Endangered Species

Paleo scientists tell us that there are more extinct species of once-living organisms than there are living ones.   Nearly twice as many extinct as alive.  That in itself says that most of us should be looking over our shoulder for causes that might result in our own demise. This thought came to mind when we took up the task of writing about rare and unusual plants in central Texas.

We often link the loss of habitat to the endangerment of a species.  The poster bird of central Texas that is so often cited in this regard is the Golden Cheeked Warbler. It only nests in a few counties in central Texas and it makes use of strips of ashe juniper bark to line its nest.  It is an elusive bird, most people have never seen it, but more have heard its call.  This bird does not come calling at your bird feeder like a Northern Cardinal.  Another example, this one in bold contrast to the Golden Cheeked Warbler is the Great Tailed Grackle.  This is the black bird that patrols the parking lot of the local surpermarket looking for fresh bugs on the fronts of cars, and then nests in the trees of the parking lot to be close to food.  It has even learned to watch the automatic doors of the market so that when they open this crafty fellow flies in, looks for food scraps and then flies out as soon as the doors open again.  Now, that is adaptation, a skill that this bird should teach the Warbler.

Some species seem to be locked in to their environment and when that environment changes one or more of the parameters that the species depends on, it becomes threatened and seen as endangered.

Armed with these thoughts on endangered species, we visited the US Fish and Wildlife Laboratory in Hays County to consult with the Regional Botanist Chris Hathcock.  Chris manages the facility that allows botanists like himself to research the nearly extinct Texas Wildrice.

Texas Wildrice (Zizania texana) now grows only in the first stretch of the San Marcos River, from where this river emerges from a spring until the bottom sands become silty and the current slows considerably.  It only grows in the upper stretch of the river because it is a perennial reproducing by tillers, it needs clear, moving water and a sandy bottom to survive.  It once grew in the Comal Springs to the south of the San Marcos River, but those springs went dry in the 1950s from excessive  ground water pumping and the native rice died and never recovered. The moving water is critical because this plant, with most of its leaves underwater, needs carbon dioxide from the water, just like all chlorophyllic plants.  Moving water provides a continuous supply of carbon dioxide.  Thus, carbon dioxide is also a critical part of the water composition.  And, of course, clarity of the water is critical because the leaves need sunlight.

The research facility at the Fish and Wildlife facility has several tanks where the botanists grow wildrice under conditions which duplicate the San Marcos River, including the water, having pumped it from the Edwards aquifer, the source of the springs.  One of the purposes of maintaining a colony of  wildrice plants in this herbarium bank is to restore the plant to the river should the native plants  be killed by some singular temporary external event.
That's good should a singular event occur, but what if the basic nature of the springs changes to an extent that the wildrice no longer can exist?  Have we then lost a valuable plant or have we incurred irrecoverable change to a natural spring?  Probably the loss of a natural spring is more significant than the loss of Texas Wildrice.  In effect, the wildrice is our canary in the coal mine.