Arundo is a hydrophyte and uses a large amount of water to supply its very high   growth rate. In the presence of water, Arundo has the ability to grow in various   types of soil, including in saline conditions. Since this species is drought tolerant   and adapts to many weather and soil structures, one of the ways it outcompetes   local vegetation is by using all the available water. Arundo consumes around 16.7   mm/day compared to 0.9-1.6 mm/day for mixed riparian vegetation. Reports   consistently find it uses 10-15 times more water than native riparian plants, and in   the arid west this can be up to 110 times more. A study of the Santa Ana water   basin in 1993 found 56,200 acre-feet of water transpired from Arundo equaling   $12 million at the Metropolitan Water Association (MWA) rates.

 Removing Arundo from local watersheds in California decreases fire hazards and   the damage caused by fires. The presence of Arundo increases fire hazards due to   its fuel load, intensity and ignition sources. This increased fuel load paired with   Arundo’s optimal, well-ventilated structure allow fires to thrive. In addition, the   reed’s vertical structure assists fires in burning the crown of taller shrubs and trees,   which increases the frequency and extent of fires. Once ignited, fires burn hotter in   habitats with Arundo. In addition, Arundo-infested riparian habitat can facilitate .   movement across the landscape – fires can more easily spread and burn a larger   amount of area. Further, Arundo regrows three to four times quicker than native   vegetation, allowing it to colonize more space and act as a positive feedback   mechanism for these events.

 Arundo modifies the geomorphology of riparian environments and takes over   riverine habitat in which it is found. While Arundo roots reinforce river banks, the   stands that fall into the river redirect the flow of water, resulting in steeper banks   and increased channel depth. Stands can also get trapped in waterways causing   physical obstructions to natural water flow, thereby increasing the risk of flooding to   adjacent lands. Large stands are especially hazardous because Arundo’s shallow   root system is easily dislodged and banks may collapse exacerbating erosion. In   addition, during large floods Arundo increases stream roughness, creating debris   dams at bridge crossings. A 1993 flood at Camp Pendleton in San Diego is   largely attributed to Arundo; the military spent millions of dollars in damage repairs   and have since been managing the surrounding plant community more closely to   prevent future incidents.

 Arundo is an excellent colonizer and decreases the quality of invaded habitats.   There are 22 federally endangered species impacted by Arundo, in addition to   other local species. The most threatened of these species are the Least Bell’s Vireo   and Arroyo toad. Although Arundo can have direct biotic impacts, such as   competition with native plants, most of the damage comes from abiotic   modification. The vegetation density makes it difficult for land animals to find   shelter and the lack of horizontal structure makes it unsuitable for birds. Animals do   not eat or nest in it. Local plant species lose land space and are shaded by tall   stands. These abiotic alterations are exacerbated with fire or flood events that   promote Arundo spread.