Yesterday, we made a great discovery on the Southern South Westland coastline while filming a programme on NZ's wild and natural coasts. At Arnotts Point, site of the first recorded South Westland contact between Maori and European in 1813, there has been a remarkable recovery of the rare native sea spurge plant Euphorbia glauca. This sea coast plant is in serious decline throughout New Zealand because of coastal housing and farming development, grazing by introduced mammals and because of weed competition. Everywhere that it survives on mainland New Zealand it is particularly vulnerable to possum browsing. It is thriving on some offshore islands where there are no browsing mammals and some local Councils such as Wellington City Council are now planting it around the city.
In 2009, the Knights Point and Arnotts Point seacliffs north of Haast were treated by DOC though a carefully managed helicopter 1080 trickle feed and spreader programme. DOC West Coast recognised that these bluffs had high numbers of possums that were seriously impacting on large forests of rata, fuchsia and wineberry and Colenso's mistletoe in silver beech, all vital as food for native birds.
The 1080 application was totally impossible by any ground methods. The sea cliffs here are hundreds of metres high and in many places covered in almost impenetrable kie kie and supplejack.
The results have been spectacular in terms of the recovery of the tree species and the kill of possums, rats and stoats.
Until yesterday however no one realised that the programme has also allowed the recovery of Euphorbia glauca, the seriously threatened sea milkweed. At Arnotts Point, the vegetated rocky bluffs above the ocean formerly bare of any Euphorbia have now got extensive areas of this threatened plant. What I think has happened is that its rootstock survived from pre possum times here and it was always being browsed to the ground by possums every time any leaves sprouted on the root stock. Finally in 2009, with the possums eradicated, it has burst out with leaves and has now even flowered and seeded here.
Previously we knew that Euphorbia glauca was growing in 2 places on rocky bluffs about 8 km south of Arnotts Point near a place called Cole Creek. However for 20 years before the 1080 application resulting in the drastic reduction in possum numbers, these bluffs of Arnotts Point never showed any evidence of Euphorbia.
Euphorbia is considered extinct in the wild in Canterbury and only known from a few sites elsewhere on the West Coast. The world's best known Euphorbias or milkweed family are the "giant euphorbias" of Mt Kenya, the Mountains of the Moon and other mountain ranges of Africa.
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Euphorbia_glauca.JPG (86.5 KB, 6 downloads) 1 year old - Euphorbia_glauca.JPG (86.5 KB, 11 downloads) 1 year old