Occupying over 140,000 km2 (54,000 mi2), the Chihuahuan Desert is the second largest desert in North America and includes much of the Mexican states of Chihuahua, Coahuila, Durango, Zacatecas and San Luis Potosi, as well as large parts of... more
Occupying over 140,000 km2 (54,000 mi2), the Chihuahuan Desert is the second largest desert in North America and
includes much of the Mexican states of Chihuahua, Coahuila, Durango, Zacatecas and San Luis Potosi, as well as large parts
of New Mexico and the Trans-Pecos region of Texas in the U.S. Of the arid ecoregions in the world, the Chihuahuan Desert
ranks at the top with regard to plant diversity. This incredible ecoregion is also noted for its endemism, with over 670
species of plants and nearly half of its freshwater fish found nowhere else in the world. The Chihuahuan Desert faces a
variety of threats, including habitat loss and fragmentation, climate change, changing wild fire regimes, and deterioration of
its freshwater resources. We review these threats as well as the conservation response to them, which includes a diversity of
public-private partnerships operating at regional to local scales. We conclude with a summary of conservation priorities for
the future, which highlights the importance of a binational response that directly addresses the main drivers of decline, is
based on lessons learned from past conservation efforts, expands natural resource monitoring, and builds on momentum of
small scale conservation efforts for greater impact.
includes much of the Mexican states of Chihuahua, Coahuila, Durango, Zacatecas and San Luis Potosi, as well as large parts
of New Mexico and the Trans-Pecos region of Texas in the U.S. Of the arid ecoregions in the world, the Chihuahuan Desert
ranks at the top with regard to plant diversity. This incredible ecoregion is also noted for its endemism, with over 670
species of plants and nearly half of its freshwater fish found nowhere else in the world. The Chihuahuan Desert faces a
variety of threats, including habitat loss and fragmentation, climate change, changing wild fire regimes, and deterioration of
its freshwater resources. We review these threats as well as the conservation response to them, which includes a diversity of
public-private partnerships operating at regional to local scales. We conclude with a summary of conservation priorities for
the future, which highlights the importance of a binational response that directly addresses the main drivers of decline, is
based on lessons learned from past conservation efforts, expands natural resource monitoring, and builds on momentum of
small scale conservation efforts for greater impact.
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Seagrasses comprise a substantive North American and Caribbean Sea blue carbon sink. Yet fine-scale estimates of seagrass carbon stocks, fluxes from anthropogenic disturbances, and potential gains in sedimen-tary carbon from seagrass... more
Seagrasses comprise a substantive North American and Caribbean Sea blue carbon sink. Yet fine-scale estimates of seagrass carbon stocks, fluxes from anthropogenic disturbances, and potential gains in sedimen-tary carbon from seagrass restoration are lacking for most of the Western Hemisphere. To begin to fill this knowledge gap in the subtropics and tropics, we quantified organic carbon (C org) stocks, losses, and gains from restorations at 8 previously-disturbed seagrass sites around the Gulf of Mexico (GoM) (n = 128 cores). Mean natural seagrass C org stocks were 25.7 ± 6.7 Mg C org ha − 1 around the GoM, while mean C org stocks at adjacent barren sites that had previously hosted seagrass were 17.8 Mg C org ha − 1. Restored seagrass beds contained a mean of 38.7 ± 13.1 Mg C org ha − 1. Mean C org losses differed by anthropogenic impact type, but averaged 20.98 ± 7.14 Mg C org ha − 1. C org gains from seagrass restoration averaged 20.96 ± 8.59 Mg ha − 1. These results, when combined with the similarity between natural and restored C org content, highlight the potential of seagrass restoration for mitigating seagrass C org losses from prior impact events. Our GoM basin-wide estimates of natural C org totaled ~ 36.4 Tg for the 947,327 ha for the USA-GoM. Including Mexico, the total basin contained an estimated 37.2–37.5 Tg C org. Regional US-GoM losses totaled 21.69 Tg C org. C org losses differed significantly among anthropogenic impacts. Yet, seagrass restoration appears to be an important climate change mitigation strategy that could be implemented elsewhere throughout the tropics and subtropics.
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Data about flow rate, fishing intensity, and expenditures made by anglers can be used to capture some of the recreational value of waterways in economic terms in a way that avoids a number of the weaknesses of the most commonly used tools... more
Data about flow rate, fishing intensity, and expenditures made by anglers can be used to capture some of the recreational value of waterways in economic terms in a way that avoids a number of the weaknesses of the most commonly used tools such as the contingent valuation method.
Furthermore, recreational fishing may spur more economic activity than competing uses of riverine flows such as agriculture. This suggests that potential opportunity cost in regards to recreation ought to be a factor considered in management decisions.
Furthermore, recreational fishing may spur more economic activity than competing uses of riverine flows such as agriculture. This suggests that potential opportunity cost in regards to recreation ought to be a factor considered in management decisions.
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New multivariate time-series methods have the potential to provide important insights into the effects of ecosystem restoration activities. To this end, we examined the temporal effects of dam removal on fish community interactions using... more
New multivariate time-series methods have the potential to provide important insights into the effects of ecosystem restoration activities. To this end, we examined the temporal effects of dam removal on fish community interactions using multivariate autoregressive models to understand changes in fish community structure in the Eightmile River System, Connecticut, USA. We sampled fish for 6 years during the growing season; 1 year prior to, 2 years during, and for 3 years after a small dam removal event. The multivariate autoregressive analysis revealed that the site above the dam was the most reactive and least resilient sample site, followed in order by the below-dam and nearby reference site. Even 3 years after the dam removal event, the stream was still in a recovery stage that had failed to approximate the community structure of the reference site. This suggests that the reorganization of fish communities following dam removals, with the goal of ecological restoration, may take decades to centuries for the restored sites to approximate the community structure of nearby undisturbed sites. Results from this study also highlight the utility of multivariate autoregressive modeling for examining temporal interactions among species in response to adaptive management activities both in aquatic systems and elsewhere.
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As global sea levels and natural resource demands rise, people around the world are increasingly protesting environmental threats to their lives and livelihoods. What are the conditions under which these peaceful environmental protests... more
As global sea levels and natural resource demands rise, people around the world are increasingly protesting environmental threats to their lives and livelihoods. What are the conditions under which these peaceful environmental protests are violently repressed? This paper uses the random forest algorithm to conduct an event analysis of grassroots environmental protests around the world. Utilizing a database of 175 grassroots environmental protests, we found that: (1) a large proportion (37 %) of the protests involved violent repression; (2) most of the violence (56 %) was directed against marginalized groups; and (3) violence was geographically concentrated the global south in Latin America and Asia. The primary predictors of violence were political empowerment, GDP per capita, industry type, the presence of marginalized groups, and geographic region. Our analysis reveals a complex relationship between governance, resource extraction, and international funding that often resulted in human rights violations against marginalized groups.
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Sea grasses are foundation species for estuarine ecosystems. The available light for sea grasses diminishes rapidly during pollutant spills, effluent releases, disturbances such as intense riverine input, and tidal changes. We studied how... more
Sea grasses are foundation species for estuarine ecosystems. The available light for sea grasses diminishes rapidly during pollutant spills, effluent releases, disturbances such as intense riverine input, and tidal changes. We studied how sea grasses' remote-sensing signatures and light-capturing ability respond to short term light alterations. In vivo responses were measured over the entire visible-light spectra to diminishing white-light on whole-living-plants' spectral reflectance, including 6 h of full oceanic-light fluences from 10% to 100%. We analyzed differences by various reflectance indices. We compared the sea grasses species responses of tropical vs. temperate and intertidals (Halodule wrightii, and Zostera marina) vs. subtidal (Thalassia testudinum). Reflectance diminished with decreasing light intensity that coincided with greater accessory pigment stimulation (anthocyanin, carotenoids, xanthins). Chlorophyll a and Chlorophyll b differed significantly among species (Thalassia vs. Halodule). Photosynthetic efficiency diminished at high light intensities. The NDVI index was inadequate to perceive these differences. Our results demonstrate the leaf-level utility of data to remote sensing for mapping sea grass and sea grass stress.
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We examined the effects of the Zemko Dam removal on the Eightmile River system in Salem, Con-necticut, USA. The objective of this research was to quantify spatiotemporal variation in fish community composition in response to small dam... more
We examined the effects of the Zemko Dam removal on the Eightmile River system in Salem, Con-necticut, USA. The objective of this research was to quantify spatiotemporal variation in fish community composition in response to small dam removal. We sampled fish abundance over a 6-year period (2005–2010) to quantify changes in fish assemblages prior to dam removal, during drawdown, and for three years following dam removal. Fish population dynamics were examined above the dam, below the dam, and at two reference sites by indicator species analysis, mixed models, non-metric multidimensional scaling, and analysis of similarity. We observed significant shifts in fish relative abundance over time in response to dam removal. Changes in fish species composition were variable, and they occurred within 1 year of drawdown. A complete shift from lentic to lotic fishes failed to occur within 3 years after the dam was removed. However, we did observe increases in fluvial and transition (i.e., pool head, pool tail, or run) specialist fishes both upstream and downstream from the former dam site. Our results demonstrate the importance of dam removal for restoring river connectivity for fish movement. While the long-term effects of dam removal remain uncertain, we conclude that dam removals can have positive benefits on fish assemblages by enhancing river connectivity and fluvial habitat availability.
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Pine-oak forests of the Southwestern United States contain a unique mixture of species that are distributed across light, temperature, and moisture resource gradients. Pines and oaks in this region have developed an array of physiological... more
Pine-oak forests of the Southwestern United States contain a unique mixture of species that are distributed across light, temperature, and moisture resource gradients. Pines and oaks in this region have developed an array of physiological and structural mechanisms that promote their success in hot, dry environments with high incident solar radiation. This article reviews the structural and physiological mechanisms responsible for the current abundance and distribution patterns of pines and oaks in high elevation woodlands of the Southwest. It highlights the niche differentiation of species as functions of their stress tolerance or avoidance strategies. This review reveals that pinyon pines are generally more stress tolerant than oaks, but that oaks are more tolerant of extreme growing conditions than other pines of the Southwest. While limited information exists that describes the physiological ecology of some of the pines and oaks in this biogeographical region, there are many opportunities for future research that could contribute to a more holistic understanding of species-environment relationships in Southwestern forests.
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The Sky Island archipelagos of the Sierra Madre Occidental contain diverse, highly endemic, and topographically complex ecosystems, yet the local and landscape-scale controls on woody plant dominance and diversity patterns are poorly... more
The Sky Island archipelagos of the Sierra Madre Occidental contain diverse, highly endemic, and topographically complex ecosystems, yet the local and landscape-scale controls on woody plant dominance and diversity patterns are poorly understood. This study examines variation in woody plant species composition in relation to a suite of environmental variables (i.e., elevation, potential soil moisture, soil type, geologic substrate, and heat load) in the Chiricahua National Monument, Arizona (CHIR). Nine vegetation types were identified using cluster analysis that varied by species composition and plant life form. Non-metric multidimensional scaling and correlation analyses identified significant relationships between vegetation composition and elevation, potential soil moisture, and heat load. Rarefied species richness varied among vegetation types, and in relation to topography, with higher species richness occurring on more topographically complex sites. β (species turnover) and γ (landscape) diversity were also high in CHIR compared to other temperate forests. This study highlights the importance of local- and landscape-scale environmental controls on species diversity and vegetation patterns in Madrean evergreen woodlands.
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To investigate the relationship between the altitudinal distribution of Quercus laceyi and Q. sideroxyla and their physiological responses to drought, we measured relative water content (RWC), water potentials (Ψ(predawn) and Ψ(midday)),... more
To investigate the relationship between the altitudinal distribution of Quercus laceyi and Q. sideroxyla and their physiological responses to drought, we measured relative water content (RWC), water potentials (Ψ(predawn) and Ψ(midday)), photosynthesis (A(max)), stomatal conductance (g), chlorophyll fluorescence (F(v)/F(m)), and spectral reflectance (400-1100 nm) five times during a 7 wk acute drought. Quercus laceyi was drought tolerant, while Q. sideroxyla was a drought avoider; Q. laceyi tolerated lower RWC (Q. sideroxyla = 54%, Q. laceyi = 44%), Ψ(pd) (Q. sideroxyla = -2.6 MPa, Q. laceyi = -3.3 MPa), and Ψ(md) (Q. sideroxyla = -4.5 MPa, Q. laceyi = -6.6 MPa). The F(v)/F(m) also declined first in Q. sideroxyla in wk 6, whereas F(v)/F(m) did not decline in Q. laceyi until wk 7. A(max) and g fell in wk 4, 6, and 7 in drought seedlings of both species, suggesting a decline in CO(2) assimilation during the drought. Leaf spectral reflectance increased with time in response to decreases in leaf photosynthetic pigment concentrations in latter weeks of the drought. The results suggest a close association between the altitudinal distributions of these species and their adaptation to water stress.
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To investigate the relationship between the altitudinal distribution of Quercus laceyi and Q. sideroxyla and their physiological responses to drought, we measured relative water content (RWC), water potentials (Ψ(predawn) and Ψ(midday)),... more
To investigate the relationship between the altitudinal distribution of Quercus laceyi and Q. sideroxyla and their physiological responses to drought, we measured relative water content (RWC), water potentials (Ψ(predawn) and Ψ(midday)), photosynthesis (A(max)), stomatal conductance (g), chlorophyll fluorescence (F(v)/F(m)), and spectral reflectance (400-1100 nm) five times during a 7 wk acute drought. Quercus laceyi was drought tolerant, while Q. sideroxyla was a drought avoider; Q. laceyi tolerated lower RWC (Q. sideroxyla = 54%, Q. laceyi = 44%), Ψ(pd) (Q. sideroxyla = -2.6 MPa, Q. laceyi = -3.3 MPa), and Ψ(md) (Q. sideroxyla = -4.5 MPa, Q. laceyi = -6.6 MPa). The F(v)/F(m) also declined first in Q. sideroxyla in wk 6, whereas F(v)/F(m) did not decline in Q. laceyi until wk 7. A(max) and g fell in wk 4, 6, and 7 in drought seedlings of both species, suggesting a decline in CO(2) assimilation during the drought. Leaf spectral reflectance increased with time in response to decreases in leaf photosynthetic pigment concentrations in latter weeks of the drought. The results suggest a close association between the altitudinal distributions of these species and their adaptation to water stress.
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Trees are a major threat to power line security across forested regions of the world. We developed a decision support system for identifying locations in Connecticut, USA where trees have grown tall enough to make contact with... more
Trees are a major threat to power line security across forested regions of the world. We developed a decision support system for identifying locations in Connecticut, USA where trees have grown tall enough to make contact with transmission lines during storms. We used the Random Forest algorithm, danger tree presence/absence data, and 25 raster environmental datasets to develop (1) an understanding of the abiotic environmental settings that host danger trees and (2) a spatially explicit map of danger tree distributions across Connecticut power line corridors. Danger trees were prevalent in locations (1) with an infrequent history of storms; (2) forested and residential land uses; and (3) low to middle elevations. Products from this research can be transferred to adaptive right-of-way management because they present managers with key information on where danger trees are likely to occur, and the methods presented herein have great potential for future application to other regions managers seek to identify high priority areas for danger tree removal.
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Research Interests: Remote Sensing, Forest Ecology And Management, Fire Management, Landscape, Biological Sciences, and 15 moreEnvironmental Sciences, Ecosystem Restoration, Regression Analysis, Cluster Analysis, Environmental Variables, Digital Elevation Model, Classification and Regression Tree, Oak forest, Forest Inventory, Stand Density, Hierarchical Cluster Analysis, Vegetation Mapping, Field Data, Stand Structure, and Gradient Analysis
Vegetation management is a critical component of rights-of-way (ROW) maintenance for preventing electrical outages and safety hazards resulting from tree contact with conductors during storms. Northeast Utility’s (NU) transmission lines... more
Vegetation management is a critical component of rights-of-way (ROW) maintenance for preventing electrical outages and safety hazards resulting from tree contact with conductors during storms. Northeast Utility’s (NU) transmission lines are a critical element of the nation’s power grid; NU is therefore under scrutiny from federal agencies charged with protecting the electrical transmission infrastructure of the United States. We developed a decision support system to focus right-of-way maintenance and minimize the potential for a tree fall episode that disables transmission capacity across the state of Connecticut. We used field data on tree characteristics to develop a system for identifying hazard trees (HTs) in the field using limited equipment to manage Connecticut power line ROW. Results from this study indicated that the tree height-to-diameter ratio, total tree height, and live crown ratio were the key characteristics that differentiated potential risk trees (danger trees) from trees with a high probability of tree fall (HTs). Products from this research can be transferred to adaptive right-of-way management, and the methods we used have great potential for future application to other regions of the United States and elsewhere where tree failure can disrupt electrical power.
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Trees are a major threat to power line security across forested regions of the world. We developed a decision support system for identifying locations in Connecticut, USA where trees have grown tall enough to make contact with... more
Trees are a major threat to power line security across forested regions of the world. We developed a decision support system for identifying locations in Connecticut, USA where trees have grown tall enough to make contact with transmission lines during storms. We used the Random Forest algorithm, danger tree presence/absence data, and 25 raster environmental datasets to develop (1) an understanding of the abiotic environmental settings that host danger trees and (2) a spatially explicit map of danger tree distributions across Connecticut power line corridors. Danger trees were prevalent in locations (1) with an infrequent history of storms; (2) forested and residential land uses; and (3) low to middle elevations. Products from this research can be transferred to adaptive right-of-way management because they present managers with key information on where danger trees are likely to occur, and the methods presented herein have great potential for future application to other regions managers seek to identify high priority areas for danger tree removal.
Research Interests:
Vegetation management is a critical component of rights-of-way (ROW) maintenance for preventing electrical outages and safety hazards resulting from tree contact with conductors during storms. Northeast Utility’s (NU) transmission lines... more
Vegetation management is a critical component of rights-of-way (ROW) maintenance for preventing electrical outages and safety hazards resulting from tree contact with conductors during storms. Northeast Utility’s (NU) transmission lines are a critical element of the nation’s power grid; NU is therefore under scrutiny from federal agencies charged with protecting the electrical transmission infrastructure of the United States. We developed a decision support system to focus right-of-way maintenance and minimize the potential for a tree fall episode that disables transmission capacity across the state of Connecticut. We used field data on tree characteristics to develop a system for identifying hazard trees (HTs) in the field using limited equipment to manage Connecticut power line ROW. Results from this study indicated that the tree height-to-diameter ratio, total tree height, and live crown ratio were the key characteristics that differentiated potential risk trees (danger trees) from trees with a high probability of tree fall (HTs). Products from this research can be transferred to adaptive right-of-way management, and the methods we used have great potential for future application to other regions of the United States and elsewhere where tree failure can disrupt electrical power.