Before Europeans moved into the region San Antonio would have been part of a vast grassland savannah. However due to western agricultural practices and the removal of large native herbivores cedar and mesquite trees now dominate the area.
This picture is a small example of the biome that at one point would have covered nearly all of the hill country with a vast sea of native grasses, buffalo, ground nesting birds, and various other native species that now struggle to adapt to the new modern landscape.
https://tpwd.texas.gov/landwater/land/habitats/hillcountry/vegetation/
