Ecology & Early History

The Headwaters Sanctuary is primarily a riparian forest, meaning it is near a river or creek and supports plants adapted to periodic flooding. This forest is fairly young as most trees are only 25 to 30 years old. Much of this land has been cleared repeatedly in the last 70 years (see aerial photos below). Even so, very old live oak trees exist at the west and south edges of the sanctuary on slopes less suitable for pasture or cropland. As this forest matures, the mix of plant species will change slightly. The dominance of hackberry and cedar elm is about what we would expect in a forest of this age. Over time, slower-maturing trees will gain a foothold, and species like pecan, Texas oak, Texas persimmon, and walnut will flourish. See a list of plants documented in the sanctuary.

Because we are surrounded by dense development and busy roads, the sanctuary does not support wide-ranging mammals like deer (though they do like to visit). We are home to smaller critters such as raccoons, skunks, possums, mice, and foxes. We are a haven for birds, too. Wrens, warblers, kingfishers, cardinals, hawks, and owls are common. Waterbirds like wood ducks, egrets, and herons can be found when the water is high. See our bird list.

Headwaters Timeline:

Ancient Roots - Europeans Fuel Change - Modern Times at Headwaters

These aerial photos illustrate the changes in the landscape in the Headwaters area over 70 years.  The outline roughly represents the boundaries of the Headwaters Sanctuary.

Hildebrand Avenue runs east to west along the bottom of the photos.  The diagonal in the upper left corner is the Olmos Dam.  The buildings in the lower right are on the campus of the University of the Incarnate Word.

Ancient Roots

Pre-historic Period
Paleo-Indians camp at San Antonio Spring (aka Blue Hole) and set fires to help in the hunting of mastodons (ancient cousins of the elephant), mammoths, and bison. These fires change what was a forested landscape into a grassland mosaic with scattered woodlands. (10,000 - 6,000 BCE*)

Archaic Period
Post-Ice Age period of natural climate warming. As central Texas becomes drier, people increasingly camp near rivers and streams, where food and shelter are now more plentiful. Mega-game like mammoths and
mastodons disappear from central Texas. Hunting shifts to bison, elk, deer, antelope. (6,000 BCE - 700 CE**)

Coahuiltecans camp seasonally at the San Antonio River, which they call Yanaguana, trading, and holding ceremonies. Coahuiltecans continue setting fires to manipulate the distribution of game animals. Herbivores (plant eaters) generally prefer young growth, higher in protein. Recently burned areas attract herbivores because of the nutritious new growth they produce, thus creating reliable hunting spots...not unlike the modern Texan practice of feeding corn at a deer blind! (700 - 1690 CE**)

*BCE = Before Christian Era
**CE = Christian Era
Europeans Fuel Change

Spanish soldiers and missionaries bring their farming and cattle-raising practices to Texas. Missionaries work to convert Coahiltecans at the same time that northern Apaches increase violent raids into the are. Most Coahiltecans move into the missions for protection, and the nomadic hunter-gatherer lifestyle declines markedly, as do fire frequencies. (1690 - 1836 CE**)

Anglo-Texans station the Texas Army at the Blue Hole, and claim ownership of this gathering spot sacred to the Native Americans. The surrounding land about (280 acres) is sold to James Sweet, then to Colonel George Brackenridge, and then to the Sisters of Charity of the Incarnate Word. The property is used for livestock and crop production, as is much of the surrounding landscape. European patterns of landownership dominate; and the landscape becomes fragmented by fences, roads, and buildings. Many fire-dependent grasslands are replaced by forests and woodlands. Free-ranging herbivores decline, because of hunting pressure and changes in land management. Bison disappear. (1836 - 1900 CE**)

**CE = Christian Era
Modern Times in the Headwaters

San Antonio grows enormously. Groundwater pumping lowers the water table, and the Blue Hole and the San Antonio River are no longer permanently flowing. San Antonio capitalizes on the river as a tourist attraction and celebrates the Blue Hole as its headwater spring.
Local Coahuiltecans begin efforts to reconnect with their heritage and resume ceremonies at the Blue Hole, under an agreement with the Sisters of Charity of the Incarnate Word. The Headwaters Sanctuary is established to protect and promote the natural and cultural resources remaining on 53 acres of undeveloped land and water owned by the Sisters. (1900 - 2007 CE**)

**CE = Christian Era