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\"In this history of Cuba, Louis A. Pâerez proposes a new Cuban counterpoint: rice, a staple central to the island's cuisine, and sugar, which dominated an export economy 150 years in the making. Pâerez shows how the logic of the sugar trade resulted in the development of an agriculture for consumers abroad at the expense of consumers at home. In the process, dependency on food imports, a signal feature of the Cuban economy, was set in place\"-- Provided by publisher.

Improving the protection level of river ecological flow (e-flow) can disrupt the balance of interests among various stakeholders in a region, potentially slowing down the protection process. To mitigate these negative impacts, we introduce a conceptual decision-making framework for modeling river e-flow, based on a dynamic equilibrium between the supply and demand of stakeholders. In this model, the willingness to pay for river e-flow protection is defined as the compensation supply from beneficiaries, while agricultural economic losses represent the compensation demand from affected parties. Illustrated with the Linjiacun section of the Baoji segment of the Weihe River (BSWHR), the main conclusions are as follows: (1) A conceptual decision-making framework for modeling the river e-flow is proposed, and deemed reasonable and feasible through rational analysis; (2) The e-flow of rivers in a typical dry year was 6.64 m 3 /s, and it increased with the increasing runoff; (3) The impact of changes in living standards and runoff on the e-flow in rivers was revealed, leading to the proposal of two policies for e-flow management; (4) This paper qualitatively analyzed the contrasts and relationships between the newly proposed model and mainstream methods (detailed in introduction), discussing the advantages, applicability, and prospect of this decision-making model. This model can provide an important theoretical and technical basis for the optimal management of water resources.

A hybrid power system uses many wind turbine generators (WTG) and solar photovoltaics (PV) in isolated small areas. However, the output power of these renewable sources is not constant and can diverge quickly, which has a serious effect on system frequency and the continuity of demand supply. In order to solve this problem, this paper presents a new frequency control scheme for a hybrid power system to ensure supplying a high-quality power in isolated areas. The proposed power system consists of a WTG, PV, aqua-electrolyzer (AE), fuel cell (FC), battery energy storage system (BESS), flywheel (FW) and diesel engine generator (DEG). Furthermore, plug-in hybrid electric vehicles (EVs) are implemented at the customer side. A full-order observer is utilized to estimate the supply error. Then, the estimated supply error is considered in a frequency domain. The high-frequency component is reduced by BESS and FW; while the low-frequency component of supply error is mitigated using FC, EV and DEG. Two PI controllers are implemented in the proposed system to control the system frequency and reduce the supply error. The epsilon multi-objective genetic algorithm ( ε -MOGA) is applied to optimize the controllers’ parameters. The performance of the proposed control scheme is compared with that of recent well-established techniques, such as a PID controller tuned by the quasi-oppositional harmony search algorithm (QOHSA). The effectiveness and robustness of the hybrid power system are investigated under various operating conditions.

A novel polar fuzzy (PF) control approach for a hybrid power system is proposed in this research. The proposed control scheme remedies the issues of system frequency and the continuity of demand supply caused by renewable sources’ uncertainties. The hybrid power system consists of a wind turbine generator (WTG), solar photovoltaics (PV), a solar thermal power generator (STPG), a diesel engine generator (DEG), an aqua-electrolyzer (AE), an ultra-capacitor (UC), a fuel-cell (FC), and a flywheel (FW). Furthermore, due to the high cost of the battery energy storage system (BESS), a new idea of vehicle-to-grid (V2G) control is applied to use the battery of the electric vehicle (EV) as equivalent to large-scale energy storage units instead of small batteries to improve the frequency stability of the system. In addition, EV customers’ convenience is taken into account. A minimal-order observer is used to estimate the supply error. Then, the area control error (ACE) signal is calculated in terms of the estimated supply error and the frequency deviation. ACE is considered in the frequency domain. Two PF approaches are utilized in the intended system. The mission of each controller is to mitigate one frequency component of ACE. The responsibility for ACE compensation is shared among all parts of the system according to their speed of response. The performance of the proposed control scheme is compared to the conventional fuzzy logic control (FLC). The effectiveness and robustness of the proposed control technique are verified by numerical simulations under various scenarios.

The distribution of water resources is usually characterized by spatial heterogeneity, resulting in different water supply and demand pressures within the basin. Therefore, the analysis of water resources supply and demand balance and the mapping of water resources spatial flow can be an effective suggestion for the regional water resources allocation to relieve the regional water pressure. The uneven distribution of water resources in the Dongjiang River Basin is significant, and how to effectively allocate water resources in the Dongjiang River Basin has become a major focus of research. Based on the multi-source data of the Dongjiang River Basin from 2005 to 2020, this paper uses the SWAT model and water demand model to establish the spatial flow model of water resources supply and demand, and uses the subbasin-scale to explore the spatial distribution and flow of water resources supply and demand, obtaining the spatial scope and flow of water resources supply and beneficiary areas in the basin. The results show that (1) the water supply in the Dongjiang River Basin has been decreasing year by year, and the water demand has been increasing from 2005 to 2015, leading to an increase in the imbalance between supply and demand, and there is a significant reduction in industrial water use from 2015 to 2020, resulting in a reduction in the imbalance between water supply and demand; (2) the supply and demand pressure of water resources in the Dongjiang River Basin has obvious spatial heterogeneity, showing that the pressure of water use in the middle and upper reaches is small, while the pressure of water use in the lower reaches is large; (3) under the framework of spatial service flows of water resources supply and demand, this paper obtains three main beneficiary area ranges, which are Dongyuan County of Heyuan City, Yuancheng District of Heyuan City, and the main urban area of Shenzhen Dongguan Huizhou, and specifies the flow of service flows. This study can not only provide reasonable suggestions for water resources allocation in the Dongjiang River Basin but it also provides references for water resources management in other basins.

Ecological infrastructure plays a crucial role in strengthening the relationship between humans and the environment by optimizing ecological space and resource allocation in urban environments. However, there are few studies on the functional assessment and spatial and temporal evolution of ecological infrastructure and its layout optimization. In this study, we developed an ecological infrastructure optimization method based on ecosystem service supply, demand, and flow in Yantai City as the study area; identified the spatial extent of urban ecological infrastructure and its spatial and temporal changes based on the spatial quantification of multiple ecosystem services; assessed whether the existing ecological infrastructure could satisfy the needs of the urban residents by calculating the ecosystem service supply and demand indexes; and used the spatial quantification of ecosystem service flows to optimize the spatial layout of urban ecological infrastructure. This study shows that, from 2010 to 2018, ecological infrastructure in Longkou, Zhaoyuan, and Laiyang decreased, contrasting with the growth in the existing peripheral areas. The study found a clear spatial mismatch between the supply and demand of ecosystem services, especially in the central urban areas, suggesting that the existing infrastructure was unable to satisfy the needs of high-demand areas. This study assessed the peripheral areas of the city using comparative ecological radiation force (CERF), including 314.64 km2 of environmentally beautiful village units as key components of ecological infrastructure in Yantai City. These findings are crucial for sustainable environmental management and urban development strategies.

Understanding the response of the mechanisms driving ecosystem services (ESs) to socioecological factors is imperative for regional sustainable ecosystem management. However, previous studies of the mechanisms driving ESs have focused more on the degree and direction (positive and negative) of effects on ES supply or the supply–demand balance, while their nonlinear response processes have not been fully considered. In this study, a theoretical framework was developed through integrating land use/land cover data and supply and demand matrices with random forest models to assess response processes, including the relative importance and marginal effects, of essential factors that drive ES demand, supply, and supply–demand balance. Using the Yangtze River Economic Belt (YREB) as an example, our results indicated that the ES deficit regions (332 of 1070 counties or 14.45% of the area) of the YREB were located mainly in the three national urban agglomerations. Moreover, this study indicated that natural environmental factors (such as slope and precipitation) significantly influence the supply and supply–demand balance of ESs, while socioeconomic factors (such as cropland ratios and population density) profoundly influence the demand for ESs. However, cropland ratios were the most important drivers of ES supply, demand, and supply–demand balance in the YREB. Moreover, three types of response processes were identified in this study: logarithmic increase, logarithmic decrease, and volatility increase. Specific driving factors (e.g., proportion of cropland area, precipitation, population density, and slope) had significant threshold effects on the supply–demand balance of ESs. The turning points that can be extracted from these response processes should be recommended for ecosystem restoration projects to maintain regional sustainable ecosystem management.

In sub-Saharan Africa, the high demand for wood-based cooking fuels calls for urgent policy action to steer the cooking energy sector towards more sustainability. While the subnational scale is growing in importance for policy planning, current energy assessments still only consider individual entities without taking into account resource flows. Ignoring flows of biomass cooking fuels in supply–demand assessments is a system boundary problem that can lead to misleading policy recommendations. In this paper, we tackle the boundary problem in subnational supply–demand assessments and provide a tool to support knowledge-based decision-making on the management of biomass cooking fuels in sub-Saharan Africa. Using Kitui County as a case study, we developed and tested an approach consisting of a supply model, local demand model, balance model, availability model, and adjusted balance model. The balance model only considers local fuel supplies and demand, whereas the adjusted balance model also considers external demand, which reduces the locally available supply of fuel. The results show that fuel demand and supply are spatially heterogeneous and vary between wood-based and non-woody fuels, and that the transport distance of fuels strongly affects local fuel availability and determines whether the supply–demand balance is positive or negative. We conclude that subnational energy policies should consider geographical distribution of supply and demand, aim to increase the fuel mix, consider external demand in supply–demand assessments, and differentiate between fuels for self-consumption and the market.

Although the theory of ecosystem services (ESs) is important for guiding land-use planning, knowledge of ESs trade-offs and supply–demand mechanisms is still lacking, and the characteristics of the correlation between the size of trade-offs and the balance between supply and demand along the precipitation gradient have not yet been clarified. In order to supplement this area of knowledge of ESs, we selected 30 small watersheds in high-, medium- and low-precipitation areas as study units. A biophysical model and socio-economic data were used to calculate supply and demand for carbon sequestration, soil conservation and water yield. Redundancy analysis and regression analysis were used to study the ESs trade-offs, the supply–demand dynamics, and the characteristics of their correlation. The results were as follows. (1) The supply and balance between supply and demand of the three ESs, the trade-off between carbon sequestration and water yield and the trade-off between soil conservation and water yield trended downwards from the high-precipitation area to the medium-precipitation area to the low-precipitation area. (2) The primary factors influencing balance between supply and demand with regard to carbon sequestration in high-, medium- and low-precipitation areas were population density and soil organic-matter content, and the size of the conditional effects were greater than 53%. The dominant factor affecting the balance between supply and demand with regard to soil conservation in the three precipitation areas was slope gradient, and the conditional effect was greater than 40%. The most significant determinants of balance between supply and demand with regard to water yield in the three precipitation areas were grassland area, forest area and precipitation, and the conditional effects were greater than 22%. (3) The most significant determinants of the trade-off between carbon sequestration and water yield in high-, medium- and low-precipitation areas were forest, soil organic-matter content and population density, and the conditional effects were all greater than 45%; the primary factors affecting the trade-off between soil conservation and water yield in high-, medium- and low-precipitation areas were grassland and slope gradient, and the conditional effects were all greater than 24%. (4) The relationship between the balance between supply and demand and trade-off size often followed a quadratic function; the next-most-common relationship was a monotonous nonlinear response, and a linear response relationship was relatively rare. This study revealed the factors influencing balance between supply and demand and trade-offs with regard to ESs and the characteristics of their correlations in areas with different degrees of precipitation, which provided a new idea for the synchronous regulation of ESs in the context of conflicts and supply–demand imbalance.

Nepal is one of the least developed countries in the world, with more than 80% of the population engaged in agricultural production and more than two-fifths of the population still living below the poverty line. Ensuring food security has always been a key national policy in Nepal. Using a nutrient conversion model and an improved resource carrying capacity model as well as statistical data and household questionnaires, an analysis framework for food supply balance is developed in this study, which quantitatively analyzes the balance of food supply and demand in Nepal from the perspectives of food and calories during the period 2000–2020. Nepal’s agricultural production and consumption have increased significantly, and the diet has been relatively stable over the past two decades. The diet structure is stable and homogeneous, with plant products occupying the absolute position in overall dietary consumption. The supply of food and calories varies widely from region to region. Although the increasing supply level at the national scale can meet the needs of the current population, the food self-sufficiency level cannot meet the needs of the local population development at the county level due to the influence of population, geographical location, and land resources. We found that the agricultural environment in Nepal is fragile. The government can improve agricultural production capacity by adjusting the agricultural structure, improving the efficiency of agricultural resources, improving the cross-regional flow of agricultural products, and improving international food trade channels. The food supply and demand balance framework provided a reference for achieving balance between the supply and demand of food and calories in a resource-carrying land and provides a scientific basis for Nepal to achieve zero hunger under the framework of the Sustainable Development Goals. Furthermore, development of policies in order to increase agricultural productivity will be critical for improving food security in agricultural countries such as Nepal.