Urban development in Auckland has reduced the number and quality of places where native plants can grow. Since the 1850s around 30 native plants have silently disappeared from the region. Others have declined so much they are now listed as threatened with extinction. There are 200 threatened plants in Auckland, including mistletoes, orchids, shrubs, ferns, vines, grasses, herbs, mosses and one root parasite. They grow in a variety of habitats from quite modified places like urban streams, roadsides and beaches, to more natural areas such as wetlands and forests.
Why are they threatened?
Kowhai ngutu-kaka (kakabeak)
Plant populations decline for a number of reasons. Part of the Department of Conservation’s (DOC’s) job is to find out what the threats are and how to control them. Weeds threaten native plants by competing for space and stopping seeds germinating by smothering the ground. They also shade out plants that need light.
Animals, such as goats, possums, pigs, rats and deer, feast on defenceless native plants. They also eat the flowers, seeds and seedlings of native plants preventing their regeneration. Garden snails and caterpillars of the white cabbage butterfly eat some of our most threatened plants. Plant diseases may also play a part.
Some plants rely on native animals for survival. The rare root parasite Dactylanthus taylorii, for example, needs short tailed bats to pollinate its flowers, and coastal cress (Lepidium oleraceum) relies on breeding seabirds to enrich the soil.
What's DOC doing?
Protecting threatened plant populations in the wild is DOC’s key plant conservation goal in Auckland. The department uses a range of measures to look after threatened plants. Some are fenced off or caged to keep browsing animals at bay. Animal pests are also controlled. Weeding, sometimes by hand in sensitive locations, is often crucial to these plants’ survival in Auckland.
Growing threatened plants at the Auckland Botanic Gardens and other sites provides some insurance in case wild populations are destroyed. These plants can be transferred back into the wild when the threats at natural sites are brought under control.
The survivors
Four examples of threatened plants that have hung on in small populations within inner Auckland City are the tiny annual fern (Anogramma leptophylla), the endangered fully aquatic moss (Fissidens berteroi), a lava field herb (Geranium solanderi) and a dwarf mistletoe (Korthalsella salicornioides). These plants are a window into the past when Auckland was a place where native plants prospered. They all grow in places which are legally protected and highlight the importance of even the smallest city reserve as a refuge for our native threatened plants.
Learn more about threatened plants
Most people haven’t noticed the loss of native plants from Auckland. But by learning more about which plants are native to Auckland and where they grow, you can support plant conservation efforts. Many of our threatened plants can be found in the Auckland Botanic Gardens in Manurewa where you can see them up close and learn more about their habitats and the threats they face.
Visit the website of the New Zealand Plant Conservation Network to find out more about threatened plants:
www.nzpcn.org.nz
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