Date of Award

2020

Document Type

Honors Thesis (Open Access)

Department

Colby College. Environmental Studies Program

Advisor(s)

Philip Nyhus

Second Advisor

Nicholas Record

Third Advisor

Loren McClenachan

Abstract

North Atlantic right whales (Eubalaena glacialis) are endangered. Understanding the role environmental conditions play in habitat suitability is key to determining the regions in need of protection for conservation of the species, particularly as climate change shifts suitable habitat. This thesis uses three species distribution modeling algorithms, together with historical data on whale abundance(1993 to 2009) and environmental covariates to build monthly ensemble models of past E. glacialis habitat suitability in the Gulf of Maine. Then, the models are projected onto the year 2050 for a range of climate scenarios. Specifically, the distribution of the species was modeled using generalized additive models, boosted regression trees, and artificial neural networks, and the environmental covariates included sea surface temperature, bottom water temperature, bathymetry, a modeled Calanus finmarchicus habitat index, and chlorophyll. The 2050 projections used downscaled climate anomaly fields from RCP 4.5 and 8.5. The relative contribution of each covariate changed seasonally, with an increase in the importance of bottom temperature and C. finmarchicus in the summer when model performance was highest. Additionally, there was a negative correlation between model performance and sea surface temperature. The 2050 projections indicated decreased habitat suitability across the Gulf of Maine during the months assessed, with the exception of narrow bands of suitability along the Scotian Shelf in August, September, and October. The results suggest that regions outside of the current areas of conservation focus may become increasingly important habitats for E. glacialis under future climate scenarios.

Keywords

North Atlantic right whale, Eubalaena glacialis, species distribution models, ensemble models, climate change, habitat suitability

Available for download on Saturday, May 22, 2021

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