Resilient Forests: Managing Deer to Let Eastern Park Forests Regrow

Hungry deer can strip much of the vegetation within their reach.

Why there are so many deer

Deer love edges — where yards, fields and farms meet forest — and the eastern United States is full of them. Add the loss of top predators such as wolves and mountain lions, and deer numbers have exploded over the past several decades.

Deer numbers have risen sharply in the East. NPS.

What they do to forests

A healthy forest needs enough seedlings and saplings to replace the canopy after a disturbance. Park Service Inventory and Monitoring (I&M) data and other long-term records show that many eastern parks lack that regeneration after decades of over-browsing.

• Deer prefer the native plants and trees they evolved with.
• That pressure opens space and resources for invasive plants, which flourish where deer are dense.
• Without deer management, forests can't replace themselves after microbursts, insect outbreaks or ice storms, and drift toward thickets of invasive shrubs as old trees die.

I&M forest monitoring tracks deer browse and the number and kinds of young trees to predict whether a park's forest can regrow. Many eastern parks are in Imminent Failure or Probable Failure — their forests will eventually become shrub thickets without intervention.

Forest regeneration status in eastern national parks. NPS.

Where deer management works

Managing deer comes first. Parks in the Park Service's Region 1 can build on neighbors' experience: Catoctin Mountain Park and Rock Creek Park have seen seedlings increase as deer numbers fell. That's a start, not a guarantee: small seedlings take years, and face many threats, before they become saplings able to reach the canopy.

As deer declined, seedlings increased. NPS.

Rock Creek Park before deer management: very little regrowth on the forest floor. NPS.

The same forest since the park's ongoing deer management plan began. NPS.

A decision path

Managing deer to reverse regeneration failure. NPS.

1. Where regeneration is in imminent or probable failure, begin deer management planning, start or continue deer and forest monitoring, and manage deer adaptively as the forest responds.
2. If invasive plants are blocking regrowth, manage them in high-priority stands.
3. If native young trees don't establish, plant native seedlings.
4. If taller seedlings and saplings are present, thin the subcanopy to give them light, and keep monitoring.

Watch

How forest monitoring revealed the problem in eastern parks, and how Gettysburg National Military Park, Rock Creek Park and Catoctin Mountain Park are addressing it (5 minutes, 54 seconds). National Park Service.

More: the Case Studies in Deer Management StoryMap. The series continues with invasive plants and pests and forest complexity.

Sources

Based on "Resilient Forests Initiative – Managing Deer Impacts," Managing Resilient Forests Initiative for Eastern National Parks, National Park Service; a work of the United States government in the public domain. The film is the Park Service's own. A privately copyrighted photograph of two deer is not reproduced.