Ciénega San Bernardino - Wetland Restoration

Science Center Objects

Desert marshes, or ciénega, are extremely biodiverse habitats imperiled by anthropogenic demands for water and changing climates. Given their widespread loss and increased recognition as important wildlife habitat, remarkably little is known about restoration techniques.

Desert marshes, or ciénega, are extremely biodiverse habitats imperiled by anthropogenic demands for water and changing climates. Given their widespread loss and increased recognition as important wildlife habitat, remarkably little is known about restoration techniques.

The U.S. Fish and Wildlife Service established the San Bernardino National Wildlife Refuge (SBNWR) in 1972. Cattle were removed and unde­sired woody plants were treated. Desired woody plants were planted and gabions were installed to reduce erosion and stabilize arroyos. The first gabion constructed on the SBNWR was in 1984, with nineteen to follow.In 2000, the Cuenca Los Ojos (CLO) Foundation acquired the Ciénega San Bernardino and other properties downstream of the SBNWR in Sonora, Mexico and restoration began immediately. Construction of gabions on CLO began in 2001 and continues today. By 2013, 46 loose-rock wire gabions and one check dam were built on CLO.

Vegetation at four riparian sites were in Ciénega San Bernardino in 2000, six to nine months after grazing ended at CLO (Minckley 2013). Research to develop detailed topographic surveys using terrestrial and airborne LiDAR and remote sensing, coupled with hydrological modeling, field observation, and stream-flow sensors is being done to assess the impacts of restoration efforts on sediment and hydrology at CLO (Delong and Henderson 2012; Henderson and DeLong 2012; Jemison et al. 2012). A large interdisciplinary group of scientists is working to integrate field surveys of bees, birds, and plant species to document potential reestablishment of historic wetland plant and animal communities there; findings include increases in stream flow, riparian vegetation, ciénega acreage, and vertebrate populations (Pulliam 2012).

In this study, we examine the effects of gabions (wire baskets filled with rocks used as dams) on vegetation in the Ciénega San Bernardino, in the Arizona, Sonora portion of the US-Mexico border, using a remote-sensing analysis coupled with field data. The Normalized Difference Vegetation Index (NDVI), used here as a proxy for plant biomass, is compared at gabion and control sites over a 27-year period during the driest months (May/June). Generalized linear models (GLM) were used to estimate the effects of precipitation and the presence or absence of gabions when NDVI changes were detected. Area where gabions were located demonstrated a maintained greenness, with some increase; areas without demonstrate a decline in vegetation density—associated with the precipitation trend (drought; Fig. 1). 

Average NDVI plotted over time

Figure 1. Average NDVI plotted over time in San Bernardino at treated and control sites, in relationship to annual precipitation.

(Public domain.)

Over this period, green-up occurred at most sites where there were gabions and at few of the control sites where gabions had not been constructed. When we statistically controlled for differences among sites in source area, stream order, elevation, and interannual winter rainfall, as well as comparing before and after the initiation of gabion construction, NDVI values increased around gabions and did not change or were negative where there were no gabions. NDVI at gabion sites does not respond prior to gabion construction but NDVI at gabion sites demonstrates a strong response to precipitation after the gabions are built (Fig. 2). 

Field data from 2000 to 2012 of plant cover, species richness, and species composition suggest all these measured increased and corroborate the NDVI findings. The response of vegetation to gabions demonstrated here over a 10-year period suggests that long-term restoration of a mature ciénega is possible. This research documents the positive influence of gabions when sites are targeted for stream restoration and the potential to ameliorate drought conditions for a desert ciénega (Norman et al 2014 In Review). 

Map depicting areas in the San Bernardino Wildlife Refuge

Figure 2. Map depicting areas in the San Bernardino Wildlife Refuge and Cuenco los Ojos, where gabions have been installed (marked with X) and other control sites, with levels of increasing or decreasing vegetation signatures portrayed by green or brown circles, depending.

(Public domain.)

***We are now working on an evaluation of effects of land management activities on streamflow, sediment transport, and groundwater/surface-water interactions in Silver Creek and Guadalupe Canyon, with the Bureau of Land Management and the Malpai Borderlands Group.

For more information, go to: San Bernardino Wildlife Refuge and the Cuenca Los Ojos Foundation websites.