Ephemeral wetlands in Aotearoa | New Zealand kettle holes: geographic range, botanical biodiversity values and underlying land tenures

Ephemeral wetlands are naturally uncommon ecosystems that have become threatened in Aotearoa | New Zealand and include many glacially derived kettle holes (kettles) of the South Island. These kettles can be easily overlooked as wetlands, particularly when in a dry phase, thereby increasing their vulnerability. To aid conservation planning and management of this threatened ecosystem, we identified and mapped all detectable individual kettles in the South Island (n = 1802) and used geographic and survey data to evaluate patterns in their distribution, floristic diversity, land tenure, changes in land tenure over time, legal status, and the occurrence of Threatened plants and lichens. Ninety-five percent of kettles were found in Waitaha | Canterbury, mostly in Te Manahuna | Mackenzie Basin, and most were small (< 0.6 ha) and close to other kettles. Altogether, kettles occupy just 0.004% of Aotearoa’s land area. Sixty-eight percent of kettles were found on either freehold land or pastoral lease land, with 10% of these protected by conservation or Queen Elizabeth II covenants; 29% of kettles were on public conservation land. Of the 29%, over half (60%) were on Stewardship Land. Therefore, kettles generally have limited protections that are dependent on their land managers. We completed plant and lichen surveys for 269 of the mapped kettles. We recorded 443 plant and lichen taxa; 128 were exotic species, 314 were indigenous, and one had uncertain biostatus. Occurrence of plants in Threatened or At Risk categories did not differ by land tenure or legal status of the kettles, so preservation of these wetlands needs to occur across all land tenures to ensure representative protection of kettles and their botanical values. Pairing desktop mapping with a flora survey shows that kettles are remarkable plant biodiversity hotspots, especially given they occupy such a small land area in Aotearoa.