**Preface to "Current Issues in Natural Resource and Environmental Economics"**

This Special Issue collects twelve studies that explore current issues concerning the environment and sustainability. The selected papers review and investigate various issues such as the nexus between trade and climate, the spatial interaction between economy and territory, climate justice in an intergenerational sustainability framework, resource rents, human development and economic growth in the case of Sudan as well as the mobility restrictions and e-commerce in the case of Madrid Centre during the COVID-19 lockdown. At the level of firms, there is a study about the development of corporate sustainability assessment methods for oil and gas companies followed by the environmental exigencies and the efficient voter rule.

In a game theory setup, one study presents some results on the control of polluting firms in dynamic Nash and Stackelberg patterns. Two other works refer to spatial patterns and the fiscal impacts of environmental taxation in the EU and the provision of new evidence on cereal supply response in smallholder agriculture in the case of Ethiopia. Finally, we have present two more studies on the economics of waste prevention concerning second-hand products in the case of Germany and economic sustainability among women in South African rural communities in the case of herbal-based cosmeceuticals.

Let us then consider each study in particular. The research of Cisco and Gatto focuses on the interrelations of sustainability and climate justice based on the use of the overlapping generations (OLG) model under an intertemporal framework. The central aim of the study was to identify the necessary conditions for sustainable development under climate justice imperatives between generations. The researchers called for reduced leisure and consumption patterns as a move away from the business-as-usual scenario for reducing emissions and their impact on the environment. Ultimately, enhanced intergenerational sustainability and climate change will flourish.

The research of Balogh and Mizik on the trade-climate nexus elucidates the potential of trade agreements to help countries to achieve their climate goals. The review focused on papers of the period of 2010 to 2020 and specifically on issues of the effectiveness of trade agreements, different national interests, emission leakage, and protectionism. The main conclusion of the paper was that the largest GHG-emitting countries (China, US, EU) are gaining more from trade negotiations than developing countries. In conclusion, the literature review provided a series of policy practices that might reduce emissions and provide incentives for climate mitigation policies.

The study conducted by Mosconi et al. focused on the revision of the Environmental Kuznets Curve (EKC) based on the spatial interaction between economy and territory in order to broaden the choice of efficient management solutions. The EKC identifies the relations between the degradation of nature and the level of income of an economic system, especially in terms of the governmental policies in high-income countries. However, the authors emphasized the potential for improving the role of space in EKC, specifically in terms of the impact of spatial variability on the nexus between income and environment. Briefly, the proposed multi-scale investigation of degradation processes at the local level might incorporate more traditional, cross-country, and cross-region practices. In short, spatial scales are important parameters in ecological economics.

The study of Mohamed shed light on the relationship between natural resource rents, human development, and economic growth in Sudan during 1970–2015. The conducted analysis was achieved by using co-integration and vector error correction modelling (VECM). The first tests confirmed a long-run equilibrium between the studied parameters. Moreover, the second tests showed positive relationships (except one parameter); nevertheless, this pattern changed in the long run. Furthermore, a long-run Granger causality test demonstrated a causal relationship between the study's parameters. In conclusion, the study proposed more governmental support on natural resource rents for a sustainable future in Sudan, via the creation of virtuous economic circles between human development and economic growth.

The study of Villa and Monzon focused on the importance of urban logistics on sustainability ´ imperatives during the era of COVID-19, when phenomena emerged, such as a change in urban mobility and an increase in e-commerce. The case study area was Madrid Central, where the results showed a significant decrease in transportation in comparison to the pre-COVID-19 era. The delivered parcels increased substantially because of Light Commercial Vehicles (LCV) which satisfied package delivery needs. To recapitulate, the period of COVID-19 posed a challenge to urban logistics, in response to which attempts were made to impose new mobility models in large cities with high volumes of e-commerce deliveries. This study by Ponomarenko et al. concerns the decreasing production at oil and gas facilities and necessitates the development of new operating fields. Briefly, there are changes in states' policies because of novel offshore projects of private companies, which paved the way especially for corporate social responsibility (CSR) companies. This was achieved via two sustainable development indicators. The proposed methodology showed that oil and gas companies differ significantly in terms of corporate sustainability, making clear that such indicators provide practical significance to a company's CSR planning.

In the paper of Anderson, the environmental exigencies and the role of the ''efficient voter rule" are displayed. Policymakers have sought mechanisms that coordinate private incentivization and societally urgent conditions, concerning the internalization of individual's behavior impacts. Nevertheless, Anderson concluded that recent remedies to effectively manage such externalities failed to provide satisfactory results. Finally, it is advisable that a simple voting mechanism to achieve socially optimal decisions under uncertainty be imposed.

In this paper, Halkos and Papageorgiou monitored the conflict between the group of polluting firms, and any social planners who aimed to control the emissions generated during the production process. Both require different processes in terms of the control policies' standards (maximization for firms; minimization for social planners). This paper belongs to the special class of differential games, also known as, 'state separatable differential games'. The cornerstone of these games is the coincidence of the Nash equilibrium with the Markovian equilibrium; furthermore, in the case of hierarchical moves, analytical solutions could be obtained easily. Moreover, a sensitivity analysis was developed for the model's crucial variables. Lastly, a comparison between the two types of equilibrium for the game showed the conflict's intensity for cases in which the polluting firms act as the leader in the hierarchical move game.

The study by Paszto et al. observed the possible spatial patterns in environmental and fiscal ´ impacts on public budgets of EU countries for the years 2008 and 2017, via the grouping according to their environmental taxation performance. Based on two cluster analysis (CA) methods, Ward linkage and K-nearest neighbors (spatial) CA, potential geographical links were observed. Consequently, in 2008 the countries were naively grouped into "the West and ''the East", as the West had higher environmental tax revenues in comparison to the east. However, in 2017 these borderlines were blurred because of the high diversification between the countries, in terms of environmental taxation on national budgets.

In the paper of Tenaye the importance of increasing agricultural production in developing countries and specifically in Ethiopia is described. The examined period spanned the years 1994-2009 and the study investigated the dynamic supply responses of major cereal crops to price and nonprice factors. The results showed the influence of both the planted areas and produced yields of major crops by the aforementioned factors, in parallel with farmers' capability of analyzing market signals and responding accurately to alterations in prices of staple crops. The author also concluded that the growth of Ethiopian agriculture could be based partly on the the augmentation of agricultural prices. Briefly, it is advisable that a fine-tuned balance be developed between government intervention and market solutions, which might ultimately improve yield production via reformed agronomic practices.

The specific study concluded that 'reuse' remains a "niche phenomenon" and that consumers seem to waste economic opportunities associated with the buying and selling of second-hand products in Germany. Hence, the research by Wilts et al. sheds light on the incentives and barriers of second-hand product markets and applies a theoretical background of transaction costs to explain the existing consumption patterns. Waste of valuable unused products in households occurs because of barriers in the transition to sustainable consumption. Furthermore, the study exhibited the paradox that consumers buy new products, although they are aware that second-hand products save money and promote climate protection.

The economic potential(s) of the natural herbal-based cosmetic and cosmeceutical enterprise was the focus of the study regarding the improvement of Vhavenda women's welfare. Using a purposive sampling technique with 79 Vhavenda women, a descriptive and an inferential (Tobit regression) statistical analysis was performed, in addition to a budgeting analysis. As a result, the study by Ndhlovu et al. can provide considerable outcomes regarding this marginalized herbal-based cosmetic and cosmeceutical enterprise.

> **George Halkos** *Editor*
