Thursday, June 24, 2010

Astragalus ertterae

Walker pass milkvetch

There are plants in the Mojave that have very wide distribution, and there are some that have extremely limited ones. One of the later, in fact, one of the most extreme cases, is the Walker Pass Milkvetch, a member of the pea family. The entire known, and confirmed population of this plant is limited to a handful of individuals located on one section of the Pacific Crest Trailnorth of Walker Pass. The original site records only showed 1 plant, but in recent years, there has been some recruitment, and now the population has exploded to 14 plants.

This extreme endemism is an example of how limited in distribution a plant species can be. And the fact that the entire population is located directly adjacent to a regularly traversed hiking trail may seem like a concern. However, the obscurity of the plant is its shield in this case. Yes, there may only be 14 of them, but most people are walking the PCT are not climbing the banks, which is where the plant grows. Still, like all rare plants, there is some degree of danger to it, since it has such a limited known distribution. In all likelihood, there are other populations, which have, thus far, not been identified.

Friday, June 11, 2010

Special status species

In the Mojave, we are blessed/cursed with a large number of plant species, a significant number of which are rare or special status. This means that when we at the BLM are working on implementation of various projects, we have to look very carefully at where the proposals are located.

Special status plants are not uniformly rare, but are all protected by our policy. Some of our species, such as Cymopteris deserticola, the desert cymopteris, have a relatively large population. However, this doesn't mean that they are not rare, because they are only found in very specific habitats, and very few locations. This is like having an island which is the only location you can find the species, yet it is very abundant there. If you bulldoze the island to make houses, you have eliminated the only place that the species is found. So even though it was abundant, you've completely wiped it out. Or consider that with many of these plants, you can actually get a relatively accurate count of how many plants there are in the entire population. Try doing that with something like Larea tridentata, and you come to realize that there is a big difference between the two.