NoVA Protected Lands and Conservation Easement Atlas

OverviewDataset Summary

This is the first unit-level protected-lands inventory published specifically for Northern Virginia: every fee-owned protected area and conservation easement in USGS PAD-US 4.1 that touches the nine jurisdictions, cleaned of 1,180 duplicate records (36.7 percent of the raw extract), clipped to the region, and cross-validated against the Virginia DCR Conservation Lands Database with 96.8 percent footprint agreement. The deduplicated atlas holds 2,034 units - 1,296 fee tracts and 738 conservation easements - whose dissolved footprint covers 127,763 acres, 15.3 percent of NoVA's land.

Attribution per unit includes GAP protection status (the federal biodiversity-mandate scale), public access, owner and manager, normalized easement holder, establishment year where recorded, and NoVA-clipped acreage. Military installations (32,563 acres: MCB Quantico, Fort Belvoir, Arlington National Cemetery and six smaller sites) ship as a separate reference layer excluded from every statistic, following PAD-US convention for proclamation boundaries.

Why This DatasetThe Problem It Solves

Ask how much of Northern Virginia is protected and you will not find an answer - PAD-US is national and duplicate-ridden, DCR's database is statewide with different conventions, and no county publishes a regional rollup. Meanwhile the region is in a land-use collision: the world's largest data center market expanding westward, a Rural Crescent under rezoning pressure, county open-space goals citing "30x30", and a conservation easement movement that has quietly locked up a sixth of Loudoun County. Planners, land trusts, and developers are all negotiating against a protected-lands base map that did not exist.

This atlas answers the question with defensible numbers: which land is protected, by what mechanism, held by whom, open to whom, and with what level of legal permanence - unit by unit, jurisdiction by jurisdiction.

MethodologyHow It Was Built

All Virginia PAD-US 4.1 Fee and Easement features intersecting a NoVA envelope were fetched from the USGS ArcGIS service (5,135 raw features), geometry-repaired, clipped to the 9-jurisdiction union built from Census TIGERweb county boundaries, and stripped of sub-0.1-acre boundary slivers. Acreage was recomputed on clipped geometry in EPSG:32618; each unit was assigned to its largest-overlap jurisdiction (78 units cross boundary lines).

Deduplication: PAD-US aggregates the same easement from multiple submitters - Virginia Outdoors Foundation easements appear under two holder spellings whose footprints overlap on 24,630 of 24,709 acres. After holder-name normalization, a greedy spatial pass removed any feature at least 60 percent covered by the union of already-kept features in its holder group (easements) or unit-name/jurisdiction group (fee): 1,180 duplicates out, 2,034 units kept, and every statistic recomputed.

Jurisdiction statistics use dissolved footprints (union of geometries), so residual overlaps are never double-counted. Separate footprints were computed for fee, easement, GAP 1-2, and open-access subsets against TIGER land area. Military boundaries came from the PAD-US Proclamation class (Des_Tp=MIL). Cross-validation against the DCR Conservation Lands Database (1,899 clipped units) showed 96.8 percent footprint agreement, with every residual discrepancy researched and documented. A haversine DBSCAN (eps 1,500 m, min_samples 5) on the 738 easement points resolved 19 conservation corridor clusters.

Key FindingsWhat the Data Shows

• NoVA is halfway to "30x30" on paper, but not in substance. 15.3 percent of the land base is protected, yet only 3.6 percent (29,881 ac) carries GAP 1-2 biodiversity protection.
• Two conservation models split the region. Fairfax County: 17.1 percent protected, 98 percent fee-owned public land. Loudoun County: 16.4 percent protected, 87 percent private easements (47,280 ac). Prince William County holds the biodiversity core - 7.1 percent of its land is GAP 1-2, led by 12,200-acre Prince William Forest Park.
• The Virginia Outdoors Foundation holds 51 percent of all easement acreage - 178 easements, 27,696 dissolved acres. Old Dominion Land Conservancy (10,353 ac), Land Trust of Virginia (6,921 ac), NVCT (117 easements, 3,055 ac) and the Virginia Board of Historic Resources (120 easements, 3,016 ac) follow.
• DBSCAN resolves 19 easement clusters, 11 in Loudoun (36,356 of about 41,000 clustered acres). The largest - 151 easements, 18,738 acres - fills the Between-the-Hills / Catoctin corridor of western Loudoun.
• The inner suburbs conserve almost nothing for biodiversity: Arlington, Alexandria, Fairfax City, Falls Church and Manassas all sit at 0.00-0.05 percent GAP 1-2.
• Manassas Park City is the proportional leader at 17.3 percent protected - essentially the 247-acre Blooms Park complex on Bull Run, also the region's highest GAP 1-2 share (12.8 percent).
• Only 42 percent of the protected footprint is open to the public. Fairfax's fee parkland provides 36,568 open-access acres; easement-heavy Loudoun offers 8,171 against 47,280 acres of predominantly closed easement land.

Analytical UsesWhat You Can Do With This

• 30x30 and open-space goal tracking: dissolved GAP-status footprints give planners a defensible, repeatable baseline for conservation reporting.
• Development due diligence: screen parcels for recorded conservation encumbrances before acquisition - the western Loudoun easement belt is an 18,700-acre-plus no-build landscape invisible in zoning maps.
• Land trust targeting: the cluster geography shows where easement outreach has saturated versus thin - Prince William's Rural Crescent holds just 5,050 easement acres.
• Data center siting: overlay against transmission corridors to see where the easement belt constrains westward expansion of the Loudoun/Prince William market.
• Park equity: join the open-access footprint to census demographics to quantify who actually has access to the protected land base.

Synthesis OpportunitiesWhat It Combines With

Protected lands x data center inventory (Days 7/33): buffer the easement belt against substation and transmission corridors to map the developable-land squeeze on the westward data center frontier - a quantified constraint map for the region's dominant industry.

Protected lands x tree canopy change (Day 48): compare 2011-2021 canopy trajectories inside versus outside the protected footprint, per GAP class - an empirical protection-effectiveness test of whether easements actually hold canopy.

Open-access footprint x park access gap (park-access day): recompute green-space deserts counting only genuinely open-access protected land; closed easements and restricted federal land drop out of the supply side.

Easement clusters x wetland development pressure (Day 53): intersect high-pressure wetland clusters with the unprotected gaps between easement clusters to produce a ranked acquisition list for land trusts.

LimitationsKnown Caveats

• Military lands excluded by design: MCB Quantico (23,018 NoVA ac), Fort Belvoir (8,323 ac), Arlington National Cemetery and six smaller DOD sites live in the military_installations reference layer, not the statistics. DCR counts these as federal fee land - the largest inter-source convention difference.
• PAD-US easement completeness lags DCR: roughly 2,700 acres of ODLC and VA DHR easements in DCR CLD are absent from PAD-US/NCED, so the footprint may be understated by up to about 5 percent. Army-managed refuges on Fort Belvoir (Accotink Bay, Jackson Miles Abbott) are carried only inside the military boundary.
• Dedupe is heuristic: 1,180 records were removed by a 60-percent spatial-coverage rule within holder/unit groups; a few legitimately stacked easements may have been collapsed. Dissolved acreage is unaffected.
• Establishment year covers only 41 percent of units (86 percent of easements, 15 percent of fee land), so no temporal animation ships and growth analysis is reliable for easements only.
• GAP status classifies management intent, not ecological outcome; GAP 4 easements may still deliver real habitat value.
• Great Falls Park and Theodore Roosevelt Island are subsumed in George Washington Memorial Parkway multipart records rather than appearing as named units.

Data DictionaryFields in the GeoPackage

The military_installations layer carries unit_name, own_name, mang_name, desig_type, gis_acres_full, nova_acres, fips, and jurisdiction for the 9 DOD reference boundaries. The clusters GeoPackage adds cluster (DBSCAN id, -1 = noise) on easement representative points.

Jurisdiction BreakdownResults by Jurisdiction

Sources & CitationsAll Data is Openly Licensed

• [1]U.S. Geological Survey Gap Analysis Project. Protected Areas Database of the United States (PAD-US) 4.1. ArcGIS feature service, accessed July 12, 2026. Public domain.
• [2]Virginia Department of Conservation and Recreation, Natural Heritage Program. Virginia Conservation Lands Database. ArcGIS-hosted service (data edit April 2026), accessed July 12, 2026.
• [3]U.S. Census Bureau. TIGERweb State and County boundaries (current vintage), accessed July 12, 2026.