New Zealand’s indigenous biodiversity is often concentrated in ecosystems that are historically rare.
Ecosystems such as ephemeral wetlands, bluffs, karst, geothermal vents and coastal turfs, may collectively contain half of our nationally threatened plant species.
Unfortunately, many historically rare ecosystems are poorly understood, and at the same time are small and vulnerable and often highly threatened.
Maintaining threatened rare ecosystems is an eight-year research programme led by Susan Wiser from Landcare Research.
In New Zealand, there is a diverse array of small, rare ecosystems that tend to occur in extreme, typically treeless, environments. They have been rare since before humans arrived, which is the rationale for the term historically rare (also known as originally rare or naturally rare).
The objectives of the research are to identify historically rare ecosystems nationally, describe their flora and fauna, determine major threats, and develop a framework to ensure their effective conservation management.
Susan says the first goal for the researchers was to identify historically rare ecosystems in New Zealand. ‘This resulted in a structured list that defines 72 types,’ Susan explains.
‘We then selected four systems to look at more intensively. These are shingle beaches, gumlands in Northland, granite sand plains, and granite gravel fields.
‘Shingle beaches are widespread around New Zealand, had never been surveyed nationally for plants or invertebrates, are highly threatened by urbanisation, weeds, adjacent agriculture and introduced animals, and contain both threatened plants and fauna and endemic plants.’
Shingle beaches are a mixture of sand, water-smoothed gravel and cobbles.
They occur where rivers deliver large quantities of shingle to the coast or where nearby coastal cliffs containing gravel are being eroded.
These beaches are particularly common on the east and south coasts, for example, between Christchurch and Dunedin.
They also occur on the Taranaki and Wellington coasts.
The highest-quality shingle beaches are in Fiordland.
The research studied those shingle beaches where at least 50% of the top substrate was gravel and where vegetation was supported above the high tide line.
The researchers visited most of the shingle beaches around the country.
‘We set up random sampling systems at 61 beaches,’ says Susan.
‘At each beach we recorded the plants, determined the nature of the substrate, focused on the characteristics of adjacent vegetation, and collected invertebrates.
‘Of the 463 plant species found, 50% were exotic. The most frequent exotics were the grass Holcus lanatus (Yorkshire fog), the perennial herbs Hypochaeris radicata (catsear) and Plantago lanceolata (narrow-leaved plantain), and the annual herbs Sonchus oleraceus (sow thistle) and Anagallis arvensis (pimpernel).
‘Drier, warmer sites with more gravel than sand had more exotics, whereas the rare native species were found in all geographic areas but not on the most gravelly sites.
Left: Rowan Buxton assessing gravel size on a sampling plot at Gore Bay in North Canterbury.
Above: Shore convolvulus Calystegia soldanella (left) and knobby club rush Isolepis nodosa (right) were the most frequent native plants found on shingle beaches.
Left: Rare plants observed on shingle beaches included (top) Raoulia aff. hookeri (declining), (middle) Euphorbia glauca (declining) and (bottom) Muehlenbeckia ephedroides (declining).
Susan adds that there were several notable finds in the many hundreds of invertebrate specimens collected.
‘The rare egg-laying velvet worm (peripatus) Ooperipatellus viridimaculatus was discovered on one of the few shingle beaches on the West Coast of the South Island.
Additionally, several specimens of Maaminga marrisi, one of only two endemic species belonging to the newly discovered wasp family, Maamingidae, were found at two shingle beach sites.
The exotic ant, Hypoponera confinis, is new to New Zealand and is known only from one shingle beach locality.
‘There is now a need to explore the relationships between shingle beaches and other communities such as coastal turfs,’ explains Susan.
‘A lot of these systems are interrelated but we don’t know how the relationships work.
'For example, Muehlenbeckia ephedroides is found in riverbeds and behind dunes as well as on shingle beaches.
'Finding out the affinities between the systems will give us a better understanding of them.’
Shingle beaches are prone to invasion by numerous exotic herbs, grasses and shrubs, especially when near urban or agricultural areas.
‘A lot of the sites are incredibly weedy,’ says Susan.
‘Lupin and gorse are major invaders and near settlements, garden plants including gazanias, South African ice plants and succulents are encroaching.
On drier east coast beaches such as those at Kaikoura, Centranthus ruber (red valerian) will easily take off.
‘One aspect we need to explore is how weeds change the structure of the ecosystems.
The native species produce little leaf litter but the invasive species produce a lot more which stabilises the systems.
By understanding the distribution and abundance of exotics and how they change the ecosystems, we can work out which sites can be restored and which ones are lost.’
Other threats to shingle beaches are 4WD vehicles damaging the vegetation and the impact of rabbits and hares.
Coastal development is an ongoing threat.
With the rapid rise in coastal development, covenanting can help to preserve New Zealand’s rare shingle beaches.
‘These areas have a unique combination of species,’ says Susan.
‘Protecting coastal ecosystems saves them from development and the weed and pest control associated with covenanting helps to retain our distinctive biodiversity.
‘Such small and vulnerable areas are an ideal focus for local conservation management.
'Private landowners can protect natural features on land they own adjacent to the coast with QEII covenants.
'Protecting the land between a beach and a cultivated area would act as a buffer, allowing us to continue to appreciate these rare systems.’
For more details of the research visit the Landcare Research website
Open SpaceTM Magazine No. 76, July 2009 © QEII National Trust