How Disturbance Impacts Wildlife

By Lauri Turner, Forest Wildlife Program Manager, Deschutes National Forest, Supervisor’s Office.

Direct Effects

Collisions – result in mortality or injury and could have population level changes if dealing with low density populations
Habitat Loss – direct loss of habitat due to road/trail construction
Indirect Effects

Habitat degradation
Increased compaction – may reduce vegetation or not allow burrowing into soil
Increased sedimentation potential
Spread of invasive species
Trampling of vegetation
Loss of habitat components like snags, down woody material, etc.
Habitat Quality
Disturbance (Human Presence or Noise)
Wildlife displacement
Habitat avoidance – lower densities near roads/trails
Acute or chronic physiological damage (i.e. hearing loss)
Increased energy expenditure
Physical injury due to panicked responses
Interference with normal activities (ie. Feeding, breeding)
Impaired communication among individuals or groups
Increased stress hormones
Altered behaviors
Communication Confusion

Human made noise has the potential to interfere with animal communication signals, sounds animals listen for orientation, and predator-prey detection
Can result in nest abandonment
Can cause problems with intra-species communication (i.e. can’t hear mating calls during breeding season) – causes problems with detection, discrimination, and localization of appropriate signals
Interferes with ability to capture prey
May emulate natural sounds and cause inappropriate effects (i.e. emerging during the wrong season)
Physiological Effects

Increased stress hormones leads to reduced reproductive success
Increase energy expenditures (i.e. flushing, fleeing)
Connectivity and Barriers

High landscape connectivity is a landscape that has few barriers and where animals move freely – moving through different habitats in order to meet daily and life needs
High landscape connectivity allows for movements to re-populate areas and minimizes inbreeding
Barriers that impede movement result in higher mortality, lower reproductive success, and smaller populations
Isolation caused by barriers to movement can reduce gene flow leading to genetic effects
High home range overlap leads to territory packing

Road and trails result in large patches being dissected into smaller patches
Reduces interior forest habitat and increases edge effect
They are long and linear which equates to more edge effect
Impacts are not all equal – some areas may experience greater impacts like riparian areas where there is high diversity
Major Science Used

Forman, R.T., D. Sperling, . J.A. Bissonette, A.P. Clevenger, C.D. Cutshall, V.H. Dale, L. Fahrig, R. France, C.R. Goldman, K. Heanue, J.A. Jones, F.J. Swanson, T. Turrentine, and T.C. Winter. 2003. Road Ecology: Science and Solutions. Island Press. 481 pp.
Forman, R.T. and L.E. Alexander. 1998. Roads and their major ecological effects. Annu. Rev. Ecol. Syst. 29:207-231.
Gaines, W.L., P.H. Singleton, and R.C. Roger. 2003. Assessing the cumulative effects of linear recreation routes on wildlife habitats on the Okanogan and Wenatchee National Forests. Gen. Tech. Rep. PNW-GTR-586. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 79 pp.
Knight, R.L. and K.J. Gutzwiller. 1995. Wildlife and Recreationists: Coexistence through Management and Research. Island Press. Washington D.C.

And many more scientific references. I can provide a list if needed.