Oh what a difference a few years makes. Just four years ago, the rare California shrub known as the Indian Knob mountain balm (Eriodictyon altissimum) was poised to drop off the endangered species list after the threats to its existence had mostly been abated. This week, however, the U.S. Fish and Wildlife Service (FWS) decided to keep the plant's protections in place because a dangerous new threat has emerged.

Indian Knob mountain balms exist in just five locations in western San Luis Obispo County. In 1994 the rapidly growing but short-lived plants were placed under protection by the Endangered Species Act (ESA) because some of those locations were threatened by residential development, oil drilling and surface mining. Fifteen years later, as part of the normal five-year review process required under the ESA, the FWS found that some of the mountain balm’s habitats had been conserved. Although threats remained in other locations, FWS recommended that the species be downgraded from "endangered" to "threatened."

Recommendations like that don't automatically kick-start the process to downgrade a species, however, so in the intervening years the mountain balm's legal status remained unchanged. Then in 2011 the Pacific Legal Foundation, a conservative organization that advocates for personal property rights, petitioned the FWS to reclassify the shrub and four other species. That petition, along with a later lawsuit, initiated an FWS review of E. altissimum to determine if it really should be downlisted.

Ironically, that lawsuit-inspired review, published December 11 in the Federal Register, found that the Indian Knob mountain balm is now more endangered than it was four years ago due to the emergence of an invasive African plant. Perennial or purple veldt grass (Ehrharta calycina), first brought to California decades ago as a drought-resistant grass for grazing cattle, has now spread throughout the southern coastal region of the state. The worst-hit region: San Luis Obispo County, home of the Indian Knob mountain balm.

The FWS found that this new plant "is having a negative effect" in all five E. altissimum habitats, a situation that won't get better anytime soon. Veldt grass has already proved difficult to eradicate because of the speed at which it grows and reproduces. Mountain balm seedlings will likely face increased competition, and because three of the five populations contain fewer than 50 plants, the new competition is a major threat.

Meanwhile wildfires—or the lack of them—also pose a danger. Chaparral species like the mountain balm depend on fires to clear tall old plants and cause seeds to germinate. But human development in the region has changed the fire pattern, and no fires have occurred in the Indian Knob region for 50 years. Although the full ecology of E. altissimum is poorly understood, similar species tend to sprout new plants and growth after fires, even though only 1 to 5 percent of seeds survive. The lack of flames over the past few decades may have contributed to the mountain balm's decline.

In a final twist, however, the FWS found that the threat of potential future fires poses too great to risk to such a small population. In fact, the mountain balm population is now so low in places that future fires would likely further endanger them. And even though human development has lessened the rate of natural fires, the threat of future fires has increased because of the now-abundant veldt grass. Worse still, veldt grass also thrives after fires, which means it could become an even more intense competitor to the mountain balm if any new fires occur.

Since the 2009 review two populations of Indian Knob mountain balms have disappeared. Four of the five remaining populations are on conserved land. The fifth is on private property.

Photo by David H. Chipping courtesy of the U.S. Fish and Wildlife Service