Coastal Dunes - Species that Matter - Coastal Wattle
The intention is that the following is the first of a series of perspectives on species that live in our area, focusing on dunes, dune wetlands and estuaries along this west coast of the lower North Island. Often you’ll see upbeat material, covering threatened species that are doing well, or not so well, on this coast. Sometimes I’ll rant about problem species.
Because this time of year is the peak season for identifying it, I’ll start this series with a problem species. Coastal wattle, a.k.a. ''Acacia longifolia sophorae'' is the number one threat to our dunes and dune wetland environment on this coast. Here in Foxton Beach, to see this problem at scale, look at the south bank of the Manawatu River. There were formerly dunes along that shore well back in from the coast, but those dunes are all but gone, overgrown with a wide belt of coastal wattle from the plantation pine to the estuary. The native dune flora and fauna have disappeared under a coastal wattle forest:
https://inaturalist.nz/observations/92336911
We have other problem spots in the Foxton Beach area. A stalwart community team works with District Council to eliminate this from the dunes south of Foxton Beach township. On the north side of Foxton Beach at the end of Brown Terrace about one hectare of dune vegetation has gone lost to large, well established stands of coastal wattle.
To familiarise yourself with this species, as it has a characteristic flower in August/September:
https://inaturalist.nz/observations/89883519
The bright yellow flowers are identifiable from a distance this time of year.
The wattle problem is particularly obvious around Himatangi Beach:
https://inaturalist.nz/observations/89607860
The dunes are completely covered around the main beach entrance. To the north dozens of hectares of coast wattle forest have eliminated the original dune vegetation. To the south of Himatangi Beach settlement, some of the most scientifically interesting dune wetlands anywhere are under threat from encroaching coastal wattle.
This problem does not stop there, but is severe at Tangimoana, right past the Rangitikei estuary, and on to the mouth of the Whanganui River.
We have a particularly clean dune area around the north side of the Manawatu River mouth. Within the Manawatu Estuary Ramsar site[1] the dunes are free of coastal wattle, and are maintained that way by a dedicated team of volunteers. Further south than the Manawatu River, the coastal wattle problem is out of control too. The dunes are being overgrown to Waitarere Beach, and beyond. One of the finest examples of dune wetland on this coast is the 4km stretch between Kuku Beach and Waikawa Stream, but especially at the south end, the coastal wattle is running amok, over a host of native dune wetland species that deserve better.
This problem was originally created by the New Zealand Forest Service, and its predecessors, in their ambitious plans to plant New Zealand’s dunelands with pine forest[2]. With these plantations now commercialized it is difficult to push the current leaseholders of those forests to be responsible for the mess.
A retired scientist formerly associated with Landcare Research, Dr. Richard Hill, had been working for years to certify a species of invertebrate which preys on Acacia species, including coastal wattle. Whether this is a viable answer, I can’t say, but I’d like to find out more about the status of that work, as an option to consider. Our coastal dunes and their wetlands are unique, in New Zealand and wider. Dealing with this species would be a major step toward preserving them.
[1] Some pointers to the Manawatu Estuary Ramsar site:
https://www.wetlandtrust.org.nz/get-involved/ramsar-wetlands/manawatu-estuary/
https://www.metrust.org.nz/about-the-estuary
https://www.doc.govt.nz/globalassets/documents/parks-and-recreation/places-to-visit/wellington/manawatu-estuary-mgt-plan-2015-2025.pdf
https://www.horowhenua.govt.nz/Places-Events/Parks-Reserves-Recreation/Hartley-St-ReserveSunset-WalkwayManawatu-Estuary-Foxton-Beach
https://en.wikipedia.org/wiki/Manawatu_Estuary https://en.wikipedia.org/wiki/Manawatu_Estuary
Comments
Thanks for this, Arnim, very interesting and something I hadn't heard about before.
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