11 Aug 2011

Weeds and Vegetation Plots on Raoul Island

From Our Changing World, 9:34 pm on 11 August 2011

By Alison Ballance

Examples of weedy plants on Raoul Island

Weeds in the ‘pet plant’ line-up near the hostel on Raoul Island (left) include Brazilian buttercup (centre) and black passionfruit (right). (Images: A. Ballance)

Subtropical Raoul Island is highly modified, and although introduced cats, rats and feral goats have been eradicated, it still bears a weedy legacy from many years of farming and horticultural efforts in the late 1800s, mainly by the Bell family. Made famous in the book ‘The Crusoes of Sunday Island’, the Bell family grew fruit –  including Raoul’s well-known oranges – and vegetables to trade with passing whalers. For many years Department of Conservation staff and volunteers have run a weeding programme (PDF) on the island, aiming to rid the island of the most destructive weeds. Alison Ballance joins DoC biodiversity ranger Sian Potier to meet some of the worst weedy offenders, displayed in a ‘pet plant line-up’ near the hostel.

Nicky Atkinson and Sue Bennett surveying a permanent vegetation plot on Raoul Island

But first Alison heads into the forest where botanists Sue Bennett (above right) and Nicky Atkinson (above centre) are resurveying permanent vegetation plots put in place to monitor how the vegetation changed following the rat eradication in 2002. Their work was proving more challenging than usual due to large amounts of damage caused by Cyclone Bune which passed over the islands at the end of March 2011.

Damage caused by Cyclone Bune to nikau palms and pohutukawa trees

Cyclone Bune knocked out the tops of many nikau palms (centre) and blew over many pohutukawa (right), but native seedlings (left), which are more abundant since rats were eradicated from the island, should be able to take advantage of the extra light caused by gaps in the canopy (images: A. Ballance).