Date of Award
1-2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
College/School
College of Science and Mathematics
Department/Program
Earth and Environmental Studies
Thesis Sponsor/Dissertation Chair/Project Chair
Clement Alo
Committee Member
Pankaj Lal
Committee Member
Aparna Varde
Committee Member
Jamie Strange
Abstract
The combined impacts of land use and climate change pose significant challenges to bumblebee populations in the Northeast United States (NEUS), a region characterized by dense urbanization, diverse landscapes, and exposure to climate extremes. As urban and suburban areas expand, the loss of agricultural lands and open spaces alters habitat availability for bumblebees, which rely on grasslands, meadows, and forest edges for nesting and foraging. Simultaneously, the NEUS is experiencing an increase in extreme climate events, including prolonged heatwaves, heavy precipitation, and shifts in temperature patterns. Using CMIP6 climate model projections, we analyzed trends in nine climate indices. Our results show consistent warming trends, with an increase in warm extremes like warm days and warm nights (TX90p, TN90p) and variability in precipitation patterns consecutive wet days and the maximum 5-day precipitation amounts (CWD, RX5day). CDD remains largely stable, showing a slight decrease (-1%) under SSP 2-4.5 and a minor increase (1%) under SSP 5-8.5. Contrastingly, consecutive wet days (CWD) increase slightly by 3% and 4%, respectively, across both scenarios. The Heat Wave Duration Index (HWDI) shows dramatic increases, rising by 363% under SSP 2-4.5 and 668% under SSP 5-8.5, highlighting a significant intensification of heat waves. Other precipitation-related indices, such as heavy precipitation days (R10) and maximum 5-day precipitation (Rx5day), also show moderate increases, with R10 rising by 9–10% and Rx5day by 10–12%. Temperature-related indices show stark changes, particularly in extreme cold and warm events. The percentage of cold nights (TN10p) declines significantly by 70% under SSP 2-4.5 and by 83% under SSP 5-8.5, while cold days (TX10p) decrease by 67% and 80%, respectively. Conversely, warm extremes see large increases, with warm nights (TN90p) increasing by 137% under SSP 2-4.5 and 212% under SSP 5-8.5, and warm days (TX90p) rising by 144% and 222%, respectively. These changes emphasize the strong amplification of heat-related events and the reduction of cold extremes as greenhouse gas emissions increase. Climate extremes can be exacerbated by changes in land use. We investigate potential land use changes in New Jersey based on an artificial neural network to model land use change in New Jersey. We find that, as expected, urban land uses continue to expand into the midcentury (0.48% and 0.51% from 2020-2035 and 2035-2050 respectively), but surprisingly, conservation efforts help evergreen needleleaf forests to expand as well (28.01% and 16.84% from 2020-2035 and 2035-2050). Agricultural lands, despite conservation policies, decline in our model (-15.73% and -14.10% from 2020-2035 and 2035-2050). Contribution of agricultural lands towards agrivolatic use may be necessary for New Jersey goals for clean energy capacity for solar. One potential avenue to mitigate these losses and address the goals for clean energy is to manage financial incentives for farmers to adjust their land uses towards dual use solar-agriculture. With careful installation of these solar farms, there can also be increased potential for pollinator health improvements. By coupling modeled land use change projections with climate data, we model the future habitat suitability of six bumblebee species, including generalists like Bombus impatiens and specialists like Bombus pensylvanicus. Our findings highlight significant declines in suitable habitats due to the combined pressures of urban expansion, agricultural loss, and climate extremes. Certain subspecies are particularly vulnerable, with fragmented and declining habitats under scenarios of high emissions and intense land use change. On average, habitat losses outweigh gains for most species and models, with losses increasing over time. In SSP2-4.5, Bombus pensylvanicus exhibits the highest vulnerability, with average losses of 63.60% and gains of only 34.18% in 2050–2020, making it the most at-risk species. Conversely, Bombus griseocollis shows a more favorable trend, with average gains exceeding losses (51.64% gain vs. 46.14% loss in 2050–2020), suggesting it is the least vulnerable species. The other species, including Bombus bimaculatus, B. fervidus, B. impatiens, and B. perplexus, show mixed but generally negative trends, with losses ranging between 53–57% by 2050–2020. Across all species and models, habitat losses generally outweigh gains, with losses increasing in magnitude from 2035–2020 to 2050–2020. In SSP5-8.5, the most vulnerable species is B. pensylvanicus, which exhibits the highest average habitat loss (64.30%) and the lowest average gain (36.77%) by 2050–2020. Conversely, B. griseocollis demonstrates relatively balanced trends, with the highest average gain (54.89%) and losses slightly lower at 56.11%, making it the least vulnerable species. Other species, such as B. impatiens, B. perplexus, and B. bimaculatus, experience moderate gains (ranging from 41–46%) but significant losses (52–57%), resulting in net habitat declines. Model trends show some variability, but all predict greater habitat loss over time, with losses typically exceeding 50% for most species by 2050–2020. Models like MPI-ESM1-2-HR and MIROC6 predict slightly higher gains for certain species, while others like EC-Earth3-Veg and GISS-E2-1-G predict more substantial losses. These results emphasize the need for conservation strategies that address both land use planning and climate adaptation, such as preserving pollinator-friendly habitats, enhancing connectivity between fragmented landscapes, and mitigating urban heat island effects. This study investigates the intertwined impacts of land use and climate change on bumblebee populations in the NEUS, offering insights for climate-related resilience in a rapidly changing environment.
File Format
Recommended Citation
Prasad, Archana, "Exploring Coupled Land Use -- Climate Change Impacts in the Northeast United States from 2020-2025 with Implications for Bombus Habitat Suitability" (2025). Theses, Dissertations and Culminating Projects. 1503.
https://digitalcommons.montclair.edu/etd/1503
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