Ecosystem structure influences human health outcomes as the basis for green prescriptions

The role of Nature ^**^** in supporting human life, health, and well-being has been recognized and appreciated since ancient times, and has become a topic of scientific investigation with early studies dating back several decades. In recent years, this field has gained renewed attention and methodological refinement, driven by interdisciplinary frameworks and advances in environmental psychology, ecology, and health sciences, including new ecosystem-based approaches that highlight the deep human dependence on Nature for both mental and physical health. Among Nature-based Interventions that aim at exposing people to the natural environment, Green Prescriptions (GRx) represent a promising strategy to address human health challenges in ways that can also support environmental sustainability, in line with the Planetary Health framework. However, significant gaps remain in our understanding of the specific ecological factors that influence health outcomes during therapeutic activities in natural settings; in particular, it remains unclear how ecosystem structure and functions modulate health responses in individuals. This nine-month pilot study examined the therapeutic efficacy of GRx within a Mediterranean woodland ecosystem, to assess if and how variations in ecosystem structure influence health outcomes in individuals with complex chronic conditions. Using a novel aggregated index to characterize four distinct woodland patches, we identified a gradient in structural complexity where greater ecosystem functionality was consistently associated with greater alleviation of psychological and physical symptoms. Notably, health outcomes were independent of weather conditions and participants' baseline connectedness to Nature, whereas temporal dynamics and the presence of peaks in the productivity of some species influenced both perceptions and physical responses. This underscores the intrinsic role of ecosystem properties and dynamic functions in modulating human health responses, while also suggesting the potential presence of a complex set of signals pervading complex ecosystems that is worth further exploration. The results demonstrated cumulative health benefits, including significant reductions in medication use over time, particularly among individuals with respiratory challenges and chronic pain. Furthermore, participants showed improved environmental awareness and behavior, embracing the interconnectedness principle, which is integral to effective environmental conservation. This study highlights the potential of well-functioning ecosystems to serve as co-effectors in healthcare interventions, advancing the goals of Planetary Health while reinforcing the importance of preserving ecological integrity. (**In this paper, "Nature" is written with a capital "N" to indicate the living biosphere and the abiotic matrices (soil, air, and water) in which life is embedded, including the ecological processes they sustain. This capitalization reflects the scientific perspective of Nature not merely as a passive backdrop, but as an active ecological system that interacts and influences human health. It also avoids confusion with "nature" as the intrinsic quality of a phenomenon**).