Natural Areas Threats and Management

What is natural areas management?

Active natural area management includes any activity designed to remove or retard negative influences on an ecosystem to the extent possible, including but not limited to, the impact caused by invasive plant species, invasive pests and pathogens, and white-tailed deer.

  • Mowing a meadow to slow natural succession and the invasion by woody plants.
  • Removing an invasive species such as garlic mustard from Holden woodlands.
  • Fencing individual plants or large natural areas to prevent white-tail deer browse.

Natural Areas management also includes any activity taken to optimize habitat to promote the reproductive success of our native plant or animal species such as:

  • Removing competing vegetation to allow more sun reach a plant and allow it to flower.
  • Delaying mowing meadows until the animal, bird and insect species completes their life cycle of egg to adult; or a specific plant species completes their life cycle of flower to seed.
  • Providing nesting boxes for the Eastern Bluebird and continued monitoring by Holden’s volunteer Bluebird program.

Threats to our natural areas

Natural areas through Northeast Ohio are faced by a wide variety of threats. These threats include urban development pressures, invasive plant species, diseases, animal threats, including insects, white-tail deer browse, earthworms, introduced diseases, and insects and climate change.   

Invasive Plant species

Any plant that grows outside of its natural range is considered exotic. If it responds to its new environment with rapid growth, and if it can quickly establish itself over large areas of land then it is considered invasive.

How does this happen?

When humans were introduced into North America we brought plants with us from our country of origins. Plants have been introduced for agricultural purposes, horticultural purposes, and in some cases, purely by accident. However, when a plant species is introduced outside its natural range, it is also outside the natural range of its natural controls that can include any herbivores, parasites and diseases. Free from these natural controls, some exotic plants experience rapid and unrestricted growth, become invasive in their new environments, and reduce ecosystem diversity and function.

Why aren't all exotic plant species invasive?

The primary factors which contribute to a plant’s ability to invade include its life cycle, annual or perennial; how it spreads, as a vine or by seed; its capacity for abundant seed production; its high seed germination rate; how long-lived

its seeds are; and how rapid it can mature to its seed-producing stage. The quicker it can reproduce itself, the quicker it can invade and overwhelm the native plant species which previously occupied the land.

Why do we care?

Invasive plant species are the second greatest threats to the natural ecosystems of the world today. Only direct habitat destruction poses a greater threat to the future of biological diversity. Invasive species disrupt the ecology of natural

ecosystems by displacing native plant and animal species and reduce biological diversity by reducing the amount of light, water, nutrients and space available to native species.


See list of plants that are invasive in Northeast Ohio?

For more Information:


The introduction of exotic plant species have resulted in the escape of plant pathogens which have greatly impacted our local flora, such as Dutch Elm Disease, Beech Bark Disease, Chestnut Blight and Dogwood Anthracnose.

Animal Threats


Introduced insects that have impacted Holden include European Beech Scale, Gypsy Moth and Emerald Ash Borer.


White-tail Deer

White-tail Deer were extirpated from Ohio in the late 1800s but were re-introduced to Ohio in the late 1920s. Browsing by white-tail deer has a negative impact on all Holden collections. Deer browse destroys specimens propagated or purchased for the designed landscape. Browsing severely limits ecological function of natural areas when whole age classes and layers of woody species disappear from the landscape. Holden has protected a landscape matrix of woodland and grassland that is coincidentally optimal habitat for whitetail deer. Deer exclosure studies within the natural landscape produce quantifiable data on the impact of whitetail deer on the landscape. Infrared aerial surveys document the population density of whitetail deer in and around the Holden landscape. Historical density for whitetail deer in northeastern Ohio is eight deer per square mile. Current whitetail deer density is 29 deer per square mile. Whitetail deer are one of the strongest negative pressures on Holden landscape and require management plans to reduce population density.


Did you know that there are no native earthworms in glaciated North America? For many of the same reasons that earthworms are useful in a vegetable garden, they are harmful within our native woodlands that evolved with earthworms. Studies conducted by the University of Minnesota show that at least seven species of earthworms are invading Minnesota’s hardwood forests and causing the loss of tree seedlings, wildflowers, and ferns. Invading earthworms eat the leaves that create the duff layer and are capable of eliminating it completely. Big trees survive, but many young seedlings perish, along with many ferns and wildflowers. In areas heavily infested by earthworms, soil erosion and leaching of nutrients may reduce the productivity of forests and ultimately degrade fish habitat. For more information on invasive earthworms visit the Minnesota Department of Natural Resources web site.


Land Protection

Holden owns more than 3,600 acres, but it is impossible on many levels to own all the land necessary to protect the great regional biodiversity that creates the landscape we think of as The Holden Arboretum. In 1992, Holden started a conservation easement program in order to work with our neighbors to protect local watersheds and expand the protection of Holden’s significant natural areas by land conservation on private or public properties. Holden currently holds conservation easements on 21 properties that total approximately 1,400 acres.


What is a Conservation Easement?

A conservation easement is a specialized interest in land that restricts the owner’s use of property in specified ways and designates the holder of the easement with enforcement responsibilities. Its purpose is to protect the natural, scenic or historic values of the property. A conservation easement is granted in perpetuity and will apply to all future owners.


Ecological Restoration


Ecosystems and plant communities can lose parts of their ecosystem function when important components of ecosystem function are lost. To complete the natural areas management loop it may be necessary, based upon the best scientific data, to restore degraded ecosystems by:

  • Re-establishing plant layers, age classes of plants or species composition within Holden natural areas to provide forest interior birds a place to nest.
  • Restoring cold-water habitat within streams by removing impediments to flow.
  • Restoring depth to a vernal pool so that sufficient water depth persists long enough for amphibians to complete their life cycle.