- There are an estimated 19,250 trees adjacent to the Caltrain right of way between San Francisco and Gilroy.
- Approximately 1,727 trees (9% of the total) would be impacted by the two-track electrification project.
- Most of the impacted trees grow on private property, which makes any pruning or removal subject to local tree ordinances. (Trees on railroad land are not subject to tree ordinances.)
How does the situation change with four electrified tracks? While the corridor generally provides sufficient space for four tracks, many more trees would be impacted because electrified tracks would be moved closer to the edges of the right-of-way than envisioned in the tree survey, which only studied impacts from electrification of the two existing tracks. One would expect many more trees to be impacted by the proximity of high voltage wires.
The Vegetation Grief Index
One possible way to quantify the relative HSR impacts to trees along the rail corridor is to combine the vegetation intensity index with the corridor width from San Francisco to San Jose. It's an interesting exercise because more trees will be impacted where the corridor is narrow. Take the sum of the vegetation intensity on both sides of the corridor, subtract two (so that we don't count "generally clear" areas), and simply divide by the width of the corridor. This is the formula for a Vegetation Grief Index (VGI), which is highest when the corridor is narrow and the vegetation is dense. The result is shown at left.
Interestingly, the VGI exceeds 3 in those communities (such as Burlingame, Atherton, Menlo Park and Palo Alto) that are the most worried about the HSR project and have formed the Peninsula Cities Consortium to advocate for their concerns. More generally speaking, the VGI seems to be an excellent predictor of anti-HSR sentiment among residents.
That might suggest that a key position is missing from the Peninsula Rail Program: a full-time certified arborist.