Spartina anglica - Townsend's grass

Common cordgrass is native to Southern England. The grass is a hybrid of the European native small cordgrass S. maritima and the North American smooth cordgrass S. alterniflora ^[2].

This American alien species probably ended up in Southampton at the English south coast before 1870 via the ballast water of ships. On the salt marshes (the area that only floods at spring tide) around Hythe, a coastal town in the area, smooth cordgrass hybridised with the native small cordgrass ^[3]. This created the hybrid S. townsendii, which was unable to reproduce. Around 1890, a fertile hybrid was created from this sterile plant by a chromosome doubling (polyploidy), namely the common cordgrass S. townsendii var. anglica ^{[4, 5]}. It is this latter fertile species that reached our regions. 

First observation in Belgium

In 1924, common cordgrass got transported from England and planted as a silt catcher in the former ‘Zuid-Sloe’ estuary ^[6]. Due to the embankment of this area, the port and industrial area ‘Vlissingen-Oost’ ^[7] was established there in 1962. This area is situated on the east bank of the Dutch part of the Western Scheldt and belongs to our study area. The first observation on Belgian territory dates back to 1936 ^[8].

Spreading in Belgium

The common cordgrass is a pioneer species and is typically found on silt and wet soils. This cordgrass occurs in salty to very brackish water in salt marches (areas that are dry during low tide and submerged during high tide) and low mudflats. In our regions, the species occurs in the Scheldt estuary (on brackish salt marches near Doel), the Yser estuary in Nieuwpoort, the Bay of Heist and Zwin Nature Park in Knokke  ^{[9, 10]}.

Spreading in neighbouring countries

In 1906, common cordgrass was transported for the first time to the European mainland, more specifically to Normandy (France). In 1924, more than 50 plants were transported from England to the Netherlands and planted in the Dutch Sloe estuary. In the following years, the species got planted in other estuaries. Afterwards, the expansion of the distribution area went quickly, and the plant established itself in almost all suitable places. As a result, common cordgrass is now common in the Wadden Sea and Delta region ^{[11, 12]}.

In addition to the Dutch part of the Wadden Sea, common cordgrass got also planted in the German and Danish parts in the 1930s. In Germany, there were about 70,000 shoots planted. In both countries, common cordgrass appeared to thrive well ^[13].

On the European mainland, its distribution area stretches along the Atlantic coasts of France to the Baltic Sea ^{[5, 13]}. The species is widespread along the east and west coast of the United Kingdom and Ireland, except for Scotland ^[14]. Certain populations of estuaries in Southern England have been in decline for some decades. It is presumed that the decrease of these 80-year-old populations has a natural cause.

Common cordgrass has been introduced to Ireland, Australia, New Zealand, North America and China. In all these countries, the species is invasive. However, introductions to South America and South Africa were unsuccessful ^[15]. Currently, common cordgrass is found in Europe between 48-57°N, in China between 21-41°N, and in Australia and New Zealand between 35-46°S ^[15].

The seeds of smooth cordgrass are believed to have ended up in England via the ballast water of a ship from North America. After the creation of common cordgrass – from hybridisation between smooth cordgrass and small cordgrass – its distribution area expanded due to the deliberate introduction and planting as protection against coastal erosion and land reclamation ^[5].

Common cordgrass has some features that explain the success of this alien species. The species grows fast, has high fertility and is an aggressive colonizer. Once established, the plant can multiply asexually or vegetatively via the growth of rhizomes. Because of its invasive character, the natural ecosystem of mudflats can get quickly overgrown with common cordgrass ^[16].

Because of the fleshy rhizomes, the species is more resistant to erosion than any other halophilic plant present in our regions. Common cordgrass thrives up to one meter below the average high tide line. Thus, during high tide, this plant is submerged ^[12].

Common cordgrass thrives best in soft and silty soils ^[12]. In colder regions, the species encounters difficulties in producing fertile seeds ^[5]. It thrives best at temperatures between 10 and 25°C. It prefers soils where the pore water has a salinity between 0.1 and 0.2 Molar ^[12], which corresponds approximately to 6.3 and 12.6 PSU. Undiluted seawater – salinity of 35 PSU – would be too salty for the species to survive and, therefore, limits its distribution ^[11].

This non-native species can reproduce and extend its distribution in two ways. On the one hand, there is sexual reproduction, where the produced seeds are carried away by the sea currents or wind and get deposited in new places. On the other hand, common cordgrass can reproduce asexually or vegetatively by the continuous growth of the rhizomes. Sudden changes in the sedimentation patterns and fluctuating climate conditions favour this species and its spread ^[12].  

Common cordgrass is very productive and can represent a significant proportion of organic matter within an ecosystem. This organic matter is food for grazers, such as ducks, geese and other aquatic birds ^{[13, 15]}. The expansion of common cordgrass – after depositing sediment – allows the development of new types of marsh vegetation, including common sea-lavender Limonium vulgare and herbaceous seepweed Suaeda maritima ^[17]. Despite these positive effects, this species can also be harmful to the ecosystem ^[13]:

• Loss of habitat, e.g. of soil organisms, aquatic birds and migrating seabirds
• Loss of breeding sites of fishes
• Replacement of native plant species and the (often) more species-rich faunal communities that live in association with them
• Reversal of the successive developmental stages in salt marshes and mudflats systems.

The expulsion of the native small cordgrass and the overgrowth of other native species, such as the long-spiked glasswort Salicornia procumbens, by common cordgrass, has greatly altered the appearance of mudflats and salt marches (specifically in Belgium). The result is a reduction in the intrinsic natural value, whereby the arrival of this alien species has severely disturbed the natural zoning of the vegetation in mudflats and salt marches ^{[5, 12]}. These changes have a negative impact on the soil organisms – such as the ragworm Hediste diversicolor and the European mud scud Corophium volutator (an amphipod) ^[13] – seabirds, including waders and seagulls ^[18]. Therefore, it is not surprising that common cordgrass has been given the nickname ‘mudflat pest’ by many nature conservationists.

From an agricultural point of view, the species is also far from appreciated. Dutch meadows used to grow common saltmarsh-grass (Puccinellia maritima) used to grow were very popular with cattle farmers. These salty plants give the meat a typical taste that is highly appreciated by many gastronomes. Common cordgrass is much less preferred by the cattle, although the young underground parts or rhizomes are grazed upon by Greylag geese Anser anser ^[12]. Furthermore, common cordgrass can change the properties of the soil, causing it to contain less oxygen. Plants (including common cordgrass) find it difficult to survive in oxygen-depleted soils ^[16].  

An example of the invasive character of common cordgrass is the colonization of the Bay of Arcachon in the southwest of France. In 1985, the species was observed there for the first time. Common cordgrass appeared to spread very quickly, and by the end of the 1990s, hundreds of hectares of mudflats and salt marches were dominated by the species. In 1997, a scheme was developed to eradicate this alien species via the injection of instant glue in the soil to destroy the rhizomes ^[19].

Before the Second World War, plants got sprayed with copper sulfate to destroy them. Later, attempts were made to control the species with the herbicides Dalapon and Fenuron in combination with the excavation of the seedlings ^{[5, 20]}. The use of chemical pesticides – including Dalapon – has now been banned for environmental reasons. Other effective mechanical control techniques are the suffocation of the plants by covering them with plastic, trampling and repeated burning ^[13]. However, these techniques are relatively expensive, not very efficient for large-scale usage, and sometimes fail due to the influence of the tides, e.g. in the case of using plastic coverings ^{[13, 15]}.

Between 2000 and 2007, common cordgrass along the west coast of the U.S. (Washington State) was controlled biologically by introducing the planthopper Prokelisia marginata ^[21]. This insect, which feeds exclusively on the nutritious sap (phloem) of cordgrass species, is also present along the Belgian coast since 2011 ^[22].

The common cordgrass is nominated as one of the 100 most invasive species in the world ^[23]. Despite the threat to the conservation of natural mud and salt march systems, there is a lack of knowledge about the ecological and economic impacts of this species ^[13]. Therefore, hardly any measures have been taken so far. This species may benefit from global warming and become even more abundant in the near future ^[13].

This plant can grow to a height of 130 cm and has long, fleshy rhizomes. The stiff, grey-green leaves can be 50 cm long and 15 mm wide and end in a hard and fine tip. A complete overview of the characteristics of this species can be found in the scientific literature ^[12].

Common cordgrass is the ideal plant for natural land reclamation and to stabilize coastlines. The dense root structures retain the coastal sediments very well, and the stems encourage the deposition of extra sediment. Moreover, this species can colonise open mudflats much faster and closer to the sea than any native competitor. In the past, this led to massive planting of this species, even far into China ^[5]. However, in other places, this species is rather feared than desired.

[1]          World Register of Marine Species (WoRMS) (2020). Spartina anglica C.E. Hubbard. [http://www.marinespecies.org/aphia.php?p=taxdetails&id=234043] (2020-11-17).

[2]          Ayres, D.R.; Strong, D.R. (2001). Origin and genetic diversity of Spartina anglica (Poaceae) using nuclear DNA markers. Am. J. Bot. 88(10): 1863-1867. [http://www.vliz.be/imis/imis.php?module=ref&refid=207303]

[3]          Stapf, O. (1913). Townsend’s grass or ricegrass. Proceedings of the Bournemouth Natural Science Society 5: 76-82. [http://www.vliz.be/imis/imis.php?module=ref&refid=120926]

[4]          Gray, A.J.; Marshall, D.F.; Raybould, A.F. (1991). A century of evolution in Spartina anglica. Adv. Ecol. Res. 21: 1-62. [http://www.vliz.be/imis/imis.php?module=ref&refid=117255]

[5]          Eno, N.C.; Clark, R.A.; Sanderson, W.G. (Ed.) (1997). Non-native marine species in British waters: a review and directory. Joint Nature Conservation Committee: Peterborough. ISBN 1-86107-442-5. 152 pp. [http://www.vliz.be/nl/imis?module=ref&refid=24400]

[6]          Wolff, W.J. (2005). Non-indigenous marine and estuarine species in the Netherlands. Zool. Meded. 79(1): 3-116. [http://www.vliz.be/en/imis?module=ref&refid=101200]

[7]          Wikipedia, de vrije encyclopedie (2018). Sloe. [https://nl.wikipedia.org/wiki/Sloe] (2018-08-02).

[8]          Verloove, F. (2006). Catalogue of neophytes in Belgium (1800-2005). Scripta Botanica Belgica, 39. National Botanic Garden of Belgium: Meise. ISBN 90-72619-71-4. 89 pp. [http://www.vliz.be/en/imis?module=ref&refid=185912]

[9]          Herrier, J.-L. (2007). Het beheerplan van het strandreservaat De Baai van Heist, in: Coördinatiepunt Duurzaam Kustbeheer. "De zandbank te Heist, een boeiend fenomeen", Seminarie Scharpoord Knokke-Heist, 19 oktober 2007: abstracts en powerpoint presentations. Coördinatiepunt Duurzaam Kustbeheer: Knokke-Heist: pp. 1-25. [http://www.vliz.be/imis/imis.php?module=ref&refid=120929]

[10]        Van Landuyt, W.; Hoste, I.; Vanhecke, L.; Van Den Bremt, P.; Vercruysse, W.; de Beer, D. (Ed.) (2006). Atlas van de flora van Vlaanderen en het Brussels Gewest. Nationale Plantentuin van België/Instituut voor Natuur- en Bosonderzoek/Flo.Wer: Brussel. ISBN 90-726-1968-4. 1007 pp. [http://www.vliz.be/nl/catalogus?module=ref&refid=170947]

[11]        Adema, F.; Mannema, J. (1979). De Nederlandse slijkgrassen. Gorteria 9: 330-334. [http://www.vliz.be/imis/imis.php?module=ref&refid=120934]

[12]        Weeda, E.J.; Westra, R.; Westra, C.; Westra, T. (2003). Nederlandse oecologische flora: wilde planten en hun relaties. IVN/KNNV Uitgeverij: The Netherlands. ISBN 90-5011-129-7.  pp. [http://www.vliz.be/imis/imis.php?module=ref&refid=56259]

[13]        Nehring, S.; Adersen, H. (2006). NOBANIS - Invasive Alien Species Fact Sheet - Spartina anglica. NOBANIS - North European and Baltic Network on Invasive Alien Species: Copenhagen. 13 pp. [http://www.vliz.be/imis/imis.php?module=ref&refid=207302]

[14]        Preston, C.D.; Pearman, D.A.; Dines, T.D. (Ed.) (2002). New atlas of the British & Irish flora: an atlas of the vascular plants of Britain, Ireland, the Isle of Man and the Channel Islands. Oxford University Press: Oxford. ISBN 0-19-851067-5. 910 pp. [http://www.vliz.be/imis/imis.php?module=ref&refid=168803]

[15]        Global Invasive Species Database (2005). Species profile: Spartina anglica. [http://www.issg.org/database/species/ecology.asp?si=76&fr=1&sts=sss&lang=EN] (2011-08-02).

[16]        Gray, A.J.; Benham, P.E.M. (Ed.) (1990). Spartina anglica: a research review. ITE Research Publication, 2. Her Majesty's Stationery Office: London. ISBN 0-11701-477-X. 80 pp. [http://www.vliz.be/imis/imis.php?module=ref&refid=120935]

[17]        Hoys, M. (1995). Ecologisch streefbeeld voor het op te richten staatsnatuurreservaat "De IJzermonding" te Nieuwpoort-Lombardsijde: studie uitgevoerd in opdracht van AMINAL, Afdeling Natuur. Universiteit Gent, L.P.: Gent. 45 pp. [http://www.vliz.be/nl/catalogus?module=ref&refid=24987]

[18]        Minchin, D. (2009). Spartina anglica Hubbard, common cordgrass (Poaceae, Magnoliophyta), in: DAISIE (Delivering Alien Invasive Species Inventories for Europe). Handbook of alien species in Europe. Invading Nature - Springer Series in Invasion Ecology, 3. Springer: Dordrecht: pp. 297. [http://www.vliz.be/imis/imis.php?module=ref&refid=135057]

[19]        ICES Advisory Committee on the Marine Environment (2006). Report of the Working Group on Introductions and Transfers of Marine Organisms (WGITMO) 16-17 March 2006 Oostende, Belgium. CM Documents - ICES. CM 2006(ACME:05). ICES: Copenhagen. 330 pp. [http://www.vliz.be/en/imis?module=ref&refid=111237]

[20]        Doody, J.P. (Ed.) (1984). Spartina anglica in Great Britain: a report of a meeting held at Liverpool University on 10th November 1982. Focus on Nature Conservation, 5. Nature Conservancy Council: Huntingdon. ISBN 0-86139-279-5. 72 pp. [http://www.vliz.be/imis/imis.php?module=ref&refid=120937]

[21]        Grevstad, F.S.; Wecker, M.S.; Strong, D.R. (2004). Biological control of Spartina. in Third International Conference on Invasive Spartina. 2004. San Francisco: San Francisco Estuary Invasive Spartina Project of the California State Coastal Conservancy.

[22]        De Blauwe, H. (2011). De slijkgrascicade Prokelisia marginata (Hemiptera: Delphacidae), een exoot gebonden aan Engels slijkgras Spartina townsendii, verovert nu ook de Belgische kust. De Strandvlo 31(3-4): 80-88. [http://www.vliz.be/imis/imis.php?module=ref&refid=211692]

[23]        Lowe, S.; Browne, M.; Boudjelas, S.; De Poorter, M. (2000). 100 of the world’s worst invasive alien species: a selection from the Global Invasive Species Database. The Invasive Species Specialist Group (ISSG), a specialist group of the Species Survival Commission (SSC) of the World Conservation Union (IUCN): Auckland, New Zealand. 12 pp. [http://www.vliz.be/nl/catalogus?module=ref&refid=303186]

VLIZ Alien Species Consortium (2020). Spartina anglica – Common cordgrass. Non-indigenous species in the Belgian part of the North Sea and adjacent estuaries anno 2020. Flanders Marine Institute (VLIZ). 7 pp.