Studies on the control of Spartina have shown mechanical removal leads to a 42.8% increase in plant density in subsequent growing seasons compared to control areas that were left unmanaged. [1] This is because this grass propagates via underground rhizomes and any activity which fragments and redistributes those rhizomes will increase the rate at which it can spread compared to natural expansion.
How could Spartina be controlled?
- Chemical spraying will slow the expansion of Spartina, though the effect is short-lived and recovery to 100% of former density occurs within 1-2 years. (1,2)
- Smothering with dredged substrate or covering with plastic sheeting for a complete growing season has been shown to be effective in controlling Spartina (3,4)
- Complete removal of substrate containing the rhizomes which extend 30-40 cm underground is an effective treatment [2]
What will happen if we do nothing?
As noted in https://www.facebook.com/groups/353912892854904/posts/353920626187464 the Spartina growth on the North Wirral foreshore is constrained within a zone with specific conditions of salinity and silt delivery. That zone is moving as the accretion continues. Now that that raking and spraying has stopped favouring Spartina over its competitors, it is more or less irradicated from the upper beach. That process will continue to happen as the beach profile changes.
References
1. First record of Spartina alterniflora in southern Africa indicates adaptive potential of this saline grass
2. A systematic review of the effectiveness of management techniques used in the control of invasive estuarine cordgrass Spartina species
3 The Effects of Smothering a Spartina alterniflora Salt Marsh with Dredged Material
4. Hammond, M, 2001, The experimental control of Spartina anglica in estuarine salt marsh #spartina