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Scientific Investigations Report 2012–5162

Early Detection of Invasive Plants—Principles and Practices

By Bradley A. Welch, Paul H. Geissler, and Penelope Latham

Thumbnail of and link to report PDF (9.34 MB)Abstract

Invasive plants infest an estimated 2.6 million acres of the 83 million acres managed by the National Park Service (NPS) in the United States. The consequences of these invasions present a significant challenge for the NPS to manage the agency’s natural resources “unimpaired for the enjoyment of future generations.” More NPS lands are infested daily despite diligent efforts to curtail the problem. Impacts from invasive species have been realized in most parks, resulting in an expressed need to control existing infestations and restore affected ecosystems. There is a growing urgency in the NPS and other resource management organizations to be proactive. The NPS I&M Program, in collaboration with the U.S. Geological Survey (USGS) Status and Trends Program, compiled this document to provide guidance and insight to parks and other natural areas engaged in developing early-detection monitoring protocols for invasive plants. While several rapid response frameworks exist, there is no consistent or comprehensive guidance informing the active detection of nonnative plants early in the invasion process. Early-detection was selected as a primary focus for invasive-species monitoring because, along with rapid response, it is a key strategy for successful management of invasive species. Eradication efforts are most successful on small infestations (that is less than 1 hectare) and become less successful as infestation size increases, to the point that eradication is unlikely for large (that is greater than 1,000 hectares) populations of invasive plants. This document provides guidance for natural resource managers wishing to detect invasive plants early through an active, directed monitoring program. It has a Quick-Start Guide to direct readers to specific chapters and text relevant to their needs. Decision trees and flow charts assist the reader in deciding what methods to choose and when to use them. This document is written in a modular format to accommodate use of individual chapters. It may also be approached in a linear fashion, as a sequence of steps leading to a comprehensive approach to early-detection. Our primary audience comprises resource professionals within the National Park Service (NPS) Inventory and Monitoring (I&M) Program’s networks of parks, but we think that the knowledge and experience captured in this document is more broadly applicable to include other natural areas professionals. We have chosen to emphasize the technical side of invasive species early-detection because this is the arena in which most professionals need more guidance. This approach includes but is not limited to complex techniques that may seem to be just beyond the budgetary and (or) time-bound grasps of some resource professionals. Nonetheless, we have provided low-cost options.

First posted September 3, 2014

For additional information contact:
Program Coordinator for Status and Trends
Ecosystems Mission Area
U.S. Geological Survey
12201 Sunrise Valley Drive, MS 301
Reston, VA 20192

Or visit the Status and Trends Program Web site at:

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Suggested citation:

Welch, B.A., Geissler, P.H., and Latham, Penelope, 2014, Early detection of invasive plants—Principles and practices: U.S. Geological Survey Scientific Investigations Report 2012–5162, 193 p.,

ISSN 2328–031X (print)

ISSN 2328–0328 (online)




Invasive Plant Early-Detection Decision Tree

Quick-Start Guide

Extended Abstract

Chapter 1. Introduction

Chapter 2. Plant Invasion Process—Implications for Land Managers

Chapter 3. Strategic Approach to Early Detection

Chapter 4. Early Detection Strategy—Scope, Goals, and Objectives

Chapter 5. Prioritizing Species and Sites for Early-Detection Programs

Chapter 6. Predicting Risk of Invasive Species Occurrence—Remote-Sensing Strategies

Chapter 7. Predicting Risk of Invasive Species Occurrence—Plot-Based Approaches

Chapter 8. Sampling and Survey Design

Chapter 9. Process of Model Assessment and Evaluation

Chapter 10. Data Management and Management Response Strategies

Chapter 11. Invasive-Plant Early-Detection Protocol Development in the Klamath Network-National Park Service

Chapter 12. Spatial Distribution and Risk Assessment of Johnsongrass (Sorghum halepense) in Big Bend National Park, Texas

Chapter 13. San Francisco Area Network Cast Study

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