What We’re Learning and Why it Matters: Long-Term Monitoring in the National Capital Region

After more than fifteen years of monitoring, we've learned a lot about park ecosystems, how they're changing, and what they may look like in the future.

By Crystal Chen, NCRN I&M Science Communication Intern
Field crews monitoring natural resources in the National Capital Region Network.

The National Park Service preserves some of America’s most special and treasured places. Knowing which key natural resources are found in the parks, and whether they are stable or changing, can help park managers make sound, science-based decisions about the future.

The National Capital Region Network (NCRN) is one of 32 Inventory & Monitoring networks building that knowledge. In 11 regional national parks, our scientists and partners collect long-term data on key natural resources—like plant communities, birds, and water quality—that we call "vital signs," because their condition can indicate the overall health of park resources. We analyze the results, track the changes, and provide information to decision-makers.

NCRN parks are a mix of natural and cultural areas that provide a unique glimpse into forest ecosystem health. We maintain precious biodiversity within a broader urban setting. There's still plenty we don't know, but there's a lot we do know.

What have you learned? What kinds of changes are you seeing?

The first few years of any monitoring program are devoted to figuring out what's "normal" for a given ecosystem. We collect data to establish a baseline, then determine the range of measurements that might be expected under typical conditions. With more than fifteen years of data for some resources, we’ve learned numerous key things about the ecosystems we study.

Forest Vegetation

A Forest Plot at Rock Creek Park in 2012 and 2016 Showing Seedling and Understory Regrowth

A forest in summer with green canopy and brown fallen leaves on the forest floor. A forest in summer with green canopy and brown fallen leaves on the forest floor.

Left image
2012, Before deer management

Right image
2016, On-going deer management

Forest Regeneration

Regeneration of trees is critical for the forest ecosystem. Trees provide habitat for plants and animals, filter water and air that we drink and breath, and provide the cool leafy shade enjoyed by visitors in the summer heat.
A road winds through a shady forest carpeted with invasive Japanese stiltgrass.
Invasive stiltgrass covers the forest floor along a road edge at Catoctin Mountain Park.

NPS/Thomas Paradis

Invasive Plants

More than non-native plants, native plants supply wildlife with the food and physical structure they need. Visitors and neighbors can support healthy wildlife and forests by growing native plants and removing non-native invasive plants from their yards. Invasive plants take advantage of forest stressors including: forest fragmentation, overabundant deer, forest pests, and light gaps caused by forest canopy disturbance.

Dark horizontal stripes along a beech leaf, showing signs of beech leaf disease
Beech leaf disease.


Forest Pests

  • Beech leaf disease, was first found in Prince William Forest Park in 2021 and has since been found in C&O Canal in 2023. Potential forest impacts could be dramatic and dire since beech are the most common tree species in the region.
  • As of 2023, emerald ash borer (EAB) has killed more than 80% of the white, green, and pumpkin ash trees that were present in NCR parks in 2014.
  • Since arriving in 2021, spotted lanternfly has been observed throughout NCR parks. It is unlikely to cause as much mortality as emerald ash borer, because it feeds on a wide range of plants and is rarely lethal on its own.
  • Hemlock wooly adelgid and elongate hemlock scale have killed many eastern hemlock trees. Parks (like Prince William Forest) preserve their hemlock patches with regular insecticide treatment. Hemlocks grow along streams, providing shade for brook trout that rely on cold water for survival. An NCRN census of hemlocks in 2015 found 112 standing hemlock trees, 34 of which were alive. 38% of living hemlock trees were infected with the adelgid or the scale.
  • American chestnut trees were devastated by chestnut blight fungus in the early 1900s. In 2014, we surveyed surviving American chestnuts in all parks except Antietam and Manassas. We documented 234 trees. Most were small and showed no signs of flowers or fruit.
  • A summary of forest pests through 2023 describes current and upcoming threats to NCR parks.

Sea Level Rise

A spotted salamander emerges from under a pile of leaf litter.
Spotted Salamander (Ambystoma maculatum)

NPS / C. Shafer


Kentucky warbler.
Kentucky warbler.

D. Tallamy


Stream Biota

Trees standing in water in a vernal pool
Vernal pool.


Stream Water

  • Winter road salting is one of many factors that is increasing water conductivity in streams. Conductivity shows the level of dissolved material in streams. High levels cause harm to fish and aquatic invertebrates who can’t survive in increasingly salty water. In the larger DC area, our monitoring data shows the otherwise unseen downstream effects of pollution from many sources.
  • Streams in Rock Creek Park and Antietam National Battlefield have high concentrations of phosphorus and nitrogen. This can cause algae to grow faster than ecosystems can handle.
  • We recorded very low summer-time levels of dissolved oxygen at Young’s Branch (the main watershed in Manassas National Battlefield). In the summer, low water levels allow for higher water temperatures and lower oxygen levels that stress aquatic life. In some years, the stream completely dries up. Aquatic life that can’t withstand drying or can’t repopulate quickly once the stream is flowing again, will be severely harmed.
  • Brook trout rely on coldwater streams at Catoctin Mountain Park. Based on our modeling, we expect to have no coldwater streams within the next 50 years in NCRN parks. This means that brook trout will no longer be a part of our aquatic ecosystems. Check out this map of coldwater refugia (and learn how to use it).
Visibility of Washington Monument on good and bad visibility days

Air Quality

Supporting Information

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    Tags: ncrn

    Antietam National Battlefield, Catoctin Mountain Park, Chesapeake & Ohio Canal National Historical Park, George Washington Memorial Parkway, Harpers Ferry National Historical Park, Manassas National Battlefield Park, Monocacy National Battlefield, National Capital Parks-East, Prince William Forest Park, Rock Creek Park more »

    Last updated: May 21, 2024