Bradley, Bethany

Job Title

Associate Professor, Department of Environmental Conservation, College of Natural Sciences

Last Name

Bradley

First Name

Bethany

Discipline

Natural Resources and Conservation

Introduction

I am interested in predicting how terrestrial ecosystems will respond to anthropogenic disturbance and climate change. I focus primarily on non-native invasive plants, with a goal of better understanding the biogeography of invasion risk.

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Search Results

Now showing 1 - 10 of 54

Frequency of invasive plant occurrence is not a suitable proxy for abundance in the Northeast United States
(2017-01-01) Cross, Tyler; Finn, John T; Bradley, Bethany A
Measuring and predicting invasive plant abundance is critical for understanding impacts on ecosystems and economies. Although spatial abundance datasets remain rare, occurrence datasets are increasingly available across broad regional scales. We asked whether the frequency of these point occurrences can be used as a proxy for abundance of invasive plants. We compiled both occurrence and abundance data for 13 regionally important invasive plants in the northeast United States from herbarium records and several contributed distribution datasets. We integrated all available abundance information based on infested area, stem count, percent cover, or qualitative descriptions into abundance rankings ranging from 0 (absent) to 4 (highly abundant). Within equal-area grid cells of 800 m, we counted numbers of occurrence points and used ordinal regression to test whether higher densities of occurrence points increased the odds of a higher abundance ranking. We compiled a total of 86,854 occurrence points in 34,596 grid cells, of which 26,114 points (30%) within 11,976 cells (35%) had some form of abundance information. Eleven of the 13 species had a slight but significantly positive odds ratio; that is, more occurrence points of a species increased the odds that the species was abundant within the grid cell. However, the predictive ability of the models was poor (κ < 0.2) for the majority of species. Additionally, most grid cells contained only one or two occurrence points, making it impossible to infer abundance in all but a few locations. These results suggest that currently available occurrence datasets do not effectively represent abundance, which could explain why many distribution models based on occurrence data are poor predictors of abundance. Increased efforts to consistently collect and report invasive species abundance, ideally estimating both infested area and average cover, are strongly needed for regional-scale assessments of potential abundance and associated impact.
Regional Invasive Species & Climate Change Management Challenge: Gardening with climate-smart native plants in the Northeast
(2020-01-01) Bradley, Bethany A; Bayer, Amanda; Griffin, Bridget; Joubran, Sydni; Laginhas, Brittany B.; Munro, Lara; Talbot, Sam; Allen, Jenica M.; Barker-Plotkin, Audrey; Beaury, Evelyn M.; Brown-Lima, Carrie; Fusco, Emily J.; Mount, Hailey; Servais, Bailey; Morelli, Toni Lyn
An estimated 80% of ornamental plants for sale are non-native. This means that the average yard does a poor job of supporting native flora and fauna. By shifting our plantings towards natives, we can dramatically increase the diversity of bees, butterflies, birds and other animals. In contrast, non-native plants do not support local food webs and can become invasive. Native plants increase biodiversity and reduce risks associated with invasive species, which supports resilient ecosystems in the face of climate change.
Invasive species risk assessments need more consistent spatial abundance data
(2018-01-01) Bradley, Bethany A; Allen, Jenica M.; O'Neill, Mitchell W.; Wallace, Rebekah D.; Bargeron, Charles T.; Richburg, Julie A.; Stinson, Kristina
Spatial abundance information is a critical component of invasive plant risk assessment. While spatial occurrence data provide important information about potential establishment, abundance data are necessary to understand invasive species’ populations, which ultimately drive environmental and economic impacts. In recent years, the collective efforts of numerous management agencies and public participants have created unprecedented spatial archives of invasive plant occurrence, but consistent information about abundance remains rare. Here, we develop guidelines for the collection and reporting of abundance information that can add value to existing data collection efforts and inform spatial ecology research. In order to identify the most common methods used to report abundance, we analyzed over 1.6 million invasive plant records in the Early Detection and Distribution Mapping System (EDDMapS). Abundance data in some form are widely reported, with 58.9% of records containing qualitative or quantitative information about invasive plant cover, density, or infested area, but records vary markedly in terms of standards for reporting. Percent cover was the most commonly reported metric of abundance, typically collected in bins of trace (25%). However, percent cover data were rarely reported along with an estimate of area, which is critical for ensuring accurate interpretation of reported abundance data. Infested area is typically reported as a number with associated units of square feet or acres. Together, an estimate of both cover and infested area provides the most robust and interpretable information for spatial research and risk assessment applications. By developing consistent metrics of reporting for abundance, collectors can provide much needed information to support spatial models of invasion risk.
Near-Real-Time Monitoring of Insect Defoliation Using Landsat Time Series
(2017-01-01) Pasquarella, Valerie J.; Bradley, Bethany A; Woodcock, Curtis E.
Introduced insects and pathogens impact millions of acres of forested land in the United States each year, and large-scale monitoring efforts are essential for tracking the spread of outbreaks and quantifying the extent of damage. However, monitoring the impacts of defoliating insects presents a significant challenge due to the ephemeral nature of defoliation events. Using the 2016 gypsy moth (Lymantria dispar) outbreak in Southern New England as a case study, we present a new approach for near-real-time defoliation monitoring using synthetic images produced from Landsat time series. By comparing predicted and observed images, we assessed changes in vegetation condition multiple times over the course of an outbreak. Initial measures can be made as imagery becomes available, and season-integrated products provide a wall-to-wall assessment of potential defoliation at 30 m resolution. Qualitative and quantitative comparisons suggest our Landsat Time Series (LTS) products improve identification of defoliation events relative to existing products and provide a repeatable metric of change in condition. Our synthetic-image approach is an important step toward using the full temporal potential of the Landsat archive for operational monitoring of forest health over large extents, and provides an important new tool for understanding spatial and temporal dynamics of insect defoliators.
Accounting for aboveground carbon storage in shrubland and woodland ecosystems in the Great Basin
(2019-01-01) Fusco, Emily J.; Rau, Benjamin M.; Falkowski, Michael; Filippelli, Steven; Bradley, Bethany A
Improving the accuracy of carbon accounting in terrestrial ecosystems is critical for understanding carbon fluxes associated with land cover change, with significant implications for global carbon cycling and climate change. Semi‐arid ecosystems account for an estimated 45% of global terrestrial ecosystem area and are in many locations experiencing high degrees of degradation. However, aboveground carbon accounting has largely focused on tropical and forested ecosystems, while drylands have been relatively neglected. Here, we used a combination of field estimates, remotely sensed data, and existing land cover maps to create a spatially explicit estimate of aboveground carbon storage within the Great Basin, a semi‐arid region of the western United States encompassing 643,500 km2 of shrubland and woodland vegetation. We classified the region into seven distinct land cover categories: pinyon‐juniper woodland, sagebrush steppe, salt desert shrub, low sagebrush, forest, non‐forest, and other/excluded, each with an associated carbon estimate. Aboveground carbon estimates for pinyon‐juniper woodland were continuous values based on tree canopy cover. Carbon estimates for other land cover categories were based on a mean value for the land cover type. The Great Basin ecosystems contain an estimated 295.4 Tg in aboveground carbon, which is almost double the previous estimates that only accounted for forested ecosystems in the same area. Aboveground carbon was disproportionately stored in pinyon‐juniper woodland (43.7% carbon, 16.9% land area), while the shrubland systems accounted for roughly half of the total land area (49.1%) and one‐third of the total carbon. Our results emphasize the importance of distinguishing and accounting for the distinctive contributions of shrubland and woodland ecosystems when creating carbon storage estimates for dryland regions.
Regional Invasive Species & Climate Change Management Challenge: Nuisance Neonatives. Guidelines for Assessing Range-Shifting Species
(2020-01-01) Laginhas, Brittany B.; Morelli, Toni Lyn; Barker-Plotkin, Audrey; Beaury, Evelyn M.; Cousins, Elsa; Joubran, Sydni; Nelson, Michael; Talbot, Sam; Bradley, Bethany A.
Native species will need to shift their ranges northward and upslope to keep pace with climate change in the Northeast U.S. However, this may cause some range-shifting species to have undesirable consequences in their expanded range. We provide a framework to identify the likelihood that a range-shifting species will become problematic and offer suggestions to minimize impacts from these species in the recipient habitat.
Regional Invasive Species & Climate Change Management Challenge: Prioritizing range-shifting invasive plants High-impact species coming to the Northeast
(2020-01-01) Bradley, Bethany A; Allen, Jenica M.; Griffin, Bridget; Laginhas, Brittany B.; Rockwell-Postel, Mei
Prevention of new invasions is a cost-effective way to manage invasive species and is most effective when emerging invaders are identified and prioritized before they arrive. Climate change is projected to bring nearly 100 new invasive plants to the Northeast. However, these plants are likely to have different types of impacts, making some a higher concern than others. Here, we summarize the results of original RISCC research that identifies high priority, range-shifting invasive plants based on their potential impacts.
Invasion and Global Change Meta-analysis Data
(2021-01-01) Lopez, Bianca E.; Allen, Jenica M.; Dukes, Jeffrey S.; Lenoir, Jonathan; Vilà, Montserrat; Blumenthal, Dana M.; Beaury, Evelyn M.; Fusco, Emily J.; Morelli, Toni Lyn; Sorte, Cascade J. B.; Bradley, Bethany A.; Bradley, Bethany; Bradley, Bethany
We conducted a global meta-analysis to investigate invasions, abiotic global environmental changes, and their combined effects on native species, communities, and ecosystems.We searched the Web of Science Core Collection for articles and reviews that were available in English through September 30, 2020. Search terms were chosen to identify papers reporting impacts of invasions with one of six abiotic global environmental changes (GECs: warming, nitrogen deposition, O2 depletion, drought, CO2 addition, and altered pH). We assessed the titles and abstracts of the 5,662 returned papers and retained those that reported the ecological effects of: (a) one or more invasive species; (b) one or more GECs; (c) both invasive species and a GEC together; and (d) also reported data for a control treatment (no invasion and at current or ambient environmental conditions). From each study, we recorded data on means and variances of each measured response in the three treatments and control; the response measures (categorized into "response classes"); the introduced invasive species and hypothesized mechanism by which the invasion impacted the ecosystem; the type of GEC factor(s) manipulated; the ecosystem setting where the experiment took place (marine, terrestrial, or freshwater); and the type of experiment (laboratory/greenhouse, field, or mesocosm).
Regional Invasive Species & Climate Change Management Challenge: Taking Action. Managing invasive species in the context of climate change
(2020-01-01) Beaury, Evelyn M.; Barker-Plotkin, Audrey; Brown-Lima, Carrie; Fusco, Emily J.; Griffin, Bridget; Joubran, Sydni; Laginhas, Brittany B.; MacLean, Meghan Graham; Munro, Lara; Nelson, Michael; Talbot, Sam; Bradley, Bethany A
Climate change is likely to alter the timing and effect of invasive species management, as well as the suite of species we are managing. Despite concern about the effects of climate change, lack of information about how and when to take action is a barrier to climate-smart invasive species management. Here, we outline strategies for incorporating climate change into management along with examples of tools that can inform proactive decision-making.
Global Plant Invaders: a compendium of invasive plant taxa documented by the peer-reviwed literature
(2020-01-01) Laginhas, Brittany B.; Bradley, Bethany A; Bradley, Bethany; Bradley, Bethany
The purpose of the global invaders database was to create a list of non-native, invasive plant species reported worldwide in the English language scientific literature reported in Web of Science.