Interacting effects of forest management, biodiversity and climatic events on human health

Adopting a Planetary Health perspective, BEhealthy will address these overarching objectives:

• To quantify the effects of changing forest management intensity and related changes in forest structure and biodiversity on human physical and mental health.
• To elucidate the trade-offs or co-benefits between different management-driven forest characteristics and health outcomes.

The work is organized around four Work Packages, with specific objectives:

• To assess forest microclimate characteristics relevant for thermal comfort of forest workers and visitors, to quantify the thermal buffering capacity of forests, and to compare them between forests of differing management intensity, structure and tree diversity in different regions. (WP1)
• To quantify phytoncide concentrations and composition (chemodiversity) in forests of differing management intensity, structure and tree diversity in different regions and to determine seasonal patterns (spring vs. summer vs. autumn) of phytoncide abundance. To characterise the effect of climate extremes (e.g., heat waves) on phytoncide levels and composition. (WP2)
• To assess mental health effects associated with forest management intensity, structure and tree diversity and their underlying drivers. To assess whether forest biodiversity-mental health linkages differ across seasons due to alterations in visual distinctiveness of tree and plant species (e.g., summer vs. autumn). To quantify the contribution of the human senses for forest biodiversity-mental health linkages and which sense people primarily engage (e.g. visual vs. olfactory). (WP3)
• To understand the mechanisms underlying the effects of forest management and forest characteristics on health outcomes, and to disentangle direct/indirect effects on health-related ecosystem functions and psychophysiological health outcomes. To assess synergies/trade-offs between forest biodiversity related health benefits/detriments found for microclimate, phytoncide chemodiversity and mental well-being. (WP4)

WP 1: Microclimatic buffering of different forest types

1. Microclimatic buffering is strongly enhanced inside forests as compared to open-land conditions (grassland sites), because of the sheltering effect of the tree canopy.
2. Within forests, thermal buffering capacity is highest in unmanaged stands followed by uneven-aged single-tree selection forests and even-aged forests, because of higher share of broadleaved species and higher structural complexity in unmanaged or selection forests.
3. Increasing tree species richness strengthens the thermal buffering capacity of microclimate because of higher canopy packing, leading to more pleasant conditions for humans.
4. Physiologically equivalent temperature (PET) during hot sunny days decreases with increasing tree diversity, increasing share of shade tolerant and of deep-rooting species, while on cold windy winter days it is tempered with increasing tree diversity, increasing share of evergreen and of shade-tolerant species in the mixture.

WP 2: Phytoncide composition and concentrations in different forest types

1. Within forests phytoncide concentrations are considerably exceeding the concentrations at open-land (grassland) reference sites.
2. Conifer dominated stands contain higher phytoncide concentrations than stands dominated by broadleaved deciduous trees, due to higher emission rates of conifers.
3. Within forests, phytoncide diversity is higher in unmanaged stands and uneven-aged stands under single-tree selection than in even-aged forests, because of higher biodiversity and higher structural complexity in unmanaged or selection forests.
4. Phytoncide concentrations in stands with comparable biodiversity are determined by stand structure and microclimate. Stands which have developed close canopies contain higher concentrations than stands with open canopy because of lower dilution by turbulence and lower phytochemical degradation of these highly reactive compounds (due to lower UV radiation penetrating the canopy).
5. Phytoncide concentrations differ between macroclimates (three Exploratory regions), current meteorological conditions and seasons (different plant phenology and climatic conditions), with higher concentrations in summer at higher air temperatures and light intensities.

WP 3: Mental health and well-being in different forest types

1. Being in a forest opposed to a non-forest control increases mental wellbeing outcomes.
2. Less managed forests with greatest compositional and structural diversity elicit greatest mental wellbeing effects, while even-aged forests have the lowest. This effect is mediated by increased perceived biodiversity.
3. Forest biodiversity – mental health linkages are more pronounced for forest structural diversity when compared to forest compositional diversity.
4. Forest biodiversity – mental health linkages increase as a function of the number of senses included when experiencing the forest as a manipulation of people’s mindfulness. This effect is mediated by the greater accuracy of perceived biodiversity through engaging more senses.
5. Forest biodiversity – mental health linkages are most pronounced in seasons with greatest visual distinctiveness, i.e. in autumn.

WP 4: Integration and synthesis: assessing microclimate and BVOCs effects on mental health

1. Inhaling BVOCs opposed to non-nature VOCs increases psychophysiological health outcomes.
2. Greater chemodiversity positively influences psychophysiological health outcomes through an enriched smellscape.
3. Forest biodiversity buffers the microclimate, while enriching chemodiversity and providing an enriched sensoryscape, resulting in synergistic effects regarding psychophysiological health outcomes.

WP 1:

• Microclimate measurements (air temperature (Tair), relative humidity (RH), mean radiant temperature (Tmrt) and wind speed (U).
• Calculation of Physiological Equivalent Temperature (PET) to assess thermal comfort and stress of humans exposed to the local meteorological conditions.

WP 2:

• Collection of forest air (or air from reference sites) at defined flow rates over glass cartridges filled with adsorbing matrices.
• Analysis pf phytoncide concentrations by gas chromatography-mass spectrometry following thermodesorption and a cryofocussing step.

WP 3:

• Conduction of a survey-based forest intervention study with participants.
• Assessment of mental health (anxiety symptoms), restoring capacities (perceived stress, perceived restorativeness) and building capacities (spiritual wellbeing).
• Assessment of physiological stress via saliva cortisol levels, heart rate, heart rate variability and blood pressure.

WP 4:

• Analysis of the functional links between forest characteristics, health related ecosystem functions and psychophysiological health outcomes (see conceptual framework), tested using Structural Equation Modelling.
• Conduction of a controlled lab experiment on the effects of chemodiversity on mental health and associated biomarkers.