Palynology for Sustainability: A Classical and Versatile Tool for New Challenges—Recent Progress

1. Introduction

Palynology deals with several topics closely linked to sustainability [1] as it has always acted as a bridge between different research fields within environmental sciences [2,3,4]. This centenary discipline, which studies both fossils and modern pollen and spores, represents a landmark in multidisciplinary research on both past and current environmental issues [5,6]. In addition, palaeoenvironmental studies based on pollen analysis from sediments and archaeological layers offer a long-term perspective for understanding ecosystem responses to different human and climate triggers [7,8,9,10]. In this sense, recent palynological research has repeatedly demonstrated that, since prehistory, past cultures have strongly relied on natural resources, with nature and culture being interrelated and interdependent [11,12]. There is (archaeo)botanical evidence showing that cultural choices have been combined/plotted according to social and environmental characteristics to enable human populations to cope with environmental and climatic changes in different regions (e.g., [13,14]). In prehistory, this ensured social resilience by using multi-functional land uses to exploit nature without compromising the environment [15,16,17,18,19], while in historical phases, the pressure of human activities impacted in a clearer manner with the help of rapid advances in techniques in different regions [20,21,22,23,24].

In the field of palaeoecology, pollen, non-pollen palynomorphs, and sedimentary charcoal are excellent bioindicators for detecting human impact and landscape development [25,26,27,28,29,30,31]. This Special Issue brings together several interdisciplinary bio-geo-archaeological investigations on on-site/off-site palynology carried out in Holocene contexts to disseminate the role of pollen as a marker of biodiversity, environmental transformations, and human–plant ecological interactions. Three main themes emerge from the papers: A—long floristic lists that are comprehensive enough to significantly contribute to our understanding of plant biodiversity in archaeological sites; B—improved knowledge of plant biodiversity through studies on detailed pollen morphology; C—examples of research from modern analogues to long core reconstructions. Regarding points A and B, the sites are part of BRAIN, the Botanical Records of Archaeobotany Italian Network, and are therefore also referenced by their ID numbers in the database [32].

2. The Three Main Themes of the Special Issue

2.1. A. Long Floristic Lists from Archaeological Sites

Although palynology has a known key role in the understanding of archaeological environments [33], archaeopalynology has only considerably developed in recent decades thanks to rigorous collaboration with archaeologists, correct sampling strategies, interdisciplinary interpretations, and the refinement of extraction methods from sediments in contexts that do not perfectly preserve pollen and macroremains [34,35,36].

Zappa and colleagues [37] study the Neolithic pile-dwelling archaeological site of Palù di Livenza (NE Italy), which developed over several phases between the 6th and 5th millennia BP. The on-site palynological analysis of the trench PaluON1 clearly shows that the settlement caused local interference with the hygrophilous ecosystem, with people adopting a multiple land-use economy. During the occupation phases, different vegetation cover, the use of woody resources, cereal and flax fields, and animal husbandry or pastoral practices were evident, as well as plant processing within the village. Vegetation responses to environmental changes were forced by both climatic fluctuations and human pressure. The settlement favoured the spread of synanthropic plants and the presence of regional and local fires. Interestingly, after the abandonment due to changing conditions, swamps and hygrophilous woods returned to the site, showing a rapid rewilding to the pristine environment.

Tecchiati and colleagues [38] investigate the Late Neolithic–Bronze Age site of Colombare di Negrar di Valpolicella in the Lessini Mountains (N Italy). Integrated data from pollen and plant macroremains indicate a close relationship between natural resources and the socio-economic development of the territory. The on-site palynological analysis reveals that natural clearings in the wood favoured the establishment of the houses. The proximity to the forest ensured supply for leaf forage, timber, and wild fruits such as hazelnut and walnut. The forest cover was characterised by a mixed oakwood with Ulmus and Tilia species, suggesting cool conditions. In the riparian forests, which thrived on moist soils, hygrophilous trees were present alongside Vitis vinifera. The multiple land-use economy consisted of a sylvo-pastoral and crop farming mixed system, where most of the natural resources were offered by a hilly landscape characterised by great ecological and phytogeographical diversity.

Gattiglia and colleagues [39] report the results of an interdisciplinary study conducted at the Charterhouse of Calci, in central Italy. Pollen was extracted from a unique set of contexts that are particularly challenging for palaeoenvironmental interpretation: the three monks’ gardens—those of the Prior, the Apothecary, and the Master. The palynological records mostly document horticultural and gardening practices across different phases, from the Middle Ages to the recent period. Beautiful flowers and ornamental plants and aromatic and medicinal herbs grew in the gardens (see also [40]). To complete the environmental reconstruction, green spaces outside the cloister walls, consisting of courtyards and orchards, were also sampled. Evidence of arboriculture was recognised based on records of chestnut, olive tree, almond tree, and grapevine. Overall, pollen analysis provided valuable insights into both individual and collective activities carried out by the monks, including the cultivation of gardens and the surrounding green spaces as well as the management of local hilly woods.

2.2. B. Knowledge of Biodiversity from Pollen Morphology

Biodiversity trends are among the primary targets of palynological research [41,42]. In palaeopalynology, investigations on flora and taxonomy may reach a level of knowledge that often parallels modern taxonomical studies, also involving molecular sciences. However, based on the intrinsic morphology of pollen [43], there are similar questions regarding floristic presence and distribution that can be further explored with the help of records from past contexts.

In the paper by Tecchiati et al. [38], mentioned above, the presence of lime hybrids has been recorded based on the intermediate morphology of pollen grains. The two distinguishing features are intermediate size and exine between Tilia cordata and T. platyphyllos pollen. Although the possibility of discriminating natural hybrids in Tilia is known [44], this can be regarded as the first evidence of such hybrids in Italian palaeorecords and from archaeological contexts.

Mercuri and colleagues [45] describe a rare case of multiporate pollen of Poaceae observed in Takarkori rockshelter, an archaeological site in southwestern Libya, in the central Sahara. The records dated between the early and middle Holocene. This monocotyledon family is typically anaporate, but the production of additional pores is attributed to polyploidy and hybridisation in some species. Overall, palaeoenvironmental research at this site testified to a long period of occupation with phases of plant gathering. The presence of multiporate pollen reveals that grasses faced several kinds of stress in the central Sahara, such as climate change in earlier phases, while human pressure became stronger during the following periods. These environmental changes triggered adaptive responses in polyploids, which were able to produce multiporate pollen.

Clò and colleagues [46] report a study on wild grapevine populations growing in the River Crati Natural Reserve, in southern Italy. Wild grapevines have declined in the IUCN Red List of Threatened Species as a consequence of anthropogenic disturbance and habitat destruction. A population of Vitis vinifera subsp. sylvestris lives in a rewilding wet forest close to the Ionian Sea, including dioicous plants. The results of the dendroecological and palynological study support molecular evidence of a viable population. Pollen dimorphism in this species was especially studied, as it may be very important, given that its domestication history involves the transition from monoecious to hermaphroditic flowers. Interestingly, abortive, inaperturate pollen is produced by female flowers. The implications of this variability in past pollen spectra are still not fully understood, although a case of female pollen has recently been published for a Bronze Age archaeological site [47].

2.3. C. From Modern Analogues to Long Core Reconstructions

Quaternary palaeoecologists have pressed conservationists to consider palaeoecological studies in their management plans to include a historical perspective on changes in biodiversity [48,49], biotic responses to environmental change, and ecosystem dynamics [50,51].

Studies on pollen dispersion have shown that pollen assemblages recorded in natural traps can generally provide an accurate representation of the local vegetation [52,53,54,55]. Attolini and colleagues [56] investigate recent pollen samples from 201 plant populations in NW Italy. Pollen was collected from moss polsters, and vegetation was recorded using phytosociological methods. The growing interest in recent pollen deposits is reflected in the expansion of databases like the EMPD [57], with a continually increasing number of contributors. This research fills gaps in pollen rain studies in the Mediterranean mountains and coastal areas, providing new data for interpreting fossil pollen spectra. While certain vegetation types, like tree-dominated plant communities, are easily identified through recent pollen deposition, others, like shrublands and Larix forests, present more complexity. Some tree taxa (e.g., Pinus, Quercus, Alnus) are overrepresented in areas where their cover is low, suggesting an extra-local contribution. Herbaceous and shrubby communities, with low pollen dispersal, are often poorly represented, and regional influences are more evident. Pollen threshold values were calculated, indicating pollen percentages that help distinguish locally produced pollen from that transported over long distances.

Masci and colleagues [58] outline the importance of comparing palaeoecological data with subsequent land uses in changing cultures. They presented the high-resolution pollen analysis of a sediment core drilled from Paliouras Lagoon in the Halkidiki Peninsula, in Greece. The palynological research allowed the reconstruction of environmental dynamics during the last 4000 years, revealing different main vegetation and landscapes corresponding to different historical phases. In other words, distinct phases of human–environment interactions corresponded to different cultural phases. From the Late Bronze Age until the Late Roman period, the Mediterranean vegetation was largely alternated with mixed deciduous forest and pine stands. In Roman times, intensive land management was visible, with evidence of arboriculture (Olea, Castanea, and Vitis) and cereal cultivation (Secale and Hordeum group). Then, an expansion of forests and the abandonment of fields marked a period of reduced human pressure determined by warfare-related crises. During the Ottoman period, the massive increase in pastoral activities was possibly linked to the significant demographic growth of the nearby city of Thessaloniki.

Kafetzidou and colleagues [59] analyse a long pollen record from the Gulf of Corinth, a biodiversity hotspot in central Greece, as part of the International Ocean Discovery Program (IODP). This study reveals no significant shifts in arboreal pollen between glacial and interglacial periods. Mediterranean and mesophilous taxa remain abundant, with cool mixed evergreen needleleaf and deciduous broadleaf forests in interglacials and graminoid–forb and xerophytic shrubs in glacials. These data support the hypothesis that the Gulf of Corinth acted as a refugium for tree species during Quaternary climate cycles.

3. Conclusions

In conclusion, this Special Issue effectively highlights the significant contributions of interdisciplinary palynological studies, both on- and off-site, with a focus on Holocene contexts. The papers collectively present an integrated approach that combines extensive floristic lists, advances in detailed pollen morphology, and the use of modern analogues [57] to reconstruct long core sequences. This comprehensive framework enhances our understanding of plant biodiversity, environmental changes, and human–plant interactions over time [60].

Such an approach opens new pathways for future research, reinforcing the crucial role of palynology not only in reconstructing past environments and human activity but also in addressing current and future challenges related to sustainability [61]. As suggested by the title “Palynology for Sustainability: A Classical and Versatile Tool for New Challenges”, pollen-based analyses offer valuable insights into past ecosystems, helping to inform environmental and conservation strategies, and enhancing our capacity to tackle modern ecological and climatic issues.