Repurposing Waste from Aggressive Acacia Invaders to Promote Its Management in Large Invaded Areas in Southwestern Europe

Several Acacia species are aggressive invaders outside their native range, often occupying extensive areas. Traditional management approaches have proven to be ineffective and economically unfeasible, especially when dealing with large infestations. Here, we explain a different approach to complement traditional management by using the waste from Acacia management activities. This approach can provide stakeholders with tools to potentially reduce management costs and encourage proactive management actions. It also prioritizes potential applications of Acacia waste biomass for agriculture and forestry as a way of sequestering the carbon released during control actions. We advocate the use of compost/vermicompost, green manure and charcoal produced from Acacia waste, as several studies have shown their effectiveness in improving soil fertility and supporting crop growth. The use of waste and derivatives as bioherbicides or biostimulants is pending validation under field conditions. Although invasive Acacia spp. are banned from commercialization and cultivation, the use of their waste remains permissible. In this respect, we recommend the collection of Acacia waste during the vegetative stage and its subsequent use after being dried or when dead, to prevent further propagation. Moreover, it is crucial to establish a legal framework to mitigate potential risks associated with the handling and disposal of Acacia waste.