The reconstructed record shows that a large cooling event associated with the Younger Dryas lowered estimated mean July temperatures at Lake Prokoško by approximately 2.3°C, a change intermediate between estimates from Alpine lakes and those farther east. The lake, which covers 4.8 hectares at an elevation of 1,670 metres in the Vranica Mountains of the Dinaric Alps, also records a later Middle Holocene interval in which estimated summer temperatures may have exceeded present-day levels. These findings emerge from a paleoclimate reconstruction based on biological, chemical and physical evidence preserved in lake sediments, rather than from direct instrumental measurements.

Lake Prokoško occupies a climatically significant position between Western, Central and Eastern Europe. Over thousands of years, remains from the surrounding landscape and the lake’s own ecosystem accumulated in bottom sediments, providing material for reconstructing regional environmental and climatic history. One study, published in Palaeogeography, Palaeoclimatology, Palaeoecology, focused on rapid changes between approximately 16,000 and 10,000 years ago during the Late Glacial and beginning of the Holocene. A separate study in Quaternary Science Reviews traced conditions through the Holocene to the present, extending the interpretation of the sediment sequence across the full period represented by the two investigations.

Chironomids, a group of aquatic insects also known as non-biting midges, supplied the principal temperature indicator. Their larvae occupy lake sediments and differ in their preferences for water temperature, oxygen levels and nutrient conditions. After moulting, larvae leave chitinous head capsules that sink to the lake bed, where they can be preserved for tens of thousands of years. The researchers identified the species represented in different sediment layers and compared the fossil assemblages with faunal and climate data from hundreds of modern European lakes. This comparison supported estimates of mean July temperature, while the accompanying pollen, sediment, organic-matter and chemical records provided evidence about forests, soil erosion, lake productivity and other environmental changes.

The oldest layers examined reflect cold conditions near the end of the last glacial period. At around 14,600 years ago, reconstructed mean July temperatures around Lake Prokoško were below 8°C. They subsequently rose by approximately 2.6°C within a comparatively short interval, reaching around 10.2°C. The reconstruction associates this warming with increased biological activity in the lake, spreading vegetation and more stable conditions in the catchment. The youngest sediments in the study cover the most recent millennium, where the chironomid community reflected not only temperature changes but also centuries of alpine grazing, greater nutrient input and the later expansion of nutrient-rich conditions.

The early warming ended abruptly when the Younger Dryas began around 12,900 years ago, the last major cooling episode at the close of the last glacial period. Estimated mean July temperatures at Lake Prokoško fell by approximately 2.3°C to about 7.9°C. Cold-water chironomid species became more abundant, while increased erosion transported more clastic material into the lake. Comparisons with reconstructions elsewhere in Europe revealed a marked spatial contrast: summer cooling of 3–4°C has been reconstructed at many Alpine lakes, whereas decreases in the Eastern and Southern Carpathians were generally less than 1°C. The Lake Prokoško estimate falls between those geographic extremes.

The researchers connect this west-to-east gradient, which becomes weaker toward the east, to oceanic and atmospheric changes in the North Atlantic region. For the Carpathian Basin, the contrast illustrates that the same large-scale climatic event can produce different responses in Western, Central and Eastern Europe. Lake Prokoško consequently provides a regional reference point for examining how the magnitude of a shared climate signal varied geographically. The researchers also emphasize that alpine lakes respond sensitively to relatively small temperature changes: variations in ice-cover duration, water stratification, oxygen content and biological activity can accompany those changes, making small mountain lakes useful environmental archives.

Warming resumed at the end of the Younger Dryas. Between approximately 11,800 and 11,400 years ago, reconstructed mean July temperatures increased by around 2.9°C. By about 10,500 years ago, they may have reached approximately 12.6°C. The lake became more productive, its ice-free season lengthened, and closed-canopy forests developed in the catchment, reducing erosion. Temperatures did not remain constant throughout the Holocene. Around 6,800 years ago, reconstructed mean July temperatures may have reached approximately 14°C, meaning that some summers around Lake Prokoško were warmer than those experienced today. The researchers distinguish this Middle Holocene warmth from present-day warming: the earlier conditions were mainly seasonal and driven by gradual changes in Earth’s orbital parameters that increased Northern Hemisphere summer insolation, whereas current warming is global, year-round, more rapid and primarily associated with human-caused greenhouse gas emissions.

A cooling trend began around 6,000 to 5,500 years ago during the Neoglacial transition toward a cooler Late Holocene. Reconstructed mean July temperatures fell from approximately 14°C to around 12.8°C, then to 11.8°C by about 5,670 years ago. Pollen evidence indicates that people were altering the landscape around the lake by the end of the Neolithic, approximately 6,000 years ago. Plants associated with grazing and open habitats became more common, followed later by more intensive forest use and the expansion of open areas. The same sediment archive therefore records both reconstructed climatic variability and the growing influence of human land use, although it does not by itself establish that human activity caused the temperature changes documented in the sequence.

Later Holocene temperatures continued to vary. Around 3,000 years ago, another significant cooling began, with mean summer temperatures falling from approximately 14.7°C to 12°C. Around 2,000 years ago, reconstructed temperatures rose during the Roman Warm Period, reaching approximately 13.3°C. Over the past millennium, centuries of alpine grazing opened the surrounding landscape and increased the nutrient load entering Lake Prokoško. The chironomid community changed significantly around 700 years ago, and species preferring more nutrient-rich waters became increasingly common over the following 500 years. Together, the two studies show that the lake’s fossil and sediment record captures environmental responses shaped by both regional climate change and local human transformation, while also demonstrating that estimates for individual periods remain reconstructions derived from sediment proxies and modern comparative data.

Subject of Research: Paleoclimate reconstruction of summer temperature variability in the Western Balkans

Article Title: Where three climate zones meet

Article References: Where three climate zones meet. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: Lake Prokoško, Western Balkans, summer temperatures, paleoclimate, chironomid fossils, Younger Dryas, Holocene, climate reconstruction, land use, alpine lake, three, climate

The subspecies was described by Joseph Müller in 1903 from Vrbica by Vransko blato, near Vrana Lake in Mediterranean Croatia. Its type material is held in the Civic Museum of Natural History in Trieste, Italy. For the analysis, researchers assembled 82 records collected across the Western Balkans over roughly 130 years: 81 from Croatia and one from Slovenia. The database combined information from scientific publications, 56 entomological-collection records, 10 literature-derived records and four direct field observations. The Global Biodiversity Information Facility contained no records of the subspecies when accessed on 20 January 2025. Records were organized by decade, collection date and biogeographical region, with pre-1975 observations classified as historical and those from 1975 onward classified as recent.

The researchers used a chronogeonemy analysis, which examines the temporal and spatial dimensions of changes in a species’ occupied area, to reconstruct trends in the subspecies’ Croatian distribution. They also compared land cover at Vrbica and nearby Biljane Donje using the Third Military Survey of the Habsburg Empire from 1869 to 1887, CORINE Land Cover data from 1980 and 2018, and chi-squared tests of changes between broad Level 1 and finer Level 3 land-cover categories. A separate gap analysis intersected known Croatian records with national parks, nature parks and Natura 2000 sites under the Habitats and Birds Directives. The combined approaches were intended to assess both historical change and the coverage provided by the current protected-area network.

Only six Mediterranean records were recovered, all from mainland Croatia rather than the Adriatic islands. Three originated in northern Dalmatia near Zadar, including the type locality at Vrbica and Biljane Donje near Vrana Lake; two came from the Istrian Peninsula; and one came from the Draga Valley near Rijeka. The most recent Mediterranean record dates from 1968, while the type locality has produced no record for more than 120 years. The authors interpret this pattern as local extinction rather than simply an absence of observations. Surveys of carabid beetle assemblages in wetland and riparian habitats have repeatedly covered the region, including work around Vrana Lake and on the Istrian Peninsula. At Vrana Lake, more than 85 pitfall traps and hand sampling during the vegetation season failed to detect the subspecies.

Historical maps show that the landscapes supporting the early records no longer resemble the sites where the beetle was found. The nineteenth-century military survey depicts broad marshes around Vrana Lake, including Vransko blato at the type locality. Comparison with CORINE maps showed that the wetland was fully drained and the remaining marshes near the lake were restricted to a narrow strip along its northwestern edge. At Biljane Donje, the former Terljuge wetlands were also drained. Between 1980 and 2018, broad-leaved forest disappeared within the Biljane Donje study area, transitional woodland and shrub declined, and pasture increased. Statistical comparisons identified significant changes in the broad land-cover categories there, with a chi-squared value of 41.45 and p < 0.001, as well as significant changes within the finer categories, all at p < 0.001.

Some of the habitat transformation at Vrana Lake preceded the formal establishment of protected areas. Work on the Prosika Canal lowered the lake’s water level by approximately three metres and allowed water to drain toward the Adriatic Sea. Further canal deepening and a land-reclamation project completed in 1948 subsequently converted most of the surrounding wetland ecosystem to farmland. An ornithological reserve was established at Vrana Lake in 1983, the Vrana Lake Nature Park followed in 1999, and Natura 2000 sites were designated. The authors conclude that these measures came too late to preserve the beetle’s Mediterranean population because the relevant habitat changes had already occurred. The apparent success of protected-area coverage therefore did not correspond to the subspecies’ continued persistence at the type locality.

The Continental region of Croatia presented a different pattern. The subspecies has been recorded there since the late 19th century, with the earliest precisely localized record dating from March 1896 in Osijek. The number of records fell between the two world wars and during the postwar period, then rose sharply from 2000 onward, especially during 2000 to 2010. The authors note that reduced entomological research may partly account for the earlier scarcity of observations, while the more recent increase may also reflect greater sampling effort. Nevertheless, they interpret the pattern alongside the continuing presence of populations as evidence that the large Continental wetlands support the subspecies. Protected areas covered 14 of 16 known Continental localities, or 88%. Across all precisely georeferenced Croatian records considered in the gap analysis, 18 of 22, or 82%, were inside protected areas.

Most recent Continental records come from wetlands along the Sava, Drava and Danube rivers, particularly the Lonjsko polje and Kopački rit nature parks. Both are Ramsar-listed wetlands and among the largest remaining wetland complexes and best-preserved semi-natural habitats in the Danube Basin. The beetle occurs in open wet grasslands, pastures, reedbeds, shrubby vegetation near water and flooded lowland forest. Its ecological requirements are narrow: it is described as stenotopic and highly hygrophilous, and later larval instars and adults hunt underwater. The first larval instar lives on land. Populations include both fully winged and short-winged individuals, and the species is unusual within the genus because it retains the capacity for flight. A single winged specimen recorded on the Mura River in northeastern Slovenia in 2007 was not followed by other finds during intensive monitoring from 2007 to 2024, so the researchers regard it as accidental rather than evidence of an established Slovenian population.

Some habitat within the Continental wetlands is maintained through existing human land use. Livestock grazing and pigs rooting in wet soils create shallow depressions that hold water and form a mosaic of saturated microhabitats. These conditions are associated with the occurrence of the subspecies in Lonjsko polje. The findings do not imply that all human intervention benefits the beetle; rather, they identify grazing and rooting as specific activities that create habitat features used by the insect. The broader wetlands also support other threatened organisms, including the notostracan crustaceans Triops cancriformis and Lepidurus apus and endangered beetles. The authors therefore describe the Golden-dimpled Ground Beetle as a potential flagship and umbrella species for Continental wetland nature parks. Within Croatia, most records occurred below 200 metres, with no records in the Alpine region and none in surveyed peatlands.

The species already has an alarming conservation history elsewhere in Europe. Carabus clatratus is considered highly threatened and has been reported extinct in Switzerland and Italy. In Italy, the spread of the invasive Red Swamp Crayfish, Procambarus clarkii, is associated with predation on adult beetles and contributed to the species’ extinction. The Mediterranean wetlands examined in Croatia have not recorded that crayfish. Based on the beetle’s high reproductive potential and a successful reintroduction in Italy before crayfish invasion, the authors recommend restoring suitable wetland habitat and reintroducing specimens from Continental Croatia, potentially at Vrana Lake, to improve the subspecies’ prospects. More broadly, they call for revised conservation assessments, continued protection of wetlands against drainage, and use of historical distribution analysis alongside modern spatial tools so that protected-area statistics do not conceal extinctions that have already occurred.

Subject of Research: Conservation status and habitat-driven local extinction of the Golden-dimpled Ground Beetle in Croatia and Slovenia

Article Title: Extinction risk alert: evaluating conservation trends for the Golden-dimpled Ground Beetle ( Carabus clatratus auraniensis J. Müller, 1903) in Western Balkans

Article References: Brigić, A., Ružanović, L., Mlinarić, M. K., Vujčić-Karlo, S., Koren, T., Vrezec, A., & Kapla, A. (2025). Extinction risk alert: evaluating conservation trends for the Golden-dimpled Ground Beetle (Carabus clatratus auraniensis J. Müller, 1903) in Western Balkans. Nature Conservation, 59, 257-277. https://doi.org/10.3897/natureconservation.59.161038

Image Credits: AI Generated

DOI: 10.3897/natureconservation.59.161038

Keywords: Golden-dimpled Ground Beetle, Carabus clatratus auraniensis, local extinction, wetland degradation, land-use change, Croatia, Western Balkans, protected areas, chronogeonemy, Vrana Lake, Extinction, risk

Calosoma pentheri is a remarkable creature. It lives above 2,000 meters in mountain pastures with low vegetation, emerging briefly in spring just after snowcaps melt before the habitat becomes too arid. Its wings are significantly reduced, rendering it flightless, which means its populations cannot easily disperse between mountain ranges. This low dispersal capacity, combined with its disjunct geographic distribution across the Western Balkans, makes it an ideal system for studying how past climates shaped genomic structure and population dynamics in rugged mountain landscapes.

The Western Balkans are one of the main centers of endemism in the Palearctic region, shaped by rugged mountains, extensive karst systems, and complex water drainages. During the Miocene, major tectonic and climatic changes in the Eastern and Central Paratethys region drastically reshaped the peninsula, fragmenting populations and triggering geographic and genetic structuring. Unlike northern Palearctic regions covered by large ice sheets, the Western Balkans had smaller, topographically restricted ice caps, allowing regional populations to survive glacial periods rather than face local extinction. This created a dense network of microrefugia that helped maintain genetic diversity over time.

To investigate the evolutionary history of Calosoma pentheri, the research team sampled all major known populations across the Western Balkans, collecting 10 specimens of the northern lineage Calosoma pentheri pentheri and 54 specimens of the southern lineage Calosoma pentheri relictum. Fieldwork took place across Albania and North Macedonia between 2003 and 2022. Historical specimens were borrowed from natural history collections in Geneva, Munich, Basel, and Vienna, demonstrating that museum specimens can provide robust genomic data for phylogeographic analyses.

The team generated a high-quality reference genome from a freshly collected specimen of Calosoma pentheri relictum from Šar Planina in North Macedonia. PacBio HiFi sequencing produced an assembly of 214.8 Mb with 98.6% genome completeness based on the universal single-copy ortholog gene set for Insecta. They then used a hybridization capture approach called hyRAD, which employs RAD probes synthesized from high-quality DNA samples, to generate genomic data from both fresh and historical specimens. After mapping captured reads against an in silico reference catalog built from the reference genome, they recovered 10,794 single nucleotide polymorphisms and 2,278 loci for downstream analyses.

Population genomic analyses revealed clear genetic differentiation between the two lineages. Principal components analysis showed complete separation between Calosoma pentheri pentheri and Calosoma pentheri relictum, while STRUCTURE analyses supported two evolutionarily independent lineages with no signal of recent hybridization between them. Fixation indices indicated strong differentiation between the two lineages (Fst’ = 0.474) and moderate population structure within Calosoma pentheri relictum (Fst’ = 0.176). Within the southern lineage, populations from Bistra, Tetovo, and Ljuboten were distinct from the rest, while Korab and Dešat showed evidence of admixture between clusters.

Phylogenomic analyses recovered both lineages as reciprocally monophyletic with strong branch support across all datasets, whether historical samples were included or not. Divergence time estimation using 300 clock-like loci in BEAST recovered an origin of Calosoma pentheri sensu lato in the Late Miocene, with the two modern lineages splitting approximately 6 million years ago (95% credibility interval: 5.15–7.18 Ma). This indicates that the separation between the two lineages largely predated the onset of Quaternary glaciations around 2.6 million years ago.

The evolutionary scenario proposed by the researchers is shaped by climatic shifts in the Neogene. They hypothesize that the ancestor of both species likely occupied the entire range currently inhabited by both lineages during the Late Miocene, when progressive global cooling around 7 million years ago allowed a wider ancestral distribution across mid-elevation mountain ranges. As global climate warmed progressively between the Late Miocene and the Pliocene Thermal Maximum, these ephemeral refugia became too warm and both lineages dispersed to higher elevations on each side of the ancestral range. These alpine refugia functioned as isolated mountain ranges, or sky islands, with no opportunity for dispersal in flightless species.

During Pleistocene glacial periods, secondary contact between the two species may have occurred in mid-elevation glacial refugia, but this time without gene flow due to complete genetic sorting. The absence of evidence of recent admixture between the two species suggests that gene flow ceased long before the onset of Quaternary glaciations. Within each lineage, however, climatic oscillations during Quaternary ice ages triggered admixture between populations of each massif. In Calosoma pentheri pentheri, one admixture event was inferred between the ancestors of Rosni, Čakor, and Greben localities. In Calosoma pentheri relictum, two admixture events were inferred: one between Ljuboten and Korab, and another between Korab and Dešat.

The researchers conclude that both species should be regarded as bona species, in line with the morphological studies of Jeannel (1940) and Obydov (2002). Since Bruschi (2013) did not formally synonymize the two species, there is no nomenclatural act to be performed, but future work should regard Calosoma pentheri and Calosoma relictum as distinct species. The fine-scale biogeographic processes observed for these beetles likely occur in other endemic lineages of the Western Balkans. Given the pace of global climate change, the same processes of range contraction that drove these evolutionary patterns could now result in the extinction of flora and fauna in sky island archipelagoes. Many of the sampled localities are at or near the altitudinal limits of these mountains, and further range contraction fueled by global warming would lead to the unequivocal extinction of many sky island lineages in the long term.

Subject of Research: Evolutionary biology

Article Title: Climatic swings triggered incipient postglacial speciation of flightless Calosoma beetles in Western Balkan sky islands

Article References: Cardenas, C. R., Gauthier, J., Mottaz, H., Bilat, J., Hristovski, S., & Toussaint, E. F. A. (2026). Climatic swings triggered incipient postglacial speciation of flightless Calosoma beetles in Western Balkan sky islands. Frontiers of Biogeography, 19, Article e181379. https://doi.org/10.21425/fob.19.181379

Image Credits: AI Generated

DOI: 10.21425/fob.19.181379

Keywords: Calosoma, speciation, phylogeography, sky islands, Western Balkans, museomics, climate change, hyRAD, Climatic, swings, triggered, incipient

The research, led by Bojana Petrović of the Vinča Institute of Nuclear Sciences at the University of Belgrade, together with colleagues from Spain’s Institute of Environmental Assessment and Water Research and the Norwegian Institute for Air Research, was conducted at an urban background site called Ada Marina, located on Ada Ciganlija, Belgrade’s largest recreational area along the Sava River. From June 2023 to May 2024, the team collected daily filter samples using three co-located low-volume samplers, yielding 84 representative PM10 samples for analysis. What set this campaign, dubbed WeBaSOOP, apart from earlier work in the region was its unprecedented chemical scope: rather than measuring only elements or ions, the researchers quantified 34 species, including organic and elemental carbon, 27 elements, four major ions, and — for the first time in Serbia and the wider Western Balkans — a suite of specific organic tracer molecules.

These tracers are the forensic key to the study. Levoglucosan, mannosan and galactosan are anhydrosugars released when cellulose burns, making them unambiguous fingerprints of biomass combustion. Sugars and sugar alcohols such as glucose, mannitol and arabitol mark primary biological aerosol particles — fungal spores, pollen, plant fragments and microbial debris. Two-methyltetrols, meanwhile, are oxidation products of isoprene, a volatile organic compound emitted in abundance by vegetation, and serve as markers of biogenic secondary organic aerosol. Feeding this rich chemical inventory into the United States Environmental Protection Agency’s Positive Matrix Factorization model, version 5.0, the team resolved the PM10 mass into seven factors, each with a distinct chemical profile, seasonal rhythm and wind-direction signature.

The dominant factor was biomass burning, contributing 21 percent of PM10 mass annually and a striking 34 percent during the heating season from October to April. Its profile was anchored by 80 percent of total galactosan, 79 percent of mannosan and 76 percent of levoglucosan, alongside roughly half of the potassium and chloride and a third of the organic carbon. Diagnostic ratios — an organic carbon to elemental carbon ratio of 9.4 and an organic carbon to levoglucosan ratio of 8.3 — matched values reported for wood smoke across Europe. The seasonal peak aligns with a well-known reality in Belgrade: an estimated 300,000 households are not connected to the district heating network and rely largely on wood as their heating fuel. During cold spells, temperature inversions trap these emissions in a stable near-surface layer, allowing pollutants to accumulate unchecked.

Intriguingly, the study also caught biomass burning outside the official heating season. On 2 October, before heating officially begins on 15 October and with ambient temperatures around 15 degrees Celsius, concentrations of the anhydrosugar tracers spiked sharply. The ratio of levoglucosan to mannosan, which distinguishes softwood burning (ratios below about 4) from hardwood burning (around 14 to 15), averaged 8.9 for the burning factor overall but reached 18.9 in summer versus 8.0 in winter. Satellite observations confirmed active fires in Vojvodina on that October day, pointing to agricultural waste burning — a phenomenon documented in Serbia every October since 2000 — while summer contributions may also reflect charcoal combustion at the restaurants dotting the Ada Ciganlija lakeside near the monitoring site.

The second-largest source, at 18 percent, was ammonium sulphate, a secondary aerosol formed when sulphur dioxide is oxidised in the atmosphere and neutralised by ammonia. This factor carried 55 percent of total ammonium and 54 percent of sulphate, with the coexistence of ammonium bisulphate and ammonium sulphate indicating only partial neutralisation of sulphuric acid. Its high organic-to-elemental carbon ratio of 9.1 confirmed the aged, regional character of these particles. Wind analyses pointed to influences from the south and southeast, consistent with transport from the coal-fired Nikola Tesla and Kolubara thermal power plants located 25 and 50 kilometres from the city, and the Kostolac plant 60 kilometres to the east. Notably, the 2024 launch of flue gas desulphurisation at Nikola Tesla A may already be reshaping this contribution.

Mineral dust ranked third at 17 percent, characterised by crustal elements — aluminium, titanium, strontium, magnesium and calcium — and showing influence from the southwest. The campaign captured a Saharan dust outbreak on 31 March 2024, confirmed by sodium-to-aluminium and potassium-to-aluminium ratios closely matching literature values for Saharan material, and corroborated by FLEXPART footprint modelling that traced air masses back across the Sahara. But dust was not purely natural: preparatory construction for the future Belgrade metro depot at Makiš, roughly seven kilometres upwind, left its imprint on the factor’s wind polar plots, blending local construction dust with long-range transported soil.

Perhaps the most novel finding concerns the biological fraction. Two factors of biogenic origin — primary biological aerosol particles and biogenic secondary organic aerosol from isoprene — together accounted for 20 percent of PM10 mass, each contributing 10 percent. The primary biological factor, traced by sugars and sugar alcohols, peaked in the warm months and showed influence from the vegetation of Ada Ciganlija and the Košutnjak forest three kilometres away. Using the mannitol-to-arabitol ratio of 1.0, consistent with fungal spore signatures across Europe, the team estimated that 21 to 44 percent of the organic carbon in this factor derives from fungal spores. The isoprene-derived secondary factor, marked by 2-methylerythritol and 2-methylthreitol, appeared exclusively during the growing season and peaked in summer, its co-occurrence with sulphate species suggesting acid-catalysed aqueous-phase formation — a mechanism first proposed in a landmark 2004 Science paper.

The remaining sources were a mixed traffic-and-industry factor at 15 percent, blending exhaust and brake-wear tracers such as iron, antimony, copper and tin with industrial markers including arsenic, cadmium, lead and vanadium, and a smaller 9 percent factor combining aged sea salt transported from the Atlantic with road salting and local combustion emissions. Mass reconstruction independently confirmed the source apportionment: the carbonaceous fraction dominated PM10 composition at 54 percent annually, followed by secondary inorganic aerosol at 19 percent and mineral dust at 13 percent. The average PM10 concentration over the campaign was 23.9 micrograms per cubic metre — compliant with the current EU limit of 40 but exceeding both the 20 microgram limit that the new EU directive will impose from 2030 and the World Health Organization’s 2021 guideline of 15 micrograms. Winter concentrations of 28 micrograms far outstripped summer’s 19, and the daily limit was breached four times, peaking at 92 micrograms on 19 December.

The implications reach well beyond Belgrade. Because roughly a fifth of the particulate mass originates from biogenic sources that no emission control can touch, and mineral dust adds another irreducible background of around 4 micrograms per cubic metre, meeting future air quality standards will demand disproportionately deep cuts in controllable anthropogenic emissions. The study’s authors argue that targeted mitigation of residential wood burning — the largest single controllable source — offers the clearest path forward, while the identification of biogenic factors for the first time in the region provides a scientific basis for the kind of natural-source accounting that emerging legislation may eventually permit. As Europe tightens its air quality rules and the Balkans remain one of the continent’s pollution hotspots, this Belgrade campaign demonstrates how comprehensive chemical forensics can turn a hazy urban sky into a readable ledger of exactly what society burns, builds, drives and grows.

Subject of Research: Source apportionment and chemical characterization of PM10 particulate matter in Belgrade, Serbia

Article Title: Chemical characterization and source apportionment of PM10 in Belgrade, Serbia: influence of local and regional anthropogenic and natural sources

Article References: Petrović, B., Alastuey, A., Yttri, K. E., Pandolfi, M., Jovanović, M., Radović, B., Kovačević, R., Stojanović, D. B., Davidović, M., Platt, S. M., Bartonova, A., & Jovašević-Stojanović, M. (2026). Chemical characterization and source apportionment of PM 10 in Belgrade, Serbia: influence of local and regional anthropogenic and natural sources. Atmospheric Chemistry and Physics, 26(19), 14165-14184. https://doi.org/10.5194/acp-26-14165-2026

Image Credits: AI Generated

DOI: 10.5194/acp-26-14165-2026

Keywords: PM10, air pollution, source apportionment, biomass burning, Belgrade, positive matrix factorization, organic tracers, secondary organic aerosol, mineral dust, biogenic aerosols, heating season, Western Balkans

Methodologically, the study is a qualitative-dominant mixed-methods analysis built on a comparative case study design. The authors combine social constructivism, which treats international organizations as social phenomena that diffuse norms and reshape what states consider legitimate behavior, with institutionalism, which conceptualizes the same organizations as concrete mechanisms for delivering regional security and stability. Their primary evidence consists of official reports and policy documents from the EU and NATO, supplemented by academic literature, think-tank analyses and statistical indicators covering security, investment and democratic performance. Qualitative content analysis and comparative analysis were used to extract themes of stabilization, democratization, military cooperation and economic support, while secondary quantitative indicators tracked trends in citizen safety and wellbeing across the six Western Balkan countries. This dual lens matters, because a purely military reading of Balkan security misses the socio-economic roots of instability, and a purely normative reading misses the hard power that ended the shooting.

The theoretical scaffolding rests on a longer history of international organization. The authors trace the concept back to the Peace of Westphalia in 1648, which established state sovereignty as the organizing principle of international relations, through the structured diplomatic cooperation introduced at the Congress of Vienna in 1815, to the League of Nations, the first universal attempt at collective security after World War I. Although the League failed, it laid the conceptual foundation for the post-1948 explosion of multilateral institutions. The paper notes that international organizations grew from roughly 50 in the interwar period to about 80, and then surged to around 6,000 by 1980 as the Bretton Woods system, built around the US dollar as a reference currency, sought to prevent economic conflicts and maintain monetary stability and free trade. In the authors’ framing, international organization is a process, and international organizations are snapshots of that process at particular stages—a formulation borrowed from the interwar scholar Inis Claude.

Against this backdrop, the Western Balkans present a distinctive threat landscape. The region’s governments classify risks into conventional threats and weapons of mass destruction, transnational and unconventional threats, poor governance, and natural disasters. Nationalist-political, ethnic and religious tensions, together with disputes over indeterminate borders, remain the dangers most capable of destabilizing the region and reigniting armed conflict. Yet the study emphasizes a second, quieter threat: weak institutions, corruption and organized crime, which erode the state’s capacity to protect its own population. When states cannot guarantee basic security, the authors argue, the importance of international security organizations is reaffirmed—the United Nations as the largest multilateral body deploying peacekeeping missions, and NATO as the intergovernmental regional alliance dedicated to peace, security and defense. These dynamics also created urgency for Europe to assume greater responsibility for international peace and to present itself as a global strategic actor.

The empirical core of the paper documents how that responsibility has been exercised on the ground. Following NATO’s 1999 campaign in Kosovo, the UN-mandated security force KFOR was deployed under Security Council Resolution 1244 to provide security and monitor the withdrawal of Serb armed forces, and it continues as a peacekeeping force supporting the Kosovo Security Force. After nearly eight years of UN administration, Kosovo’s unilateral declaration of independence in 2008 created conditions for the EU to launch EULEX in November 2008 through the so-called six-point plan, a mission covering rule of law responsibilities in politics, justice and customs. In Bosnia and Herzegovina, the overall security situation was relatively stable by 2012, but corruption and organized crime persisted as significant challenges; the EU closed its police mission EUPM in June 2012, an operation born of the bloc’s crisis-management ambitions, while continuing to support the rule of law. The European Commission, through its annual country reports, continues to monitor judicial independence, the fight against corruption and organized crime, democratic governance, public administration reform and fundamental rights across the region.

The enlargement framework itself functions as a security instrument, and the study maps each country’s position within it with technical precision. Montenegro began its accession process in December 2011, opened negotiations in 2012, and held its 2016 parliamentary elections under a revised and transparent legal framework characterized by general respect for fundamental freedoms, though progress on media freedom and the economy remains outstanding. Serbia was granted EU candidate status in March 2012 and opened the first negotiating chapters in December 2015, with the pace of talks tied explicitly to rule-of-law progress and the normalization of relations with Kosovo. Albania received candidate status in June 2014 and has advanced on key priorities, including justice reform and the judicial vetting process, but low conviction rates for organized crime offenses such as money laundering and trafficking remain a sticking point. Bosnia and Herzegovina submitted its EU application in February 2016, while Kosovo has taken major steps toward visa liberalization, conditioned on ratifying its border agreement with Montenegro and strengthening the fight against organized crime. Croatia, an EU member since 2013, illustrates the post-accession challenge: the Commission’s reports flag economic performance, public administration, state-owned enterprises and lingering clientelism as areas demanding reform.

On the military dimension, the paper draws on analysis from the Kosovo-based think tank KIPRED to argue that NATO’s arrival fundamentally altered the regional balance. First, the security situation stabilized and armed conflict was discouraged, transforming a region of war-torn societies with hostile neighborly relations into a relatively peaceful one. Second, NATO influenced the transformation of mass territorial-defense armies into smaller professional forces, reducing offensive capabilities against neighbors. Third, NATO enlargement played a crucial role in closing off attempts at violent border change. Fourth, the Partnership for Peace channeled defense cooperation exclusively through Brussels, ending hopes of bilateral or regional counter-balancing alliances. The same analysis, however, flags a genuine concern: Serbia’s defense cooperation with Russia, which includes the Joint Serbo-Russian Center for Response to Emergency Situations—the first such center Russia has opened in Europe since the Cold War—joint military maneuvers, and Serbia’s observer status in the Russian-led Collective Security Treaty Organization’s parliamentary assembly. The study contends that Russia exploits troubled ethnic relations in countries outside the EU and NATO—Bosnia and Herzegovina, Kosovo and North Macedonia—to re-extend its influence, finding fertile ground wherever Brussels shows indecision and US leadership on enlargement wavers.

Threat perceptions within the region itself are strikingly asymmetric, and the authors treat this asymmetry as data. Bosnia and Herzegovina and North Macedonia consider the threat of armed conflict almost non-existent; Albania and Kosovo predict a significant decline; Croatia and Montenegro judge it greatly reduced; Serbia treats it merely as reduced. None of the six completely rules out armed conflict, which could arise mainly from attempts at violent border change, though the possibility of a successful offensive against neighbors is judged small. In military capabilities and defense industry, Serbia and Croatia dominate, while the other states’ forces are marginal: Albania’s military budget stands at roughly 101.75 million euros, Bosnia and Herzegovina’s at around 46 million, and Kosovo’s at 42.03 million with an expected increase. Serbia projects Kosovo as a direct conventional threat and a troubled entity, and the paper suggests Belgrade maintains military planning for unforeseen situations against Pristina. KIPRED’s assessment is sobering: short of a conventional offensive to annex territory north of the Ibar, any Serbian-Kosovar conflict would likely be protracted, with both sides suffering comparable domestic and foreign political injury. The study concludes that the only rational path is normalization of defense relations through confidence-building measures, alongside Kosovo’s membership in the Partnership for Peace, which could eventually allow KFOR’s withdrawal while preserving stability.

The discussion and conclusion sections broaden the lens to non-traditional security. The reduction of large-scale armed conflict confirms the stabilizing impact of NATO’s military presence and broader Euro-Atlantic engagement, supporting the argument that international organizations function as security providers and confidence-building mechanisms in fragile regions. But security has evolved beyond military threats: organized crime, corruption, irregular migration and refugee flows continue to undermine institutional consolidation, and external dangers such as international terrorism and violent extremism—including the threat posed by ISIS—demonstrate the interconnectedness of regional and global security, demanding cooperation in intelligence sharing, border management and social resilience. The authors classify the region’s unfinished transformation into three processes—stabilization and state-building, democratization and institution-building, and Euro-Atlantic integration—and warn that stabilization built from the outside, running in parallel with democratization, risks instability where credible measures overlook conflict leaders. Their verdict is measured: international organizations have been instrumental in stabilizing the Western Balkans, but long-term security depends on addressing internal vulnerabilities alongside external risks through comprehensive, multidimensional engagement—a finding that resonates far beyond the Balkans for every fragile region where peace is being engineered from the outside in.

Subject of Research: The role of international organizations, particularly the EU and NATO, in regional security and stability in the Western Balkans

Article Title: Role of international organizations in the security of the Western Balkans

Article References: Oxha, S., Rushiti, F., & Mirtezani, L. (2026). Role of international organizations in the security of the Western Balkans. Discover Global Society, 4(1), Article 204. https://doi.org/10.1007/s44282-026-00562-9

Image Credits: AI Generated

DOI: 10.1007/s44282-026-00562-9

Keywords: Western Balkans, NATO, European Union, regional security, international organizations, Kosovo, Serbia, EULEX, KFOR, Euro-Atlantic integration, organized crime, Russia