Analysis options for estimating status and trends in long-term monitoring

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This chapter describes methods for estimating long-term trends in ecological parameters. Other chapters in this volume discuss more advanced methods for analyzing monitoring data, but these methods may be relatively inaccessible to some readers. Therefore, this chapter provides an introduction to trend analysis for managers and biologists while also discussing general issues relevant to trend assessment in any long-term monitoring program. For simplicity, we focus on temporal trends in population size across years. We refer to the survey results for each year as the “annual means” (e.g. mean per transect, per plot, per time period). The methods apply with little or no modification, however, to formal estimates of population size, other temporal units (e.g. a month), to spatial or other dimensions such as elevation or a north–south gradient, and to other quantities such as chemical or geological parameters. The chapter primarily discusses methods for estimating population-wide parameters rather than studying variation in trend within the population, which can be examined using methods presented in other chapters (e.g. Chapters 7, 12, 20). We begin by reviewing key concepts related to trend analysis. We then describe how to evaluate potential bias in trend estimates. An overview of the statistical models used to quantify trends is then presented. We conclude by showing ways to estimate trends using simple methods that can be implemented with spreadsheets.

Additional publication details

Publication type Book chapter
Publication Subtype Book Chapter
Title Analysis options for estimating status and trends in long-term monitoring
ISBN 9781139022422
DOI 10.1017/CBO9781139022422.016
Year Published 2012
Language English
Publisher Cambridge University Press
Publisher location Cambridge, UK
Contributing office(s) Forest and Rangeland Ecosystem Science Center
Description 26 p.
Larger Work Type Book
Larger Work Subtype Other Government Series
Larger Work Title Design and Analysis of Long-term Ecological Monitoring Studies
First page 253
Last page 278