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Inferential consequences of modeling rather than measuring snow accumulation in studies of animal ecology

Ecological Applications

By:
, , , , , , and
DOI: 10.1890/12-0959.1

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Abstract

Abstract. It is increasingly common for studies of animal ecology to use model-based predictions of environmental variables as explanatory or predictor variables, even though model prediction uncertainty is typically unknown. To demonstrate the potential for misleading inferences when model predictions with error are used in place of direct measurements, we compared snow water equivalent (SWE) and snow depth as predicted by the Snow Data Assimilation System (SNODAS) to field measurements of SWE and snow depth. We examined locations on elk (Cervus canadensis) winter ranges in western Wyoming, because modeled data such as SNODAS output are often used for inferences on elk ecology. Overall, SNODAS predictions tended to overestimate field measurements, prediction uncertainty was high, and the difference between SNODAS predictions and field measurements was greater in snow shadows for both snow variables compared to non-snow shadow areas. We used a simple simulation of snow effects on the probability of an elk being killed by a predator to show that, if SNODAS prediction uncertainty was ignored, we might have mistakenly concluded that SWE was not an important factor in where elk were killed in predatory attacks during the winter. In this simulation, we were interested in the effects of snow at finer scales (<1 km2) than the resolution of SNODAS. If bias were to decrease when SNODAS predictions are averaged over coarser scales, SNODAS would be applicable to population-level ecology studies. In our study, however, averaging predictions over moderate to broad spatial scales (9–2200 km2) did not reduce the differences between SNODAS predictions and field measurements. This study highlights the need to carefully evaluate two issues when using model output as an explanatory variable in subsequent analysis: (1) the model’s resolution relative to the scale of the ecological question of interest and (2) the implications of prediction uncertainty on inferences when using model predictions as explanatory or predictor variables.

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Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Inferential consequences of modeling rather than measuring snow accumulation in studies of animal ecology
Series title:
Ecological Applications
DOI:
10.1890/12-0959.1
Volume
23
Issue:
3
Year Published:
2013
Language:
English
Publisher:
Ecological Society of America
Contributing office(s):
Northern Rocky Mountain Science Center
Description:
11 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Ecological Applications
First page:
643
Last page:
653
Number of Pages:
11
Country:
United States
State:
Wyoming
Additional Online Files(Y/N):
N