Which trees are important and why? Comparison of ES supply and their perception by residents.

Ecosystem Services (ESs) concept may have many important applications, one of which is more effective tree management, especially relevant in urban areas. Due to limited space, local decision-makers must make competing decisions about protecting, planting, and removing trees in these areas (related to both public and private spaces), often the subject of conflicts. Thus, a common shared understanding of ESs provided by trees is crucial for developing compromise solutions. Meanwhile, objectively the most valuable trees in the city are not necessarily the same as those that residents value most. The cascade model indicates that people value those benefits they recognize as contributing to their well-being. Costanza et al. argue that ESs should not be understood directly as benefits, but they also notice that although the concept is quite well-known, its practical applications are limited. Its applicability may be increased by a better understanding of the relationship between the provision of ES and its influence on human well-being. The meaning of this relation may be particularly relevant in the case of trees. Their numbers are declining due to urbanization [5], although they do, after all, provide a great variety of ES to city residents [6]. This research proposes a methodological approach that enables valuation assessment of trees, including both ESs supply and the values residents attribute to trees regarding the benefits they appreciate. We address this challenge using multi-criteria analysis, fuzzy set theory, and Analytical Hierarchy Process. In this study, three data sources are proposed to identify valuable trees: (1) Airborne Laser Scanning (ALS LiDAR) point cloud enabling the location and biometric characteristics of trees and estimation with the i-Tree Eco model (USDA Forest Service) of some ESs they provide (air purification, sun protection, oxygen provision, and regulation of air humidity and soil moisture), (2) expert mapping providing information about other ESs related to those trees (such as providing animal habitat, food, or place of recreation) and (3) a survey with an interactive map (geo-questionnaire) for identification of trees valuable to residents in their daily lives. The proposed approach was used to identify the most valuable trees in Racibórz (Poland). The analysis included 17 ESs representing four classes of services: provisioning, regulating, habitat, and cultural ones (following [5]), considering their relative
importance [1]. The applicability of obtained valuation maps was shown by comparison of trees located in protected and unprotected areas (with a division on public-private land) to verify whether management strategies related to their protection are sufficient. Based on the proposed evaluation method, the most valuable tree-covered areas may be indicated regarding both ESs they provide and their influence on residents’ well-being. Moreover, it can objectify tree protection strategies by localizing protected areas that residents underestimate when they are situated too far away from their residence or some barriers influence their accessibility. It also enables the localization of those tree-covered areas to be more valuable in residents’ perception than it might seem by analyzing only the ES supply.