Planting key to dune survival

 

By Peter Nicholas

Twenty-eight years after re-vege-tation of Mangawhai’s distal spit be-gan following the disastrous breach, the work of planting more than 10,000 spinifex and pingao plants annually on the dunes is as critical now as it was in 1996.

Since 1993 more than 200,000 in-digenous sand-binding species have been planted on the dunes.

However no more than 50 per-

cent have survived annually. In some years, like in 2007, the annu-al planting of 10,000 spinifex and pingao plants has been completely wiped out by storms.

It is certain that without the plant-ings on the Spit over the years, there would be nothing to catch and hold the sand and another breach of the Distal Spit during a bad storm could well have been possible.

Jerry Pilmer leads the Man-gawhai Harbour Restoration Soci-ety’s (MHRS) annual planting pro-gramme on the Distal Spit. During August and September Jerry and his group of 40 to 50 volunteers carry out the planting programme.

The MHRS Society is unable to plant later in the spring, or before the end of February, because of the need to keep away from nesting birds. Planting earlier would be of

no use as winter storms would de-stroy the fledgling plants.

Jerry and his team plant spinifex (sometimes referred to as silvery sand grass) and pingao (also known as golden sand sedge) mainly around the 1.5 kilometres of fenc-ing that lines the eastern coast of the Spit. A total of 21 fences have been constructed on the spit, located in a pattern of sections and angles aimed at catching the sand and building “bunds” or dunes close to the coast-line.

Spinifex is used to hold loose sand and planted in lines, whereas pingao is planted in groups of 15-

plus and is especially useful in catch-ing blown sand.

The task of stabilising dunes by planting indigenous sand-binding species, has continued for far longer than it was ever envisaged.

Back in 1996 when plantings first began, the then president of the Har-bour Restoration Society, Mr Jim

Wintle, said that plantings “could continue for up to 10 years.”

He said at the time: “The shade-cloth fences erected on some parts of the bund will aim to catch the sand blowing around and help to build up the dunes. Our long-term aim is to stablilise the sand dunes with the fencing and planting programme.“

When planting first began, sand binding seeds were grown at a nurs-ery which had been set up in 1983 under a council PEP scheme adja-cent to the current location at the Skate Park in Molesworth Drive. That original nursery closed, but the site was re-opened in the early 1990’s

and later moved to a 2,500sqm site on land leased from the Hawkes family.

Many former well-known Man-

gawhai identities were involved in the early establishment of the MHRS nursery, including the late

Kingi Raharaha, Richard Bull and Jim Wintle.

Kingi died in 2009 after a 10-year commitment to the nursery. He looked after the nursery on a day-to-day basis.

This year the nursery closed af-ter the Hawkes family farm was des-tined for sale.

Now, Jerry Pilmer and his vol-unteers plant spinifex and pingao plants that are grown for about 12 months from seedlings that are col-lected on the Distal Spit and sent to a Bay of Plenty nursery for growing into plants. When planting is under-taken (normally 70 percent spinifex and 30 percent pingao), each plant is placed about 40cm in the ground, along with slow-release fertiliser tab-

lets, at about 1-2 metres apart.

Their plantings range from the harbour entrance as far as Tern Point.

“We’d like to increase plantings by about 10 percent in future years,” said Jerry. “But our planting window is very narrow.”

The cost of the current planting programme to the MHRS Society is approximately $20,000 per annum.

The MHRS is also involved with the Department of Conservation in pest control on the Distal Spit. Rab-bits are the main target as they eat the junior spinifex and pingao plant-ings.