A framework for assessing economic benefits of invasive aquatic plant management in Louisiana

Field: Environmental Science (Physical Sciences)

Introduction: People benefit from a wide range of aquatic ecosystem goods and services (EGS), and non-native invasive plants impact many of these benefits. EGS’ are the socially valued aspects or outputs of ecosystems that arise from self-regulating or managed ecosystem structures and processes (Murray et al. 2013). Derived from aquatic ecosystems, EGS benefits include recreational opportunities, navigation, food supply, flood control, and fish and wildlife habitat, among other uses. Non-native invasive species reduce or eliminate these benefits by altering the ecosystem structures and processes on which EGS depend. For example, dense vegetative growth of aquatic invasive plants may impede commercial navigation or reduce the probability of a recreational angler catching a fish. To counter these negative effects, multiple agencies in the U.S. spend millions of dollars annually on aquatic invasive species (AIS) control. In 2012 alone, the U.S. Army Corps of Engineers (USACE) spent $95 million on AIS control and management and Early Detection Rapid Response (EDRR) in public waters (National Invasive Species Council 2014). Despite these investments, large-scale analyses comparing AIS management costs with beneficial outcomes, such as improvements in EGS, are rare or outdated. The major challenges to such economic analyses are twofold: 1) multiple stakeholders (i.e., local, state and federal governments, and private entities) may simultaneously conduct invasive species control - resulting in disjointed records of activities or non-standardized data collection; and 2) scientific evidence needed to quantify ecosystem impacts of invasive species is often lacking (an exception is Smart et al. 2009), even though observational evidence of harm may be strong. This Information Exchange Bulletin presents a framework to analyze the benefits and costs of aquatic weed control, using the example of water hyacinth (Eichhornia crassipes (Mart.) Solms) in Louisiana, and includes preliminary analysis of costs and treatment effectiveness. Although this Information Exchange Bulletin examines a particular case study, the methodology presented is transferable to other species and control programs. Water hyacinth is a particularly useful case study species because, in contrast to many other AIS, substantial data are available (from 1974 – present) to inform analysis of control costs and EGS impacts. Furthermore, because the species is widespread in Louisiana, the types of harm are diverse, and the magnitude of harm is potentially substantial. The control benefits of water hyacinth are analyzed by examining the differences between distribution and seasonal growth with management, and its likely distribution and seasonal growth without management. These differences are used to analyze treatment effectiveness in terms of reducing plant extent or density and effects on human uses and values. A main objective of the analysis is to estimate monetary values for as many changes in EGS benefits — due to control — as possible. However, if important benefits cannot be monetized, they will be quantified with non-monetary benefit indicators, as described in the methods below. Finally, the costs of management are assessed using data gathered from multiple agencies. This economic analysis effort is ongoing, and this bulletin is the first to describe the methods and preliminary results.