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Costs to Ecuador's rice sector during the first decade of an apple snail invasion and policy recommendations for regions at risk

Abstract:

Invasive Alien Species (IAS) can become a tremendous burden to national economies; however, few studies have quantified the economic impacts of IAS, particularly for developing nations. The golden apple snail, Pomacea canaliculata (Lamarck), was introduced into Ecuador in 2005. By 2012, the snail had affected 94% of Ecuador's rice-growing areas. We used government surveys of rice production and snail distributions, as well as yearly production costs and rice prices, to estimate snail-associated losses to rice productivity and profitability between 2005 and 2015 – the first decade of P. canaliculata in Ecuador. Based on the intensity of the invasion and changing management practices, we estimate that the golden apple snail caused accumulated losses of 35.65 K tons of rice grain (worth US$23.10 M) with further productivity losses (lost inputs and labour) of US$9.61 M (total = US$32.71 M), until 2015. Based on survey information, we estimate that 90% of affected fields were treated with pesticides during the 5 years following initial establishment of the snail on individual rice farms. Pesticides potentially saved up to $10 M in damage during peak snail densities in 2012. By 2015, prophylactic molluscicide treatments were costing the nation US$15.24 M annually (including application costs: accumulated 10-year cost = $123.46 M, assuming 90% coverage). Increasing pesticide and labour costs, but relatively stable farm-gate rice prices, suggest that the continued chemical control of golden apple snail in Ecuador is economically unsustainable. We discuss possible alternatives to prophylactic molluscicide applications that can increase the economic and environmental sustainability of rice production in the face of high densities of apple snails during post-introduction outbreaks. We suggest that nations at high risk from invasive apple snails (e.g., Bangladesh, India, Colombia and Peru) could avoid substantial losses by pre-emptively researching and adopting mechanized crop establishment practices that not only reduce labour costs, but also prevent potential damage from apple snails to rice.