Features of limestone ecosystems

Limestone ecosystems consist of landforms such as cliffs, rocky slopes, and flat rock surfaces made mostly of calcium carbonate. These often form spectacular landscape features scattered in small, isolated patches across Aotearoa New Zealand. These precious ecosystems are rare and in decline, along with the biodiversity they harbour.

As well as being visually striking, they are culturally important and offer commercial and recreational value. Many are considered sacred (wāhi tapu) and have special spiritual significance for mana whenua. They are also true biodiversity gems with many rare species.

Limestone plant species

Population: There are over 152 limestone plant species. More than 50 of these are ranked Nationally Critical, the highest threat level in New Zealand. Many are found at a single site.

New Zealand status: Endemic

Conservation status: Nationally Critical

Threats: Invasion by pasture weeds, herbivory from stock and pests, human impact, habitat loss, disease

Other threats: Weather events and climate change effects, swarding grass invasion creates extremely high fire risk

Restoring limestone ecosystems

Since 2020, DOC has been working alongside Te Rūnaka o Moeraki to explore ways to restore and manage two sites in Canterbury:

• Wai o Toura/Gards Road Scenic Reserve (19 hectares)
• Waipata/Earthquakes Scientific Reserve (27 hectares).

Both reserves are culturally significant and home to Nationally Critical plant species like the Waitaki broom and limestone gentian. While current efforts are barely holding the line, applying this work at a greater scale will turn the tide and restore a fully functional, self-sustaining ecosystem.

Restoring these areas will not only safeguard endangered ecosystems but also provide a best-practice guide for similar projects across the country. It would create healthy habitats for unique species to thrive and give many threatened species a new lease on life.

The smaller Wai o Toura Reserve is an ideal site to demonstrate the benefits of landscape scale ecosystem restoration; the site is fully fenced, stock grazing has been removed and there is ongoing browsing animal (rabbits and hares) and woody weed (broom, gorse and boxthorn) control.

If successful, future work can be further scaled-up to restore the Waipata Scientific Reserve, the second DOC site in the Waitaki Valley, as well as other limestone ecosystems across the country, using what's learnt from the restoration activities at Wai o Toura.