DOI: 10.5061/dryad.1g1jwsv9g
title: Decreasing landscape carbon storage in western US forests with 2˚C of warming

description: Changing climate is altering the amount of carbon that can be sustained in
 forest ecosystems. Increasing heat and drought are already causing
 increased mortality and decreased regeneration in some locations. These
 changes have implications for landscape carbon storage with ongoing
 climate change. We used a climate analogs approach to project aboveground
 forest carbon density under +2 °C warming above the pre-industrial climate
 for western US forests. We calculated analogs for the current climate and
 under +2 °C warming and associated carbon density for each time period. We
 found that in most ecoregions, maximum carbon density values are projected
 to decline, and the interquartile range of carbon density values is
 projected to narrow. Using mean carbon density values, we project a 796 Tg
 decline in landscape carbon storage across the western US. As tree
 mortality increases, the transition from live to dead carbon will increase
 fuel buildup and fire hazard in many ecosystems. Greater fire hazard and
 increased susceptibility to insects from drought could cause carbon
 density changes to occur more rapidly than our climate-only projections.
 This may have substantial implications for forest-based carbon offset
 projects.
description: # Decreasing landscape carbon storage in western US forests with 2˚C of
 warming Dataset DOI: [10.5061/dryad.1g1jwsv9g](10.5061/dryad.1g1jwsv9g) ##
 Description of the data and file structure These data and code are for the
 manuscript 'Decreasing landscape carbon storage in western US forests
 with 2˚C of warming'. Data are from publicly available sources,
 including TerraClimate and TreeMap. The code uses these data to calculate
 analogs of carbon density under the projected +2 degrees C climate data
 from TerraClimate. **Usage Notes:** * **CSV**: Text files storing tabular
 data where rows represent observations and columns represent variables;
 viewable in text editors, spreadsheets, or analytical tools like R. *
 **TIFF/TIF**: Spatially referenced raster image files used for landscape
 data (e.g., vegetation, topography); viewable in GIS software or R. *
 **SHP**: Shapefiles store vector GIS data (points, lines, polygons) for
 geographic features; require accompanying files (.dbf, .prj, etc.) and can
 be used in R, Python, or GIS tools. * **R**: Script files containing R
 code for data processing, analysis, and visualization; comments start with
 `#` and are not executed. ### Files and variables #### File:
 treemap_w_us_crop_classify.tiff **Description:** 30m aboveground forest
 biomass data in Mg/ha from the TreeMap data set, which was developed by
 interpolating US Forest Service Forest Inventory and Analysis plot data
 ([https://doi.org/10.2737/RDS-2021-0074).](https://doi.org/10.2737/RDS-2021-0074) #### File: treemap_w_us_crop_classify_4km.tiff **Description:** 4km aboveground forest biomass data in Mg/ha. These are the 30m data aggregated to 4km to align with the 4km TerraClimate data. #### File: LF16_EVT_200_3.csv **Description:** Landfire Existing Vegetation Type data ([https://doi.org/10.5066/P1XVKXRL](https://doi.org/10.5066/P1XVKXRL)). These data provide the vegetation types associated with the TreeMap data. ##### Variables * VALUE: Ecological Systems code used by LANDFIRE * EVT_NAME: Ecological Systems name in the LANDFIRE EVT legend * LFRDB: Database value * EVT_FUEL: Ecological Systems code used for Fuel product development * EVT_FUEL_N: Ecological Systems class name used for Fuel product development * EVT_LF: Vegetation lifeform (e.g., Tree, Shrub, Herb, Sparse) * EVT_PHYS: Vegetation lifeform (e.g., Tree, Shrub, Herb, Sparse) * EVT_GP: Collapsed vegetation type code * EVT_GP_N: Collapsed vegetation type name (e.g., Grasslands and Steppes, Hammocks, Longleaf Pine) * SAF_SRM: Society of American Foresters/Society for Range Management cover type * SAF_SRM2: Society of American Foresters/Society for Range Management cover type 2 * EVT_ORDER: Vegetation Physiognomic Order (FGDC Classes) * EVT_CLASS: Vegetation Class (FGDC Classes) * EVT_SBCLS: Vegetation Subclass (FGDC Classes)  * R: Red color value range/255 * G: Green color value range/255 * B: Blue color value range/255 * RED: Red color value range 0 - 1 * GREEN: Green color value range 0 - 1 * BLUE: Blue color value range 0 - 1 #### File: new_SAF_SRM_2.csv **Description:** This is the forest and rangeland cover classification from the Society of American Foresters and Society for Rangeland Management ([https://www.fs.usda.gov/nrm/documents/fsveg/cse_user_guides/R3FG_appendix.pdf](https://www.fs.usda.gov/nrm/documents/fsveg/cse_user_guides/R3FG_appendix.pdf)). ##### Variables * ECO_NAME: Ecoregion name * SAF_SRM2_NEW: Crosswalk to Society of American Foresters and Society for Range Management cover type 2. * SAF_SRM2: Crosswalk to Society of American Foresters and Society for Range Management cover type 2. #### File: terraclimate_4km_1986_2015_climatevariables.tiff **Description:** TerraClimate data for the period 1986-2015, the reference period in our analysis. [https://www.climatologylab.org/terraclimate.html](https://www.climatologylab.org/terraclimate.html) #### File: ecoregion_nature_conservancy-20250804T211301Z-1-001.zip **Description:** A .shp file of western US ecoregions. #### File: W_us_TMIN_annual_2C_scaled_proj_1986_2015.tiff **Description:** Mean minimum monthly temperature (deg C) for the coldest month under +2 degrees C warming from TerraClimate. #### File: W_us_TMAX_annual_2C_scaled_proj_1986_2015.tiff **Description:** Mean maximum monthly temperature (deg C) for the warmest month under +2 degrees C warming from TerraClimate. #### File: W_us_CWD_annual_2C_scaled_proj_1986_2015.tiff **Description:** Mean annual climatic water deficit (mm) under +2 degrees C warming from TerraClimate. #### File: W_us_TMIN_annual_1986_2015.tiff **Description:** Mean minimum monthly temperature (deg C) for the coldest month from 1986-2015 from TerraClimate. #### File: W_us_AET_annual_2C_scaled_proj_1986_2015.tiff **Description:** Mean annual actual evapotranspiration (mm) under +2 degrees C warming from TerraClimate. #### File: W_us_CWD_annual_1986_2015.tiff **Description:**  Mean annual climatic water deficit (mm) from 1986-2015 from TerraClimate. #### File: W_us_TMAX_annual_1986_2015.tiff **Description:** Mean maximum monthly temperature (deg C) for the warmest month from 1986-2015 from TerraClimate. #### File: W_us_AET_annual_1986_2015.tiff **Description:** Mean annual actual evapotranspiration (mm) from 1986-2015 from TerraClimate. #### File: Conif_HUC12_shapefile-20250804T211205Z-1-001.zip **Description:** A .shp file of western US HUC12 watersheds. #### File: Part2-plotting_script.R **Description:** R script for generating the figures in the manuscript #### File: Part1-climate_analog_post_processing.R **Description:** R script for running the climate analog procedure ## Code/software The code is for R. We used R version 4.3.3 for the analysis and plotting.