Background

Arundo donax, an introduced riparian plant species (commonly referred to as giant reed), has significant negative impacts on water availability, water quality (i.e. sediment loads, temperature, pathogens, nutrient loading, flow modification), habitat, fires, and infrastructure. Arundo transpires water at a rate that is 5x higher than native vegetation. Analysis from Cal-IPC’s Arundo donax Distribution and Impact Report (March 2011) demonstrates that for every one-acre of Arundo removed, 20 acre-feet per year (AFY) of water would be available downstream for capture/recharge into the San Fernando Groundwater Basin and for in-stream flows along the Glendale Narrows.

Arundo becomes so dominant in riparian systems that it changes hydrological and geomorphic processes that determine plant and wildlife community structure. These changes occur through alteration of flood disturbance and introduction of fire disturbance. Altered flood and fire regimes promote Arundo dominance and suppress native vegetation. In addition, Arundo stands can significantly increase fuel loads and fire frequency potential (acting as both an ignition source and fire conveyance across riparian areas). 

Arundo also out-competes all native vegetation, impacting environmental resources and habitat beneficial uses. It has almost no biological value–no insects or wildlife feed on it, few organisms inhabit stands (i.e. poor nesting structure for birds), and stands impede movement in and through riparian zones. This directly impacts many terrestrial endangered and threatened species such as least Bell’s vireo, southwestern willow flycatcher, arroyo toad, and many others. Aquatic threatened and endangered species (e.g. Santa Ana sucker) are also affected by Arundo’s alteration of sedimentation processes, water temperature, eutrophication, and pathogens. 

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View the Arundo donax rating profile at Cal-IPC.