How the Gypsy Moth Risk Map was constructed

Sandy Liebhold, Gino Luzader, NEFES, Morgantown

The Gypsy Moth Risk Map was constructed from the following data:

  • FIA Forest Type group map of the US
  • FIA plot data
  • 1995 GM quarantine map
  • predictions of future GM spread

    First we took the FIA US Forest Type Group Coverage:

    Then we selected all forest type groups that contain suceptible forest types (Oak-pine, Oak-hickory, Oak-gum-cypress, Elm-ash-cottonwood, and Aspen-birch):

    We excluded any counties where less than 10% of land area is covered by forests that have > 20% BA preferred spcies. This effectively excluded large areas where there is a negligable amount of susceptible forest. (This coverage was generated from FIA plot data as described by Liebhold et al. J. Forestry 95: 20-24):

    We obtained the 1995 Gypsy moth Quarantine from the Code of Federal Regulations:

    We used the boundary of the 1995 quarantine to generate a multiplier coverage. At the 1995 boundary we randomly selected 75% of all pixels (1 km). This multiplier linear decreased to zero at the 315 km beyond the 1995 boundary. This is the predicted gypsy moth boundary in 2010 based on a spread rate of 21 km / yr (assumes no STS). The multiplier decreased to 25% 250 inside of the boundary and the rest of the generally infested area was 25%. The effect of this is that outbreaks and their impacts are expected to be gratest as gypsy moth first spreads into an area and then will continue at lower levels once it has been established.

    Here's what the multiplier coverage looked like:

    So in the end we multiplied everything together and got this: The final Gypsy Moth Risk Map - 2010

    The final Gypsy Moth Risk Map - 2010 Thinned 50%

    The final Gypsy Moth Risk Map - 2010 Thinned 70%