Grassland & Savanna Extent (Southeast Conservation Blueprint Indicator)

Reason for Selection Native grasslands and savannas are important for many endemic species, provide critical habitat and food for pollinators, and are often hotspots for biodiversity. Once a predominant ecosystem type, grasslands and savannas have significantly declined from their historical extent. In part because of the regular disturbance (e.g., mowing, fire) typically required to maintain high-quality grasslands, they are difficult to detect through remote sensing and are not well-captured by other indicators. In addition, grassland and savanna birds are experiencing significant declines and are [currently off-track for meeting the SECAS 10% goal], so it is important that the Blueprint capture known and potential habitat. Input Data * [Texas Ecological Mapping Systems]: [statewide raster], accessed 12-2023 * [Oklahoma Ecological Systems Map]: [download the raster], accessed 12-2023 * [Protected Areas Database of the United States] (PAD-US): [PAD-US 3.0] national geodatabase - Combined Proclamation Marine Fee Designation Easement; [PAD-US 4.0] national geodatabase - Combined Proclamation Marine Fee Designation Easement * [National Land Cover Database] (NLCD): [2021 Land Cover], [2021 U.S. Forest Service (USFS) Tree Canopy Cover], [2013 Land Cover] (from 2016 data release), and [2013 USFS Tree Canopy Cover] (from 2021 data release) * 2020 [LANDFIRE Biophysical Settings] (BPS) [LF 2.2.0]; [access the data] * 2020 [LANDFIRE Existing Vegetation Type] (EVT) [LF 2.2.0]; [access the data] * U.S. Geological Survey (USGS) [Watershed Boundary Dataset] (WBD), accessed 1-5-2023: HUC12s; [download the data] * [Southeast Blueprint 2025 extent] Known grasslands * Known grassland prairies dataset for the Middle Southeast subregion, provided by Toby Gray with Mississippi State University in Oct 2020 (available on request by emailing [rua_mordecai@fws.gov]); this is an improved version of the [Known Prairie Patches in the Gulf Coastal Plains and Ozarks (GCPO)] layer * Known Piedmont prairie locations in the South Atlantic subregion: We identified known prairie locations by requesting spatial data on known prairies from the 74 members of the Piedmont Prairie Partnership mailing list and other prairie managers (Wake County Open Space program and Prairie Ridge Ecostation in NC). We combined that information with known locations in Virginia aggregated by the Virginia Natural Heritage Program (available on request by emailing [rua_mordecai@fws.gov]). * Grassland polygons from the Catawba Indian Nation, provided by Aaron Baumgardner, Natural Resources Director, in July 2023 (for more information email [rua_mordecai@fws.gov]) * Grassland polygons from two iNaturalist projects in Texas: [erwin-park-prairie-restoration-area], [stella-rowan-prairie] * Confirmed prairie remnants and prairie plantings from the 2017 U.S. Geological Survey (USGS) [grassland quality and pollinator habitat potential in Southwest Louisiana] project * [Dixon Water Foundation Texas ranch boundaries], accessed 4-8-2025 * Lathrop Island, FL savanna boundaries, provided on 3-24-2025 by the U.S. Fish and Wildlife Service (U.S. FWS), available on request ([rua_mordecai@fws.gov]) * Smiley Meadow Preserve boundaries, provided in October 2024 by The Nature Conservancy (TNC) Texas (also available on [the ]TNC lands public layer) * Grassland polygons for Key Cave National Wildlife Refuge in Alabama, provided by the U.S. FWS on 3-30-2023, available on request ([rua_mordecai@fws.gov]) * Southeastern Grasslands Institute polygons from [selected iNaturalist projects]. We used only projects with polygons digitized at a fine resolution and did not include projects with more coarse polygons covering a large area. Specific projects used were: * allegheny-mountains-riverscour-barrens, big-south-fork-riverscour-barrens-1, big-south-fork-riverscour-barrens-2, big-south-fork-riverscour-barrens-4-us, big-south-fork-riverscour-barrens-6, biodiversity-of-piedmont-granite-glades-outcrops, bluff-mountain-fen, caney-fork-sandstone-riverscour-barrens-and-glades, clear-creek-sandstone-riverscour-barrens, clear-fork-river-riverscour-barrens, craggy-mountains-mafic-outcrops-and-barrens, cumberland-plateau-escarpment-limestone-barrens, cumberland-river-limestone-riverscour-glades, daddy-s-creek-riverscour-barrens, dunbar-cave-prairie-restoration, eastern-highland-rim-limestone-riverscour-glade, emory-river-sandstone-riverscour-barrens, falls-of-the-ohio-river-limestone-riverscour-glade, flat-rock-cedar-glades-and-barrens-state-natural-area, grasshopper-hollow-fen, gunstocker-glade, hiwassee-river-phyllite-riverscour-glade, ketona-dolomite-barrens, laurel-river-riverscour-barrens-and-glades, lime-hills-limestone-barrens, limestone-barrens-of-the-western-valley-of-the-tennessee-river, little-mountains-limestone-barrens, little-river-canyon-riverscour-barrens-and-glades, moulton-valley-limestone-glades, mulberry-fork-of-black-warrior-river-riverscour-barrens-and-glades, muldraugh-s-hill-limestone-barrens, nashville- basin-limestone-glades, new-river-riverscour-barrens, obed-river-sandstone-riverscour-barrens, outer-bluegrass-dolomite-barrens, ridge-and-valley-sandstone-outcrops, rock-creek-sandstone-riverscour-barrens, rockcastle-river-sandstone-riverscour-barrens, shawnee-hills-sandstone-glades-and-outcrops, southern-blue-ridge-mountains-grass-balds, southern-blue-ridge-mountains-serpentine-barrens, southern-blue-ridge-phyllite-outcrops, southern-ridge-and-valley-limestone-glades, southern-ridge-and-valley-shale-barrens, southern-ridge-and-valley-siltstone-barrens, tennessee-ridge-and-valley-dolomite-barrens-and-woodlands-tn-us, the-farm-prairie-and-oak-savanna, tin-top-road-savanna, western-allegheny-escarpment-limestone-barrens, western-highland-rim-limestone-glade-and-barrens, western-valley-limestone-barrens-decatur-co-north-us, western-valley-limestone-barrens-hardin-wayne-cos, western-valley-limestone-barrens-perry-co, western-valley-silurian-limestone-barrens, white-s-creek-sandstone-riverscour-barrens-and-glades, folder-six-glades Mapping Steps * Combine all known grasslands polygons into one layer and convert to raster. Create a mask based on 2021 NLCD classes ‘Developed, medium intensity’ (23) and ‘Developed, high intensity’ (24) to remove parts of the known grasslands that have been recently developed. Assign the remaining known grassland pixels a value of 7. * From the 2021 and 2013 NLCD landcover, create two rasters that only include classes with possible grasslands and savannas (one for each timestep). The classes included are based on NLCD classes that overlap known grassland and savanna polygons. Any class that covered >1% of known grasslands and savannas is included: 31 Barren Land, 41 Deciduous Forest, 42 Evergreen Forest, 43 Mixed Forest, 52 Scrub/Shrub, 71 Grassland/Herbaceous, 81 Pasture/Hay. * Use LANDFIRE EVT group name (EVT_GP_N = ‘Longleaf Pine Woodland’) to add as possible grasslands wet longleaf pine savannas that can be classified as forested wetland by NLCD. Add these to both the 2013 and 2021 possible grassland and savanna timesteps. * Use LANDFIRE BPS to identify historic grasslands in the western part of the region that wouldn’t typically have trees by selecting the following values in the BPS_NAME field: ‘Southern Blackland Tallgrass Prairie’, ‘Central Mixedgrass Prairie’, ‘Chihuahuan Loamy Plains Desert Grassland’, ‘Southeastern Great Plains Tallgrass Prairie’, ‘Western Great Plains Sand Prairie’, ‘Western Great Plains Shortgrass Prairie’. This will be used to define where canopy cover thresholds apply in the next step. * For the two possible grassland and savanna rasters created above, use the 2013 and 2021 NLCD USFS Tree Canopy Cover to refine the depiction of potential grasslands and savannas for each year. Remove 1) forest with ≥ 60% canopy cover and 2) Western relatively treeless grasslands with >0% canopy cover (as defined by the LANDFIRE BPS earlier). * Make a combined possible grassland and savanna raster that only includes pixels that are possible grasslands and savannas in both 2013 and 2021. This removes temporary grasslands and savannas that result from clearcuts. * From the Texas and Oklahoma ecological systems maps, extract classes that predict areas invaded by mesquite, a non-native tree that spreads aggressively in the grasslands and savannas of the Southwest and disrupts natural ecosystems through its heavy water consumption. For Oklahoma, this is VegName = ‘Ruderal Mesquite Shrubland’. For Texas, this is CommonName = ‘Native Invasive: Mesquite Shrubland’. Combine these and use them to remove from the possible grasslands and savannas layer areas that are no longer grassland or savanna due to mesquite invasion. The resulting layer represents potential grasslands and savannas. * To identify likely grasslands and savannas, overlay the potential grasslands and savannas raster with select polygons from PAD-US 4.0. To pull out types of protected lands that commonly manage grasslands and savannas, we used GAP status, designation type, manager name, and easement holder. We also identified a number of protected areas directly by name that had important areas of grassland and savanna but weren’t captured by the other rules. * GAP status (GAP_sts) 1 or 2: Gap status 1 and 2 refer to areas managed for biodiversity that are not subject to extractive uses like logging and mining. GAP status 2 is technically intended to encompass areas where disturbance events are suppressed, but in practice, most protected areas in the Southeast that actively manage grasslands and savannas are classified as GAP status 2. * Designation type (Des_Tp) of ‘NWR’, ‘MIL’, ‘NF’, or ‘NG’ (i.e. National Wildlife Refuge, military installation, National Forest, or National Grassland) * Manager name (Mang_Name) of ‘RWD’ (i.e. Regional Water District) * Local manager name (Loc_Mang) of ‘Ducks Unlimited (Wetlands America Trust)’ * Easement holder (EsmtHldr) of ‘Tall Timbers Research Station & Land Conservancy’ * Unit name (Unit_Nm) of ‘Point Washington State Forest’, ‘Pine Log State Forest’, ‘M. C. Davis - Seven Runs Creek Conservation Easement’, ‘Nokuse Plantation Conservation Easements’, ‘Tate’s Hell State Forest’, ‘Box-R Wildlife Management Area’, ‘Aucilla Wildlife Management Area’, ‘Snipe Island Unit’, ‘Big Bend Wildlife Management Area’, ‘Goethe State Forest’, ‘Amelia Wildlife Management Area’, ‘Powhatan Wildlife Management Area’, ‘Cumberland State Forest’, ‘Appomattox-Buckingham State Forest’, ‘Haw River State Park’, ‘R. Wayne Bailey - Caswell Game Land’, ‘Medoc Mountain State Park’, ‘Embro Game Land’, ‘Dupont State Forest’, ‘Hanging Rock State Park’, ‘Bladen Lakes State Forest’, ‘Whitehall Plantation Game Land’, ‘Suggs Mill Pond Game Land’, ‘Bushy Lake State Natural Area’, ‘Pondberry Bay Plant Conservation Preserve’, ‘Green Swamp Game Land’, ‘Holly Shelter Game Land’, ‘Chowan Swamp Game Land’, ‘Brookgreen Gardens’, ‘Cary State Forest’, ‘Suwannee Ridge Mitigation Park Wildlife and Environmental Area’, ‘Adams-Alapha Ag & Conservation Easement’, ‘Twin Rivers State Forest’, ‘Chattahoochee Fall Line Wildlife Management Area’, ‘Enon Plantation’, or ‘Georgia-Alabama Land Trust Easement #214’, ‘Covington Wildlife Management Area’, ’ Magnolia Branch Wildlife Reserve’, ‘Little River State Forest’, or ‘Susan Turner Plantation’, or have the local name (Loc_Nm) ‘Sandhills Game Land’, ‘Blackwater River State Forest’, ‘Three Lakes Wildlife Management Area’, ‘Herky Huffman/Bull Creek Wildlife Management Area’, ‘Triple N Ranch Wildlife Management Area’, ‘Whaley Conservation Easement’, ‘Babcock Ranch Preserve’, ‘Withlacoochee State Forest’, ‘Lake Wales Ridge State Forest’, ‘EVERGLADES HEADWATERS NATIONAL WILDLIFE REFUGE AND CONSERVATION AREA’, ‘Seminole State Forest’, ‘Schofield Tract’, ‘LAKE WALES RIDGE NATIONAL WILDLIFE REFUGE’, ‘Platt Branch Mitigation Park Wildlife and Environmental Area’, ‘Fisheating Creek/Lykes Brothers Conservation Easement’, ‘Bright Hour Watershed’, ‘Fred C. Babcock-Cecil M. Webb Wildlife Management Area’, or ‘BICY’ * PAD-US 4.0 is missing state wildlife management area boundaries in Oklahoma. Extract those from PAD 3.0 by using a combination of state name, designation, and GAP status criteria: State_Nm = ‘OK’ AND Loc_Ds = ‘State Wildlife Management Area’ AND GAP_Sts IN (‘1’,’2’). Add the results to the polygons from PAD-US 4.0 generated in the previous step. * Many areas of city-owned land in PAD-US are classified as GAP status 2, but don’t appear to be managed for biodiversity. These are often golf courses, ball fields, and other recreational amenities that are not beneficial for biodiversity. Further filter the merged PAD-US layer to include only GAP 2 city-owned land (Mang_Name = ‘CITY’) if it has the following local designations: ‘Conservation Area’, ‘Conservation Park’, ‘Local Conservation Area’, ‘Natural Area’, ‘Nature Park’, ‘Nature Preserve’, ‘Nature Reserve’, ‘Preserve’, ‘Regional Nature Preserve’, ‘Wildlife Area’, or ‘Wildlife Refuge’. * Use the ArcGIS Region Group function to remove any single isolated likely grassland and savanna pixels. Single isolated pixels are often mapping errors that do not represent ecosystems within the intended scope of this indicator. The resulting layer represents likely grasslands. * Use Region Group to separate patches of likely grassland and savanna that are >10 acres and those that are ≤10 acres. Grassland birds like grasshopper sparrows avoid patches <10 acres (Dechant et al. 2002, Slater 2004). Assign pixels in >10 acre patches a value of 6 and those in <10 acre patches a value of 5. * Use Region Group to identify likely grassland and savanna patches >5 acres to use as cores for identifying pollinator buffers. While important pollinators can persist in patches smaller than those needed for grasslands birds, larger patches are more likely to support the diversity of plants and nesting habitat needed to support a diverse pollinator community. * Combine known grasslands and savannas with likely grassland and savanna patches >5 acres into a single class to create pollinator buffers. Buffer by 300 m to align with foraging distances for solitary bees (Antoine and Forrest 2021, Zurbuchen et al. 2010). * Use NLCD 2021 to remove any open water in the pollinator buffers. Assign the remaining pollinator buffer pixels a value of 4. * Use the Zonal Statistics function to identify HUC12 subwatersheds that contain at least one known or likely grassland/savanna patch >5 acres. These subwatersheds will be the grassland/savanna hubs. This is intended to elevate potential grasslands that are nearby other established grassland patches. We used subwatersheds as the summary unit because they are: 1) ecologically based boundaries 2) smaller than counties, and 3) a unit often used to focus conservation actions. The output from this step is “HUC12_knownOrLikely5acPlus.tif”, which is also used in the grassland and savanna restoration indicator. * Use LANDFIRE Biophysical Settings to create a raster of places with a historic fire interval (FRI_ALLFIR) of 9 years or less. That aligns with the role of regular fire in maintaining the grasslands and savannas of the Southeast. * Add additional historic grassland and savanna areas where the LANDFIRE BPS vegetation group (GROUPVEG) is either ‘Savanna’ or ‘Grassland’. That adds other grasslands and savannas that are maintained by disturbance other than fire. * Remove areas where the LANDFIRE BPS vegetation group (GROUPVEG) is ‘Shrubland’. This removes historic shrublands that were introduced based on fire history. * Use 2021 NLCD to remove any areas classified as 95 Emergent Herbaceous Wetlands from the historic grasslands and savannas layer to remove fresh and saltwater marshes. Assign the remaining historic grasslands pixels a value of 1. The output from this step is “historicGrass_notMarsh.tif”, which is also used in the grassland and savanna restoration indicator. * Use conditional statements to combine all rasters together to get the final indicator values, retaining the highest value a pixel can have. * Create an additional output layer to be used in the grassland and savanna restoration indicator (“testHistoricNotCurrentGrass_selectedPAD_SECAS.tif”). To get this layer, first use Extract by Mask to identify historic grassland and savanna in protected lands that commonly manage grasslands and savannas. This is based on two rasters created earlier in the mapping steps. Then remove areas that are currently potential, likely, or known grasslands. That results in a layer depicting areas that are historically but not currently grassland or savanna and are in protected lands that commonly manage grasslands and savannas. * Adding zero values helps users better understand the extent of this indicator and makes this indicator layer perform better in online tools. Any pixel within the extent of the HUC12 subwatersheds that does not receive a score from the above steps receives a value of 0 (not identified as grassland/savanna). All pixels outside the extent of the HUC12 subwatersheds (i.e., ocean) are coded as NoData. * As a final step, clip to the spatial extent of Southeast Blueprint 2025. Note: For more details on the mapping steps, code used to create this layer is available [in the Southeast Blueprint 2025 Data Download] under > 6_Code. Final indicator values Indicator values are assigned as follows: 7 = Known grassland/savanna 6 = Likely grassland/savanna >10 acres 5 = Likely grassland/savanna ≤10 acres 4 = Pollinator buffer around known or likely grassland/savanna 3 = Potential grassland/savanna in grassland/savanna hub 2 = Potential grassland/savanna outside grassland/savanna hub 1 = Historic grassland/savanna 0 = Not identified as grassland/savanna Known Issues * Some known grassland and savanna locations are omitted due to confidentiality concerns around potential poaching and disturbance of rare plant species. * Some important grasslands and savannas on private land and in protected areas managed for multiple use are underprioritized. * Some small areas of non-grassland and non-savanna are overprioritized due to the coarseness of the 30 m NLCD pixels. This often happens in places where a single pixel overlaps with both a dirt road and dense forest. That overlap makes it look like a savanna. Roadside edges in general are a challenge for this indicator. Roadsides can be important refugia for many grassland and savanna plants, so the indicator does not remove then. However, this also results in many roadsides being overprioritized. * Some small areas of savanna and sections of powerline rights-of-way are underprioritized due to the coarseness of the 30 m NLCD pixels. This often happens where a single 30 m pixel overlaps with an area where >60% of the pixel looks forested, despite there being significant savanna-like openings in the remaining 40%. * Some grasslands that have been fully invaded by shrubs other than mesquite are overprioritized. * This indicator may underestimate the extent of historic grasslands and savannas in the Kentucky portions of the Western Pennyroyal Plain. LANDFIRE predicts grassland and savanna in this area but also includes more extensive areas of wet forests with closed canopies than other sources. Much of this area is now converted to agriculture, making it more difficult to estimate historic conditions. * This indicator overestimates likely grasslands in some areas in the Everglades Headwaters National Wildlife Refuge proclamation boundary. Many, but not all, pastures in that area function similarly to native grasslands. * This indicator overestimates likely grasslands in some areas of beach without vegetation (e.g., Santa Rosa Island just west of Destin, FL). Methods to improve this issue in the future are under development. * Some temporary grasslands in tree plantations, which are probably no longer grasslands now, are still included in the indicator. While the indicator attempts to remove temporary grasslands from tree plantations, a relatively small number of pixels do get missed by the current methods. Improved remote sensing products could fix this issue in the near future. Disclaimer: Comparing with Older Indicator Versions There are numerous problems with using Southeast Blueprint indicators for change analysis. Please consult Blueprint staff if you would like to do this (email [hilary_morris@fws.gov]). Literature Cited Antoine C. M., Forrest J. R. K. (2021). Nesting habitat of ground-nesting bees: a review. Ecol. Entomol. 46, 143–159. doi: 10.1111/een.12986. [[https://resjournals.onlinelibrary.wiley.com/doi/full/10.1111/een.12986]]. Baldwin, H.Q., Allain, L.K., and Hartley, S.B., 2017, Grassland quality and pollinator habitat potential in Southwest Louisiana: U.S. Geological Survey data release. [[https://doi.org/10.5066/F76M359X]]. Dechant, J. A., M. L. Sondreal, D. H. Johnson, L. D. Igl, C. M. Goldade, M. P. Nenneman, and B. R. Euliss. 1998 (revised 2002). Effects of management practices on grassland birds: Grasshopper Sparrow. Northern Prairie Wildlife Research Center, Jamestown, ND. 28 pages. [[https://pubs.usgs.gov/unnumbered/93877/report.pdf]]. Dewitz, J., 2023, National Land Cover Database (NLCD) 2021 Products: U.S. Geological Survey data release. [[https://doi.org/10.5066/P9JZ7AO3]]. Dewitz, J., 2019, National Land Cover Database (NLCD) 2016 Products (ver. 3.0, November 2023): U.S. Geological Survey data release. [[https://doi.org/10.5066/P96HHBIE]]. Landscape Fire and Resource Management Planning Tools (LANDFIRE), Earth Resources Observation and Science Center (EROS), U.S. Geological Survey. Published 2022-09-28. LANDFIRE 2020 Biophysical Settings (BPS) CONUS. LF 2020. Raster digital data. Sioux Falls, SD. [[https://landfire.gov/vegetation/bps]]. Landscape Fire and Resource Management Planning Tools (LANDFIRE), Earth Resources Observation and Science Center (EROS), U.S. Geological Survey. Published 2022-09-28. LANDFIRE 2020 Existing Vegetation Type (EVT) CONUS. LF 2020. Raster digital data. Sioux Falls, SD. [[https://landfire.gov/vegetation/evt]]. Slater, G.L. (2004, October 7). Grasshopper Sparrow (Ammodramus savannarum): a technical conservation assessment. [Online]. USDA Forest Service, Rocky Mountain Region. Accessed February 24, 2024. [[https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5182057.pdf]]. Southeast Conservation Adaptation Strategy. 2021. Recent Trends in Southeastern Ecosystems (2021): Measuring Progress toward the SECAS Goal. [[https://secassoutheast.org/pdf/SECAS-goal-report-2021.pdf]]. U.S. Department of Agriculture, Natural Resources Conservation Service. 2010. Management considerations for grassland birds in northeastern haylands and pasturelands. Wildlife Insight. Washington, D.C. [[https://www.bobolinkproject.com/docs/NRCS_Grassland_leaflet.pdf]]. U.S. Geological Survey (USGS) Gap Analysis Project (GAP), 2022, Protected Areas Database of the United States (PAD-US) 3.0: U.S. Geological Survey data release. [[https://doi.org/10.5066/P9Q9LQ4B]]. U.S. Geological Survey (USGS) Gap Analysis Project (GAP), 2024, Protected Areas Database of the United States (PAD-US) 4: U.S. Geological Survey data release. [[https://doi.org/10.5066/P96WBCHS]]. Yang, L., Jin, S., Danielson, P., Homer, C., Gass, L., Case, A., Costello, C., Dewitz, J., Fry, J., Funk, M., Grannemann, B., Rigge, M. and G. Xian. 2018. A New Generation of the United States National Land Cover Database: Requirements, Research Priorities, Design, and Implementation Strategies, ISPRS Journal of Photogrammetry and Remote Sensing, 146, pp.108-123. [[https://doi.org/10.1016/j.isprsjprs.2018.09.006]]. Zurbuchen, A., Landert, L., Klaiber, J., Mueller, A., Hein, S., Dorn, S., 2010. Maximum foraging ranges in solitary bees: only few individuals have the capability to cover long foraging distances. Biol. Conserv. 143, 669–676. [[https://doi.org/10.1016/j.biocon.2009.12.003]].