Earth observation and social media: Evaluating the spatiotemporal contribution of non-native trees to cultural ecosystem services

Understanding how non-material benefits from ecosystems, known as cultural services, are shaped by non-native biota is paramount to manage biological invasions and achieve the Sustainable Development Goals (SDGs). Despite recent advances, assessments of cultural services still lack an explicit temporal dimension, which is relevant for developing monitoring systems. Here, we evaluate the spatiotemporal contributions of non-native trees to landscape aesthetics and nature recreation in a National Park in Portugal. We use a multimodel framework to understand how those cultural services (evaluated from social media photos) relate to the environmental context (physical and visual accessibility, and wilderness; derived from ancillary GIS data) and landscape visual-sensory features (colour diversity, landscape heterogeneity, and vegetation functioning). The latter were computed from satellite imagery (MODIS and Sentinel-2 MSI sensors) for the four seasons of the year: Winter, Spring, Summer and Autumn. We found that, during Autumn, contributions of non-native trees prevailed mostly in landscapes with greater colour diversity (green-band, Sentinel 2). During Spring, their contributions prevailed in landscapes with lower wilderness and heterogeneous levels. In Winter, those contributions were less evident in more remote areas. As for Summer, no significant relations were found for those cultural contributions. These results are congruent with the phenology of dominant tree species: deciduous natives occurring with coniferous non-natives and evergreen invaders, leading to higher colour diversity in Autumn, versus the dominance of blooming invaders in accessible areas during Spring. Results also seem to match the seasonal dynamics of touristic demand in the National Park: the pursuit of wilder areas for ecotourism in Winter, versus the experience of popular recreational activities in Summer. We discuss the usefulness of Earth observations in the research of cultural services and, particularly, for supporting SDG targets 15.8 (on invasive species), 8.9 (touristic revenues) and 12.8 (nature awareness).