Each year, the acreage of Texas' natural brush country converted for agricultural and residential uses increases. Fortunately, thanks to a generous donation to The Nature Conservancy, an example of South Texas thornscrub is protected at the 683-acre Mesquite Brushland Preserve. As one of the few undisturbed natural areas in Duval County, the ecological and historical value of this site is immense. Furthermore, the impressive biological inventory and diversity of this intact system is ideal for scientific and educational purposes.
In 1980, Dr. Richard Albert, a University of Texas graduate, expressed interest in donating his property south of San Diego to The Conservancy. The area was exposed to only limited disturbance throughout the years of Dr. Albert’s ownership thanks to his strong commitment to conservation. During his life, he harbored an unwavering interest in wildlife and natural history. When Dr. Albert died in 1990, Mesquite Brushland was bequeathed to The Conservancy.
Various amphibians and reptiles occupy the scrub woodland of the preserve. The Texas toad, Texas spotted whiptail, Texas spiny lizard, bullsnake, and Taylor's ground snake are a few of the site's documented inhabitants. The preserve also supports the threatened Texas Tortoise. Birds such as white-tailed hawk, cactus wren, groove-billed ani, green jay, and scissor-tailed flycatcher have been sighted on the property. Coyotes, javelina and white-tailed deer find refuge on the tract.
The botanical value of Mesquite Brushland is reflected in the more than 200 species of plants documented on the preserve. This large diversity of brushland and grassland vegetation is a testament to the natural state of the site.
Four plant communities have been identified on the preserve. Mesquite-hairyseed paspalum and Mesquite-spiny hackberry form the two woodland-oriented communities. The shrubland-type associations are mesquite-mixed brush and amargosa-brasil. Mesquite and huisache are the dominant woody species. Grasses include fringed signal grass, buffalograss, love grass, and windmill grass.
Adding to the ecological value of the site are the occurrence of some endemic and endangered plant species. The milkpea and Texas senna are examples of preserve plants unique to South Texas. The most significant species supported by the preserve is the Federally endangered black lace cactus. These extremely rare cacti, with their beautiful lavender flowers and lacy netlike pattern of dark spines, suffer from habitat destruction and poaching throughout their range. Mesquite Brushland is one of the few protected areas on which this endangered plant exists.
Site management programs have thus far focused on biological inventories. In 1989, an amphibian and reptile population survey was conducted. A survey and assessment of the preserve's plant communities was conducted in 1990, and in 1997 a study of woody plant distribution and encroachment patterns was undertaken. These and future surveys are necessary to establish and monitor long term stewardship programs for the property.
The preserve has great potential for long-term research on succession, restoration and biodiversity. Comparisons between this site and ecologically disturbed brush areas in South Texas provide an opportunity to examine the effects of anthropogenic environmental deterioration. Additional biological inventories and studies are planned for the preserve.
Lower Rio Grande Valley (PDF)
The preserve is located in the flat terrain and semiarid climate of the South Texas brush country in Duval County, a few miles south of San Diego, Texas.