The decline of early successional habitat

I’m currently doing my master’s research on the habitat of New England cottontails. These bunnies have experienced dramatic population decline since the mid-1900’s because their habitat has become less abundant and more fragmented[1]; a habitat consisting of early successional plant communities with dense thickets of vegetation.

Like this rabbit, New England cottontails are limited by suitable habitat these days. Photo via wikimedia commons. 

Like this rabbit, New England cottontails are limited by suitable habitat these days. Photo via wikimedia commons. 

Lots of other interesting species in New England require early successional habitat too, and many are also in decline, like the American woodcock and some warblers. A frequently asked question is, “so why is there less early successional habitat here now than there used to be?” Also, “what is early successional habitat?”

What is it?

Plant communities change over time and this process is called succession. For example, a forest is not as static as it may seem- it changes due to fires, hurricanes, climatic changes, wind, floods, glacial events, and human disturbances. (See my blog post on disturbances for more on this!) A recently disturbed forest will look different from a mature one. It will have different plant species, and the vegetation will likely be shorter and denser, with variation depending on the severity of the disturbance. That brambly thick mess of vegetation is what is considered early successional habitat and some wildlife species need this type of habitat to survive. Different species need slightly different habitats- some species may prefer a young forest of birch and alder saplings, where another may prefer a shrubbier community with blueberries and grasses. What all types of early successional habitats have in common are that they are ephemeral; the plant community will change over time, and the presence of these habitats are dependent on disturbances to exist. 

An example of early successional habitat bordering a forest. Photo credit: Alena Warren

An example of early successional habitat bordering a forest. Photo credit: Alena Warren

Why is there less early successional habitat in New England now than there used to be?

There are a few reasons that likely contribute to the declining abundance of early successional habitat. One reason is that fewer farms are being abandoned now than in the past. Abandoned fields have historically made a large contribution of early successional habitat to the landscape, but at this point, most of those fields have reverted to mature forests [2]. Of course, human farmers weren’t always a part of the New England landscape and so other disturbances must have had a role. Some more possible reasons for the decline are:

  • Management: property owners don’t want to see brambly messes, so they alter their landscape to produce either mature forests or open fields/lawns that are more aesthetically appealing or economically rewarding.
  • Fire suppression: New England no longer experiences naturally occurring wildfires and/or fires created by Native Americans that would create early successional plant communities.
  • Development: the potential effects of development are two-fold (at least):
    • Development “fragments” early successional habitat, making it less useful for wildlife species that prefer large swaths of habitat or require habitat patches to be connected. 
    • Development has replaced natural areas prone to early successional habitat, like floodplains, coastal shrublands, etc.  

Disturbances are a natural part of the ecosystem; storms, fires, etc. create diversity. If we are seeing a decline in disturbances and the resulting habitat types, perhaps we need to take an active role in creating those habitats. 

What can be done about it?

It seems likely that human actions have contributed to the decline of early successional habitats in New England. In order to conserve these habitats and the wildlife species that rely on them, many government agencies and other groups are trying to increase the amount of early successional habitat in New England. Property owners or managers can learn about how to create or maintain early successional habitat, and even apply for financial assistance to do the work.

Examples and Additional Reading:

American Woodcock Habitat Management

NRCS Working Lands for Wildlife Program

New England Cottontail Habitat Management

References:

1.            Fenderson, L. E., Kovach, A. I., Litvaitis, J. A. & Litvaitis, M. K. Population genetic structure and history of fragmented remnant populations of the New England cottontail (Sylvilagus transitionalis). Conserv. Genet. 12, 943–958 (2011).

2.            Litvaitis, J. A. Response of Early Successional Vertebrates to Historic Changes in Land Use. Conserv. Biol. 7, 866–873 (1993).