Recent change in vegetation productivity and phenology across the Bathurst caribou range Katherine Dearborn 1,2 and Ryan Danby 2 1 Wilfrid Laurier University, Department of Biology (Waterloo, ON) 2 Queen’s University, Department of Geography and Planning (Kingston, ON)
Barren-Ground Caribou in Canada Government of the Northwest Territories
Bathurst Herd Rapid decline • 2003: 180,000 • 2015: 20,000 • 2018: 8200 Many possible causes of this decline
Northern Vegetation Change • Tundra “greening” and boreal “browning” Beck and Goetz 2011. Env. Res. Letters
Northern Vegetation Change • Earlier snowmelt, longer growing seasons Park et al. 2016. Env. Res. Letters
Vegetation Change & Caribou • “Greening” probably not good More tall shrubs = decline in lichen and • cottongrass Tall shrubs impede movement • • “Browning” might be good Thinning forests = increase in lichen? • • Earlier start to growing season probably good More forage available •
Research Questions 1. How has vegetation productivity and phenology changed within the Bathurst herd’s range over the past 18 years? 2. How do the direction and magnitude of this change vary between the calving grounds and the entire annual range ?
Methods – MODIS Data Vegetation index • data NDVI and EVI • 250-m resolution • 16-day composites • 406 images from • Feb. 2000 to Sep. 2017 May 09, 2000 May 25, 2000 Jun 10, 2000 31,321,351 pixels in • Jun 26, 2000 Jul 12, 2000 each image Jul 28, 2000
Methods – Curve Fitting • Fit a curve to EVI values for each pixel • Raw values were weighted by pixel quality Extracted slope and p-value of each regression 2000 2005 2010 2015
Results – Change in Productivity Sig. increase: Annual – 13.5% Calving – 8.6% Sig. decrease: Annual – 1.3% Calving – 0.5%
Results – Change in Length of Season Sig. increase: Annual – 15.9% Calving – 29.3% Sig. decrease: Annual – 0.0% Calving – 0.0%
Summary Spatial variability in type and rate of change: 1. Greening has occurred in summer portions of range, but not in calving grounds 2. Length of season has increased substantially in southern portion of calving grounds 3. Virtually no browning or decrease in length of growing season anywhere in the range
Discussion & Implications 1. Greening in summer range Less suitable forage for caribou? • A response to absence of caribou? • 2. Longer growing season in calving grounds Beneficial to caribou? • 3. Lack of browning trends Trends in boreal forest productivity are largely • driven by wildfire
Future Work Why has change been so spatially variable and how is it affecting the Bathurst herd? 1. Field sampling & shrub 2. Caribou movement analysis ring width analysis using GPS collar data Photo: GNWT
Acknowledgements Thanks to: Greg King, Carolyn Bonta, Robin Mennell, Joel Koop, Danielle Lebre, and • Emily Grishaber for their contributions to the project Lars Eklundh for help with Timesat software • Jennifer Baltzer for helpful suggestions along the way • GNWT for providing Bathurst herd range maps • This is part of Project #187 of the Government of the Northwest Territories Department of Environment and Natural Resources Cumulative Impact Monitoring Program Visit rangechange.ca for more info!
Thank-you! Questions?
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