Thursday, November 19, 2009

Franciscan Manzanita buried viable seed mitigation

The rediscovery of Arctostaphylos franciscana Eastw. [A. hookeri G. Don ssp. franciscana (Eastwood) Munz ] right in the path of a critical highway project and news reports of what is planned to mitigate the problem have not mentioned one critical factor: buried viable seed. Buried seeds are genetic individuals, and take under the endangered species act can be extended to include any removal of individuals from the gene pool. If we mitigate the problem only by propagation, and later planting ex situ, a take will occur because unique genotypes that exist only as buried viable seed will not be provided for.


It might seem a little fishy that the prior known sites for A. h. ssp. franciscana were on serpentine on Mt. Davidson, while the Doyal Drive site is (probably) on stabilized dunes (?), but both A. hookeri ssp. franciscana and A. h. ssp. ravenii Wells were once sympatric on Mt. Davidson (Roof, 1976 Four Seasons Vol. 5) whereas now both are reduced to single remnant individuals on non-ultramatic substrata. The substrate character of the Arctostaphylos hookeri ssp. franciscana site is relevant: buried viable seed might be well distributed both horizontally and vertically over a considerable distance about the newly discovered single bush if in fact the soils there are loose or sandy, and even if the soils are not sand, buried seed is someplace out there and vulnerable.


In order to fully mitigate potential impacts to Arctostaphylos hookeri ssp. franciscana, a program of salvage intended to capture buried viable seed will be required. Yes, it sounds nuts, but soil excavation and processing should be conducted. Volumes of soil excavated from the site need to be trucked to a experimental site, aliquots inspected directly for seeds, while the bulk needs to be processed to induce germination. How to do this: conduct research. Should the soil be cold stored until the research indicated how to proceed? Should the soil be mechanically scarified? Fire simulated? Again, conduct research.


A billion dollar highway project is not likely to be halted in spite of the rediscovery of an 'extinct' plant, but a fraction of the cost needs to be diverted to the conservation of the Franciscan Manzanita. A stimulus plan to gain a better understanding of manzanita biology is needed.

1 comment:

gluesenkamp said...

You make very good points. One correction: the Golden Gate Bridge A. francisciana plant I found is actually growing in serpentine soil, with a small outcrop of serpentinite under the plant. Very cool!

I also think that the soil should be salvaged, with similar actions taken for similar soil in adjacent areas --much of the Doyle Drive roadside being scraped by construction work has beautiful serpentine/serpentinite underneath, and there could be all kind of miracles in that soil waiting to be set free.

Finally, I am calling it San Franciscan manzanita. That is a recognized common name, and I think helps to put it in a better perspective.

We drove this species extinct once before, digging up the last couple individuals and exiling them to some foreign dirt. Now we have a second chance. To save it? To remove it again? Perhaps we will have to dig up the last wild plant, once again, but if we simply dig and replant then it shows that little has changed since 1940. We must do something more, something that demonstrates our improved understanding of and commitment to biodiversity conservation. If we have to move it, then we have an obligation to move it to a new home. We have to find an appropriate nearby site, do significant site preparation and restoration. Then we must bring the other San Franciscan manzanitas back from the diaspora, plant them alongside their natural neighboring species, and give them a new home where they can flower, bear seed, and produce baby manzanita plants to continue the lineage. That will cost a lot of money, but will be something of which we can ALL be proud.