  Citation: Drobnjakovi´ c, M.; Pani´ c, M.; Stanojevi´ c, G.; Doljak, D.; Kokotovi´ c Kanazir, V. Detection of the Seasonally Activated Rural Areas. Sustainability 2022, 14, 1604. https:// doi.org/10.3390/su14031604 Academic Editors: Piotr Prus, Marko D. Petrovi´ c and Julia A. Syromiatnikova Received: 30 November 2021 Accepted: 6 January 2022 Published: 29 January 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). sustainability Article Detection of the Seasonally Activated Rural Areas Marija Drobnjakovi´ c* , Milena Pani´ c , Gorica Stanojevi´ c , Dejan Doljak and Vlasta Kokotovi´ c Kanazir Geographical Institute “Jovan Cviji´ c” Serbian Academy of Sciences and Arts, Djure Jakši´ ca 9, 11000 Belgrade, Serbia; m.panic@gi.sanu.ac.rs (M.P.); g.stanojevic@gi.sanu.ac.rs (G.S.); d.doljak@gi.sanu.ac.rs (D.D.); v.kokotovic@gi.sanu.ac.rs (V.K.K.) * Correspondence: m.drobnjakovic@gi.sanu.ac.rs Abstract: Rural areas have been usually observed through agriculture; however, today, it is broadened with various activities. In Serbia, it has been characterized by unbalanced development, which has led to a declining vitality and depopulation. The main goal of this research is detection of seasonally activated rural areas in Serbia, expressed through the population fluctuation, temporary settlement, or occasional use of residential and economic facilities, and identification of spatial patterns of seasonal use. This research applied an innovative proxy—nighttime lights (NTL)—as a complementary tool to statistical analyses, which are conducted in the GIS environment. The calculation encompassed two seasonality coefficients: one based on the NTL and the second based on statistical data on tourist turnover. The spatial frame applies settlement level and micro level (pixels), while temporal includes monthly values for the period 2015–2019. The obtained results highlight tourist activity as the main cause of seasonal activation of rural areas. The largest seasonal fluctuations were registered in mountain areas and spa resorts. For mountain areas, the highest seasonality is in the winter months (peak—January/February), and lowest is in the summer season. The seasonal character of spa centers indicates the similar trend, generally less pronounced (peak—January), however, with higher seasonality during the summer. Keywords: rural areas; seasonality coefficient; nighttime lights (NTL); tourism; Serbia 1. Introduction Globalization is changing and permeating spaces. It produces a territorial transfor- mation and the new trends within economic activities [1]. It is a complex connection and interdependence of localities that reflects the compression of time and space, which in the context of rural areas turn them into a field of permanent change shaped by economic cycles, trade fluctuations, technological innovation, migrations, politics, and environ- ment quality [2]. Rural space becomes an arena of actors that cause interdependent and multidimensional structural transformations of various elements—landscape, population, economy, and habits, introducing it to the process of restructuring [3,4]. Rural areas, for a long time, have been understood and observed through agriculture, which emerged as a dominant shaping factor. However, in the postmodern context, agri- culture is gradually being replaced or broadened with different rural activities. It could not be considered as the only factor of rural development, nor could concrete rural devel- opment be achieved only through the “expropriation from agriculture” [5]. Alternatives to agriculture employment can be seen in the activities related to agricultural production (food industry, forest fruits and herbs collection, healthy food production, etc.), developing a range of service industries (tourism, recreation, crafts, trade, culture, art, etc.), and in regard to this, the development of the so-called home business [6]. With the introduction of new contents and services, rural areas are being reshaped, becoming more similar to urban ones. Therefore, the boundary between rural and urban areas is becoming less clear, with a tendency to be completely blurred [7]. A space of continuous transformations is created, which represent transitional forms between these two extreme constructs (suburbs, Sustainability 2022, 14, 1604. https://doi.org/10.3390/su14031604 https://www.mdpi.com/journal/sustainability