by Kristen Tyson, M.A.
Native range replaced by grass monoculture
So what’s
the big deal about changing Texas? The survey was completed so long ago that
surely the variation in climate and the natural order of “only the strong
survive” has something to do with it? Let’s see. “Changes caused by humans are
often different from those to which natural communities are adapted, causing
drastic alteration of land use and landscape patterns, including their inherent
abiotic and biotic elements (Schmidly 2002).” Variations in population are seen
as the main culprit in regards to an altered Texas. And when a population
grows, land is needed to sustain it. So how have Texans altered the state since
the survey was completed?
The Texas
population in 1900 was a mere 3 million, whereas today the population is at an
estimated 26 million. Over the years, “land cover was altered principally by
human activity, including farming and agriculture, ranching and raising of
livestock, logging of forests, suppression of natural fire, and construction
associated with expanding urbanization (Schmidly 2002).” Thus, lands have
transformed, with different habitats emerging that often choke out the natural
habitat, depleting native plant and wildlife species. Also, environments that
were once fluid and continuous are now fragmented, opening the possibility for
invasive vegetation to take over where former flora existed. “In general, the
chances of losing native animal and plant species and disrupting ecological
functions increase when the patterns of natural habitats and disturbance are altered
(Schmidly 2002).”
River bend erosion
Not only are
the lands impacted, but so are water sources. The need to store water or avert
the flooding of the plains has absolutely changed the topography of Texas.
Natural streams and rivers that once ebbed and flooded at the mercy of Mother
Nature are now diverted or covered up. Rivers are seen as the link to “our land
and water ecosystems” (Schmidly 2002), but nearly every natural river has been
changed, varying the natural order of habitats that depended on fresh water to
sustain it. Even the drilling of oil wells and pumping of natural spring taps
has led to the decline or depletion of natural springs. Pollution from invasive
species, runoff from streets, and pesticide dumping make their way into these
waters, harming marine species that depend on this freshwater to mature.
Changes to the landscape have altered wetlands as well. “Interior wetlands
account for 80 percent of the total wetland acreage in the state, [yet] Texas
has lost one-half of its coastal wetlands and 60 percent of its terrestrial
wetlands in the past two hundred years (Schmidly 2002).” This trend is allowed
to continue thanks to the penetration of saltwater, damming up of water
sources, and pollution from numerous contributors.
Before Texas
even became a state, fires were a means of “shaping the landscape and land
cover” (Schmidly 2002), but as time progressed, overgrazing left little
vegetation to burn and when there were natural fires, they were quickly
suppressed. “Before fire suppression, Texas ecosystems were accustomed to
frequent, low-severity wildfires that facilitated landscape and habitat
diversity by providing opportunities for the establishment and maintenance of
early successional species and communities (Schmidly 2002).” Now native plants
and shrubs are choked out by less desirable trees and insects are forced to
play a major role in the diets of wildlife. Even plants that were introduced as
a landscape plant or to halt erosion, notably salt cedar, have spread in such
mass proportions that native plants are no longer evident across the state. These invasive plants tend to soak up more
water that is a precious commodity during the ever present Texas droughts.
Salt cedar
Research
suggests that “railroads were a mechanism for the expanded distribution of
mesquite through rapid and extensive movement of livestock in the late
nineteenth and early twentieth centuries”, whereas the “suppression of fire was
primarily responsible for initiating the invasion of juniper (Schmidly 2002).” Mesquites,
juniper, salt cedar and prickly pear were allowed to spread, where grasses used
to thrive, from Mexico into south Texas and later into the southern plains
(Schmidly 2002). Eventually riverbeds and streams witnessed bunches of growth
and after just fifty years, mesquite and other species had dominated the plains
and grasslands of Texas.
Due to the
excessively high overgrazing rates across the state, plant diversity and
rangelands were altered in each ecoregion. “Cool season grasses and other
preferred forage species declined, herbaceous plant and litter cover were
reduced, [and] soil erosion, flooding, and arroyo cutting” were all affected by
the year-round grazing of livestock. Fortunately, new grazing methods have been
adopted and certain habitats have been allowed to improve, signifying a
positive return to recuperating rangelands.
Overgrazed habitat
However, the
most devastating factor to the landscape is habitat fragmentation. This is a
“process by which stands of native vegetation become smaller and discontinuous
because of the clearing of land for various purposes, such as agricultural,
residential, or commercial use (Schmidly 2002).” Depending on the size and
quality of a specific plant or animal species, some are merely reduced while
others are totally eliminated “because of loss of genetic diversity,
catastrophes, or an imbalance in relations of competing species, predators, and
their prey (Schmidly 2002).” Even the shift from large acreage farms and
ranches to smaller, multiple owner properties has led to habitat fragmentation.
Acreage that remained in one family for generations is now split into multiple
tracks, further altering the land available for natural wildlife to flourish.
From the
time of the survey to the present, drastic changes have been noted in the
presence and population of animals as well. With the ever evolving natural
habitat and population pressures, 35 percent of mammals that were documented in
the survey are now extinct or endangered (Schmidly 2002). Several key trends
have been recognized as the cause of the mammal decline.
Notably,
many of the native species, including bison, pronghorn, and feline species,
were already on a marked decline when the survey was completed. These animals
were quickly followed by bears, wolves, and bighorn sheep, to name a few. It is
interesting to note that the “nine species that became extinct were all large,
herbivorous or predatory species [thanks to]exploitation and habitat alteration
by humans (Schmidly 2002).” It’s easy to conclude that the loss of bison and
sheep led to a change in wolf and coyote behavior. Not only did these species
hybridize, but without bison, these canines began to pursue cattle, and quickly
became the prey as widespread hunting quickly knocked out whole populations in
many states.
Coyote
As mammal
populations were reduced by human hunting and influence, others were negatively
affected by a decrease in suitable habitat and home ranges, which led to a
profusion of animals in one area. Declines of certain species have been
“associated with overgrazing of grasslands by domestic livestock, uncontrolled
hunting, and extensive cultivation of prairie habitat (Schmidly 2002).”From
disappearing pronghorn antelope to poisoned prairie dogs, each species reacted
to these threats in various ways. Select species slowly stopped reproducing
where others adapted to a more welcoming, albeit less hospitable environment.
Mountain lion were once witnessed across the nation, but are now phantoms that
indiscriminately appear on game cameras in the Desert Mountains of Texas and
the Edwards Plateau.
Yet, mammals
like the pygmy mouse, armadillo, bats and squirrels, which once restricted
themselves to a particular distribution range, can now be found in nearly every
region of the state. These expansions have been attributed to “progressive
climatic change, encroaching human civilization, overgrazing, and decimation of
large carnivores (Schmidly 2002).” This may seem like a positive effect, but
can too many of one thing be bad? Especially if the “thing” is a rodent who can
spread like wildlife when unimpeded?
The last key
trend is a problem passed along the family tree of the animals themselves.
Specific groups are prone to reduced numbers thanks to biological traits that
prevent them from reproducing in large quantities. Mammals like bats and
herbivores, and their carnivore enemies, are limited by climatic and habitat
changes, disturbances to their home ranges, or lack of valuable resources. For
instance, bats are dependent on caves and if this small detail is overlooked,
then bats will become extinct, in essence. Not all species can adapt every part
of their life to meet their daily needs. Add in the stress of insufficient food
and security, and you have a dying species. Thankfully, endangered species laws
have protected and promoted numerous species who were on the cusp of
extinction, but Texas mammals are not out of the woods yet.
There are
still species on the list as endangered in our own state: bats, black bear,
coatimundi, wolf, ferret and jaguar, are just a few. Threatened animals
include: bats, rodents, grizzly bear (extinct in Texas), with the cottontail,
skunk and fox following close behind. Certainly there are more animals that
will face this same fate considering the growing population of humans and
encroaching subdivisions and mini-malls that appear on the Texas horizon. “The impact of over-exploitation, largely
through over-harvesting and unregulated hunting, severely impacted wildlife at
the beginning of the twentieth century. As we look to the next millennium, loss
of habitat, landscape fragmentation, and the commercialization of wildlife
undoubtedly will impact our landscapes, habitats, fauna, and flora (Schmidly
2002).”
Habitat encroachment
Now to
answer the question posted at the beginning of this blog: has the state of
Texas changed simply because of climatic and evolutionary influences? If you
answered yes, then I will guess you have never witnessed the beauty of a
caprock sunrise or stopped to take a picture of native wildlife doing what they
do, thus there is no hope for the wildlife or plains of Texas. If you answered
no, then you are 100% correct. So what
is to be done, when it is evident that human populations will not stop growing
nor will the need for land to facilitate them?
Yes, I am a realist and there
are insurmountable challenges to face in terms of conservation and land
stewardship modifications, but they are challenges, nothing more. When Bailey
and his men needed just one more plant or animals species for their collection
of a region, yet met endless terrain and the evasion of such a species, did
they quit? Did they settle for less and simply move on believing there was no
point or no hope? No, they stayed in that area until they captured the elusive
species and were all the more victorious for the story they could tell about
capturing it. Their journals were filled with stories about solitude,
desperation, and wonder. They left Texas with a deeper understanding of her
native wildlife and landscape. Can you say you want the same thing? What about
for your children, or grandchildren? Imagine a Texas without native wildlife,
short of what you can see at a zoo or a taxidermy museum even. It’s never too
late until the fate of Texas becomes one massive feedlot or cement block, and
like Bailey and his fellow surveyors believed, every piece of Texas counts.
Schmidly, D. J.
2002. Texas Natural History: A
Century of Change. Texas Tech University
Press.
Lubbock, Texas, U.S.A.