Lomatium cookii population monitoring in the Illinois Valley, Josephine County, Oregon

EXECUTIVE SUMMARY

Lomatium cookii is endemic to southwestern Oregon, and is listed as endangered by the State of Oregon and by the U.S. Fish and Wildlife Service (USFWS).  Populations discussed in this report are located in the Illinois Valley in Josephine County.  Long-term monitoring has occurred at French Flat since 1990, at Rough and Ready since 1994 and at Indian Hill since 1997.  Data from these efforts are used to track population dynamics at all sites and create a population viability analysis for French Flat.

French Flat South

• Total population size was estimated at 81,640 individuals in 2016, a 37% increase from 2015. Average plant density was estimated at 10.2 plants m^-2.  The proportion of reproductive plants in the overall population was 26%, a 41% increase from 2015.
• The Population Viability Analysis (PVA) indicated a 99.0% probability this population will decrease 50% in the next 20 years.  A catastrophic loss (99% population decrease) over the same period is not likely to occur (< 0.1%).

French Flat Middle

• The total population numbered 48,867 in 2016, a 6% increase from 2015.  Density was estimated at 10.5 plants m^-2.  Reproductive plants composed just under 17% of the overall population, a 74% increase from 2015.
• The PVA indicated a 97.6% probability this population will decrease 50% in the next 20 years.  A catastrophic loss (99%) over the same period is not likely to occur (0.8%).

Rough and Ready

• This population decreased 16% from 2015 to 1,818 plants in 2016.  Reproductive adults comprised 51% of the population, a 76% increase from 2015.  Barricading with boulders has successfully blocked vehicles from dumping trash in the small meadow and accessing side roads.

Indian Hill

• This population decreased 30% to 5,943 in 2016.  Reproductive adults comprised 28% of the population, a 10% increase from 2015.

Overall, populations of Lomatium cookii in Josephine County have shown increased recruitment of seedlings and population sizes have remained relatively stable.  This is likely due in part to active management of these populations by the Medford BLM, including preventing use by off road vehicles.  However, population viability analyses indicate there is still risk of serious population declines.  Proposed mining activities may have further detrimental impacts on these populations at French Flat.  We recommend continued monitoring of these populations to assess population trends, trespass by ORVs, and provide data to assess future impacts to populations from climate change, mining, or other threats.