Southwest Biological Science Center
Terrestrial Ecosystems and Restoration
Deserts of the southwestern US are replete with oil and gas deposits as well as sites for solar, wind, and geothermal energy production. In the past, many of these resources have been too expensive to develop, but increased demand and new technologies have led to an increase in exploration and development. However, desert ecosystems generally have low resilience to disturbance. More frequent, intense droughts forecast for the southwestern US will likely further hamper recovery of disturbed lands. Consequently, there is a need for new science to anticipate and mitigate the effects of energy exploration and development. The Colorado Plateau Region contains approximately 100,000 abandoned and current wells spanning 60 years of activity. These structures are spread over a variety of substrates, climate zones, elevations, and vegetation communities, with varying periods of use and time since abandonment. The overarching goal of this project is to understand how past and current energy development are impacting the social-ecological systems of the Colorado Plateau, and to identify strategies to mitigate deleterious consequences of these activates now and into the future.
Renewable energy development is expanding in southwestern deserts, including in Arizona. Energy developers look to resource management agencies to provide siting guidance on public lands where there might be conflicts with wildlife. Often, agency guidance considers species of conservation concern and economic importance, but information on comprehensive vertebrate biodiversity has been hard to incorporate. In this project, USGS researchers illustrate how biodiversity richness metrics for most vertebrate wildlife that can use an area and for sensitive guilds of wildlife such as bats, raptors, and migratory land birds can be incorporated into renewable energy siting decisions.
Although most introduced insects are relatively benign, some become high-impact pests causing widespread ecological and economic damage. Introduced insects that are specialists and feed on a single genus of plants can be high-impact as they can potentially eliminate an entire native plant genus over large areas. Luckily, most introduced insects with this feeding behavior do not become high-impact pests. However, there is great need to predict, prior to their introduction, which insects have the potential to result in high-impact invasions so risk assessment and management are informed.
A group of USGS, Forest Service, and university scientists are working together to study how ecology and evolution might be used to understand when introduced insects become high-impact. We are examining the contribution of five types of drivers toward these impacts: (1) the insects’ and host plants’ evolutionary history, (2) the hosts’ defenses or lack thereof (defense-free space), (3) presence of natural enemies or lack thereof (enemy release), (4) invader traits, and (5) geographic and temporal considerations.
Introductions of bio-control beetles (genus Diorhabda) are causing defoliation and dieback of exotic Tamarix spp. in riparian zones across the western U.S., yet the factors that determine the plant communities that follow Tamarix decline are poorly understood. In particular, Tamarix-dominated soils are often higher in nutrients, organic matter, and salts than nearby soils, and these soil attributes may influence the trajectory of community change following Tamarix defoliation and mortality. This project aims to assess the physical and chemical drivers of plant colonization after beetle-induced Tamarix decline using long-term observational studies, field and greenhouse manipulation experiments, and a focus on providing resource managers with more information regarding management decisions that could help improve southwestern riparian zone community composition and function.
Concerns about energy security and rising greenhouse gas emissions have stimulated an unprecedented increase in the push for alternative energy use, including the use of plant biomass as a source of renewable energy (bioenergy). However, meeting alternative energy goals, while also meeting food demands and mitigating potential detrimental effects of industrialized agriculture, has emerged as a critical challenge facing our nation. The southwestern U.S. provides exciting opportunities to grow biofuels, because land use in the Southwest is not currently focused on growing large amounts of food and because multiple arid-land plants are highly efficient biofuel sources. SBSC’s Southwest biofuels program takes a two-pronged approach to improving our capacity to incorporate biofuels into our national energy portfolio: (1) using remote sensing and on-the-ground techniques to improve our understanding of the potential for bioenergy and (2) assessing the environmental consequences of bioenergy development, namely, greenhouse gas emissions, air and water quality effects, soil destabilization and dust production, and effects on exotic plan invasion.
Biological soil crusts (biocrusts) are commonly found on the soil surface in arid and semi-arid ecosystems (collectively called drylands). Biocrusts can consist of mosses, cyanobacteria, lichens, algae, and microfungi, and they strongly interact with the soil. These organisms or consortium of disparate organisms, depending on the specific biocrust, are important to the functioning of ecosystems and to the organization of plant and soil communities. To download a copy of “A Field Guide to Biological Soil Crusts of Western U.S. Drylands: Common Lichens and Bryophytes”, click on the adjacent Science tab.
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We study the links among different geomorphic processes that affect river valley landscapes in the Colorado River downstream from Glen Canyon Dam, Arizona. Dam-released flows affect the deposition and retention of sandbars that serve as sources for other sand resources, such as windblown sand dunes, throughout the Colorado River ecosystem. The degree to which the landscapes are differentially affected by river, wind, rainfall, or gravity-driven redistribution of river-derived sand is called sediment “connectivity”. Connectivity is affected by several factors including the amount of sand supplied as well as physical and vegetative barriers to sand transport. Connectivity affects the condition of natural and cultural resources – such as archaeological sites – in the ecosystem. In particular, we assess the potential for Colorado River sand to enhance the preservation of river-corridor archeological resources through burial by wind deposition and/or mitigation of gully erosion.
Riparian vegetation has increased dramatically along the Colorado River downstream of Glen Canyon Dam since the closure of the dam in 1963. The spatial patterns and temporal rates of vegetation increase occur due to changes in river hydrology, dam operations, and climate. The increase in vegetation, particularly onto otherwise bare sandbars, has impacted recreational, geomorphological, biological, and cultural resources along the river. Some of the riparian vegetation is non-native, invasive Tamarix that has recently been subject to herbivory and defoliation by the northern tamarisk beetle which has been in the Grand Canyon region since approximately 2009. We use remote sensing of very high resolution multispectral imagery and lidar acquired from fixed-wind airplanes and helicopters to monitor and research the short- and long-term dynamics of riparian vegetation and associated environmental science issues in the region.
Dryland regions have been degraded by invasive species, wildfire, overgrazing, agricultural conversion, energy development, recreational activity, and urban growth. These disturbances and others are accelerated by one of the fastest growing human populations in the country and a pressing background of decreasing water availability due to drought and elevated temperatures that are projected to become more pronounced. Recovery from disturbance in face of global change pressures represents a substantial challenge to agencies that manage large tracts of land because the potential reduction and loss of ecosystem productivity could have large economic, social, and environmental costs. Restoration and rehabilitation practices are critically needed to promote recovery from disturbance, improve the health and integrity of drylands, and ensure the long-term sustainability of ecosystem services.
In the southwest US, monsoon precipitation increases sharply along a northwest to southeast gradient. Pleuraphis jamesii or galleta grass, is an important C4 grass species that spans across this large range in precipitation pattern. In this study we are assessing the ability of galleta grass to adapt to changes in the seasonality of rainfall (termed “plasticity”). In the fall of 2014, we transplanted four populations of galleta grass to a common garden field trial at the Canyonlands Research Center and allowed them to establish for one year. In 2016, we began applying three precipitation seasonality treatments to the populations: spring only, monsoon only and spring and monsoon. We are examining the phenological, ecophysiological and morphological responses to assess plasticity.
Forests in the semiarid southwestern U.S. are expected to be highly vulnerable to increasing aridity anticipated with climate change. In particular, low elevation forests and the processes of tree regeneration and mortality are likely to be highly susceptible to climate change. This work seeks to characterize how, where and when forest ecosystems will change and identify management strategies to promote resilience.