Rapid response to water hyacinth (Eichhornia crassipes) invasion in the Guadalquivir river branch in Seville (southern Spain)

Abstract

A rapid response action carried out against the invasion of water hyacinth ( Eichhornia crassipes ) in the Guadalquivir River branch in Seville (Southern Spain) is described and analyzed. Removal was implemented and coordinated by the regional environmental Council, National security forces and public companies. Immediately after its detection, the distribution and abundance of water hyacinth, and the possible origin of introduction were assessed as the basis for selecting a feasible removal method. Plants were scattered across 110 ha and a perimeter of 8.4 km. A total biomass of 1,931 kg (fresh weight) was removed between May and December 2021 by combining manual removal from water using inflatable boats, floating booms, wetsuits and fishing waders, as well as removal from the shore. In total, the action cost ca. €22,500. Most biomass (83%) was removed during the initial control phase (one month). However, most of the efforts and costs (83%) were made in the following seven months, especially for monitoring and follow-up treatments. Rapid response avoided the growth, blooming and spread that could be expected in summer, coinciding with the optimal growing conditions. Moreover, rapid response reduced ca. 50 times the biomass and control costs with respect to a delayed action (i.e., after summer). Despite the fact that monitoring required a higher effort and cost than the initial control phase, it altogether represented a great cost saving as the invasion was kept at bay. The coordination between the regional Council, National security forces and public companies has taken advantage of the specific strengths of each one of them, achieving the shortest possible response time.