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Date of Award

Fall 2023

Document Type

Masters Thesis

Department or Program Affiliation

Environmental Studies

Degree Name

Master of Arts (MA)

Department

Environmental Studies

First Advisor

Flower, Aquila

Second Advisor

Bach, Andrew J.

Third Advisor

Bauman, Jenise

Abstract

The San Juan Islands, an archipelago in the Salish Sea between Vancouver Island and the Washington coast, are one of the few places native temperate grasslands are found in western Washington State. These ecosystems are important sources of biodiversity and support many rare and endemic species. In addition to their ecological importance, native temperate grasslands have profound cultural significance to the Coast Salish peoples who historically stewarded these landscapes using traditional land management practices-particularly fire-for the production of bulb crops such as common camas (Camassia quamash). Unfortunately, these ecologically and culturally valuable ecosystems have become rare, greatly impacted by the combined pressures of changes in land use, invasive species, and the exclusion of fire from the landscape. While land managers and conservation experts are aware of the current threats facing native temperate grasslands, the lack of historical context and baseline knowledge has made it impossible to fully understand the long-term trends in extent and distribution of this ecosystem. To address this knowledge gap, I used historical landcover data and multispectral imagery to create a high-resolution, spatially explicit dataset in ArcGIS Pro, representing grassland landcover on the San Juan Islands at multiple time periods since the early years of European and American colonization. Spatial analysis of the dataset was conducted in ArcGIS Pro to quantify grassland loss between time periods, and identify landcover types replacing grasslands. The results reveal significant decreases in grassland extent between time periods, resulting in a 78% decrease in the extent of non-agricultural grasslands since 1890. These changes are primarily a result of conversion to agriculture, and encroachment or succession to forest. The spatial data and analyses created in this study help to develop the historical baseline of native temperate v grasslands on the San Juan Islands, adding to our understanding of the lingering legacy that changes in land use have had on this ecosystem, with the potential to aid in the development of effective conservation and restoration practices.

Type

Text

Keywords

San Juan Islands, grasslands, historical baseline, landcover change

Publisher

Western Washington University

OCLC Number

1408726800

Subject – LCSH

Grasslands--Washington (State)--San Juan Islands--Management; Grasslands--Effect of fires on--Washington (State)--San Juan Islands; Grassland restoration--Washington (State)--San Juan Islands; Grassland conservation--Washington (State)--San Juan Islands; Camases--Effect of fires on--Washington (State)--San Juan Islands; Land cover--Washington (State)--San Juan Islands--History; Land use--Washington (State)--San Juan Islands--History; Coast Salish Indians--Washington (State)--San Juan Islands; Multispectral imaging--Washington (State)--San Juan Islands; San Juan Islands (Wash.).

Geographic Coverage

San Juan Islands (Wash.)

Format

application/pdf

Genre/Form

masters theses

Language

English

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.

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