Using Ecological Niche Modeling to Support Species Conservation under Changing Climate

In this thesis, I explore several constraints and assumptions in ecological niche modeling. First, I examine the effects of intraspecific variation within species on predictions of species’ range shifts under changing climate. Most niche models assume that species are well-mixed within their range so that all occupancy points are informative of the species’ overall climatic tolerances. A partial way to address this short-coming is to build models for isolated populations within a species range. This method can capture within-species differences in environmental tolerances or preferences across space, thereby allowing populations within a species to respond differentially to climate change. Our results suggest that population-based models perform better in predicting the current and future distribution of species under climate change than whole species models. This first chapter provides guidance for assessing the implications of population differentiation in predictions of climate change impacts.

In chapter two, I investigate geographic fragmentation induced from laws and regulations regarding species management, regulations that may affect the survival of species that might cross diverse land ownership and state lines due to range change under climate change. We call this potential phenomenon, “regulatory fragmentation”. In the western United States, much of the landscape is fragmented into diverse land ownerships that give species different conservation statuses and thus implement different management practices for those species. Ignoring the impacts of regulatory fragmentation on species movement under climate change can lead to over-estimation of the potential for geographic range change by species as the climate changes. Here, for the first time, using ecological niche modeling and habitat connectivity analysis, I show that regulatory fragmentation can affect the survival of species when they move to newly-suitable habitat when compared to movement across a landscapes independent of regulation. The effect of regulatory fragmentation depends on whether or not the land ownership favors the movement of a particular species. Habitat connectivity analysis reveals that the best movement pathways that maximize survival given bioclimatic factors pass through a diverse and highly fragmented regulatory landscape. We recommend that managers recognize the potential important of regulatory fragmentation, alongside of other kinds of fragmentation. To account for this fragmentation, agencies must collaborate toward the conservation of engendered, threatened and rare species in a fast-changing world.