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Feature article - Joining forces: aligning ex situ and in situ threatened plant conservation programs to support regional priorities
Emma Simpkins, Senior Regional Advisor Flora at Auckland Council and Ella Rawcliffe, Botanical Records and Conservation Specialist at Auckland Botanic Gardens
Botanic gardens play a pivotal role in the conservation of threatened plant species worldwide. Their significance lies not only in preserving plant diversity ex situ but also in aligning their efforts with existing in situ plant conservation programs. By integrating botanic gardens’ conservation efforts with in situ programs, botanic gardens enhance the effectiveness of conservation actions, facilitate the exchange of knowledge and resources, and promote holistic approaches to plant conservation.
In Auckland, regional threatened plant conservation is led by the Auckland Council Environmental Services (ES) team. In the last 18 months, ES has been working on the regional threat classification of plants, identifying the pressures to each threatened species, and identifying multiple locations where these threatened plants can be managed in situ across their suite of pressures while maintaining and enhancing populations for at least the next 50 years. This has allowed us to identify those species that will be challenging to support in situ with the current tools and technology we have available. It was only natural to draw on the skills and expertise of Auckland Botanic Gardens (ABG) to work in partnership on these species to support threatened plant conservation in a strategic way.
The collaborative partnership between ES and ABG has been identified as critical to achieving regional and national native plant conservation outcomes, combining and building skills, knowledge, resources, partnerships and capability. These departments have clear responsibility and mandates to work in their respective fields — ES with in situ conservation and ABG with ex situ conservation. Working in partnership to align existing and future projects will build capacity to deliver the goals set for us through regional, national and international plans/policies.
Auckland has approximately 357 threatened species, which is almost half of the (identified) native flora in the region (Simpkins et al., 2022). A massive 224 species have been identified for potential ex situ conservation. These species have been identified based on one or more of the following factors:
• our inability to manage the key pressures, e.g. climate changes, and habitat limitations for in situ populations, based on the current conservation tools and technologies available
• species that are only found at a single location in Auckland and are therefore at risk of loss due to their limited distribution
• the highest regional threat status.
Special species this partnership has been actively working on to survey, research, seed collect and/ or propagate include:
• Korthalsella salicornioides, a native leafless mistletoe that is regionally at risk (declining) and requires research into propagation techniques for establishing new populations. In situ management has involved planting new hosts under existing hosts that are in poor health and have declined rapidly in the last few years. This species is at a limited number of locations in the region, and our hope is we can translocate it to suitable habitats if we can master the technique of ‘planting’ it (which we have done for another native mistletoe, Ileostylus micranthus). We collected 60 seeds and planted them onto six hosts at the ABG, which can be monitored in the nursery as they establish.
• Lophomyrtus obcordata, or rōhutu, highly threatened due to Myrtle Rust and is regionally vulnerable. The pressure of Myrtle Rust and pest animal browsers means we see little recruitment in the wild and this species could go extinct without conservation efforts. Fungicide treatments on in situ plants have enabled one population to produce seeds, which have been grown on and become an ex situ collection. The ongoing maintenance of this collection is more time and resource demanding than other collections, but these actions are critical to its ongoing survival.
• Pomaderris rugosa, regionally vulnerable and found in open scrub on clay and impoverished soils. Although this plant is on some offshore islands in Auckland, it exists only in one location on the mainland and the population is incredibly small. Over the last five years, we have seen plants dying each year. The remaining plants are growing in an exotic gumland and therefore cuttings and seeds have been taken to establish an ex situ collection, as well as to propagate plants to translocate to a more appropriate native gumland habitat.
• Thyridia repens, regionally endangered Native Musk, found in saltmarshes and estuaries where it is permanently damp. In situ management of exotic weeds is undertaken 2–3 timesa year to maintain an open habitat for this species, and trials of plugs for translocations are scheduled. This species has recovered slowly from being underwater after nearly a year of rain, raising concerns about its persistence long term in situ.
We are also exploring introducing Scandia rosifolia, Eleocharis neozelandica and Leptinella rotundata into ex situ collections. Relationships between iwi and landowners are currently being developed as part of the in situ work, as well as translocation plans for some species. ABG will be brought into these conversations as the plans develop. We are looking forward to future opportunities to bring more threatened plants into ex situ conservation while aligning with in situ priorities.
Further reading
Simpkins, E, Woolly, J, de Lange, P, Kilgour, C, Cameron, E, Melzer, S. (2022). Conservation status of vascular plant species in Tāmaki Makaurau/Auckland. Auckland Council technical report, TR2022/19.
