The last 60-70 years have not seen Mountain Lake in the Presidio treated well. When the Spanish came across it in 1776, Father Pedro Font wrote:
“This place and its vicinity has abundant pasturage, plenty of firewood, and fine water, all good advantages for establishing here the presidio or fort which is planned. Here and near the lake there are yerba buena and so many lilies that I almost had them within my tent.”
The lake changed most drastically when Highway 1 (Park Presidio) was put laid in. Sediment from the tunnel through the Presidio was dumped into the lake, and drains from the highway, sent oil and gas directly from the road into the lake. Once 20′ deep, its depth was lowered to only now 9′ at its maximum, and became slowly but surely full of lead.
Add to that the acid and tannins from leaves from the abundantly planted Eucalyptus trees, all sorts of odds and ends (including a carriage according to one member of the audience), and all sorts of turtles, frogs, fish and other critters (including in 1996, a Cayman alligator), the lake has changed dramatically from when Father Pedro found it.
Much of the talk about restoring the lake started when the lead was first noticed by a scientist in the 90s (and later affirmed by various agencies). People also were worried about the increasing murkiness of the lake.
Two efforts are being made to restore the lake: one is to get rid of the lead, and at least some of the sediment that was dumped there. This involves filtering sludge vacuumed up from the bottom and pumped up into bags which will are being taken to a landfill. This will also remove some of the accumulated leaf litter. Some of the eucalyptus is also being removed to reduce the amount of impact they have on the lake (many trees remain near the lake as part of a “historical forest”).
The other effort is to try and restore the lake back to more like what it once was. This involves two fairly difficult task: one is to remove the invasive species and relocate them to other places where they will not have the same impact. Already about 40 fish (carp, bass, and a couple sturgeon) and 17,000 juveniles have been removed, as well as numerous turtles. In case you are worried, these have been taken elsewhere to live out there lives — the fish to a private lake, the reptiles to Sonoma County Reptile Rescue.
The other, perhaps most complicated task is to restore native species back in the lake. This is not just animals but also plants. One group of people will be setting up a set of compatible plants species, the others will focus on bringing into the pond species that will, should, and can thrive. This is complicated not only be the problems of individual species, but also the status of endangered species and how they can be treated. Another factor — at least where amphibians is concerned is the Chytrid fungus that is having a devastating effect on many amphibian species.
It is a long term effort that will require vigilance, testing, and monitoring to make maintain the appropriate balance The depth can’t be restored to it’s prior depth because of the risk to the roadway , so pumps are also going to be utilized at least until some of the plant communities take hold.
It’s a little bit akin to a gigantic aquarium project, where you’ve had to start out with a filthy tank full of species that you are not particularly interested in.
Why go through all this work to try and re-establish this ecology? To preserve and protect biodiversity — and all the ecological functions and stability that biodiversity can provide; to test the theories and experiment with introduction frameworks of how these restorations actually happen; and last but not least to provide environmental education — engaging the local community, to bring an awareness of our urban ecology and how we interact with nature in a city, and to be a living museum for all these marvelous creatures.