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The risk assessment of urban trees is a challenge that must be addressed by many cities, in consideration of their climatology, management and spatial heterogeneity. Since these trees are in stages of aging, added to bad practices, inadequate selection and establishment, amongst others, their early elimination, and hence the loss of the ecosystem services they provide, is being promoted. For this reason, two tree risk assessment methods were developed to be applied in a complementary manner in urban parks, one basic visual (BV) and the other detailed visual (DV), both structured with the components of likelihood of failure, likelihood of impact, consequence and risk rating, being analyzed qualitatively and semi quantitatively. The methods were applied in 24 trees of Eucalyptus and Tipuana genus by two groups of assessors, experienced and inexperienced, totaling 192 assessments. Results were analyzed with a linear mixed model (LMM), which showed differences between both methods for the likelihood of failure, where the assessment of branches turned out to be the attribute with the highest impact. The methods proved to be suitable to be used in a complementary manner, since BV turns out to be efficient when it is necessary to assess a large number of trees. DV turned out to be more effective, since it was able to identify more precisely the attributes of the tree that must be considered for adequate risk mitigation and management. Therefore, their combined use is recommended for risk assessment in trees established in parks. [ABSTRACT FROM AUTHOR]

Risk assessment of urban trees is an incipient practice in Latin America, generally performed with foreign methods, due to the lack of qualified personnel and locally validated or adapted methodology. This article evaluates the application of three methods on street trees in Montevideo city, Uruguay: Tree Hazard Risk Evaluation and Treatment System (THREATS), Quantified Tree Risk Assessment (QTRA) and Best Management Practices - Tree Risk Assessment (ISA BMP). Three assessors with similar experience applied three methods in 36 trees of three widely used genera, totaling 324 assessments and 1,296 data. The methods were decomposed into the components: Likelihood of Failure, Likelihood of Impact, Consequence and Risk Rating. The data were statistically analyzed through a generalized linear mixed model (p<0.05), for the factors: assessor, method, genus, and their interactions. Results showed no significant differences among assessors, but there were differences among methods, specifically for the Likelihood of Impact and Risk Rating components. The ISA BMP method presented higher means in these last two components. Still, this method is suggested for street trees in Montevideo until a more appropriate method is adapted or developed for local conditions. [ABSTRACT FROM AUTHOR]