The urban greenness score: A satellite-based metric for multi-decadal characterization of urban land dynamics
Canada’s urban areas have experienced extensive growth over the past quarter century; however, there has been no consistent, spatially explicit approach for quantifying the loss and gain of greenness in cities nationally. Herein, we developed a novel urban greenness score metric using greenness frac...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Elsevier
2020-12-01
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| Series: | International Journal of Applied Earth Observations and Geoinformation |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S0303243420302555 |
| _version_ | 1818246091436457984 |
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| author | Agatha Czekajlo Nicholas C. Coops Michael A. Wulder Txomin Hermosilla Yuhao Lu Joanne C. White Matilda van den Bosch |
| author_facet | Agatha Czekajlo Nicholas C. Coops Michael A. Wulder Txomin Hermosilla Yuhao Lu Joanne C. White Matilda van den Bosch |
| author_sort | Agatha Czekajlo |
| collection | DOAJ |
| description | Canada’s urban areas have experienced extensive growth over the past quarter century; however, there has been no consistent, spatially explicit approach for quantifying the loss and gain of greenness in cities nationally. Herein, we developed a novel urban greenness score metric using greenness fractions from a multi-decadal time series (1984–2016) of spectrally unmixed annual Landsat satellite image composites to characterize final year (2016) greenness and its overall change for 18 major Canadian urban areas, summarized by census dissemination area (DA). The applied validation procedure confirmed correlation coefficients (ρ) ranging from 0.67 – 0.85 between reference and estimated greenness fractions, indicating that spectral unmixing is an appropriate method for extracting urban greenness from a time series of medium spatial resolution satellite imagery. Most DAs across Canada sustained a moderate (∼20 % – 40 %) or low (≲ 20 %) level of greenness between 1984 and 2016, but overall there was a decreasing trend in greenness. Eastern urban areas maintained the most greenness over time, while urban areas in the Prairies had the greatest increase in greenness. Densely populated urban areas experienced the greatest loss in greenness (16 % of DAs); whereas, urban areas with a moderately-low density experienced the greatest increase (14 % of DAs). In agreement with previous studies, we found that greenness was negatively associated with urban infilling, with lower greenness levels typically found in urban cores, and greenness loss most often found in the urban periphery in conjunction with urban expansion. Methods presented in this analysis take advantage of the open and longstanding Landsat archive, as well as multiple spatial scales, including sub-pixel unmixing techniques, pixel level greenness faction data summarized for management units, and analysis conducted nationally. The developed urban greenness score provides a comprehensive framework to understand current urban greenness and relate it to its recent past, which supports long-term strategic planning, and can be transferred to other regions across spatial and temporal scales. |
| first_indexed | 2024-12-12T14:43:18Z |
| format | Article |
| id | doaj.art-9869c72e28a745f482dfe46967608fb9 |
| institution | Directory Open Access Journal |
| issn | 1569-8432 |
| language | English |
| last_indexed | 2024-12-12T14:43:18Z |
| publishDate | 2020-12-01 |
| publisher | Elsevier |
| record_format | Article |
| series | International Journal of Applied Earth Observations and Geoinformation |
| spelling | doaj.art-9869c72e28a745f482dfe46967608fb92022-12-22T00:21:10ZengElsevierInternational Journal of Applied Earth Observations and Geoinformation1569-84322020-12-0193102210The urban greenness score: A satellite-based metric for multi-decadal characterization of urban land dynamicsAgatha Czekajlo0Nicholas C. Coops1Michael A. Wulder2Txomin Hermosilla3Yuhao Lu4Joanne C. White5Matilda van den Bosch6The Department of Forest Resources Management, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada; Corresponding authorThe Department of Forest Resources Management, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, CanadaCanadian Forest Service, Pacific Forestry Centre, Natural Resources Canada, 506 West Burnside Road, Victoria, BC, V8Z 1M5, CanadaCanadian Forest Service, Pacific Forestry Centre, Natural Resources Canada, 506 West Burnside Road, Victoria, BC, V8Z 1M5, CanadaSchool of Architecture and Landscape Architecture, University of British Columbia, 2260 West Mall, Vancouver, BC, V6T 1Z4, CanadaCanadian Forest Service, Pacific Forestry Centre, Natural Resources Canada, 506 West Burnside Road, Victoria, BC, V8Z 1M5, CanadaSchool of Population and Public Health, The University of British Columbia, 2206 East Mall, Vancouver, BC, V6T 1Z3, Canada; The Department of Forest and Conservation Sciences, The University of British Columbia, 2424 Main Mall, Vancouver, BC, V6T 1Z4, CanadaCanada’s urban areas have experienced extensive growth over the past quarter century; however, there has been no consistent, spatially explicit approach for quantifying the loss and gain of greenness in cities nationally. Herein, we developed a novel urban greenness score metric using greenness fractions from a multi-decadal time series (1984–2016) of spectrally unmixed annual Landsat satellite image composites to characterize final year (2016) greenness and its overall change for 18 major Canadian urban areas, summarized by census dissemination area (DA). The applied validation procedure confirmed correlation coefficients (ρ) ranging from 0.67 – 0.85 between reference and estimated greenness fractions, indicating that spectral unmixing is an appropriate method for extracting urban greenness from a time series of medium spatial resolution satellite imagery. Most DAs across Canada sustained a moderate (∼20 % – 40 %) or low (≲ 20 %) level of greenness between 1984 and 2016, but overall there was a decreasing trend in greenness. Eastern urban areas maintained the most greenness over time, while urban areas in the Prairies had the greatest increase in greenness. Densely populated urban areas experienced the greatest loss in greenness (16 % of DAs); whereas, urban areas with a moderately-low density experienced the greatest increase (14 % of DAs). In agreement with previous studies, we found that greenness was negatively associated with urban infilling, with lower greenness levels typically found in urban cores, and greenness loss most often found in the urban periphery in conjunction with urban expansion. Methods presented in this analysis take advantage of the open and longstanding Landsat archive, as well as multiple spatial scales, including sub-pixel unmixing techniques, pixel level greenness faction data summarized for management units, and analysis conducted nationally. The developed urban greenness score provides a comprehensive framework to understand current urban greenness and relate it to its recent past, which supports long-term strategic planning, and can be transferred to other regions across spatial and temporal scales.http://www.sciencedirect.com/science/article/pii/S0303243420302555UrbanVegetationTime seriesLandsatSpectral unmixingCanada |
| spellingShingle | Agatha Czekajlo Nicholas C. Coops Michael A. Wulder Txomin Hermosilla Yuhao Lu Joanne C. White Matilda van den Bosch The urban greenness score: A satellite-based metric for multi-decadal characterization of urban land dynamics International Journal of Applied Earth Observations and Geoinformation Urban Vegetation Time series Landsat Spectral unmixing Canada |
| title | The urban greenness score: A satellite-based metric for multi-decadal characterization of urban land dynamics |
| title_full | The urban greenness score: A satellite-based metric for multi-decadal characterization of urban land dynamics |
| title_fullStr | The urban greenness score: A satellite-based metric for multi-decadal characterization of urban land dynamics |
| title_full_unstemmed | The urban greenness score: A satellite-based metric for multi-decadal characterization of urban land dynamics |
| title_short | The urban greenness score: A satellite-based metric for multi-decadal characterization of urban land dynamics |
| title_sort | urban greenness score a satellite based metric for multi decadal characterization of urban land dynamics |
| topic | Urban Vegetation Time series Landsat Spectral unmixing Canada |
| url | http://www.sciencedirect.com/science/article/pii/S0303243420302555 |
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