Agricultural policies against invasive species generate contrasting outcomes for climate change mitigation and biodiversity conservation

Abstract

Direct consequences of biological invasions on biodiversity and the environment have been largely documented. Yet collateral indirect effects mediatedby changes in agri-environmental policies aimed at combating invasionsremain little explored. Here we assessed the effects of recent changes inwater management in rice farming, which are aimed at buffering theimpact of the invasive apple snail (Pomacea maculata, Lamarck), on greenhouse gas emissions and diversity of waterbird communities. We usedobservational data from a 2-year field monitoring (2015–2016) performedat the Ebro Delta regional scale. We found that drying rice fields reducedmethane emission rates by 82% (2015) and 51% (2016), thereby, the contribution of rice farming to climate change. However, there was a markedreduction (75% in 2015 and 57% in 2016) in waterbird diversity and abundance in dry fields compared with flooded fields, thus suggesting thatpost-invasion policies might hinder biodiversity conservation. Our resultshighlight the need for accounting for potential collateral effects during thepolicy decision-making process to design efficient agricultural managementplans that lessen undesirable agri-environmental outcomes.