Natural Resource Management in Depopulated Regions of Serbia—Birth of Rural Brownfields or Final Abandonment

Abstract

Numerous research studies have long established the causes and consequences of the depopulation of certain regions in Europe, but it seems that there are no systematic approaches to implementing the policy of managing abandoned areas. Following years of demographic decline in settlements, the 2022 census revealed depopulated clusters in Serbia—regions with 20 or fewer residents or even no inhabitants at all. The areas of depopulated settlements are growing territorially from the south towards the north. This paper adopts a broader interpretation of brownfield land, defining it as any previously used land that is no longer employed for commercial purposes, serving as the theoretical foundation. Although they seem economically hopeless, some depopulated clusters have become the subject of research for the exploitation of mineral resources such as gold, copper, zinc, uranium, lithium and coal. The main problem is that depopulated clusters have acquired an ecological stability that would be disrupted by the opening of mines and massive construction. The changes in land use were analyzed using time series data and a formal database of natural resources from these communities. The primary methodological framework was based on the correlation between population size, utilized areas, and the ecological stability coefficient. This study aimed to explore the relationship between the proportion of arable land within a spatial unit and its depopulation rate while also examining how arable land and mineral resources could influence the potential revitalization of rural wastelands in Serbia’s depopulated areas. The primary findings indicate a significant correlation between population decline and changes in the natural environment of abandoned clusters, as well as the significant potential of clusters as rural brownfields. While it is natural to continue with ecological and green space projects, the current liberal and centralized mining management policy can create major problems for the remaining population.

1. Introduction

Economic development planning at all levels of government in a country also includes the projection of the population that will form the labor force. Increasing problems related to future demographic development are occurring in Europe, which is struggling to retain the population in certain rural and especially mountainous areas. Efforts are now being made to explore spatial management options for isolated communities that have lagged in economic development and experienced depopulation, focusing on territorial policies that promote security and socio-economic stability.

Local and regional decisions have a significant impact on future population trends, particularly through political choices that shape local and regional development. Depopulation occurs as a process, shifting from one local government unit to another, between regions, and even across neighboring countries [1]. Joksimović et al. [2] compared the expansion of depopulated spaces to the gravitational power of black holes around which matter converges. Depopulation occurs hierarchically from the local to the national level; formerly used land remains abandoned, leading to unbalanced regional development of the state.

The starting point for this research was the fact that although individual settlements and parts of local government units are left without inhabitants, the natural resources in them remain. While many studies have investigated the spatial patterns of depopulation, the theoretical causes of depopulation are generally consistent; they are specific to each community, settlement, and household, which necessitates a localized approach to managing future resources [3]. Therefore, every aspect of management in the economy, society, and environment must include forecasting the local population. In the case of depopulated areas, this may mean the closure of schools, clinics, public administrations and other institutions in the future. Rationalization may also include the merging of administrative units such as municipalities. Patterns of depopulation have not changed significantly in the last 150 years. The lack of jobs and the centralization of the economy in large cities, on the one hand, were at the heart of the problem of population decline and rural depopulation, on the other. The alternative to agriculture was limited by low wages associated with declining labor demand [4]. In addition, the traditional village is characterized by more unfavorable non-economic living conditions compared to cities. Causes of depopulation may be consistent, but the specific factors and their impacts can vary by community, necessitating localized resource management approaches [5]. This approach should be encouraged by the state through the active participation of local stakeholders and institutions, ensuring transparency in the decision-making process regarding resource utilization.

Transparent decision-making is especially important in depopulated areas with protected natural resources. Without population, once-used rural resources and areas become the only potential for the future. Constructed or capitalized assets like roads, power lines, bridges, mines, railways, airports, and other buildings deteriorate when left unused and disconnected from the network of active capital resources. When arable land in mountainous regions is abandoned, farming activities often shift to lower elevations. If the forest was covered by natural vegetation before the period of farming, then abandoning the farms can lead to reforestation, which can decrease the diversity and heterogeneity of vegetation and ecosystems [6].

Depopulation and escalating demographic challenges necessitate a shift in public policy. Rural communities often struggle to identify practical and effective solutions to these complex issues. In urban settings, brownfield redevelopment projects benefit from highly skilled expert teams. Conversely, rural local governments heavily rely on external actors and experts, who are scarce in these areas [7]. The revitalization of brownfield sites in rural regions has garnered limited focus despite their significant potential for regional development. These areas encounter unique challenges absent in urban settings, such as insufficient development funding, limited staff awareness and expertise, and unresolved property rights issues. Additionally, lower demand and reduced investor interest in rural locales generally result in decreased property values [8,9,10]. A comprehensive, well-structured, research-informed, and inclusive framework for promoting brownfield regeneration, endorsed by national authorities, is crucial in motivating local stakeholders to intensify their efforts. This perspective is supported by the European Union’s (EU) emphasis on sustainable brownfield redevelopment. The EU has implemented policies and funding mechanisms to assist cities in repurposing abandoned sites, thereby fostering local community revitalization. For instance, the European Regional Development Fund and Cohesion Fund have been instrumental in supporting such initiatives [11,12].

The most common meaning of brownfield site is a property or facility that was previously used but is currently unused, although it may be partially occupied, utilized, or it may also be abandoned or contaminated. Therefore, a brownfield site cannot be utilized immediately and without prior intervention [13]. Neglected and unused brownfield sites, including abandoned agricultural lands and overgrown fields, pose significant challenges and cannot be overlooked. The United States Environmental Protection Agency (EPA) defines brownfields as properties whose expansion, redevelopment, or reuse may be complicated by the presence or potential presence of hazardous substances, pollutants, or contaminants [14].

The European Concerted Action on Brownfield and Economic Regeneration Network [15] categorizes sites according to their attractiveness for private investment using the A-B-C model. The model illustrates the economic status and opportunities for investment in brownfield regeneration.

• -. Category A: Places where the development project is primarily driven by private investment because it is assumed that the value of the land after revitalization will be higher than the cost of redevelopment.

• -. Category B: Emphasizes projects that are on the cusp of profitability and are usually financed through public-private partnerships.

• -. Category C: Includes less economically attractive sites where development projects are publicly funded and have a special legal status.

For all these reasons, it is a major challenge to plan the sustainable regeneration of brownfield sites with low levels of attractiveness for private investment [16]. The location of a brownfield site significantly influences its potential for successful regeneration. Urban brownfields often present more attractive opportunities for redevelopment compared to their rural counterparts. This is due to factors such as proximity to urban centers, well-developed transport infrastructure, and higher economic potential, which collectively offer a quicker return on investment for developers. In contrast, rural brownfields may lack these advantages, making them less appealing for redevelopment initiatives [17].

The first aim of this work was to determine the changes in utilized areas in the last 30 years and the way natural resources are managed in the largest depopulation clusters in Serbia in terms of area. The secondary aim was to determine changes in the ecological stability of used land. The third aim was to determine whether arable land, forestry facilities, extractive industries (deposits, mines), military watchtowers and all segments of the former rural economy in certain depopulated areas in Serbia could be brownfields subject to regeneration. The authors’ first hypothesis was that the decline in the number of inhabitants would have an impact on changes in land use, vegetation cover and built infrastructure. Secondly, it was expected that the abandonment of arable land would increase the area of forests, bushes and shrubs in places with natural vegetation and that most of the land would achieve ecological stability. Third, it was expected that although there are potentials and brownfields, they are mostly type C brownfields, i.e., economically less attractive locations where development projects are only possible with public funding with a special legal status.

2. Literature Review

Land abandonment, a key factor in rural landscape transformations, is evident in many regions. The concept of rural brownfield research is in its infancy and lags behind urban brownfield research. This is especially pronounced in areas with little arable land and other resources. Therefore, three models of the revitalization of abandoned villages predominate in the scientific literature: agricultural redevelopment—stimulation of agriculture, ecological and green spaces projects—leaving the environment to spontaneous, natural development while preserving habitats and establishing protected areas, and renewable energy development—using abandoned areas that have natural potential for the construction of wind farms and solar power plants.

Traditional rural areas in Europe are undergoing gradual transformation, with land, rural settlements, and farms increasingly being abandoned across many regions in Central, Eastern and Southern Europe. As these areas become deserted, the agricultural landscape loses its original rural identity. In some regions of Germany, Poland and Slovakia, land abandonment and the sale of land to large landowners were partly driven by land consolidation, extensive land use, and the loss of characteristic landscape features. The remains of large farm structures from former state farms are still visible in the landscape [18].

In the case of agriculture redevelopment, abandonment of arable land is considered a transition from cultivated croplands to natural vegetation, alternative land uses such as biofuel production or forestry, or developing grasslands for cattle farms. While abandonment can have both positive and negative effects on biodiversity and societal well-being, it is often viewed negatively, especially from an agriculture-centric perspective where recultivation is preferred. For instance, the Mediterranean landscape has undergone rapid changes in recent decades, with traditional features such as farming terraces, olive groves, and upland grasslands diminishing over the past 50 years. Population decline has led to shifts in land use, the abandonment of marginal lands, and the natural expansion of shrubs and tree species [19]. However, as seen in European landscapes like Sweden, where cultivated lands have steadily declined, alternatives such as organic beef production or forest plantations could provide viable solutions for repurposing abandoned land, highlighting a gap for further research [20]. A study by Pywell et al. [21] explored the possibilities of diversification of plant communities on former arable land. Results indicate that the most effective way to restore diverse plant communities on former arable land was deep cultivation followed by applying a diverse seed mixture with ecologically suitable species. Seed limitation was the primary challenge in establishing these communities, while high soil fertility had a smaller impact, and sowing a nurse crop did not significantly improve species establishment, with these findings being consistent across different sites.

In the Czech Republic, numerous rural brownfields have been extensively studied, particularly those originating from large-scale agricultural cooperatives established during the collectivist era. Following the transition to a capitalist system, many of these lands became obsolete, prompting initiatives for their revitalization. Notably, abandoned agricultural complexes constitute a significant portion of brownfields in the country [22]. However, the regenerated rural units were not depopulated. In a case study in the Nitra region, Slovakia, the anthropogenic impact on land was quantified in several distinct clusters using an ecological stability index. Three types of clusters were identified: with negative, neutral and positive ecological characteristics in three time periods (past, present and possible future). It was found that properly managed land consolidation projects can improve ecological stability in more than a third of the studied territory [23].

Rural abandonment presents an opportunity to redefine rural development by embracing the resurgence of nature and wildlife. In the study of Recio et al. [24], findings present essential insights for management decision-making to minimize conflicts in various local contexts, especially during the early stages of wild animal recolonization. These ideas support the creation of effective initiatives that balance long-term species conservation with reduced human-wildlife conflicts.

In China, as green space models, ecovillages have emerged as a key strategy for revitalizing depopulated rural areas through sustainable initiatives. These communities prioritize environmental sustainability by rehabilitating local ecosystems, which includes the development and preservation of green spaces. By focusing on reducing carbon emissions and enhancing biodiversity, ecovillages play a significant role in advancing the ecological restoration of rural regions. A detailed review of the Chinese government’s involvement and sustainability evaluation highlights the effectiveness of these efforts [25].

Due to the achievement of decarbonization goals, projects for energy transition using abandoned agricultural land are being developed. In the study of Ronchetti and Aiello [26], the potential of photovoltaic installations was investigated in abandoned agricultural land of the Toscana region, Italy. Using the methodology based on land cover change analysis, they found that 1.5% of the mentioned region is abandoned agricultural land, and that would be sufficient for installing a photovoltaic capacity that meets regional energy goals of decarbonization. Similarly, in South Korea, the potential for revitalizing abandoned mines as brownfield sites for solar power plants has been explored. The results have indicated sustainable economic, environmental, and sociological benefits for the local community [27].

The factors contributing to depopulation in Serbia, observed in certain regions since the early 20th century, have been thoroughly studied and analyzed. Most of the depopulated settlements are located in the border areas in the south-west and south-east of Serbia, which are generally the least economically developed regions of Serbia [28]. They can be divided into several types: pedological (agrarian overpopulation), geological (depletion of mineral resources and unprofitability of mines), political (wars, border changes, changes in the form of government, nationalization of property, and forced migration), socio-economic (poor living and working conditions in the countryside and the lack of facilities for education, treatment and security) and geographical (earthquakes, floods, erosive processes, climate changes, drying up of springs) [29,30,31,32,33,34,35,36,37,38,39,40,41,42,43].

Unlike certain Central and Eastern European nations, Serbia largely circumvented the collectivization era characterized by the establishment of large collective farms in each village. While Yugoslavia initially pursued collectivization policies between 1946 and 1952, the approach was relatively short-lived and less extensive compared to other Eastern European countries [44]. The trajectory of agricultural development in Serbia has been influenced by various region-specific factors, leading to diverse developmental paths. Currently, Serbia lacks a comprehensive public policy addressing brownfield redevelopment. However, analyses of legal frameworks and successful practices from countries like the Czech Republic and the United Kingdom have led to proposals aimed at establishing such policies [45].

Another external factor has a strong influence on land use in depopulated areas. The energy transition has put agricultural land in the background and led to an increased demand for critical raw materials (CRM) [46], which is why new research is being carried out, and mines are being opened, especially in previously undeveloped or difficult-to-access regions. Apart from the linear approach to exploitation (take-make-dispose), in some countries, there is a depletion of non-renewable deposits and a concentration of raw materials in processing and production countries (such as China) [47]. The challenges of this approach are also evident in the difficult working conditions and the violation of labor rights (exposure to toxic chemicals, underage labor). In countries with long resource extraction traditions but with weak institutions, mining booms generate corruption, rent-seeking, and even violence in small mining communities [48]. Depopulated areas in Serbia exhibit diverse geological compositions, reflecting their unique formations and mineral wealth. Most of the mineral exploration is situated in a few mountain zones: (a) the zone between the Vidojevica and Pasjača mountains, which consists of Proterozoic crystalline rocks, gneisses, and marbles, (b) Stara Planina Mt., lies on a varied substratum of Silurian and Cambrian igneous and ultramafic rocks, Mesozoic limestones, and Paleozoic greenschists, (c) the Svrljig mountains including Cretaceous limestones and Paleogene sandstones, notably lacking significant metal deposits, (d) the Rogozna mountain within the Vardar Zone contains a Paleozoic ophiolite belt in the north and a Neogene dacite-andesite complex, abundant in lead, zinc, copper, gold, and iron. Notably, exploration at the Medenovac site has confirmed the presence of ore containing 0.5 g/t gold, 9 g/t silver, 0.2% copper, and 1.6% zinc [49,50,51,52,53].

In the last ten years, Serbia has seen increased exploration for lithium, cobalt, nickel, copper and platinum, which are on the list of 32 CRMs, but also for some other minerals that are not on this list (gold, silver). This brings mining into conflict with the principles of a healthy environment and raises numerous ethical questions about the necessity of mining, e.g., the pollution of water and water catchment areas, the disposal of spoil heaps and the use of arable land. Investors in exploration work are primarily focusing on depopulated areas because opposition to the opening of mines is less than in densely populated areas, and the problem of population displacement is practically non-existent. The largest number of companies investing in mining exploration come from Canada (Mundoro, Dundee Precious Metals, Golden Age Resources, and Medgold Resources), Australia (Konstantin Resources Pty Ltd., Ibaera Capital, Jadar Lithium, and Raiden Resources) and China (Zijin), and more than 50% of companies exploring mineral resources in Serbia were registered after 2015.

We started with the fact that individual settlements and parts of local communities remain without inhabitants, but the natural resources in them are preserved. Whether and how they continue to be used depends, among other things, on the revitalization policy, which can go in four directions:

• -. Stimulating the primary economic sector;

• -. Leaving the resources to the free market;

• -. Developing all functions other than agriculture; and

• -. Revitalizing the ecosystem (reforestation and protection of natural assets).

3. Materials and Methods

Given that the historical reasons for depopulation, regional development policies and management of underdeveloped areas differ across countries, a universal methodology for identifying the potential of depopulated settlements does not exist. This is largely due to the varying resources available in these areas, as well as the presence of brownfields linked to both agricultural and non-agricultural activities. A major difference with urban brownfields is the absence of a working population, which, on the one hand, puts all farmland, forests and mineral resources in the context of brownfields, but on the other hand, means that revitalization can be carried out by actors from other regions or that the population attracted by economic gain is drawn to repopulate abandoned settlements (recolonization). Therefore, not only one but several methods were chosen to enable a multi-criteria analysis of the space. The first method involved the statistical separation of settlements with 20 or fewer inhabitants, the average age of which was higher than the national average. Then, clusters of at least two such settlements were formed, and basic indicators of terrain morphology and the area of used land were calculated. The second methodology was used to calculate the correlation between the number of inhabitants and the area used in the given clusters. The third method calculated the coefficient of ecological stability and thereby confirmed changes in the ecosystems of depopulation clusters during the period 1990–2018.

The spatial scope of the study is the areas of depopulation clusters in Serbia, which were delineated according to the 2022 census by settlements [2]. A cluster can consist of at least two settlements with 20 or fewer inhabitants whose areas/cadastral municipalities are adjacent to each other. From the total of 47 depopulation clusters, those whose area is larger than the average cluster area (>72 km²) were selected. The clusters are named according to the geographical or administrative units to which they belong (mountains, rivers, municipalities or historical regions). After identifying the clusters, several field surveys were conducted to determine whether the census data corresponded on the ground, i.e., whether the depopulation clusters were almost left without residents and what changes were occurring in them [2,54].

In the Global Mapper v22.1 GIS application, which is based on two open databases, Aster GDEM v3 Worldwide Elevation Data and Copernicus Land Monitoring Service (CLMS) (CLC 1990, 2000, 2012, 2018) with a 100 m grid, basic morphometric features of the terrain as well as characteristics of the land used for the period 1990–2018 were calculated. The open database of the Geological Information System of Serbia (GEOLISS) was used to analyze the geological resources used.

Correl (X, Y) time series correlation method based on the Pearson correlation formula [55],

(1)$\mathrm{Correl}(\mathrm{X},\mathrm{Y})={\displaystyle \frac{\sum (x-\overline{x})(y-\overline{y})}{\sqrt{\sum {\left(x-\overline{x}\right)}^2\sum {(y-\overline{y})}^2}}}$

where $\overline{x}$ and $\overline{y}$, are the sample means in average (array 1) and average (array 2), in the correlation of the time series of the number of inhabitants in the 1991, 2002, 2011 and 2022 censuses (array 1) with the data on the land used (Corine Land Cover) in 1990, 2000, 2012 and 2018 (array 2) was carried out. A correlation of 1.0 indicates a perfect positive correlation, and −1.0 indicates a perfect negative correlation. The aim was to determine the correlation coefficient, i.e., the relationship between the decrease in the number of inhabitants and the decrease or increase in certain areas (Corine Land Cover Classes: 211—Non-irrigated arable land, 242—Complex cultivation patterns, 243—Land principally occupied by agriculture, with significant areas of natural vegetation, 321—Natural grassland, 311- Broad-leaved forest, 312—Coniferous forest, 313—Mixed forest, 324—Transitional woodland and shrub) within depopulation clusters. The closer the coefficient was to +1, the more significant the correlation between the two series. All selected databases have their limitations, but they give an insight into the broader picture of the territorial level of clusters larger than 72 km².

To generalize the changes in the used land, the ecological stability coefficient was used. It is the relationship between types of land that are considered ecologically stable on the one hand (P3—grasslands, meadows, P4—forests, pastures, P5—water areas with hydrophilic habitats) and types of land that are considered ecologically unstable on the other (P0—built-up areas, roads; P1—intensively used arable land; P2—intensively used orchards, vineyards, and meadows). The equation of the coefficient of ecological stability (CES) is:

CES = ((P5 + P4 + P3))/((P2 + P1 + P0))(2)

The variables denote the reduced areas, that is, the coefficients assigned to them according to the degree of ecological stability. CES is <0.4 for landscapes/spaces with very low ecological stability, 0.41–0.80 indicates low ecological stability, 0.81–1.20 indicates ecological stability, and >1.21 indicates high ecological stability [23,55,56,57].

4. Results

The proposed methodology led to several results that quantified the changes in the depopulation clusters and established ecological stability. The selected 13 clusters are located between 43°36′42″ and 42°25′47″ N, comprising 197 settlements with 20 or fewer inhabitants, 13 of which are uninhabited. In total, only 1656 inhabitants lived in the 13 largest depopulation clusters in Serbia in 2022 (Figure 1). For comparison, one of the largest villages in Serbia, Laćarak, has 9858 inhabitants. The average age of the population is 62.5 and ranges from 49.1 in Cluster 13 to 69.5 in Cluster 2. The clusters consist of mountain villages in southern Serbia, which contain abandoned houses, agricultural properties and buildings, roads, water, and electricity networks. The average altitude of the cluster is between 629 and 1307 m (Table 1), which in the past limited the economy to extensive agriculture, forestry, and mining.

Due to the modest agricultural resources, no large settlements other than traditional villages could develop because of agricultural overpopulation. In the period 1991–2022, the number of inhabitants fell from 12,273 to 1656 and the population density from 5.8 to 0.7 inhabitants per km². During the period 1990–2018, in the total area share, CLC classes 242 and 243 (main cultivated areas) were reduced by 4.9%, class 311 (broad-leaved forest) was reduced by 0.5%, class 321 (natural grasslands) increased by 0.8%, and classes 324 and 313 (transitional vegetation and mixed forest) increased by 4.1% (Figure 2). The decline in the area under deciduous forest was not linear. A visible decrease was observed in the period 1990–2002 when deciduous forest was intensively used for firewood during the economic and energy crisis in Serbia. This was followed by mild reforestation, disrupted by illegal logging, in the period 2011–2018. These data depict the general process of the transition from the era in which extensive agriculture was one of the key activities to the present day, in which natural ecosystems are being renewed, and former cultivated areas are being converted into meadows, shrubs, and forests.

In the investigated period, in 9 out of 13 depopulation clusters, a significant correlation between the number of inhabitants and arable land was recorded. In other words, the decrease in the number of inhabitants was accompanied by a decrease in arable land and complex cultivation patterns (CLC classes 242 and 243). In four clusters, a positive correlation was recorded exclusively for forests (CLC classes 311, 312, and 313), which are therefore located on mountains with a modest pool of arable land. In clusters number 4 and 5 (Table 1), there is also a significant correlation with the decline of the area under the meadows, which indicates the growth of thickets and bushes. Cluster 1 is also characterized by an increase in forested areas—reforestation. Besides the constant population decrease in the last 30 years, clusters 7, 9, 10, 11, 12, and 13 are characterized by the decline of areas under forest, especially deciduous, which can be attributed to illegal logging. In total, in the investigated clusters, the forest area was reduced from 1327 km² to 1311 km².

To determine the preservation of naturally occurring ecosystems and sustainable ways of using land and forests and also to confirm changes in the used land, we calculated the coefficient of ecological stability for each of the 13 clusters (Table 1).

In the period 1990–2018, the CES increased from 3.6 to 4.7. After 2018, and based on the used areas, the researched depopulation clusters have the category of high ecological stability (average CES is greater than 1.21). CES ranges from 1.4 (Cluster 5) to 19.8 (Cluster 7). In 10 clusters, there is an increase in ecological stability; in 2 clusters, ecological stability is decreasing (clusters 6 and 12), and in 1 cluster, it is stagnating (Cluster 3). The variability of ecological stability is caused by the increase or decrease of the area under forests, which occurs for several reasons (illegal logging, drought, and fires). These results move the clusters away from the traditional definition of brownfields, i.e., existing environmental problems that require urgent regeneration. Twenty-four years ago, the surface structure of the mentioned areas was slightly different, and the biggest difference in terms of ecological stability occurred in Cluster 2, which includes villages on Stara Planina (Balkan Mt.). That area was the first to experience demographic emptying and degradation of settlements. Long-term ecological stability in most clusters led to the protection of certain natural units within them (Nature parks: ‘Radan’—Cluster 1, ‘Stara Planina’—Cluster 2; Areas of exceptional characteristics: ‘Vlasina’—Cluster 6 and ‘Ozren-Jadovnik’—Cluster 13; Special nature reserve: ‘Jerma’—Cluster 9). In this way, the surfaces used as a resource have a new potential application in tourism.

The third synthetic goal of this work was to determine whether depopulation clusters can be rural brownfields due to new or potential forms of their use through the regeneration of arable land, forestry, mines and tourist resources. Certain depopulation clusters in Serbia are located within geological units that have mineral resources and were exploited in the past. A sudden change in the exploration of mineral resources and the granting of exploration permits was the amendment to the ‘Law on Mining and Geological Exploration’ in 2015, which removed the power to grant exploration permits from local communities (municipalities) and transferred decision-making to the Ministry of Mining and Energy. This centralized the management of mineral resources and put mineral explorers in a favorable position vis-à-vis the population in the resource regions or—in the case of this article—the depopulation clusters. Field research has determined that mineral resource exploration has begun in several clusters.

Cluster 1 is the largest depopulation cluster in Serbia, with a constant decrease in population from 1991 to 2022. The population during that period decreased from 2751 to 372. It is a hilly-mountainous terrain subject to fluvial erosion and excessive denudation. It has deposits of copper, lead and zinc within the metallogenetic unit “Lece-Halkidiki”. Until now, metals and non-metals have not been exploited in the area of this cluster. As of 2024, part of the cluster on Radan Mt. is protected as a Nature Park, which limits any further exploitation of natural resources (Figure 3).

Cluster 2 is an area built of some of the oldest rocks in Serbia. The average slope angle is 18.2°, and the substratum in the valleys is susceptible to fluvial erosion, scouring and dredging. Uranium ore reserves was found in the settlements of Gabrovnica, Aldina reka, Radičevac and Papratna, as well as iron, gold, silver and copper ores near the villages of Repušnica and Aldinac. A uranium mine operated in Gabrovnica from 1963 to 1965, after which the area around the mine was closed to the public. The population decreased from 1187 to 137. The quarries exploit limestone near the village of Gradište, tuffs and marble near Repušnica, and graphite slate near Pričevac. Since the ecological stability of the cluster, these activities have a degrading influence. Within the Stara Planina nature park, in the Aldinac and Repušnica fields, the Ministry of Mining and Energy issued a permit to the company ‘Aldin Do Exploration Ltd.’ for the exploration of gold and copper deposits on an area of 4644 hectares, which contradicts the policy and laws on nature protection (Figure 3).

Cluster 3 has an average slope of 12.8°, dominated by limestone; the terrain is subject to karst processes, the prevalence of which contributes to the diversity of surface and underground forms. The population decreased from 1054 to 162. An important natural resource of Cluster 3 (Visok-Vidlič Mt.) is the lignite deposits near the village of Mazgoš, along the border with Bulgaria, and from 2024, a decision was made to develop a detailed regulation plan and begin exploitation. In the fields of the villages of Brebevnica and Bačevo, investigative works have been carried out since 2022 for the construction of a solar power plant.

On the territory of Clusters 4 and 8, permits were issued for the exploration of copper, gold, limestone, lead and zinc in several locations—settlements: Selište, Braina, Krtok. The area of this and Cluster 9 is a military-politically sensitive territory because it is located in the belt along the administrative border with Kosovo and Metohija (Figure 3). Population in these three clusters decreased from 2764 to 393.

In Cluster 5, within the territory of villages Babin Kal and Bukurovac Dol, as well as along the regional road Bela Palanka-Svrljig, in two larger and several smaller quarries, limestone is exploited. The problems are dust and damage to the road, which caused the locals to protest. This has not been a cause for protest so far, but it could significantly affect the quality of life of the remaining population, given that the average age is 67.5 years. The company ‘Mineral grupa d.o.o.’ received permission to explore gold deposits on the territory of 9200 hectares within the cadastral municipality of Miranovac.

As part of Cluster 6, research is being carried out on the Čemernik and Vardenik mountains in the villages of Bitvrdja, Vučadelce and Topli Do (Cu, Mo). And in this high-mountain cluster, the number of inhabitants has decreased from 568 to 47.

Mining on Rogozna Mt. within Cluster 9 took place intensively in several pits in the period 1957–1968 under the management of the ‘Trepča Mining and Smelting Basin’ (within the part of the mountain belonging to the Autonomous Province of Kosovo and Metohija). The southern part of the depopulation cluster of Rogozna, around the settlements of Pasji potok, Vojkoviće, Rajetice, Zlatare, Smilov Laz, Bare and Lopužne, is now the belt of the so-called The ‘gold rush’ in Serbia, i.e., the intensification of exploration work and the applications of foreign companies for mining concessions (localities Zlatni Kamen, Šanac and Medenovac). The biggest problem is the potential active workforce since the population decreased from 912 to 91.

On the territory of Cluster 10, in which the population decreased from 624 to 79, in the territory of the village of Nevlja, possibilities for copper exploitation are being explored by Kingstown Resources DOO, Belgrade. In Cluster 12, there are deposits of molybdenite, chalcopyrite, pyrite and quartz that have not yet been exploited, but several lead and zinc mines are active in the wider area (Kriva Feja complex).

Interesting brownfield sites are abandoned military outposts along the border of Serbia and Bulgaria. There are several facilities built by the military in strategically excellent locations. They have a complete infrastructure (electricity, a central heating system, macadam roads, a water source, auxiliary facilities, great viewpoints and excellent visibility), and most of the watchtowers are still in excellent condition, having been abandoned in 2006. In the territory of Clusters 3 and 10 alone, 9 out of the 11 military outposts facing Bulgaria have been abandoned. In neighboring countries, the regeneration of such facilities has mainly been directed towards conversion into tourist accommodation facilities (hostels, mountain lodges) or scientific research bases.

5. Discussion

The results indicate important changes in the natural environment that populations are slowly abandoning, as well as resources that remain as potential for the regeneration of settlements or spaces. Established abandoned clusters in Serbia pose a challenge to sustainable resource management, demographic policy, and security at all levels of governance in the country. In addition to development problems and population loss, field research provides a picture of difficult-to-access areas of abandoned villages threatened by fires, floods, erosion and the uncontrolled increase in the number of large game. The modest areas of arable land in all investigated clusters are correlated with the decline in the number of inhabitants and indicate a lack of interest in the regeneration of agricultural production as one of the primary activities in the past. The decrease in arable land led to a further decile in overall land diversity. The reduction of arable areas further reduced the diversity of the total areas. Such a process spreads from one settlement to another, from one to another micro-region, which corresponds to the conclusions from the work of Firmino et al. [1]. Even if there is a potential for agriculture redevelopment proposed in studies by Prischchepov et al. [20] and Pywell [21], realizing this model of revitalization requires a holistic approach that considers regional characteristics, natural and climatic changes, and risks such as erosion, soil degradation, and ecosystem impact. Successful land reclamation depends on infrastructure investments, the adoption of modern agro-technologies, and a commitment to sustainable development principles. In the case of depopulated clusters in Serbia, results clearly indicate a decrease in arable land in depopulated clusters, accompanied by a lack of young farmers. However, due to the large percentage of land covered by forests, sustainable timber exploitation is partly a solution for the remaining population. Unlike abandoned agricultural land in some European countries, according to the study of Jaszczak et al. [18], big properties such as agricultural brownfields in depopulated clusters in Serbia are not interesting to investors who buy land and expand their holdings. The increase in forest cover has opened up some old wildlife habitats, but rewilding projects such as those presented by Recio et al. [24] are not feasible except under strictly controlled conditions within the boundaries of natural resources managed by a state agency. Redefining the lives of the remaining population in harmony with wildlife is not currently feasible due to a lack of conflict management. The use of abandoned land for renewable energy production, especially mini-hydropower plants, has in the past caused conflict between local residents and investors due to its unprofitability and high environmental impact. However, the approach proposed in the works of Ronchetti and Aiello [26] and Choi and Song [27] could perhaps be applied in clusters where there is potential for this while preserving existing ecological stability.

The natural vegetation, consisting of pastures, forests, bushes and thickets, has regenerated in those clusters where it was native even before the cultivation of arable land. The remaining arable land, where abandoned agricultural cooperatives and other facilities remain, where erosion processes and landslides occur, and the associated villages remain a kind of rural brownfield. The changes in the depopulation clusters are not positively influenced by the proximity to high-quality roads, as some of the settlements in clusters 3, 5, 6, 7, 10 and 12 are close to the international E-network. This confirms the authors’ first hypothesis about the correlation between population decline, reduction of arable land and ecosystem regeneration.

As a confirmation of the second goal of this paper, the change in the ecological stability coefficient (CES) was also determined. Based on the results, there are no major environmental problems in the depopulation clusters because the ecological stability coefficient has been increasing in almost all clusters in the last 30 years. Therefore, these areas do not require urgency through brownfield regeneration. The management of individual clusters was partially taken over by the Institute for Nature Conservation of Serbia by establishing nature parks and other protected areas. This should limit activities that degrade the environment. An unexpected discovery in this work is that within the depopulation clusters, in some locations, protected natural assets overlap with areas where state agencies have allowed investors to explore for the purposes of mineral exploitation. This could lead to a potential conflict in the relationship between the local community and mine investors in the future. Similar to the findings in previous studies, mining can easily enter into conflict with the principles of a healthy environment in the broader area [46,47,48]. In the depopulated areas (Clusters 6 and 12) investigated in this paper, high levels of toxic elements near former and current lead, zinc, and copper mines have already been proven, posing an ecological risk to surface and groundwater [59].

According to the definition of the criteria for setting aside brownfields, depopulation areas in Serbia meet several criteria: a) the underutilization of space, b) the space has been abandoned for more than three years, c) the possession of basic traffic and utility infrastructure, and d) construction of buildings. In the researched clusters, brownfield locations—villages, can be considered those in which research or exploitation of mineral resources was carried out before: Gabrovnica, Aldina reka, Radičevac, Papratna (Cluster 2), Mazgoš (Cluster 3), Pasiji Potok, Smilov Laz, Vojković, and Zlatare (Cluster 9). This confirms that the deposits and facilities of the former extractive industry in depopulation clusters can be subject to the regeneration of the waste field. The fact that private investors are interested in research in depopulation clusters refutes the initial hypothesis that potential regenerated brownfields exclusively belong to type C. According to the definition of attractiveness for the revitalization of brownfields [15], out of 13 clusters, 4 are in Category A, 2 are in Category B, five are in Category C, and 2 cannot be classified as brownfields (Table 1). Therefore, even though they are depopulated, the investigated areas are very attractive in terms of exploitation of natural resources.

6. Conclusions

The results of this paper open a new research question: how beneficial or dangerous is the regeneration of mining brownfields for the local communities of the depopulated areas as well as the wider region? Although natural resources are a real factor in the revitalization of depopulated clusters, as well as other rural areas in Serbia, based on current practice, it is unlikely that the population will remain or resettle. The threat to the environment in the future is certainly represented by the planned mines in the areas where ecological stability has been established in this paper. Instead of retaining the remaining population or attracting a new population, mining pits can affect the permanent displacement of the remaining population from the depopulation clusters. Although they could be useful for the regeneration of depopulated areas, mineral resources must not represent a limitation for ecological stability and human life. In reality, mining activity threatens ecological stability. Unless the legal and regulatory framework for depopulation areas in Serbia is reviewed, as already mentioned in the discussion, 4 out of 13 clusters are attractive to investors who will likely exploit precious metals in them without government limitations or support. In two clusters, a public-private partnership is expected due to the large areas that are state-owned, while in the remaining clusters, a struggle between the interests of the local population, potential investors and nature protection agencies is expected. As an extreme to mining and giving space to the liberal market, the future direction of development based on nature protection and ecosystem revitalization is imposed.

The objectives of this study were to find the connection between depopulation and land cover changes, to determine the change in the ecological stability of previously used land, and to determine whether this land with built infrastructure can be a brownfield subject to regeneration. All objectives were achieved and responded to the author’s hypothesis: (a) the decline in the population influenced changes in land use, (b) most of the land achieved ecological stability, (c) depopulation clusters are the subject of interest to investors and some of them go beyond the scope of type C brownfields. The limitations are based on the subjectivity of the choice of criteria for depopulation clusters. Different criteria may be used in some regions to determine the number of inhabitants. In addition to the land use databases used in this work, official databases obtained from the agricultural census should also be used for more precise data. Also, economic criteria for the value of land in depopulation clusters could be added to the methodologies used in order to compare their economic value.

The future directions of resource management in the depopulation clusters of Serbia exclude the stimulation of the primary sector due to the lack of working population and unprofitability in this sector. They nevertheless include the possibility of leaving resources to the free market with the development of a non-agricultural economy within the framework of laws that ensure the revitalization of the ecosystem and provide property and legal security to the remaining population. Vertical coordination in the state-municipality-settlement relationship is necessary, as well as vertical coordination among actors of brownfield regeneration. Local governments should create a cadastre of rural brownfield sites as a basis for the revitalization of certain settlements. On the other hand, the exploitation of mineral resources is not legal in protected natural assets without a prior revision of natural, cultural and landscape values and reduction of boundaries of natural assets. Despite the objective shortcomings, we believe that such research represents the basis for the preparation of planning documents and that they must be a mandatory chapter in spatial development strategies at all levels of administration.

The goals of further research should include other possibilities for the revitalization of depopulated clusters: monitoring demographic indicators of population vitality, restoring habitats and wild animal populations, monitoring unique plants and animals, exploring thermal waters, special natural features, and the possibility for extraterritorial management of abandoned settlements, as well as the potential for using renewable energy sources such as solar and wind energy.

Data Availability Statement

Data from this article can be found as follows: a. Population data: https://data.stat.gov.rs/?caller=3104&languageCode=en-US (accessed on 23 November 2024); b. Corine Land Cover 1990–2018: https://land.copernicus.eu/en/products/corine-land-cover (accessed on 2 December 2024); c. Geological and Mineral resources exploration data: https://geoliss.mre.gov.rs/vebkarte/GeolIEP/Index.html (accessed on 3 December 2024), birn.rs; d. protected natural areas: https://a3.geosrbija.rs/zasticena_podrucja (accessed on 4 December 2024); e. terrain data: Aster GDEM v3 Worldwide elevation data, https://search.earthdata.nasa.gov/search/ (accessed on 1 December 2024).

Conflicts of Interest

The author declares no conflict of interest.

Footnotes

Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Figures and Table

Figure 1. Depopulated settlements and clusters (1–13) in Serbia in 2022. Data source: SORS [58]; Explanation: Table 1.

Figure 2. Land use classes share change.

Figure 3. Depopulation, nature protection and mineral resources exploration overlapping in southern Serbia 2022.

Table 1

Indicators of changes in depopulation clusters in the period 1990–2022.

No.	Cluster Name	Area (km2)	Average Altitude (m)	The Highest Correlation Coefficient of Cluster Inhabitants Change and Used Land Class	Coefficient of Ecological Stability1990/2018	Exploration/Exploitation ofMineral Resources	Potential Brownfield Type
1	Vidojevica-Radan	338	652	0.79—decrease of P1 and P2	2.8/4.0	Yes	A
2	Stara Planina	281	703	0.89—decrease of P1 and P2; −0.94—reforestation	6.6/18.3	Yes	B
3	Visok-Vidlič	213.5	936	0.97—decrease of P1 and P2	1.6/1.6	Yes	B
4	Kuršumlija-North	198.6	775	0.97—natural grasslands decrease; 0.92—decrease of P1 and P2	6.4/7.9	Yes	A
5	Svrljig	160.4	629	0.93 natural grasslands decrease; 0.77—decrease of P1 and P2	1.0/1.4	Yes	A
6	Vlasina	137.8	1307	0.81—decrease of P1 and P2	9.0/5.0	Yes	C
7	Crna Trava	134.9	1115	0.84—decrease of P1 and P2; 0.69—decrease of P4	16.3/19.8	No	does not belong to any type
8	Kuršumlija-South	131.4	731	0.92—decrease of P1 and P2	5.9/9.8	Yes	C
9	Rogozna	125.5	1042	0.98—decrease of P4	4.9/5.9	Yes	A
10	Burel	110.9	763	0.98—decrease of P4 0.91—decrease of P1 and P2	1.9/4.4	Yes	does not belong to any type
11	Babušnica	89.5	836	0.95—decrease of P4	6.2/11.3	No	C
12	Besna Kobila	76.2	1194	0.97—decrease of P4	11.9/10	No	C
13	Sjenica	97.8	1189	0.96—a decrease of P4	2.4/2.8	No	C
	Total/Average:	2095.5	913	-	-	-	-

Source: Corine Land Cover 1990, 2000, 2012, 2018; SORS (2023) [58]; Geoliss (2024) [49]; Explanation: P1—intensively used arable land; P2—intensively used orchards, vineyards, and meadows, P4—forests, pastures.

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