Thurston County presents tree canopy assessment; identifies canopy extent, restoration potential and prairie encroachment

County staff presented highlights of a draft tree canopy assessment at the April 16 Thurston County Planning Commission meeting, showing that roughly 61% of the rural county is covered with tree canopy and identifying areas appropriate for tree restoration, areas where tree canopy is encroaching on prairie soils, and locations with high restoration potential.

Claire, a county planner presenting the study, said the report covers tree canopy in the rural county only and is organized into 250-acre hexagons to make large-area comparisons rather than site-specific determinations. "The map we're looking at today depicts the overall tree canopy coverage throughout the entire rural county" and "the data itself is based off of lidar data that was collected by the University of Vermont with a reported 97% accuracy," Claire told the commission. (Transcript: 2636.85''' 2686.605)

Key findings presented - Extent and ownership: The presenter said the report maps over 250,000 acres of tree canopy in rural Thurston County and that 61% of the rural county is covered with tree canopy; 68% of that canopy sits on privately owned land and 48% is on land zoned for residential uses. (Transcript: 2636.85''' 2687.625) - Restoration potential: Staff showed maps highlighting hexagons with high potential for tree canopy restoration (dark purple) where there are few trees and few competing land uses. County staff excluded long-term forestry and prairie-designated land from restoration potential to avoid conflicting management goals. (Transcript: 2735.545''' 2786.8499) - Prairie encroachment: The analysis flags prairie soils covered by increasing tree canopy, noting that encroachment of Douglas fir and other conifers threatens Oregon white oak and prairie-associated species. The presenter emphasized the cultural and ecological importance of prairie and oak habitats. (Transcript: 2868.0999''' 2915.765)

Commission discussion and questions Commissioners asked how maps would inform regulations and programs. Claire said the assessment is intended to inform multiple uses: program prioritization, grant applications, regulatory tools for tree canopy conservation and potential critical-areas ordinance updates. "In the future, we hope that the tree canopy assessment report will help Thurston County and other regional planning partners prioritize programmatic restoration efforts, develop regulatory tools for tree canopy conservation, apply for funding to support tree canopy restoration efforts, understand relationships between tree canopy and other parts of the environment, restore prairie and Oregon white oak habitats, and plan for carbon sequestration efforts to combat climate change." (Transcript: 3111.2048''' 3171.875)

Commissioners raised ecological detail questions, including how genetic diversity of planted trees would be considered at the site scale, and whether the maps would be used for critical areas ordinance updates. Claire answered that the assessment is a large-scale tool to prioritize and guide work; site-level ecological decisions (for example, choosing species and seed sources) would require qualified biologists and restoration plans at the project level. Commissioners also noted that the maps do not include cities or urban growth areas (UGAs) and that wetlands and hydric soil overlays would be provided in appendices and methodology sections of the final report. (Transcript: 3329.2''' 3541.075)

Next steps and availability Staff said the final report remains in draft and will include more than 15 maps, data tables and narrative analysis. The county will complete the report, incorporate commission feedback, and make the final assessment available to the public; staff noted the work is already being used to inform the comprehensive-plan periodic update and may support grant-funded work aimed at riparian habitat protections. (Transcript: 3171.875''' 3206.4849)

Ending: Commissioners thanked staff for the "treasure map" of canopy data and encouraged completion of the methodology appendix and accessible map packet to support next-stage regulatory and restoration planning.