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Olea expansion and mosaic Landscape formation in an island Environment since human Arrival

Periodic Reporting for period 1 - OLEA (Olea expansion and mosaic Landscape formation in an island Environment since human Arrival)

Reporting period: 2020-10-01 to 2022-09-30

The OLEA-project is focused on the study of mosaic landscape formation and olive tree cultivation in the Balearic Islands during the Holocene, with special focus after the human arrival. When investigating such landscapes, islands provide vital insights for understanding cultural and environmental processes through time because they tend to amplify geographical and cultural determinants, and they appear more vulnerable and less resilient to change than mainland. While several palynological studies in the Balearics have been carried out, the vegetation dynamics in response to the human practices and fire regime are not yet fully understood despite these being crucial for understanding the observed environmental changes.

Mosaic landscapes are one of the main features of Mediterranean landscapes. Mosaic landscape implies a balance between peasant communities and the rural and natural environment. They also entail numerous direct and indirect benefits such as fire suppression, reduced erosion, sustainable management, etc. Understanding the when, why, and how of mosaic landscapes can be faced through palaeoecological research. Integrated palaeoecological and archaeological approaches are key tools to reconstruct landscape changes, anthropization rhythms and the understanding of sylvo-agropastoral practices through times. The olive tree is a prominent feature of current circum-Mediterranean landscapes and a fundamental element of the modern Mediterranean agricultural economy, it is one of the most important trees in the Mediterranean basin, economically and because of its cultural and symbolic value. This tree is one of the prominent species in maquis and garrigues from the Balearic Islands, but we do not have clear interpretations about its arrival or when the cultivation of olive trees started.

OLEA-project aimed to: a) understand the drivers implied in the spread of Olea macchia; b) trace back the history of Olea horticulture and management since the earliest human arrival to the Balearic Islands; c) assess the role of human activities and climate change in the formation and evolution of mosaic landscapes in the Balearic Islands, and d) identify how newcomers and colonisation or abandonment processes produced new types of landscapes.
Despite the slowing down caused by COVID-19 during the first year of the project, main objectives were achieved. The results were presented at the MedPalynoS 2021 & 2022 (Modena & Paestum), at the European Association of Archaeologists (Kiel) and at the Archaeological Journeys of the Balearic Islands 2022 (Eivissa). In addition, the fellow was interviewed by Balearic Media (Diario de Ibiza and Cala Millor 7) and published a dissemination paper to Focus-UNIMORE. General audience was also reached through a dissemination invited conference at the MAEF Museum (Eivissa).

OLEA-project consisted of 4 main research topics, developed at the Laboratory of Palynology and Palaeobotany (LPP, UNIMORE). We explain the main features and results below:
1) Palaeoenvironmental reconstruction. Pollen analysis from paleo-lagoons (‘off-site’ sequences: Santa Ponça and Trebalúger) confirmed important vegetation changes during the Late Holocene, including the spread of olive trees and other thermophilus taxa. In the case of Santa Ponça, this vegetation change seems to occur about a millennium later than in other sequences from Mallorca and Minorca, this is after 4000 years ago. These discordances between Balearic paleoenvironmental sequences highlight the microregional variability of landscape changes due to different anthropization rhythms, topographic and microclimate conditions. A high interdisciplinary and multiproxy approach was applied to the Santa Ponça sequence including pollen, non-pollen palynomorphs, seda-DNA, sedimentology, fire-history, and radiocarbon dating. This integrated approach will be extended in futures research and publications.

2) Onset and evolution of mosaic landscapes. The integration of both natural and archaeological sequences (“on-site”: Puig de Sa Morisca, Cala Morell and Closos de ca’n Gaià) allowed to further understand the onset of mosaic landscapes during the Bronze Age, with open environments surrounding the archaeological sites. Pollen data from archaeological sites confirmed highly humanized environments during the Bronze Age and Iron Age periods. Differences in pollen assemblages correspond to changes in landscape practices and household activities. Monumental prehistoric houses may be considered permanent places, as they are used for many centuries. Palynology has proven to be an important tool to follow up cultural evolution and climate change/adaptions through time.

3) High-resolution pollen morphology on modern Olea varieties. The pollen morphology of ancient and modern olive tree cultivars from Mallorca was analysed to detect potential morphotypes that could be related to wild vs cultivated olive tree varieties or to specific agronomic varieties of the Balearic Islands. To do so, a new image-analysis software called OLEAtool for morphopalynological research was developed to facilitate the analysis and measurements of Olea pollen. OLEAtool is a macro extension for use with the open-access and freely available image-analysis software, ImageJ.

4) Modern analogues and modelling. Modern sedimentary and moss samples were studied from different Balearic locations in order to further understand the pollen rain and non-pollen palynomorph representation from the main vegetation types of the Balearic Islands. This research furnished novel and key information to understand pollen-vegetation relationships, as well as the correlation of pollen assemblages with environmental and anthropogenic variables. Our work suggested that low pollen percentages of air-borne and high-pollen producing taxa should be interpreted with caution as they likely reflect regional dynamics. To perform such modern analogue study, it was necessary to achieve a high morphological resolution level which was only possible thanks to the LPP pollen reference collection.
The OLEA-projects implies a turning point in the palaeoenvironmental knowledge from Mallorca and Minorca, but also paving the path of new interpretations of past landscapes and olive tree cultivation through the study of modern analogues and present-day olive tree pollen morphology. Both lines of research were favourably received by both the scientific community and the wider society when presented in seminars and conferences. Also, the research on olive tree modern pollen was greatly welcomed by the experts and administration agencies working on agronomic reach on the Balearic Islands, due to the complementary applicability to present-day cultivar variety-characterization through pollen analysis using OLEAtool.

OLEA-project’s research was also very welcomed by archaeologists and palaeoecologists working on the Balearics, not only because it helps to further interpret Holocene socio-environmental dynamics, but also to improve and to develop dissemination and outreach products such as archaeological site information panels or artistic reconstruction drawings. Moreover, discussion and teaching seminars to university students had a positive impact on their formation, while the project also benefited from their comments and suggestions. Some of these students were also implied in research activities through undergraduate and master thesis.