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Title: Projecting avian response to linked changes in groundwater and riparian floodplain vegetation along a dryland river: a scenario analysis

Author
item BRAND, L. - University Of Arizona
item STROMBERG, J. - Arizona State University
item Goodrich, David - Dave
item DIXON, M. - University Of South Dakota
item LANSEY, K. - University Of Arizona
item KANG, D. - University Of Arizona
item BROOKSHIRE, D. - University Of New Mexico
item CERASALE, D. - Cornell University - New York

Submitted to: Ecohydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2010
Publication Date: 7/5/2010
Citation: Brand, L.A., Stromberg, J.C., Goodrich, D.C., Dixon, M.D., Lansey, K., Kang, D., Brookshire, D.S., Cerasale, D.J. 2010. Projecting avian response to linked changes in groundwater and riparian floodplain vegetation along a dryland river: a scenario analysis. Ecohydrology. https://doi.org/10.1002/eco.143.
DOI: https://doi.org/10.1002/eco.143

Interpretive Summary: Natural, intact, freshwater ecosystems, and the habitat they support are relatively rare in the semi-arid southwest. The water supporting these systems is often in high demand for human or agriculture use. To address this conflict, natural scientists must evaluate how human water use decisions impact hydrologic regimes and the ecological systems this water supports. In this study a model was developed that links groundwater changes with changes in riparian vegetation and changes in the abundance of breeding and migratory birds along the upper San Pedro River, Arizona. When groundwater levels decline, cottonwoods and willows progressively decline, and shrubbier species less dependent on permanent water sources increase. This results in broad shifts in the composition of the breeding bird community, with canopy nesting and water birds declining but nesting birds that nest in the middle of trees increase. When groundwater levels increase there were increases in birds which nest high in the tree canopy. When growth and groundwater pumping or recharge decisions are made, these models can be used to predict changes in riparian habitat and the bird populations they support.

Technical Abstract: Groundwater is a key driver of riparian condition on dryland rivers but is in high demand for municipal, industrial, and agricultural uses. Approaches are needed to guide decisions that balance human water needs while conserving riparian ecosystems. We developed a space-for-time substitution model that links groundwater change scenarios implemented within a Decision Support System (DSS) with proportions of floodplain vegetation types and abundances of breeding and migratory birds along the upper San Pedro River, Arizona. In groundwater decline scenarios, relative proportions of tall-canopied cottonwood/willow on the floodplain progressively decline, and shrubbier species less dependent on permanent water sources increase. These scenarios result in broad shifts in the composition of the breeding bird community, with canopy nesting and water-obligate birds declining but midstory nesting birds increasing in abundance as groundwater declines. Groundwater recharge scenarios were associated with increases in canopy nesting birds. Model outputs serve to assess the sensitivity of biotic groups to potential changes in groundwater and thus to rank scenarios based on their expected ecological impacts.