Evidence-based economic analysis demonstrates that ecosystem service benefits of water hyacinth management greatly exceed research and control costs

Abstract

Invasive species management can be a victim of its own success when decades of effective control cause memories of past harm to fade and raise questions of whether programs should continue. Economic analysis can be used to assess the efficiency of investing in invasive species control by comparing ecosystem service benefits to program costs, but only if appropriate data exist. We used a case study of water hyacinth (Eichhornia crassipes (Mart.) Solms), a nuisance floating aquatic plant, in Louisiana to demonstrate how comprehensive record-keeping supports economic analysis. Using long-term data sets, we developed empirical and spatio-temporal simulation models of intermediate complexity to project invasive species growth for control and no-control scenarios. For Louisiana, we estimated that peak plant cover would be 76% higher without the substantial growth rate suppression (84% reduction) that appeared due primarily to biological control agents. Our economic analysis revealed that combined biological and herbicide control programs, monitored over an unusually long time period (1975–2013), generated a benefit-cost ratio of about 34:1 derived from the relatively modest costs of $124 million ($2013) compared to the $4.2 billion ($2013) in benefits to anglers, waterfowl hunters, boating-dependent businesses, and water treatment facilities over the 38-year analysis period. This work adds to the literature by: (1) providing evidence of the effectiveness of water hyacinth biological control; (2) demonstrating use of parsimonious spatio-temporal models to estimate benefits of invasive species control; and (3) incorporating activity substitution into economic benefit transfer to avoid overstating benefits. Our study suggests that robust and cost-effective economic analysis is enabled by good record keeping and generalizable models that can demonstrate management effectiveness and promote social efficiency of invasive species control.

Suitability of introduced Nymphoides spp. (Nymphoides cristata, N. peltata) as targets for biological control in the United States

“…Economic losses were scored in the mid-range, which mainly represents a lack of knowledge surrounding economic impacts from Nymphoides infestations. However, losses from aquatic invasive plants can be substantial, especially when they limit navigation or water delivery and require constant management to prevent impacts (Wainger et al 2018a(Wainger et al , 2018b. Additionally, herbicide use can be tailored to minimize -but rarely eliminate -off-target effects in many cases, so scores were moderate in that category (Table 1, A5-Available means of control: Environmental damage).…”

“…Aquatic invasive plants require substantial management costs each year with the goal of preventing or mitigating their associated environmental and economic impacts (Wainger et al 2018a, Wainger et al 2018b. Management approaches may include a combination of herbicide application, physical removal, resource competition through restoration, and biological control using host-specific insect herbivore or pathogen agents.…”

“…Management approaches may include a combination of herbicide application, physical removal, resource competition through restoration, and biological control using host-specific insect herbivore or pathogen agents. Of these, biological control offers a potentially self-sustaining solution that can reap long-term economic and ecological benefits (Wainger et al 2018a, Wainger et al 2018b).…”

Living with floating vegetation invasions

“…For example, the Spanish government spent 20.9 million US$ over 4 years to use heavy machinery to physically remove floating vegetation along a 75 km stretch of the Guadiana river (EPPO 2009); two million US$ were spent on personnel costs to run a 3-year project on biological control of water hyacinths in Benin (De Groote et al 2003); and a single herbicide spraying campaign on Hartebeespoort dam in South Africa cost an equivalent of 200'000 US$ (Van Wyk and Van Wilgen 2002). Although local examples of successful control exist (Wainger et al 2018), aquatic weed invasions continue to persist in tropical and subtropical river systems to this day, and are even expanding to higher latitudes with warming climates (Kriticos and Brunel 2016).…”

Potential of aquatic weeds to improve water quality in natural waterways of the Zambezi catchment

“…Such “invasions” are infamous for their conspicuous and costly problems. The plants obstruct boat traffic, clog irrigation schemes, interfere with hydropower operations and threaten fisheries 4 , motivating expensive control campaigns that routinely fail to become sustainable long-term solutions 5 – 7 .…”