Caribou density and vegetation change

Project summary

Rapid climate warming has contributed to significant changes in Arctic and boreal vegetation over the past half century. Changes in vegetation can impact wildlife by altering habitat and forage availability, which can affect behavior and range use. However, animals can also influence vegetation through foraging and trampling and therefore play an important role in determining ecosystem responses to climate change. As wildlife populations grow, density-dependent processes can prompt range expansion or shifts. One mechanism for this is density-dependent forage reduction, which can contribute to nutritional stress and population declines, and can also alter vegetation change trajectories. We assessed the range characteristics of a migratory caribou (Rangifer tarandus) herd in east-central Alaska and west-central Yukon Territory as it grew (1992-2017) then declined (2017-2020). Furthermore, we analyzed the correlation between caribou relative spatial density and vegetation change over this period using remotely-sensed models of plant functional type cover.

Project correspondence:

Kathleen M. Orndahl [email protected]

Repository summary

This repository includes scripts and data for:

• Creating range polygons and spatial density rasters from caribou collar data
• Analyzing changes in caribou range attributes over time
• Analyzing the correlation between caribou spatial density and vegetation changes

Note that caribou collar data and some derivative products are classified as sensitive data. To request access to these data, please contact:

Torsten Bentzen, Wildlife Biologist Division of Wildlife Conservation Alaska Department of Fish and Game [email protected]

Specific information on data characteristics to included in potential requests are provided in individual scripts.

Repository details

Scripts are prepended with numbers for organization, see details below for script groupings and code type (in parentheses):

1. Process caribou collar data to produce annual, seasonal isopleths and occurrence distributions (R)
2. Tidy annual, seasonal isopleth data (R)
3. Process annual, seasonal occurrence distribution data to produce derivative products (R)
4. Summarize isopleths by season (R)
5. Calculate vegetation change within caribou spatial density levels (Google Earth Engine)
6. Calculate background rates of vegetation change (Google Earth Engine)
7. Create time series of relevant climate variables (R)
8. Create figures (R)