Risks associated with the use of the invasive reed grass, Arundo donax, for biomass production

Background/Question/Methods

Arundo donax (giant reed) is a perennial, clump-forming hydrophyte that has invaded Mediterranean, subtropical, and semi-arid riparian zones worldwide.  Arundo was introduced into North America over a century ago because of its usefulness to humans, but its widespread colonization of riparian systems from Texas to California has triggered large-scale and costly removal efforts.  Arundo is now being considered as a key species for mass propagation as a biofuel plant. Proposals for massive Arundo farms from Florida to Oregon have resulted in an outcry about the potential for an ecological catastrophe by introducing a non-native species known primarily for its invasiveness into new environments. I address whether the environmental concerns are unwarranted or whether there is cause for concern.

Results/Conclusions

Arundo reproduces primarily through asexual reproduction, and we have found no evidence of seed production in North American populations. Arundo is highly invasive in the flashy river systems of the southwest where seasonal rains scour riverbeds, dislodging the shallowly rooted plants and redistributing rhizomes downstream. Arundo quickly gains a foothold in competitor free space and forms dense populations, which choke out any remaining native plants and prevent colonization by slower growing native species. The energy industry claims that farms are being developed in 'benign' environments where hydrologic spread of Arundo is highly unlikely. Planting Arundo in locations that have markedly different hydrological regimes (where extensive erosion of wetlands is not a concern) may at first glance appear to be a viable way to ‘tame’ Arundo and exploit its upside as a plentiful biofuel source. However, relatively little is known about its biology or its potential for spread in these new environments. For example, Arundo is currently being grown on plantations in Florida, and so far, there has been no evidence of unwanted spread, but there is growing concern about the potential for a large-scale dispersal event resulting from a hurricane or associated tidal surge. The consequences of unforeseen events such as this must be weighed against the benefits of using Arundo as a biofuel. Because of the harm to habitats and wildlife that we have seen in southern California riparian systems, we strongly warn against using an aggressive plant in environments where its invasive potential has not or cannot be evaluated.