The Impacts of Land Use and Climate Change on Mojave Desert Tortoise Gene Flow Dynamics and Corridor Functionality
Jill Heaton | University of Nevada, Reno
The objective of this research is to determine how land use and climate change will impact Mojave Desert tortoise gene flow and corridor functionality within the context of multi-species interactions and landscape connectivity of military installation and other federal lands.
The approach includes five phases. Phase I will produce a series of realized desert tortoise habitat models by combining an updated present-day desert tortoise habitat model with current land use footprints, and by forecasting habitat under future climate and land use scenarios. Many studies focus on the contextual placement of discrete reserves and the ability of species to move between reserves, yet it may be more valuable to understand how corridor functionality is impacted by changes in climate and habitat suitability within the mosaic of all land use types; Phase II. In Phase III, researchers refine the models of corridor functionality across environmental gradients and the land use mosaic by quantifying genetic connectivity and diversity across the range. In Phase IV, researchers apply the ‘extended umbrella’ concept (Roberge and Angelstam, 2003) to protected and critical species to address large scale, multi-species landscape connectivity issues across the Mojave Desert. Finally, recommendations will be made on management actions and strategic partnerships that will maximize the attainment of the Department of Defense (DoD) mission while conserving Mojave Desert landscapes and their associated biota.
This project benefits DoD efforts to protect assets required for DoD mission needs, maintain or improve capabilities to train and test, ensure safe and healthy installations, or mitigate potential impacts to DoD natural and built infrastructure as required to meet DoD policy and statutory requirements as reflected in DoDD 3200.15, Sustaining Access to the Live Training and Test Domain, DoDD 4715.1E Environment, Safety, and Occupational Health (ESOH), and other guidance.
Specific technical benefits include the following:
The overarching benefit of this study is knowledge of how the DoD network of installations fits today, and into the future, with gene flow and habitat connectivity of the threatened desert tortoise and other important species captured by the tortoise umbrella. In turn, this should influence future planning such that desert tortoise populations and their habitat are protected while installation missions are still achieved. In addition, the extension of the research into potential future land use and climatic conditions allows for a more comprehensive assessment to be performed informing future management decisions. Potential collaborations among disparate land management agencies will be identified based on the federally mandated need to manage species, habitats and missions simultaneously, and in a non-stationary world of land use and climate change impacts to fundamental processes controlling the distribution and genetics of desert tortoises.
The Mojave Desert is no longer a sea of continuous desert tortoise habitat, it is permeated with broad expanses of habitat degradation, habitat fragmentation and strict barriers to tortoise movement. This is compounded by the synergies and feedback loops of land use and climate change. Because desert tortoises are long-lived and reproduce throughout their entire lifetime, currently this is a unique point in the history of desert tortoise/human interactions. Older individuals carry the genetic signature of a once largely continuously distributed population described best by isolation-by-distance, while younger individuals carry the genetic signature of more isolated populations or perhaps a metapopulation structure within the now-fragmented landscape they occupy. This genetic "legacy" held by older individuals on the landscape will disappear within the coming years as these individuals die. As such, it is paramount to sample these individuals to the greatest extent possible while the opportunity still exists. The original landscape connectivity that is stamped in these genomes has unparalleled value to establishing management goals in the Mojave. One of the most pressing issues of the time concerns how species and whole biotic communities will respond to changing climatic conditions; this research will provide novel insight into this issue that will benefit both the scientific and management communities.