence of extreme meteorological events has been increasing rapidly (droughts, floods, …), resulting in substantial harvest losses putting food security under pressure with strong indications that these will become even more prevalent under climate change. Yet, the amount of studies assessing food stability or potential climate change effects is scarce – hindering purposeful policymaking. This makes a methodological framework to assess food stability urgent

African food system and biodiversity mainly affected by urbanization via dietary shifts

The rapid urbanization in Africa profoundly affects local food and ecological systems. According to earlier research, urbanization may cause food production and biodiversity losses as agricultural or natural lands are absorbed by expanding cities. Land-use displacement effects may buffer agricultural production losses or may lead to additional biodiversity losses but are often overlooked. Moreover, impacts of dietary changes associated with urbanization are rarely considered. To address this, we combined spatially explicit projections of African urban area expansion with observed rice consumption shifts to inform a partial equilibrium model (the Global Biosphere Management Model). We demonstrate the importance of displacement effects to identify potential food production or biodiversity issues until 2050 and argue for their integration in land-use planning and policymaking across spatial scales. We identify that because of agricultural displacement, the impact of urban area expansion on food production losses is probably limited (<1%)—at the cost of additional losses of natural lands by 2050 (up to 2 Mt). We also show that considering dietary shifts associated with urbanization increases rice consumption, production (+8.0%), trade (up to +2 Mt of required import) and agricultural methane emissions (up to +12 MtCO2-equivalent yr–1), thereby underscoring the need for a systems approach in future sustainability studies

Time-varying drainage basin development and erosion on volcanic edifices

The erosional state of a landscape is often assessed through a series of metrics that quantify the morphology of drainage basins and divides. Such metrics have been well explored in tectonically active environments to evaluate the role of different processes in sculpting topography, yet relatively few works have applied these analyses to radial landforms such as volcanoes. We quantify drainage basin geometries on volcanic edifices of varying ages using common metrics (e.g., Hack's law, drainage density, and number of basins that reach the edifice summit, as well as basin hypsometry integral, length, width, relief, and average topographic slope). Relating these measurements to the log-mean age of activity for each edifice, we find that drainage density, basin hypsometry, basin length, and basin width quantify the degree of erosional maturity for these landforms. We also explore edifice drainage basin growth and competition by conducting a divide mobility analysis on the volcanoes, finding that young volcanoes are characterized by nearly uniform fluvial basins within unstable configurations that are more prone to divide migration. As basins on young volcanoes erode, they become less uniform but adapt to a more stable configuration with less divide migration. Finally, we analyze basin spatial geometries and outlet spacing on edifices, discovering an evolution in radial basin configurations that differ from typical linear mountain ranges. From these, we present a novel conceptual model for edifice degradation that allows new interpretations of composite volcano histories and provides predictive quantities for edifice morphologic evolution.</p

Investigation of freeze linings in copper-containing slag systems: Part II. Mechanism of the deposit stabilization

A major industrial problem in high-temperature liquid reaction systems is the attack of furnace components by chemically aggressive molten reactants. Freeze-lining technologies involving the deliberate formation of controlled frozen deposits are increasingly being applied to extend the range of liquid bath compositions and process temperatures that can be used; this has resulted in significant increases in process performance and productivity. It has been widely assumed that the interface between the stationary frozen layer and the agitated molten bath at steady state consists of the primary phase, which stays in contact with the bulk liquid at the liquidus temperature, T . It has been shown in the current laboratory-based studies through the use of a cold finger technique that, at steady state and in selected ranges of process conditions and bath compositions, the phase assemblage present at the deposit/liquid interface is not that of the primary phase alone. The microstructural observations clearly demonstrate that the temperature of the deposit/liquid bath interface, T , can be lower than the liquidus temperature of the bulk liquid, T . These observations point to a significant change in the mechanism and behavior of the systems. To explain this phenomenon, it is proposed that the steady-state thickness of freeze linings is not the result of equilibrium freezing but rather represents a state of dynamic equilibrium that is critically dependent on the relative rates of crystallization, mass, and heat transfer processes, occurring close to and at the deposit interface. The mechanisms taking place in the boundary liquid layer involve both partial crystallization/remelting and continuous removal of solids. This finding has important implications for the design of the high-temperature industrial reactors and selection of ranges of melt chemistries and conditions that can be used. This finding means that temperatures below the liquidus can be selected for some processes, resulting potentially in significant savings of energy and increases in throughput of pyrometallurgical reactors. The findings are generic and are not limited to the specific chemical systems reported in the article

Freeze-Lining Formation of a Synthetic Lead Slag: Part II. Thermal History

Recently, freeze linings have been selected more frequently to protect pyrometallurgical reactor walls, due to a number of advantages over conventional refractory lining such as a self-regenerating capability and the possibility of operating under high-intensity process conditions. A freeze lining is formed on a cooled reactor wall in a time-dependent temperature gradient. To model freeze-lining behavior, input data on several assumptions, such as the phase formation and the temperature at the bath-freeze-lining interface during freeze-lining formation, are needed. In order to provide experimental data, the freeze-lining formation of a synthetic lead slag system (PbO-FeO-Fe2O3-ZnO-CaO-SiO2) is investigated. A lab-scale freeze lining was produced by submerging an air-cooled probe into a liquid slag bath for 120 minutes. The temperature evolution during freeze-lining formation was estimated using the experimentally determined position and composition of the phases, the phase-temperature relations predicted with the thermodynamic computer package FactSage, and the results of reference experiments. For the studied slag system, it is concluded that heat transfer is much faster than mass transfer and crystallization. As a result, the liquid in front of the freeze lining undercools. The degree of undercooling depends on the solidification rate. It is concluded that the temperature at the bath-freeze-lining interface varies between the glass transition and liquidus temperatures of the slag bath during freeze-lining formation