Data and code from: Spatial selection undermines flood protection in U.S. wetland markets

Roychowdhury, Indumati 1 ; Moore, Frances 1

Published Oct 07, 2025; Updated Mar 11, 2026 on Dryad. https://doi.org/10.5061/dryad.b5mkkwhrr

Abstract

Wetland mitigation markets aim to offset environmental damage by allowing developers to purchase credits from previously restored wetlands. We test whether wetland credits traded in these markets offer equivalent flood protection benefits. Using newly developed, high-resolution estimates of wetland flood protection for 915 wetland markets within the continental U.S., we document a likely decline in flood-protective value due to wetland loss over the 1985 to 2021 period. Consistent with standard models of urban economic geography, wetlands lost to development exist near prior developed areas and therefore provide relatively high levels of downstream flood protection compared to wetlands created in compensation--on average 4.1 times as much, though in some cases up to 78 times. We document a high concentration of lost flood protection in Florida. While wetland markets may succeed in preserving total wetland acreage, they may systematically fail to preserve downstream flood protection services. More generally, this suggests that designing environmental markets to preserve complex bundles of spatially heterogeneous ecosystem services while still allowing meaningful compliance flexibility may be challenging.

Roychowdhury, Indumati; Moore, Frances (Forthcoming 2026). Data and code from: Spatial selection undermines flood protection in U.S. wetland markets [Dataset]. Dryad. https://doi.org/10.5061/dryad.b5mkkwhrr

Description of the data and file structure

We created a nationwide 30 m raster dataset to analyze flood protection value in wetland mitigation banks across the continental United States.

Files and variables

Data

footprints_and_buffers.shp (or footprints_and_buffers.rds): Shapefile of mitigation bank footprint polygons.
ServiceAreas_agg.shp (or ServiceAreas_agg.rds): Shapefile of mitigation bank service area polygons.
service_area_huc12_to_downstream_tracts.csv: raw output of "Upstream_iteration.ipynb", one column is HUC12 watersheds and the other column is a list of downstream census tracts.
htdt_conus.rds: Dataframe relating HUC12 watershed boundaries to all respective downstream census tracts.
huc12_boundaries.gpkg: Shapefile of HUC12 watershed polygons for the entire U.S.
LCMAP_CU_1985_V13_LCPRI.tif: Raster of land cover data from the USGS LCMAP product for 1985.
LCMAP_CU_2021_V13_LCPRI.tif: Raster of land cover data from the USGS LCMAP product for 2021.
places_fmv_vacant.tif: Raster of vacant land value data from Nolte (2020): https://doi.org/10.5061/dryad.np5hqbzq9

Code/software

We use RStudio version 4.5.1 to run all code, with the exception of one script run in Python version 3.13.0.

Script Files

create_variables.R

Creates and cleans necessary variables for analysis, including wetland raster generation, census data retrieval, and watershed-to-tract mapping.

Upstream_iteration.ipynb

Maps HUC12 watersheds to their downstream census tracts.

run_conus.R

Defines and applies a distance-decay function to wetland pixels across all mitigation banks, saving output as classified HUC12 watershed rasters.

missing_huc12s_analysis.R

Applies the distance-decay function to missing HUC12s where downstream tract centroids were out of range, assuming uniform population distribution.

run_wetlandloss.R

Identical to Run_conus.R but applied to raster of wetland loss (wetland-to-development conversion between 1985 and 2021).

mosaic.R

Stitches together individual HUC12 classified rasters into larger mitigation bank service area rasters.

extract_cell_values.R

Extracts classified cell values into dataframes for each bank footprint and service area. Also applies to the classified wetland loss raster.

summarize_ecdf_fn.R

Computes empirical cumulative distribution functions (ECDFs) for extracted cell values in each service area, for both existing and lost wetlands.

pooling.R

Creates pooling and pool mapping for mitigation banks with identical service areas geometries.

generate_main_figures.R

Generates the primary figures used in the manuscript.

generate_supp_figures.R

Produces supplemental figures for the manuscript.