Climate and health effects of different urban forest structures

Urban forests are a proven human health resource, as they restore the physical and mental health of the human body and mind. They have a positive impact on air quality and thermal conditions by reducing concentrations of gaseous and particulate pollutants and lowering air temperature, respectively. In addition, urban forests provide several important ecosystem services, including those associated with human health. Different human-place concepts, show that a close connection of humans to their natural environment is an important determinant of people's well-being. Urban forests, however, vary based on e.g., tree species composition, structure, age and diameter of trees, canopy cover, number and density of canopy layers, abundance of plant species, dead wood, visibility distance, and light conditions. In any human-centered approach, these physical forest characteristics cannot be considered independently of subjective human perception.

Thus, besides answering the question of whether different urban/peri-urban forest and open land structures are associated with different local and human bioclimatic characteristics, another major objective of the project is to collect, digitize, process, model and assess data on human physiological effects gathered during field experiments and walking studies in selected study regions within the city and the urban forest of Augsburg, Germany. Thus, the overarching research question of our study is whether "climatic" forest types are also "human physiological" and "therapeutic" forest types.

The thermal properties of the study regions will be modelled with the microclimatic model ENVI-met and validated against field measurements of climate variables like air temperature, relative humidity, and wind conditions. If successful, this will allow the calculation of further bioclimatological thermal indices such as physiological equivalent temperature (PET), predicted mean vote (PMV) or universal thermal climate index (UTCI) and the development of silvicultural scenarios. Data on physiological effects on humans will be collected during monitored thermal walks along predefined routes in and near-by the study regions, where participants will be equipped with wearable electronic devices that collect physiological data, such as heart activity. Stress levels of participants along the routes will be assessed by saliva-cortisol probes. Questionnaires will be used to collect sociodemographic data and data on participants perceived thermal and visual sensations during the walks. Subjective thermal sensations will be compared to objectively derived thermal indices based on the model results and mobile measurements taken simultaneously with the thermal walks.

Measurements of bioclimatic parameters, human physiological responses, hormone releases, and the recording of subjective well-being as well as subjective perceptions of environmental variables allow for a comprehensive analysis of positive human-environment relationships in urban forests. Thus, a qualitative and quantitative assessment of recreational effects, differentiated by different forest structures, bioclimatic parameters, and social groups, can be comprehensively presented.