Building a Useful Species Failure Profile for Tree Risk Assessment

One of the practical challenges in tree risk assessment is that species failure profile information is real, useful, and widely referenced, but it is not available in one complete, authoritative source. Assessors often carry this information through experience. Over time, they develop a sense of which species are associated with certain branch habits, structural issues, storm responses, or recurring failure patterns.

There is no single source that solves the problem

There is not one universal database that provides a complete, dependable species failure profile for all trees in all regions and all assessment contexts. What exists instead is a set of partial sources: failure databases, species-profile papers, storm-failure studies, practitioner manuals, review papers, and weather-specific guidance for conditions such as ice, wind, or saturated soils. Together they form a body of information. Separately, none of them is enough. A useful species failure profile will have to be assembled from several kinds of resources.

The strongest information is often regional and conditional

One of the most developed examples is the California Tree Failure Report Program, now represented through the Western Tree Failure Database. That work is valuable because it does exactly what assessors are looking for: it collects tree failure reports and uses them to support species and genus failure profiles. But even this strong source has limits. It is regional. It is strongest where report volume is strong. It has useful published profiles for some species, not all species. A California-based profile can be highly informative without being universal. The same species may present differently across regions, climates, management histories, and urban contexts.

The literature helps, but it does not collapse into one clean answer either. Review papers on tree risk assessment make it clear that assessor judgment still plays a large role, especially when estimating probability of failure. Observational studies help test commonly repeated assumptions, but they do not always confirm them. The Koeser study is important for exactly that reason: some defects commonly treated as obvious indicators of storm failure were not statistically significant predictors in that dataset. That does not make those defects irrelevant. It means they have to be treated carefully and contextually.

Failure is also not one single event type. A tree’s response under wind loading is not the same as its response under ice loading. A pattern associated with saturated soil and root failure is not the same as a pattern associated with branch failure during storms. Decay-related compromise, snow load, drought stress, and pruning history all shape the meaning of species information.

What the feature is really doing

Once the problem is framed correctly, the goal becomes much clearer. The goal is not to find the one source. The goal is to build a species failure profile knowledge layer from several resource types and make it available in a way that helps the assessor complete the form.

That knowledge layer would likely need to combine at least four kinds of material: published species profile material, failure database material, load-specific and event-specific literature, and broader tree risk assessment literature. Published profiles and profile-development work help document broad recurring tendencies where the literature actually supports them. Failure databases show repeated reported patterns for branch, trunk, and root failures. Load-specific studies and storm or ice guidance keep those tendencies tied to actual failure conditions. Review literature helps calibrate confidence, identify weak or mixed evidence, and prevent the software from overstating what is known.

What makes the information useful

A useful species failure profile does not need to be final. It needs to be usable.

That means it should help the assessor answer a form field more reliably and more efficiently, while still leaving the final judgment with the person doing the assessment. In practice, the application should not output something like “Species failure profile: High risk.” That compresses too much uncertainty into one label. A more useful output would look like a structured prompt built from multiple evidence sources:

Most commonly reported failure partbranch / trunk / root

Associated conditions wind, saturated soil, decay, included bark, overextended limbs, pruning history, crown architecture, or whatever the available evidence actually supports

Contextregional relevance, climate relevance, urban or non-urban setting, storm-related or decay-related context

Evidence typefailure database, profile paper, observational study, practitioner manual, review literature

Confidencehigh, medium, or low based on the strength and consistency of the sources

That structure reflects the reality of the information much better than a single rating. It also fits the existing Hammerdirt model. The system proposes something useful. The assessor decides whether it belongs in the assessment.

The real work is organization

Once this feature is understood this way, the main challenge becomes less about finding data and more about organizing it. The challenge is not simply collecting references. It is turning scattered evidence into a consistent internal structure that can be surfaced in the app. For each species-level assertion, the system would need to retain things like:

speciesfailure

partfailure

modeassociated

conditions

regionclimate

contextsource

typesource

That structure matters because it keeps the information attached to its source, its context, and its level of certainty. It prevents the app from flattening regional studies, practitioner guidance, and review literature into one undifferentiated claim. The value is not just in gathering material. The value is in building a framework that can hold different kinds of evidence without losing their differences.

Conclusion

A useful species failure profile is unlikely to come from one database, one paper, or one guide. It will have to be assembled from several kinds of resources: failure databases, published species profiles, observational studies, weather- and load-specific guidance, and general tree risk assessment literature. Caroline Herath et al, 2021. Tree Steward Manual. Virginia Cooperative Extension. https://pressbooks.lib.vt.edu/treesteward/. Chapter 11: Structural defects tree failures and Risk

van Haaften M, Liu Y, Wang Y, Zhang Y, Gardebroek C, Heijman W, Meuwissen M. Understanding tree failure-A systematic review and meta-analysis. PLoS One. 2021 Feb 16;16(2):e0246805. doi: 10.1371/journal.pone.0246805. PMID: 33592010; PMCID: PMC7886209.

Koeser, A. K., Klein, R. W., Hauer, R. J., Miesbauer, J. W., Freeman, Z., Harchick, C., & Kane, B. (2023). Defective or Just Different? Observed Storm Failure in Four Urban Tree Growth Patterns. Forests, 14(5), 988. https://doi.org/10.3390/f14050988