Description of the Project

Overview of the Project

The South Legunita Grassland Restoration Project is a 1,100 acre mesquite clearing project of semi-desert grassland in the southern portion of the Altar Valley.  The project is comprised of five phases of habitat restoration through mechanical clearing of mesquite.  Mesquite overgrowth had decreased the extent and patch size of grassland habitat and outcompeted native grasses that provide food for grassland obligates.  The project is located on the Santa Margarita Ranch, on private and Arizona State Trust Land (which has been permitted) that borders the Buenos Aires National Wildlife Refuge.  The project benefited wildlife, ranchers, non-profit partners actively engaged in collaborative conservation, hunters and recreationists who enjoy the healthy, open landscapes of the Altar Valley, and the neighboring Buenos Aires National Wildlife Refuge (BANWR).  It extended a corridor of treated areas from the BANWR onto private and State lands.

Background

The Altar Valley, south of Hwy 86, directly east of the Baboquivari Mountains encompasses approximately 457,000 acres of Arizona rangeland in Game Management Units 36 A, B, and C. In this valley, 347,000 acres were categorized by percent shrub canopy cover in a 2012 grassland quantity and composition study conducted by The Nature Conservancy. At the time it was surveyed, only 5% of this once open grassland had less than 15% shrub cover. The survey found 54% of the total area to have between 10-35% shrub cover, and suitable for restoration activities. The remaining acreage was either greater than 35% shrub invaded or not classified at all, likely due to urban encroachment.

This once open area, where shrub cover has not exceeded 35%, still supports a small population of pronghorn antelope, mostly in areas where grassland restoration has been completed, or shrub density was already low. It is the desire of the Arizona Game and Fish Department (AGFD) that shrub density be reduced to less than 10% on at least 20 square miles, or 12,900 acres, in the southern portions of the Valley in the interest of promoting pronghorn population growth and improving grassland species diversity.  Reducing the number of mesquites will also increase the groundwater recharge rate, and increase the availability of water to grasses and forbs. With more land cover, the grass will then act as a filter to clean water as it goes into the aquifer.

Benefits for Wildlife

In the AGFD’s Management Focal Area Plan for the units associated with the South Legunita Restoration Project, the need for grassland restoration to benefit pronghorn is listed as a Priority 1 Issue, and the Altar Valley Conservation Alliance is actively supporting a pronghorn population that is in decline.  This project is specifically designed to enhance pronghorn habitat by removing mesquite, offering increased visibility to allow them to better see potential threats, and allowing them more open space to run and more successfully evade predators.  The current density of woody shrubs is extremely prohibitive to vision and movement of pronghorn as well as other species.

Project History

In 2017, the Santa Margarita Ranch, which borders the Buenos Aires National Wildlife Refuge to the west, expressed an interest in expanding upon the Refuge’s grassland restoration work that has been ongoing since 2010. The integration of these two grassland enhancement projects enhances the functionality of ecosystems for grassland obligate species, including masked bobwhite quail and pronghorn.  Walter Lane, the ranch manager, contracted a cultural resources survey on 1,300 acres on the Santa Margarita Ranch, (directly west of the 1,134 acres cleared on the BANWR in 2016-17), so that as resources were made available, mesquite might be mechanically reduced on the uplands in that pasture. The Santa Margarita was first awarded funding for this project in 2018 and completed five phases of project work.