Tree-Ring Reconstructions of North American Monsoon Variability in the Southwestern U.S.

EPA Grant Number: FP917185
Title: Tree-Ring Reconstructions of North American Monsoon Variability in the Southwestern U.S.
Investigators: Griffin, Richard Daniel
Institution: University of Arizona
EPA Project Officer: Michaud, Jayne
Project Period: August 15, 2010 through August 14, 2013
Project Amount: $111,000
RFA: STAR Graduate Fellowships (2010) RFA Text |  Recipients Lists
Research Category: Fellowship - Global Change , Academic Fellowships


This project focuses on the South Hills Crossbill, restricted to two small mountain ranges in southern Idaho (100 km2), where it is an obligate seed predator of Rocky Mountain lodgepole pine (Pinus contorta latifolia). Both species are predicted to go extinct by the end of the century. Recent evidence shows a large decline in crossbill annual survival and population size that appears related to warmer temperatures. The most plausible hypothesis for the observed declines is that warmer temperatures have increased cone opening and seed shedding, which reduces seed availability for crossbills (they rely on seeds in closed cones that have accumulated and weathered over many years) and thereby decreases the carrying capacity for crossbills.


Recent declines of South Hills Crossbill (Loxia sinesciurus) appear to be associated with recent and unprecedented high temperatures during summer, which apparently cause lodgepole pine cones to open and prematurely shed their seeds. Crossbills rely upon seeds in old, weathering closed cones, so premature cone opening reduces the crossbill food supply. This project will predict future seed and crossbill abundance in a warming climate and inform a conservation plan for this species.


This project will determine the effect of increasing temperature on seed availability in closed cones of lodgepole pine, correlate seed availability with crossbill abundance, and then use a spatially explicit model to predict landscape-scale changes in crossbill abundance under different climate change scenarios. In addition, it will determine variability in heat-tolerance of cones and combine this with knowledge of localized temperatures across the landscape to provide guidance for a lodgepole reforestation plan.

Expected Results:

This research aims to provide a mechanistic understanding of phenological disruption in two vulnerable species, the South Hills Crossbill and a morphologically distinct population of lodgepole pine. This understanding will be used to predict future seed and crossbill abundance in a warming climate. These predictions will indicate vulnerability of the crossbill population and, combined with the results of this project, can be used to develop a conservation plan for the South Hills Crossbill. Without a clear conservation strategy for these species, both are likely to go extinct by the end of the century. One management tool resulting from this study will be the creation of a suitability map for planting lodgepole pine that, for example, recommends cooler sites with lower rates of cone opening for reforestation. The U.S. Forest Service is the sole landowner of the two mountain ranges in the South Hills and has the authority and experience to implement a landscape-scale reforestation effort, making habitat restoration and species conservation realistic outcomes of this project.

Potential to Further Environmental/Human Health Protection:

In addition to species-specific management implications for the South Hills Crossbill, the mechanistic understanding gained in this study will influence mitigation strategies for a host of other species. Other seed-eating species (birds and small mammals) will benefit from an understanding of how climate change is disrupting the phenology of a widespread pine. This project aims to synthesize a mechanistic understanding of a three-way (climate-lodgepole-crossbill) relationship to project climate change impacts at a landscape scale, thereby developing a modeling approach that can be applied to other sensitive species, especially other taxa of Red Crossbills that appear to be declining.

Supplemental Keywords:

climate change, habitat use, lodgepole pine, Loxia sinesciurus, population ecology, resource abundance, South Hills Crossbill,

Progress and Final Reports:

  • 2011
  • 2012
  • Final