|Tarplant in 2007|
"The report notes that tarplants in the former dairy site have dropped from 100,000 in the 1980s to 32 this year. The report cites the end of grazing, invasive species and "unmanaged public access" that led to unauthorized trails."
Tarplant numbers were not studied in the 1980s during grazing on Arana Gulch, therefore we have no baseline on which to compare current trends. A contributing factor that has not been studied is change in the timing and amount of precipitation in the area.
|Tarplant in 2011|
It is more likely that the decline has as much to do with natural local climate variation as with changes in herbivory with the removal of dairy cattle from Arana Gulch.
The recent increase in tarplant individuals suggests that changes in precipitation patterns is a possible contributing factor to tarplant success or decline and would therefore influence the success of the City's plans for industrial scale grazing on Arana Gulch..