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 53,282 individuals in 2017, a 35% decrease from 2016. Average plant density was estimated at 6.7 plants m-2. The proportion of reproductive plants in the overall population was 20%, a 20% decrease from 2016.
• The Population Viability Analysis (PVA) indicated a 99.9% probability this population will decrease 50% in the next 20 years. A catastrophic loss (99% population decrease) over the same period is less likely to occur (1.9%).
French Flat Middle
• The total population numbered 27,200 in 2017, a 44% decrease from 2016. Density was estimated at 5.8 plants m-2. Reproductive plants composed just over 18% of the overall population, a 10% increase from 2016.
• The PVA indicated a 99.8% probability this population will decrease 50% in the next 20 years. A catastrophic loss (99%) over the same period has over a fifth of a chance to occur (22.9%).
Rough and Ready
• This population decreased 10% from 2016 to 1,642 plants in 2017. Reproductive adults comprised 50% of the population, a 3% decrease from 2016. Barricading with boulders has successfully blocked vehicles from dumping trash in the small meadow and accessing side roads.
Indian Hill
• This population increased 21% to 7,213 in 2017. Reproductive adults comprised 35% of the population, a 26% increase from 2016.
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.