Documenting Land Cover and Vegetation Productivity Changes in the NWT using the Landsat Satellite Archive
Fraser, R.H1, Olthof, I.1, Deschamps, A.1, Pregitzer, M.1, Kokelj, S.2, Lantz, T.3,Wolfe, S.4, Brooker, A.5, Lacelle, D.5, and Schwarz, S.6 (1) Canada Centre for Remote Sensing, Natural Resources Canada, Ottawa, ON (2) NWT Geoscience Office, Govt of the Northwest Territories, Yellowknife, NWT (3) School of Environmental Studies, University of Victoria, Victoria, BC (4) Geological Survey of Canada, Natural Resources Canada, Ottawa, ON (5) Department of Geography, University of Ottawa, Ottawa, ON (6) NWT Centre for Geomatics, Govt of the Northwest Territories, Yellowknife, NWT Outline
1. Need for large-area monitoring in the Northwest Territories
2. Potential of Landsat image archive for northern monitoring
3. Change detection using dense Landsat image stacks
4. NWT study regions and methods
5. NWT Trend detection results – Landscape disturbances and tundra greening 1. Need for large-area monitoring in NWT • NWT is a large and sparsely populated territory facing cumulative impacts from development and climate change
NWT Mines and Exploration Projects Inuvik Annual Temperature Means (NWT Geoscience Office) (NWT Environment and Natural Resources) 1. Need for large-area monitoring in NWT
• Strong need for comprehensive environmental monitoring recently highlighted in the Rosenberg International Forum report on the Mackenzie River Basin:
“a strong, well-designed and ongoing monitoring program an absolutely essential precondition for effective management of the Mackenzie River Basin.”
• NWT Cumulative Impacts Monitoring Program (CIMP) – Supports numerous initiatives for building monitoring capacity including three projects with CCRS/NRCan involvement aimed at expanding scale of monitoring using EO
• The NRCan TRACS project also using EO to assess terrain sensitivity to permafrost degradation and potential impacts on transportation networks 2. Potential of Landsat Image Archive for Northern Monitoring
• Landsat has a spatial grain (30 m) and extent (185 km) ideal for large-area monitoring.
• A rich 28-Year (1984-2012) archive exists for Northern Canada
• Baseline monitoring and retrospective change analysis can be followed by forward monitoring WRS-2 Frame Overlap USGS Archive Holdings (CIMP study region) 3. Change Detecting Using Dense Landsat Image Stacks
LandTrendr (Kennedy et al.)
• With the opening of the Landsat archive, more change detection initiatives have exploited dense time series of imagery (Wulder et al. 2012, RSE)
Kennedy, Cohen et al. (LandTrendr), Huang et al., Masek et al., (Vegetation Change Tracker), Vogelman et al., Goodwin et al., Schroeder et al.
• Most have studied temperate forested ecosystems – few the North ParkSPACE – Ivvavik National Park Masek et al. 2012, Fraser et al., 2012 Shrub • CCRS and Parks Canada investigated potential for using Landsat image stacks to monitor northern parks (ParkSPACE) 4. Current NWT Landsat Analysis
Landsat Study Regions
Goal: Investigate potential to use Landsat archive for monitoring a range of landscape changes in NWT CIMP
Study Regions: 1.Peel Plateau and Mackenzie Delta (NWT CIMP projects) 2.Great Slave Geological Province (TRACS projects) TRACS 4. Image Stack Change Method
1. Build 25-year 2. Extract Pixel Time 3. Derive Linear Trends in Landsat Image Stack Series Values Landsat Indices Cloud/shadow/SLC masking, TOA Unique database for each pixel of (e.g. Tasseled Cap Brightness, reflectance, peak-phenology six Vegetation Indices Greenness, Wetness) screening using AVHRR/MODIS
5. Create Trend Images 6. Relate TC Trends to Changes (RBG=TCB, TCG, TCW) in Vegetation Composition (Scale up high res training data using regression trees)
6. Change Classification Product (Decision tree classifier with ancillary GIS data) Methods: RGB Composite Trend Images for Visualizing Physical Changes 1985-2012 TC Brightness Trend 1985-2012 TC Greenness Trend 1985-2012 TC Wetness Trend
RGB Composite Image Interpretation Key B=Brightness Change (red channel) G=Greenness Change (green channel) Red = W=Wetness Change (blue channel) B ↓G ↓W draining lakes (e.g. vegbare, dev.) Yellow = B G ↓W (e.g. waterveg, fire regen) Blue = ↓B ↓G W (e.g. forest succession, fire slump disturbance) gravel pit Light Blue = ↓B G W (e.g. veg growth over bare) 5. Results: Density of Growing Season Landsat Observations (1985-2012)
Mean = 17 5. Results: Landscape Disturbance Examples
Wildfires Landsat TC Trends (1985-2012)
Dates indicated from GNWT fire mapping polygons Landsat TC Trends (1985-2012) – Inuvik Area
B=Brightness Change (red channel) G=Greenness Change (green channel) W=Wetness Change (blue channel)
1968 fire
Inuvik 2003 fire Landsat TC Trends (1985-2012) – Peel Plateau Thaw Slumps Trend trajectories related to decadal evolution of retrogressive slumps
Recent 20m SPOT imagery Landsat Trends (1985-2012) – Fire and Shallow Lake Drainage Higher prevalence of lake drainage in post-fire areas likely related to permafrost degradation
Landsat TC Trends (1985-2012)
Yellow = B G ↓W (e.g. waterveg)
GNWT ELC (2005) Landsat Trends (1985-2012) – Norman Wells Area (35km extent)
Regenerating Seismic Lines
Old Disturbance and Forest Succession
Old Canol Road 1984 Landsat Ch. 3 Yellowknife Area RGB Composite Change Image (1985-2011)
Dark Blue = Red = Light Blue = Yellow = ↓B ↓G W B ↓G ↓W ↓B G W B G ↓W (e.g. vegwater) (e.g. development) (e.g. veg growth) (e.g. waterveg)
2006 Landsat Ch. 3 Along Yellowknife Highway RGB Composite Change Image (1985-2011) Dark Blue = ↓B ↓G W
Red = B ↓G ↓W
1971 Fire regen New dev. Light Blue = ↓B G W
Old hwy
Great Slave Lake Yellow = B G ↓W Drying wetlands Drying and Greening of Wetlands on Great Slave Lake
Google Earth June 28, 2004. June 18, 2012 (south is up)
Landsat Wetness Trend
Great Slave Lake water levels since 1934
Landsat Period Mining Operations (New and Abandoned)
22 26
24
30 Landsat NDVI Trends 1984-2011 Increasing Tundra (positive trends in green, negative trends in red) Productivity / Shrub Growth
Pouliot et al. 2009 AVHRR NDVI Trends Increasing Tundra Productivity Near-Anniversary Date Landsat Images 8 Years Apart
(RGB=SWIRTOA,NIRTOA,RedTOA, non-stretched, leafy vegetation appear green) July 25, 1992 July 23, 2000
Alder thicket visible in 1950 Validation: Will reacquire 1:2,000 Colour-Infrared Air Photos Captured in 1980 (Sims, 1983)
Aug 6, 1980 Aug 8, 2013
Shrub Changes? Lichen Change?
Alder thicket visible in 1950
90 m Next Step: Developing Change Classification Products from Landsat Trends Training Database Change Classes (718 polygons) Training database Landsat VI Trends
Binary Change Mask (Threshold)
Decision Tree Classification
GIS Layers Expert Decision Rules For Spatial Context
Alder thicket visible in 1950 Change Classification Product Changes Detected Over NWT Study Regions using Landsat
Natural Anthropogenic • Wildfires and regen • Municipal developments • Thaw slumps • Mining – new footprint and • Lake drainage and erosion regeneration of abandoned • Greening / increased growth of mines shrubs • Highways – new and • Succession of old disturbances regeneration of borrow pits and • Vegetation flooding Thank You
Support from: NWT CIMP NRCan TRACS Project Polar Continental Shelf Project