Because of aforementioned good adaptability to different kind of soils and weather conditions, Arundo is widespread in temperate and hot areas all over the world (Figure 1). Due to these characteristics, Arundo is often labeled as an invasive species. However, this misinterpretation comes from bad management and human incompetence. In our history, humans have incorrectly introduced crops that are originally non-invasive, important and beneficial, and were mismanaged or neglected in a similar fashion.
Figure 1 – World map of Arundo
When is Arundo invasive?
Arundo only presents problems of invasiveness in riparian areas prone to torrential flooding (Figure 2). Both naturally occurring and anthropogenic disturbance may lead to unwanted spread.
Figure 2 – Aerial view of Arundo near Big Bend National Park
On the one hand, rhizome fragments are presumed to occur when flood events disturb clumps of Arundo and wash dislodged pieces downstream.
The repeatedly mentioned issue, was in California, when the plants were brought in for erosion control along drainage canals. Arundo has invaded central California river valleys along the coast and inland and is increasing in the North Coast. It is most problematic in southern California coastal rivers where it can occupy the entire river channel.
But the role of flooding in generating fragments is based on anecdotal evidence only and has not been adequately studied. Examinations in the Tijuana River Valley, California indicate that flood events only rarely break up Arundo rootstock and wash rhizomes downstream – thus, making it difficult to argue that Arundo is invasive.
Furthermore, anthropogenic disturbances are capable of producing rhizome fragments. The use of heavy machinery in areas where Arundo is planted is very likely to produce viable fragments and subsequent downstream recruitment. In Southern California, areas where bulldozers were used for irrigation channel maintenance had densities of sprouting Arundo that were at times greater than the valley as whole. Again, proving that human mistakes have led people believe that Arundo is invasive.
The other side – non-invasive Arundo
Arundo has been grown responsibly in numerous places without problems of invasiveness with good management techniques. Arundo is only likely to be invasive when planted in riparian and floodplain systems, particularly those subject to torrential flooding. Away from such aquatic systems, there is limited potential for rhizome and stem fragments to be broken off and spread.
There are a number of examples of Arundo grown using properly managed agricultural practices showing no signs of invasiveness in countries including Spain, Greece, Italy, Australia, Hungary, Mauritius, Honduras, and the United States. To add to the list, we have had successful plantations in Brazil, China, Sudan, Romania, Slovakia, Serbia, Philippines, Madagascar – no one has ever declared Arundo invasive.
Biological facts: Is Arundo invasive?
No viable seeds
Arundo spreads by asexual means due to apparent seed sterility. This phenomenon is attributed to low levels of genetic diversity or pollen production. Viable seeds were noted in some population in Afghanistan, South Western Pakistan, and Iran, but has never been observed in North America or Europe or Australia.
Clump expansion
Currently thought to invade habitats rapidly by rhizomes and fragments only. However, during a two-year field study in the Tijuana River Valley, California, expansion of Arundo clumps via rhizomes was slow, only 0.29 m per 2 year, and new recruits from fragments were rare, only 4.7 ha per year.
Whereas layering – a mode of spread – was common in the flood zone and was 7.4 times faster than the annual expansion via rhizomes. Moreover, layering produced 25 times more new recruits than fragments. These results challenge the assumption, which presumes that most new recruits come from upstream. Contrary, most new recruits come from within the habitat, via layering, and that clumps in the flood zone expand faster than those outside the flood zone.
Good management techniques when in the Arundo energy plantation
Avoid unsuitable planting sites
Practices like developing management plans that avoid planting at sites without buffer areas and avoid feedstock production in floodplains will minimise the potential spread of the renewable fuel feedstock.
Good management technology
- Bulldozers play an important, and overlooked, role in the break-up and dispersal of Arundo. To reduce the spread of Arundo via rhizome fragments, regulatory agencies should require appropriate management practices when bulldozers are used in the presence of Arundo, and land managers should not use bulldozers when attempting to eradicate Arundo.
Using bulldozers is a classic example of humans contributing to Arundo invasivity.
- Early detection and rapid response to potential spread.
- Continuous monitoring and reporting of site conditions.
- A plan for site closure and post-closure monitoring.
- Identification of a third party auditor who will evaluate the performance of the Risk Mitigation Plan on an ongoing annual basis.
Removal of Arundo energy plantation
Biological, physical, and chemical weed control methods have been applied to Arundo with mixed success.
Small stands of feral and backyard Arundo could, in most cases, be eradicated using physical methods with care take to avoid dispersal of uprooted rhizomes. Larger stands, such as those in plantations, may require repeated herbicide treatments for eradication.
Controlling Arundo is not complicated but requires targeted timing of weed control efforts, thoroughness, and a commitment to ongoing follow-up treatment of inevitable regrowth. You can reed more about ways of terminating Arundo in our article.
What is USA and EU Plant Authorities say about Arundo as an energy crop?
USA-EPA
EPA published a direct final rule (77 FR 700) and a parallel proposed rule on January 5, 2012 (77 FR 462). EPA has determined that renewable fuel made from Arundo meets the Green House Gas reduction requirements for cellulosic biofuel under the requirements of the Renewable Fuel Standard program. EPA believes that renewable fuel from Arundo is not likely to cause or promote the introduction or spread of invasive species in the United States or elsewhere. The EPA Environmental Protection Agency ruled in July 2013 that ‘Arundo donax, a giant reed that yields three times as much ethanol per acre as corn, qualifies as a cellulosic renewable fuel’.
EU
The European Union in a publishing called Arundo Donax Productivity Net concludes that Arundo is one of the most cost-effective crops. It is environmentally friendly and presents large potential by selection and improvement to become the champion of biomass crops. In addition, the European Commission has called the giant reed one of the most cost-effective and environmentally friendly crops.
In long-term field trials Arundo was successfully established in northern Germany and showed promising biomass yields. Moreover, Arundo showed sufficient high quality of ligno-cellulosic material for energy and fibre production.
Recent study conducted in Italy has found that Arundo proves to be suitable to marginal lands, such as saline soils. Arundo can produce a good biomass feedstock, thus offering a valid alternative to the abandonment of these areas that are unsuitable for growing food crops – also in a perspective of higher temperatures.
