Model Spotlight: Species Distribution Model for Fraxinus nigra (Wisqoq; Black Ash)

In partnership with Parks Canada, the Atlantic Canada Conservation Data Centre (AC CDC) has developed a Fraxinus nigra (Wisqoq; Black Ash) species distribution model extending across mainland Nova Scotia.

Fraxinus nigra is an ecologically and culturally important species facing imminent threats (e.g., the arrival of Emerald Ash Borer in Nova Scotia; COSEWIC, 2018). The cultural significance and value of Fraxinus nigra (Black Ash; Wisqoq) cannot be understated. It has been a part of l’nuk culture since time immemorial. Its highly flexible wood, that can be peeled into thin strips, is an important component of its cultural significance (see wisqoq.ca for more information).

We used an inductive modelling approach (i.e., where potential habitat is inferred from the data), leveraging a machine learning algorithm. Our modelling goals were to:

1. Understand where potential Fraxinus nigra (Black Ash, Wisqoq) habitat is distributed in mainland Nova Scotia
2. Determine where to prioritize field work to find additional occurrences of Fraxinus nigra
3. Supply information to decision makers about high potential areas of Fraxinus nigra habitat (e.g., for management or planning applications)

We produced a 50m resolution predictive surface output showing areas of high and low probability of suitable habitat. The final model has an AUC score of 0.8403 when evaluated against training data and an AUC score of 0.8408 when evaluated against testing data.

We consulted species experts on its quality and biological feasibility. The model quality was rated by our experts as between 3-star and 4-star on a five-star scale. The experts emphasized that the selected model overestimates probable suitable habitat. Fraxinus nigra is a rare species; it is infrequent to absent in almost every area identified anecdotally (and by the model) as probably suitable.

Model details: