ARTICLE : DUNELANDS

 December 2002 :   Current status of coastal foredunes in Wellington Conservancy

A report entitled Coastal foredune vegetation in Wellington Conservancy: current status and future management has just been published by the Department of Conservation (DOC).   Coastal dune conservation has been identified by DOC as a high priority.   This report provides valuable baseline information about the status of dunes in the region.

This report identifies 10 key foredune ecosystems in Wellington Conservancy.   It contains:
• Information about the cultivation of key foredune plants
• Maps showing the distribution of five key foredune plant species (Austrofestuca littoralis, Desmoschoenus spiralis, Coprosma acerosa, Pimelea aff. arenaria and Spinifex sericeus)
• A list of past and present dune conservation projects
• Contact names and addresses for people involved in dune protection
• Recommendations for protection and restoration of coastal dunes.

Copies of the report are available from DOC, Wellington Conservancy (price $15).

John Sawyer, Biodiversity – Technical Support Officer, Wellington Conservancy Department of Conservation, PO Box 5086, Wellington, Tel: 04 470 8427; Fax: 04 499 0077, E-mail: jsawyer@doc.govt.nz

 December 2002 :   Environmental weeds of the Kapiti Coast dunelands

The beautiful coastline and dunelands of the Kapiti Region are under assault from a range of environmental weeds.   The dunes were planted in the 1930s with marram grass (Ammophila arenaria).   This stabilised the dynamic shifting natural dune systems, resulting in the displacement of much native pingao (Desmoschoenus spiralis) and spinifex (Spinifex sericeus).

The greatest threat to the coastal dunelands (and indeed all coastal areas) is boneseed (Chryanthemoides monilifera).   This South African invader can grow right to the toe of the foredunes and can form complete monocultures across dunes and on coastal cliffs.   Currently the KCDC, WRC and DOC are engaged in attempting to get rid of boneseed on the coast.

A close second to boneseed is the European native evergreen buckthorn (Rhamnus alaternus).   This plant grows freely on the dune lands but can grow well inland.   Like boneseed, this plant is bird-spread and similarily can invade native ecosystems, completely dominating the flora within a few years.

Dune smotherers such as cape ivy (Senecio angulatus) and agapanthus (Agapanthus praecox) can be very damaging to coastal areas.   These plants tend to spill down dune slopes, excluding native vegetation.   Once established these robust plants are very difficult to control.

Non-endemic native plants such as pohutukawa (Metrosideros excelsa) and karo (Pittosporum crassifolium) can be as detrimental to the Kapiti dune ecosystems as exotic weeds.   Pohutukawa not only spread rapidly onto cliffs and beaches, but are also known to hybridise freely with northern rata, threatening the longterm viability of this species.   Karo can dominate coastal vegetation and change the low forest stature of the flax and divaricating plants forest type (1-2 m) on our coastal escarpments.   Bird-spread, karo can grow throughout this zone ultimately displacing our own special flora right up to the water line.   Witness this process in action on the hills overlooking Houghton Bay.

One of the reasons put forward for the big assault on our dune lands is that New Zealand’s flora evolved without a great number of dune colonisers.   Battling amongst the plethora of dune weeds are taupata (Coprosma repens), ngaio (Myoporum laetum), flax and toetoe – but these plants are a minority.   Not only do they face stiff competition from the plants above but also there is the nasty African boxthorn (Lycium ferocissimum), and abundant wattle (Paraserianthes lophantha) and pampas grass (Cortaderia selloana).   To a lesser degree, nasturtiun (Tropaeolum majus), kikuyu grass (Pennisetum clandestinum) and tree lupin (Lupinus arboreus) are problems, and in the dune hollows blackberry (Rubus fruticosus) and cotoneaster (Cotoneaster glaucophylla).   On the toe of the foredunes exotic iceplant (Carpo brotus edulis) is also doing well.

There are many other pest plants waiting in the wings as many residents are dumping garden waste in the dune areas.   These dumpings are the reservoirs of weed invasion for the future.   Without the cessation of this practice, and the arresting of the spread of some of the worst bird-spread coastal weeds, our coastal dune lands face a difficult and uncertain future.

Mike Urlich, Biodiversity Officer – Pest Plants Greater Wellington – the Regional Counci,l PO Box 40 847, Upper Hutt, Ph: 526 5325.