Aquatic invasive species and ecosystem services: Economic effects of the worm Marenzelleria spp. in the Baltic Sea

Abstract

Abstract Impacts of alien marine species on ecosystem services have been documented in numerous studies, but estimates of the costs, with explicit quantification of the impact channels, are lacking. We calculated the costs of the invasive worm Marenzelleria in the Baltic Sea, which affects the capacity of the seabed to store nutrients, by combining the production function and replacement cost methods. The nutrient storage capacity is then regarded as an input to nutrient cleaning of the sea, with reduced capacity implying higher costs of reaching nutrient reduction targets. We developed a simple dynamic model which captured the effect of Marenzelleria on the decay rates of nutrient pools in different interconnected sea basins of the Baltic Sea. Evidence and numerical estimates indicated a decrease in sequestration of phosphorus in the different sea basins caused by occurrence of the invasive worm. The total discounted cost of this decrease was estimated for two different international nutrient policy scenarios; cost-effective abatement and current international agreement on country targets. The results showed large differences in total abatement costs between these scenarios, but the calculated cost of the species were similar. The estimated cost ranged between 290 and 1094 billion SEK, depending on the effect of Marenzelleria on sequestration of phosphorus. The average annual cost corresponds to 0.03–0.13% of total gross domestic product of the nine coastal countries. However, the cost was unevenly distributed among the countries, with Poland bearing the largest share because of its large phosphorus loads and access to low-cost abatement options.