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Imperiled Great Basin terminal lakes: Synthesizing ecological and hydrological science gaps and research needs for waterbird conservation

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Terminal lakes are declining globally because of human water demands, drought, and climate change. Through literature synthesis and feedback from the resource and conservation community, we review the state of research for terminal lakes in the Great Basin of the United States, which support millions of waterbirds annually, to prioritize ecological and hydrologic information needs. From an ecological perspective, research priorities include measuring the underlying differences in waterbird resource selection and distribution, migratory connectivity, abiotic factors that interact with prey densities to affect prey availability, and waterbird fitness or demography. Integrated links between water availability, water quality, and food webs are lacking in the literature. Scarce water availability data hinder the current knowledge of water extraction and evapotranspiration rates. Research that can address these priorities would help advance our understanding of how the Great Basin terminal lakes function as an interrelated system and support conservation efforts to reverse the decline of these critical lakes.
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BioScience , 2024, 0 , 1–15
https://doi.org/10.1093/biosci/biae126
Advance access publication date: 0 2024
Overview Article
Imperiled Great Basin terminal lakes: Synthesizing
ecological and hydrological science gaps and research
needs for waterbird conservation
Garth Herring , Ashley L. Whipple, Cameron L. Aldridge, Bryce A. Pulver, Collin A. Eagles-Smith, Rich D. Inman, Elliott L. Matchett,
Adrian P. Monroe, Elizabeth K. Orning, Benjamin S. Robb, Jessica E. Shyvers, Bryan C. Tar box, Nathan D. Va n Schmidt, Cassandra
D. Smith, Matthew J. Holloran, Cory T. Overton, David R. O’Leary, Michael L. Casazza and Rebecca J. Frus
Garth Herring ( gherring@usgs.gov) and Collin A. Eagles-Smith are afliated with the US Geological Survey, Fores t and Rangeland Ecosystem Science Center, in
Corvallis, Oregon, in the United States. Ashley L. Whipple, Cameron L. Aldridge, Rich D. Inman, Adrian P. Monroe, Elizabeth K. Orning, Benjamin S. Robb, Jes sica E.
Shyvers, Bryan C. Ta r b o x , Nathan D. Van Schmidt, and Matthew J. Holloran are afliated with the US Geological Survey, Fort Collins Science Center, in Fort Collins,
Colorado, in the United States. Bryce A. Pulver and David R. O’Leary are afliated with the US Geological Survey, Utah Wa te r Science Center, in Salt Lake City,
Utah, in the United States. Elliott L. Matchett, Cory T. Overton, and Michael L. Casazza are afliated with the US Geological Survey, Wes ter n Ecological Science
Center, in Dixon, California, in the United States. Cassandra D. Smith is afliated with the US Geological Survey, Oregon Wa ter Science Center, in Bend, Oregon, in
the United States. Rebecca J. Frus is afliated with the US Geological Survey, Nevada Wa te r Science Center, in Boulder City, Nevada, in the United States.
Abstract
Terminal lakes are declining globally because of human water demands, drought, and climate change. Through literature synthesis
and feedback from the resource and conservation community, we review the state of research for terminal lakes in the Great Basin of
the United States, which support millions of waterbirds annually, to prioritize ecological and hydrologic information needs. From an
ecological perspective, research priorities include measuring the underlying differences in waterbird resource selection and distribution,
migratory connectivity, abiotic factors that interact with prey densities to affect prey availability, and waterbird tness or demography.
Integrated links between water availability, water quality, and food webs are lacking in the literature. Scarce water availability data
hinder the current knowledge of water extraction and evapotranspiration rates. Research that can address these priorities would help
advance our understanding of how the Great Basin terminal lakes function as an interrelated system and support conservation efforts
to reverse the decline of these critical lakes.
Keywords: endorheic, migratory connectivity, saline lakes, water extraction, water use, waterbirds
Endorheic lakes (hereafter, terminal lakes ), which do not have an
outlet to an external body of water, provide unique aquatic en-
vironments within continental landscapes globally (Wang et al.
2018 ). As a group, terminal lakes span the broadest ranges of
water chemistry characteristics among inland waterbodies, cre-
ating diverse habitats that support varied ecosystem services
(Herbst 2001 ). Most terminal lakes lie in arid or semiarid re-
gions (Wurtsbaugh et al. 2017 , Wang et al. 2018 ), and there-
fore are highly sensitive to changes in water availability. In
response to growing human populations and associated wa-
ter use demands, coupled with extended drought and climate
change, the spatial extents and water quality of terminal lakes
have declined globally (Messager et al. 2016 , Gross 2017 , Wurts-
baugh et al. 2017 , Wurtsbaugh and Sima 2022 ). Worldwide, agri-
cultural (Williams 1996 , Micklin 2007 , Moore 2016) and urban
(Wurtsbaugh et al. 2017 ) water use increased by approximately
175% between 1960 and 2010 (Wada and Bierkens 2014 ), and
around the same time terminal lakes and their basins experi-
enced an extensive water loss of 106.3 gigatons per year be-
tween 2002 and 2016 (Wang et al. 2018 ). Rising temperatures in-
crease plant evapotranspiration rates, water requirements, and ir-
rigation rates for extensive agricultural areas, ultimately reduc-
ing stream ow in many regions where terminal lakes exist (Li
et al. 2019 , Doede and DeGuzman 2020 , Donnelly et al. 2020 ,
Schulz et al. 2020 , Rad et al. 2022 ). The synergy between these
stressors (drought, climate change, consumptive water use) has
resulted in many large terminal lakes (e.g., Lake Urmia, in Iran;
Poopó Lake, in Bolivia; the Aral Sea, in Kazakhstan and Uzbek-
istan) losing up to 75% of their wetted extents or volumes
(Micklin 2007 , Satgé et al. 2017 , Schulz et al. 2020 ), resulting in
catastrophic impacts on wildlife populations, including migrat-
ing birds (Parsinejad et al. 2022 ), sh (Micklin and Aladin 2008 ),
and the food webs supporting them (Micklin 2007 , Parsinejad et
al. 2022 ). This deteriorating health of terminal lakes also has
substantial socioeconomic–environmental implications, includ-
ing potential human health risks and impacts on industries that
use terminal lakes (Micklin 2007 , Satgé et al. 2017 , Wurtsbaugh
et al. 2017 ).
The Great Basin of North America encompasses the Great Salt
Lake (Utah), Lake Abert (Oregon), and numerous other termi-
nal lakes (gure 1 , see the supplemental material labeled “Study
Area”) that have experienced long-term declines in lake extent
and volume (Moore 2016 , Wurtsbaugh et al. 2017 , Donnelly et al.
2020 , Wurtsbaugh and Sima 2022 ) and severe deterioration of lake
health (Larson et al. 2016 , Moore 2016 , Senner et al. 2018 , Haig
et al. 2019 ). Despite decades of research demonstrating their im-
portance for waterbirds and other wildlife populations, funda-
mental knowledge gaps still exist concerning how the ecologic,
Received: May 30, 2023. Revised: October 8, 2024. Accepted: November 20, 2024
©The Author(s) 2024. Published by Oxford University Press on behalf of the American Institute of Biological Sciences. This is an Open Access article distributed
under the terms of the Creative Commons Attribution-NonCommercial License ( https://creativecommons.org/licenses/by-nc/4.0/), which permits
non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact
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2|BioScience, 2024, Vol. 0, No. 0
Figure 1. Location of 20 study terminal lakes within the Great Basin region of California, Nevada, Oregon, and Utah, in the United States, as identied
by the United States Congress (2022 ), Saline Lake Ecosystems in the Great Basin Program Act of 2022. The Great Basin Study Area is coterminous with
the Great Basin, and the Wa rne r Lakes in Oregon are a series of 12 interconnected lakes.
climatologic, and hydrologic connections of these terminal lake
systems form a functioning network of habitats for resident and
migratory species (gure 2 ).
Upgradient water pools in terminal lakes and their associated
wetlands because of their position at the downstream terminus
of watersheds lacking oceanic outows, providing a broad array
of ecosystem and human services. The lack of outow allows
the lakes to accumulate vast quantities of minerals and nutri-
ents (e.g., lithium, potash, salt) that are used for industrial and
agricultural processes (Wurtsbaugh and Sima 2022 ). Accumula-
tions of nutrients and minerals facilitate high primary produc-
tivity in many hypersaline terminal lakes, supporting abundant
brine shrimp populations and their commercial harvest (Saccò
et al. 2021 , Wurtsbaugh and Sima 2022 ). Terminal lakes and their
associated wetlands provide a substantial but little recognized
sink of global carbon, burying and sequestering more than 152
million metric tons of inorganic carbon annually; the deep ocean
sequesters 200 million metric tons per year (Li et al. 2017 ). The
isolation and extreme conditions of terminal lake ecosystems
create diverse habitats characterized by broad salinity ranges,
ephemeral hydrology, varying biogeochemistry, and unique bio-
diversity, including a high degree of endemism (Cooper and Koch
1984, Micklin 2010 , Zadereev et al. 2020). One key manifestation
of these factors, particularly in arid regions with limited water re-
sources, is that terminal lakes and associated wetlands provide
critical habitats for extensive populations of wildlife (Cooper and
Koch 1984, Zadereev et al. 2020, Saccò et al. 2021 , Donnelly et al.
2022 ).
The terminal lakes of the Great Basin represent a comple-
mentary network of ecosystems across a vast arid region that,
Herring et al. |3
Figure 2.
Three diagrams depicting lake, watershed, and region spatial extents and the water availability, habitat, and bird foci at each extent. (a) The
lake spatial extent is the open water portion of the lake and the adjacent aquatic environments. The water availability focus at this extent is related to
water quality. The habitat foci are related to the types, amount, and resources at lake habitats. The bird foci are evaluating bird behavior and life
stages. (b) The watershed spatial extent includes all water that exists within the dened watershed. The water availability focus is related to natural
and human water use. The habitat focus is composition, including species diversity and distribution. The bird focus is selection—or how the birds use
the watershed. (c) The region spatial extent is the Great Basin study area. The water availability foci are related to the spatial distribution and timing
of water delivery. The habitat foci are related to how habitats are congured and repeated across the region. The bird focus is related to how birds
move throughout the region.
together, provide critical resources for humans and wildlife. This
network of terminal lakes is key to supporting millions of water-
birds, including dozens of migratory species, through all stages of
their life histories (Haig et al. 2019 , Donnelly et al. 2020 , Tavernia
et al. 2021 ). However, the comparatively simple food webs associ-
ated with many of these lakes make them more vulnerable to cli-
mate change and water extractions than more complex lake sys-
tems, where greater functional redundancy provides some insur-
ance against individual species loss (Wurtsbaugh and Sima 2022 ,
Shadrin et al. 2023 ). Historically, the network structure of lakes
across the Great Basin landscape provided resilience to impacts
associated with the degradation of any single lake (Haig et al.
2019 ); however, the entire network now faces unprecedented chal-
lenges with unknown implications for the diverse wildlife pop-
ulations, human communities, and industries relying on these
lakes. Despite extensive research on some terminal lakes of the
4|BioScience, 2024, Vol. 0, No. 0
Great Basin (e.g., Great Salt Lake; see Wurtsbaugh and Sima 2022 ),
there is still considerable uncertainty regarding the ecology and
hydrology of many lakes within this region. Research and man-
agement actions are complicated by the mosaic of public and pri-
vate land ownership and the frequent lack of coordinated water
supply management within watersheds. These knowledge gaps
and management limitations hamper informed prioritization and
decision-making for conservation across the systems.
Compiling and synthesizing existing knowledge across the re-
gion to identify information gaps is a critical rst step toward pri-
oritizing and addressing ongoing threats to the Great Basin’s ter-
minal lakes. We report in the present article on the outcomes of
an approach that integrates the ecological and hydrological liter-
ature and stakeholder feedback to identify the complexities, data
gaps, and research needs associated with long-term changes to
terminal lakes of the Great Basin. We rst conducted an exten-
sive literature review to synthesize current knowledge on the ecol-
ogy and hydrology of terminal lakes across the Great Basin and to
document potential gaps in understanding. We then used a re-
source and conservation community feedback process (Wanders-
man 1981 , Martin and Sherington 1997 , Reed 2008 ) through a se-
ries of workshops across the Great Basin to supplement our under-
standing of identied data gaps and to prioritize needs for future
research and conservation efforts.
Literature synthesis and research gaps
The rst step in our effort was to gather relevant scientic pub-
lications, including journal articles, agency or nongovernmental
organization reports, books, theses, and dissertations (hereafter,
publications ). Briey, we performed a keyword search on termi-
nal lake ecology and hydrology in Google Scholar (using Publish
or Perish software; Harzing 2016 ) and Scopus (using BiblioSearch
software; see the supplemental material labeled “Methods”; Kleist
and Enns 2022 ). We then reviewed all literature and determined its
relevancy to our Great Basin terminal lakes focus, assigned liter-
ature to broad ecological and hydrological topical categories, and
then performed an information density analysis (Wilkinson and
Friendly 2009) relative to the lakes (see the supplemental mate-
rial).
Resource and conservation community
feedback
As the second step in our process, we collaborated with staff from
the Department of the Interior Ofce of Collaborative Action and
Dispute Resolution to design a workshop protocol to elicit input
from stakeholders on data gaps and monitoring priorities focused
on three geographic regions across the Great Basin study area (see
Frus et al. 2023 for specic details on the engagement process; also
see the supplemental material). Briey, to identify workshop par-
ticipants, The US Geological Survey (USGS) identied stakeholders
that represented a diverse array of organizations, bureaus, and
agencies from across the Great Basin. The list included about 200
individuals representing state and local organizations, as well as
individuals from federal, tribal, and nongovernmental organiza-
tions. An invitation was sent to everyone on the stakeholder list.
The invitation requested that organizations identify individuals
who would act as representatives of their respective organizations
to allow for equal representation of different thoughts and con-
cerns. During these workshops, using polling software (Mentime-
ter), resource and conservation community members were asked
to prioritize ecologic and hydrologic topical classications (taken
from the literature review research focus categories). The prioriti-
zation ranks were based on the importance for resolving key sci-
entic unknowns in future research in Great Basin terminal lakes
and the identication of key waterbird guilds from the perspective
of conservation needs and across the Great Basin terminal lakes.
A detailed description of the methods can be found in the supple-
mental le “Methods.” A summary of the state and local workshop
outcomes is available on the USGS Saline Lake Ecosystems IWAAs
website (USGS 2022a ,2022b ). USGS staff did not participate in pri-
oritizing exercises.
Research publications
Of the 935 publications returned from the literature search
databases, 779 publications were deemed relevant because they
were specically associated with terminal lakes within the Great
Basin or could provide comparative information from other re-
gional terminal lakes (e.g., papers on the Salton Sea, in Califor-
nia). Overall, this included 372 and 407 publication from the ecol-
ogy and hydrology query topics, of which 346 and 358 publica-
tions were specic to Great Basin terminal lakes, respectively. The
year of publication for publications investigating one or more
of the Great Basin terminal lakes ranged from 1902 to 2022
( supplemental gure S2), but the ranges varied widely among the
lakes. For most of the lakes, the earliest hydrology publications
were after 1970 ( gure S2), whereas the initial ecology publica-
tions were decades earlier for a substantial (45%) number of the
lakes ( gure S2). Overall, the publications for lakes were relatively
contemporary, with median publication years for most lakes after
2000 for either ecology or hydrology topics ( gure S2).
Resource and conservation community
evaluations
For the ecologic ranking activity, the resource and conservation
community members identied ve topical priorities: In order of
priority, those are habitat (E1), waterbird dispersal among termi-
nal lakes (E2), waterbird population abundance or trend (E3), food
or prey availability (E4), and threatened species of concern (E5),
which combined accounted for 84% of responses (table 1 ). For the
hydrologic ranking activity during the resource and conservation
community meetings, the members identied ve topical priori-
ties. In order of priority, those are water budgets (W1), water use
(W2), lake or wetland surface water (W3), hydrologic vulnerability
(W4), and water quality (W5), which combined accounted for 82%
of the responses (table 1 ).
Publication coverage of topical areas
For all categories in both ecology and hydrology topics, most pub-
lications pertained to the Great Salt Lake, in Utah (39% of all pub-
lications), followed by Mono Lake, in California (21% of all pub-
lications), and Pyramid Lake, in Nevada (10% of all publications;
gures 3 and 4 ). Conversely, Sevier Lake, in Utah; Winnemucca
Lake, in Nevada; and Silver Lake, in Oregon, were not well repre-
sented in the literature, and we found only publications pertain-
ing to waterbird population abundance or trend (priority E3) and
a few hydrological topics (gures 3 and 4 ).
Herring et al. |5
Tab l e 1. Ecological and hydrological categories grouped by re-
source and conservation community priority ranking from con-
servation community meetings or workshops.
Rank
Ecological or hydrological
priority Related publication category
E1 Habitat Waterbird habitat selection or
suitability
E2 Waterbird dispersal among
terminal lakes
Waterbird migration or
migratory connectivity
E3 Waterbird population
abundance or trend
Waterbird population dynamics
Waterbird abundance
Waterbird nesting ecology
E4 Food or prey availability Food webs or community
ecology
Waterbird foraging ecology
Waterbird prey availability
E5 Threatened species or
species of concern
All ecological categories above
(E1–E4)
W1 Wat er budget Surface
Soil
Snow
Precipitation
Ground
Evapotranspiration
Consumptive
W2 Wat er use Wa ter use
Commercial or industrial
impacts
W3 Lake or wetland surface
water
Upgradient surface water
Lake characteristics
W4 Hydrological vulnerability Hydrologic vulnerability
Degree of decline
W5 Wat er quality Tr e n d s water quality
Ecology coverage
After categorizing the 372 ecology publications into the ve pri-
ority topics describing their primary or secondary focus, 25% per-
tained to waterbird population abundance or trends (E3, n = 94),
15% pertained to food or prey availability (E4, n = 55), 13% per-
tained to waterbird dispersal (E2, n = 49), and 10% pertained to
habitat (E1, n = 38; gure 3 ). The threatened species or species of
concern (E5) category was prioritized by the resource and conser-
vation community, but we did not categorize publications into this
distinct group because the topic overlapped with categories E1–E4.
For example, snowy plovers ( Charadrius nivosus ) are a threatened
waterbird in the Great Basin and were highly represented among
the four ecological categories (15% of all ecological priority publi-
cations). Although the waterbird population abundance or trend
category (E3) contained many publications (gure 3 ), 48% were 20
or more years old (the median publication year was 2004). This
varied substantially from state to state; for example, the median
publication year for the waterbird population abundance or trend
category (E3) in Oregon was 1998. In addition, although the water-
bird nesting ecology and abundance subcategories were well rep-
resented among lakes, the waterbird population dynamics sub-
category was limited for many terminal lakes in the Great Basin
(gure 3 ). The ecological categories for habitat (E1) and waterbird
dispersal among terminal lakes (E2) were well represented among
lakes (gure 3 ), but the publications tended to be around 20 years
old with a median publication year of 2006. Finally, the ecological
category for food or prey availability (E4) was the most sparsely
investigated topic among all lakes except for the Great Salt Lake
and Mono Lake, which were the focal lakes in 51% and 29% of the
publications in the category, respectively (gure 3 ); the other 18
lakes had limited or no publications on waterbird food and prey
availability, and, for those with publications, those publications
were over 20 years old.
We also assessed the density of ecological literature across four
waterbird guilds (shorebirds, open-water birds, wading birds, and
waterfowl) to better understand guild-specic research strengths
and gaps. The ecological literature representing the waterbird
population abundance or trends category was the most published
(E3, n = 89), followed by waterbird dispersal among terminal lakes
(E2, n = 47), food or prey availability (E4, n = 46), and habitat (E1,
n = 36). The shorebird guild had the most lakes with at least one
publication (the mean was 12 publications per lake; n = 18 lakes)
among the resource and conservation community’s four highest-
priority ecological topical areas (90% of the lakes; gure 5 ). Most
of the lakes across the Great Basin lacked publications related
to shorebirds for habitat (E1), waterbird dispersal (E2), and food
or prey availability (E4) priority topics. The waterbird population
abundance or trends (E3) priority topic contained the most litera-
ture related to shorebirds, although many publications for shore-
birds in the abundance or trends category were more than 20
years old. The Great Salt Lake contained considerable literature
on all shorebird topics, but many of the publications were at least
20 years old, particularly for waterbird dispersal and habitat (g-
ure S2). The next most represented guild in the literature was the
open-water bird guild (70% of the lakes with at least one publica-
tion; the mean was 9 publications per lake; n = 14 lakes), followed
by waterfowl (65% of lakes with at least 1 publication; the mean
was 5 publications per lake; n = 13 lakes), and wading birds (45%
of the lakes had at least one publication; the mean was 3 publi-
cations per lake; n = 9 lakes; gure 5 ). The publications for most
of the lakes did not cover all resource and conservation commu-
nity priorities and our associated ecological topical areas for each
of the three remaining guilds, and the available literature tended
to be more than 15–20 years old (gure 5 ). The exception was the
Great Salt Lake, which contained recent literature across all open-
water bird guild topics. The Great Salt Lake also had waterfowl
literature for 75% of the ecological topical areas, and 60% of that
literature was less than 10 years old. Notably, there were no publi-
cations related to wading bird food or prey availability, and almost
no literature related to waterfowl food or prey availability existed
outside of Great Salt Lake (gure 5 ).
Hydrology coverage
Across the Great Basin, the water budget topic (W1) accounted
for 70% of total hydrology publications ( n = 283). Great Salt Lake,
Mono Lake, and Owens Lake were the only lakes with publications
for every water budget component (W1) and a relatively recent
median publication year (the median was 2010; gure 4 ); the wa-
ter budget components searched in the literature included sur-
face water, soil moisture, snowpack, precipitation, groundwater,
evapotranspiration, and consumptive use. The remaining 17 lakes
(90%) lacked publications for at least one of the water budget com-
ponents, and Eagle Lake, in northern California, lacked any pub-
lications pertaining to its water budget (gure 4 ). Snowpack and
soil moisture components had the least publications across the
Great Basin terminal lakes. For the other water-focused resource
and conservation community categories (W2–W5, gure 4 ), recent
Great Salt Lake publications (more than 2015 as the median) cov-
ered every water budget subcategory. The lake or wetlands surface
water category was the second most represented category across
the Great Basin terminal lakes region (W3; n = 162, or 40% of the
6|BioScience, 2024, Vol. 0, No. 0
Figure 3. Distribution of research literature addressing ecological topics across the Great Basin sorted by lake and state. The classications on the
y-axis indicate priorities ranked by natural resource and conservation community feedback: habitat (E1), bird dispersal among terminal lakes (E2), bird
population abundance or trend (E3), and food or prey availability (E4). The blank spaces indicate that no associated publications were found with that
topic or that lake.
hydrology publications), although Eagle Lake, Carson Lake, Carson
Sink, Silver Lake, and Sevier Lake all had one or no publications
related to this category. Just one lake lacked publications related
to water use or hydrologic vulnerability (Winnemucca Lake), and
several lakes lacked publications on water quality (Goose Lake,
Owens Lake, Carson Sink, Franklin Lake, Ruby Lake, Winnemucca
Lake, Lake Abert, and Sevier Lake). The median publication date
associated with water budget components was 2009, and 63% of
the publications fall between 2002 and 2017 ( gure S2). The me-
dian date of publications for most lakes and categories was 2006
or newer, although Pyramid Lake hydrology categories were an ex-
ception with most publications at least 20 years old ( gure S2).
Species abundance and trends in the Great
Basin terminal lakes
The published information on species’ abundance and trends,
movements, and migration was limited for many terminal lakes,
particularly those that are currently perennially dry (e.g., Franklin,
Silver, Sevier Lakes). Recent information was restricted to a lim-
ited set of lakes, waterbird guilds, and topical areas of research
(gures 3 and 5 ).
Most of the lakes lacked robust estimates of population size
and trends for most waterbird guilds and species. The Great Salt
Lake had the most current information for population abundance
and trends across multiple waterbird guilds, particularly shore-
birds, waterfowl, and open waterbirds, with additional informa-
tion on migratory connectivity or dispersal of open waterbirds.
Aside from monitoring at the Great Salt Lake, population eld sur-
veys are often spatially restricted or insufciently replicated in
space and time to produce robust estimates of population size and
trends for most waterbirds (e.g., Warn ock et al. 1998 , Fleskes and
Lee 2007, Senner et al. 2021 ). Tw o exceptions are the snowy plover,
which has population estimates across the Great Basin, although
those estimates are now over 10 years old (Thomas et al. 2012 ),
and Wilson’s phalarope ( Phalaropus tricolor ), for which researchers
began coordinating range-wide monitoring in 2019 (Carle et al.
2023 ). Therefore, bird responses (e.g., individual behaviors, popu-
lation abundance, and demographic consequences) to watershed
water use, hydrologic vulnerability, and habitat management ac-
tions remain poorly understood and require additional collabora-
tive research for this system (see box 1 ).
Prioritizing and meeting research objectives may be particu-
larly challenging for intrinsically rare, threatened, or endangered
species that are difcult to detect. Rare or threatened species may
demonstrate greater population variability or site occupancy at
terminal lakes because of the ephemeral nature of their habitats,
which is compounded by demographic stochasticity inherent in
small populations (Page et al. 1991 , Thomas et al. 2012 ). Although
they are outside the scope of this synthesis, there are other rare
aquatic wildlife species, such as several threatened and endan-
gered sh endemic to one or a few terminal lake systems (e.g.,
cui-ui, Chasmistes cujus ; War ner sucker, Catostomus warnerensis ;
Lahontan cutthroat trout, Oncorhynchus clarkii henshawi ) that are
Herring et al. |7
Figure 4. Distribution of research literature addressing hydrological topics across the Great Basin sorted by lake and state. The classications on the
y-axis indicate priorities ranked by natural resource and conservation community feedback: The top resource and conservation community hydrologic
priority of water budget (W1) is shown (a) with hydrologic components used to establish water budgets and (b) water use (W2), lake or wetlands
surface water (W3), hydrological vulnerability (W4), and water quality (W5). The blank spaces indicate that no associated publications were found
with that topic or that lake.
unable to disperse. Their populations are intrinsically tied to local
changes in habitat and water conditions (Wagner and Lebo 1996 ,
Beutel et al. 2001, Sedinger et al. 2012 ), suggesting relatively easier
prioritization of research activities for these species.
Waterbird responses to habitats and food
availability
The Great Basin terminal lakes serve as critical stopover and stag-
ing areas along major international yways for migratory species
including western sandpipers ( Calidris mauri; Warn o ck and Bishop
1998 ) and eared grebes ( Podiceps nigricollis Winkler and Cooper
1986 , Jehl and Johansson 2002 , Jehl and Henry 2010 , Kristen et al.
2016 , Frank and Conover 2017 , Williams and Laird 2018 ), among
others (box 2; Bishop et al. 2005 , Strahlberg et al. 2011 , Soren-
son et al. 2020 ). Surface ows (Tavernia et al. 2021 ), soil moisture
(Mendelsohn et al. 2007 ), water quality (Jehl 2001 , Roberts and
Conover 2016 , Wurtsbaugh et al. 2017 ), and water depth (Weller
et al. 1958 , Sloan 1982 , Wurtsbaugh et al. 2017 ) can affect vege-
tation and potential food resources, thereby determining habitat
availability and trends in bird abundance and distribution.
However, information on species-specic habitat suitability,
habitat selection, and food or prey availability was limited for
most of the Great Basin terminal lake systems, except for the
Great Salt Lake (gure 5 , box 1 ). At local scales, the biotic and
abiotic characteristics of terminal lakes are often categorized into
foraging and nesting habitat. Bird selection of foraging and nesting
habitat is inuenced by surrounding vegetation characteristics
(Kelchin 2000 , Ellis et al. 2015 ), benthic substrate type (Roberts and
Conover 2016 ), and the amount and type of submerged aquatic
vegetation (Delahoussaye and Conover 2020). However, the de-
gree to which hydrological conditions and lake elevation inuence
habitat suitability varies by waterbird species and lake, and the
effects may be positive (Bogiatto 1998 , Wright-Myers and Bogiatto
2007 ), negative (Kruse et al. 2003 ), or somewhat neutral (Wright-
Myers and Bogiatto 2007 ).
Brine shrimp ( Artemia spp.) and brine ies ( Ephydridae spp.) are
frequently identied as food resources of critical importance for
most waterbirds that use saline lakes in the intermountain west,
with moderate salinities providing optimal conditions for their
abundance and quality as waterbird prey (see box 2 ; Caudell and
Conover 2006 , Roberts 2013 , Sorensen et al. 2020 ). However, the
degree of plasticity in waterbird reliance on brine shrimp and
brine ies is still uncertain, with evidence of increased foraging
effort and lower waterbird abundances when conditions are poor
(Caudell and Conover 2006 ) and inability to switch from a brine
y to brine shrimp diet because of decreased energetic content
for at least one waterbird species (red-necked phalarope, Phalaro-
pus lobatus ; Rubega and Inouye 1994 ). Other macroinvertebrates
8|BioScience, 2024, Vol. 0, No. 0
Figure 5.
Distribution of ecological literature topical areas across the Great Basin sorted by waterbird guild, lake, and state. The classications on the
y-axis (E1–E4) of literature review categories are assigned for each waterbird guild based in descending priority from resource and conservation
community feedback rankings (habitat, E1; bird dispersal among terminal lakes, E2; bird population abundance or trend, E3; and food or prey
availability, E4). The waterbird guilds were dened as open-water birds, shorebirds, wading birds, and waterfowl. The blank spaces indicate that no
associated publications were found with that ecological topic or that lake.
and wetland plant seeds may be important across saline lake sys-
tems but are understudied (except at the Great Salt Lake; Roberts
2013 , Sorenson et al. 2020 ).
Along with the complexities of condition and availability of
foraging habitat, understanding the spatiotemporal drivers of
tness–habitat relationships is needed (e.g., direct links between
nest success, survival, mortality, and food resource use and avail-
ability). There were a limited number of empirical studies ( n =
25) examining direct and indirect effects of prey availability
on waterbirds in terminal lake systems. The available studies
spanned only eight waterbird species (California gull, Larus califor-
nicus ; eared grebe; American avocet, Recurvirostra americana ; red-
necked phalarope; western sandpiper; Wilson’s phalarope; Amer-
ican white pelican, Pelicanus erthrorhynchos ; snowy plover) and
were skewed to the two major migratory waterbird hypersaline
systems, the Great Salt Lake ( n = 16) and Mono Lake ( n = 8).
Research to evaluate waterbird demographic rates and tness
consequences of habitat resources or conditions is therefore
needed throughout the system for most waterbirds. Because of
this general lack of published information, the ability to link
changing ecological conditions to demographic responses across
all bird guilds and lakes is limited (box 1 ).
Understanding Great Basin terminal lakes
hydrology
Understanding water availability for the Great Basin terminal
lakes is crucial to determining the availability, variety, and quality
of avian habitats, as well as the overall watershed health of each
lake (gure 4 ). Current water availability assessments, including
water quantity and quality, are needed for most lakes within the
Great Basin to augment, update, and inform current understand-
ing of hydrologic systems at the lake, watershed, and region spa-
tial extents.
Herring et al. |9
Box 1. Waterbird abundance relative to publication numbers and resource and conservation community priorities.
We conducted a post hoc analysis to assess the frequency of publications ( y -axis) relative to the importance of each lake given
waterbird abundance ( x -axis) and change in surface area (the symbols). We categorized the number of publications in our review
by resource and conservation community priority (see table 1 for denitions). To estimate the biological importance of each lake,
we extracted the mean abundance (Fink et al. 2022) of the 15 waterbirds of interest ( supplement S2), which we then divided by
total abundance per species, then summed the relative abundances across species. Color and shape designate the percent change
in lake surface area between 1984 and 2018 (Donnelly et al. 2020 ). Symbols for Summer Lake (the circle) and Malheur (the triangle)
overlap. Results illustrate high variation in published knowledge across lakes and resource and conservation community priorities.
Great Salt Lake was both the most biologically important and the most studied terminal lake. Among other terminal lakes, there
are gaps in the frequency of studies within each resource and conservation community priority (e.g., priority W1, water budget,
there were 36 published studies at Pyramid Lake and 0 at Eagle Lake). Our analysis highlights lakes with little published knowledge,
but a more crucial takeaway is that many studies are localized to specic lakes. The ecological value of the lake does not relate to
the amount of research on it. Future research would benet from a larger-scale analysis integrating knowledge across the system
(i.e., all terminal lakes in the Great Basin or a subset of lakes that represent varying salinity and ecological importance) rather than
solely site-specic studies.
Water availability
Wat er quantity is typically informed by an assessment of the
system’s water budget and the inows and outows of a system.
Generally, the water budget inow components of terminal
lake systems’ include both surface water and groundwater
stocks, with inows from precipitation, return ow from applied
irrigation water, and lateral movement of surface and ground-
water, whereas outows are consumptive use, evaporation, and
evapotranspiration. Overall, hydrologic literature demonstrated
that surface and groundwater sources across the watersheds
of the Great Basin are driven by snowpack at high elevations,
and lake elevation is controlled by streamow inputs and direct
precipitation (Maurer et al. 2009 , Stolp and Brooks 2009 , Mo-
hammed and Tarboton 2012 , Wriston and Smith 2017, Baxter
and Butler 2020 ). Data and interpretations to identify quantity,
timing, and trends of inputs including streamow, groundwa-
ter discharge, snowpack, precipitation, and lake elevations for
terminal lake systems are decient for all of the Great Basin
watersheds.
10 | BioScience, 2024, Vol. 0, No. 0
Box 2. A cross-section diagram of a lake and adjacent wetland with habitat use and life-history information on tule
white-fronted goose, Wilson’s phalarope, snowy plover, and eared grebe.
The tule white-fronted goose ( Anser albifrons elgasi ) is a California species of special concern and feeds in shallow vegetated wetlands.
It uses only Summer Lake wetlands for migratory stopovers. Wilson’s phalaropes ( Phalaropus tricolor ) forage on the water surface,
using many Great Basin terminal lakes during its migration to South America. During their rapid molt and premigratory fattening
life stages, they rely on brine ies for food. Snowy plover ( Charadrius nivosus ) are listed as a threatened species under the Endangered
Species Act. They rely on terminal lake mudats and shorelines for their nesting, feeding, and sometimes overwintering activities.
Eared grebes ( Podiceps nigricollis ) dive to feed, reling on brine shrimp and alkali ies produced by Great Basin terminal lakes. Over
99% of the North American population relies on this food source during the fall months.
Consumptive water uses and other water budget component
outputs are signicantly reducing the water available to termi-
nal lake systems. The lakes across the Great Basin are reporting
withdrawals and diversions that exceed recharge rates, directly
decreasing lake volume (Null and Wurtsbaugh 2020 , Beamer and
Hoskinson 2021 , Garcia et al. 2022 ) and riparian area (Danskin
1998 , Tra cy 2004 , Wurtsbaugh et al. 2017 , Sterle et al. 2020 ). How-
ever, understanding consumptive use is complicated by vary-
ing reporting regulations across states and activities, as well as
differences in how each state’s laws dene surface and ground-
water concerning their hydrologic connectivity—or a lack thereof
(King et al. 2021 ). Most evaporation of terminal lake systems in the
Great Basin occurs in open water environments with rates deter-
mined by lake area (Allander et al. 2009 , Mohammed and Tarboton
2012 ). Evapotranspiration in riparian and wetland areas is another
primary output in terminal lakes and is critical for understanding
water availability (Allander et al. 2009 , Gómez-Navarro et al. 2019 ).
The data on outputs in the water budget, including evaporation
and evapotranspiration, remain poorly understood for terminal
lake systems.
Climate change affects each component of the water budget
in terminal lakes, including changes in magnitude and timing of
ow. Hydrologic conditions in the Great Basin watersheds are in-
creasingly characterized by lower year-round precipitation, spring
high ows, summer low ows, low summer soil moisture, in-
creases in drought conditions, and earlier snowmelt and runoff
(Ficklin et al. 2013 , Godsey et al. 2014 , Gutrich et al. 2016 , Hall et al.
2021 ). Although climatic factors affect terminal lake hydrology, a
limited number of studies have shown that climatic factors are
secondary to the effects of human alterations in the system (Great
Salt Lake; Baxter and Butler 2020 , Null and Wurtsbaugh 2020 ). An-
thropogenic water use has reduced water levels and ecosystem
function in many of the Great Basin watersheds (Danskin 1998 ,
Zektser et al. 2005 , Wurtsbaugh et al. 2017 ), and multiscale water
budgets along with an examination of water rights is critical for
developing meaningful solutions to water demands that benet
all sectors of society (King et al. 2021 ). With changing hydrologic
conditions, quantifying and improving the current understanding
and accuracy of individual water budget components will prove
critical as terminal lakes become more stressed from increased
water use and warming conditions. Wate r budget components are
closely linked to water quality and food webs within the Great
Basin terminal lakes and consequently play a critical role in den-
ing the availability of habitats for waterbird populations through-
out the annual cycle.
Water quality
Wat er quality in terminal lakes is a product of both natural (e.g.,
physiography, geology, soils, climate) and human-inuenced (e.g.,
land use, diversions, waste management) factors, both of which
vary considerably across the terminal lakes of the Great Basin.
Consequently, water quality is inuenced directly by atmospheric
deposition or inows of freshwater to lake systems or indirectly
through processes inuenced by climate such as net evaporation
or lake turnover and wind or upwelling, which affect lake pro-
ductivity and cycling of water quality constituents. For instance,
at Pyramid Lake, warmer water temperatures may reduce or
Herring et al. |11
eliminate the stratication of lake water, affecting water quality
and productivity (Hostetler and Benson 1994 ). Although harmful
algal blooms occur almost annually in Pyramid Lake, large blooms
are more likely to occur following years of particularly high in-
ows from the Truckee River because the inux of freshwater pre-
vents lake mixing (Galat and Verdin 1988 ). Critical water quality
constituents are varied across the different terminal lakes and can
include salinity, nutrients, sediment, and metals.
There is a lack of standardized water quality indicators across
the Great Basin terminal lakes, and those components that are
monitored or targeted are driven by local needs and regula-
tions (Galat and Verdin 1988, Mono Basin Stream Restoration and
Monitoring Program 2010 , Herbst et al. 2013 , Pyramid Lake Paiute
Tribe 2015 , Wurtsbaugh et al. 2020 , California State Water Re-
sources Control Board 2021 ). A variety of water quality compo-
nents are monitored in some of the saline and hypersaline lakes
of the Great Basin, and some of the lakes have mandated or sug-
gested water quality criteria to maintain ecosystem health, such
as Mono Lake (Herbst 2014 ) and Lake Abert (Larson et al. 2016 ,
Moore 2016 ). The management goal of these water quality targets
is to manipulate lake levels, as in the case of Mono Lake (Herbst
2014 ), although, at many lakes, there is no current management
effort (e.g., Lake Abert; Moore 2016 ). However, it should be noted
that even though there are management-mandated water quality
criteria at Mono Lake, the lake has never achieved that goal since
its inception in 1994, and is still far below the target level today.
Connection between avian ecology and
hydrology
The lack of information on waterbird foraging ecology and the
conditions that constitute their habitat is not only a result of a
paucity of monitoring data but is also inherently the result of the
highly dynamic nature of water availability in the Great Basin ter-
minal lakes. Constant uctuations in water quantity and quality
within and among the terminal lakes indicate that a systemwide
analysis is critical for understanding population-level effects of
salinity gradient, prey availability, habitat quality, and tness re-
lationships (see box 2 ). This is compounded by variation in the
needs of diverse waterbird species (e.g., shorebirds versus water-
fowl versus open waterbirds). Tw o caveats to the paucity of infor-
mation on terminal lake hydrology and waterbird responses are