botany

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[i]Caloplaca maculata[/i] - the only lichen known to be endemic to the Chatham Islands seen here growing on hard tuff. Image: Peter de Lange/DOC

Chatham Island lichens

Lichens are by definition any fungus and alga (or a cyanobacterium – oft known as blue green alga) living in symbiotic association. This overly simplistic description serves to explain away a vast amount of New Zealand’s biodiversity. There is an estimated 2000 different kinds of lichen in New Zealand of which formal descriptions exist for no less than 1706! As a rule most people ignore lichens, often mistakenly confusing them with the very different mosses and liverworts “as just lichens”. This is unfortunate, and increasingly we are beginning to appreciate that we do this at our peril. Lichens are proving to be the botanical equivalent of the canary in the cage, often providing the first warning signs of deteriorating air quality, pollution and temperature changes. Lichens too are proving useful in dating geological phenomena such as landslides and earthquakes, and lichens are major nitrogen fixers, contributing for example, 10 kg N per ha per year in the average New Zealand temperate rainforest ecosystem.

Typical clears vegetation of bamboo rush and swamp aster. Image: Amanda Baird/DOC

The South-West

The south-west of Chatham Island encompasses dramatic coastal scenery, a fertile farming belt and forested catchments rising to a moorish tableland containing lakes and low peaks. The south-west supports the most extensive forest on Chatham Island, expanses of upland bamboo rush & Chatham aster and important populations of threatened plants and animals. It is the only breeding sites in the world for taiko and the Chatham Island mudfish. The largest protected area occurs here with the Tuku Nature Reserve and adjoining South Chatham covenant at about 2,500 hectares.

The tableland is highly distinctive. The flat to undulating topography belies the fact it is the highest region of Chatham Island at 250-280m altitude. The island’s tallest peaks occur on the tableland’s northern edge.