Journal Number 98
February 2006

EDITORIAL

Are the NZ orchids heading south?
Are they "tracking a moving climate envelope?"
By Ian St George

I started looking at orchids in Otago in the early 1980's.

The history of Otago orchidologists is not extensive: early visitors making the odd discovery (Lyall's Caladenia for instance), with careful and methodical locals completing the picture.

John Buchanan's notebooks show he was a keen orchidologist on his journeys around Otago; they contain his own sketches of orchids he found, and - presumably for the purpose of identification - one of his notebooks has tracings of the orchid illustrations from Flora novae-zelandiae, the only reference work then available.

George Thompson wrote extensively about them in the 1890's - in his local newspaper column and in the Transactions. He was a schoolmaster, and his pupils collected for him, so he would be unlikely to have missed anything obvious. Others reported their southern orchid finds too.

Then in 1937 the Otago Girls High School teacher, Miss Helen Dalrymple wrote her celebrated Orchid hunting in Otago, New Zealand, with an account of all the orchids she had seen.

None of them mentioned Thelymitra pauciflora or T. formosa, yet I found both quite early in my wanderings. What we now know as T. intermedia (it was then included in T. pauciflora) is common around Dunedin, and was later found at "The Wilderness" near Manapouri too.

I found a single plant of T. formosa in the Twelve Mile valley near Queenstown, and trumpeted the find proudly, only to read of a German tourist, Dorothy Cooper's book in hand, finding it on the Routeburn track in plenty a few weeks later.

Gordon Sylvester has recently updated the NZ Native Orchid Group's mapping scheme, with reports of orchids new to several ecological regions. What is striking, as one updates the maps themselves, is that a number of these new finds extend the known southern ranges of the orchids - for instance Nematoceras "whiskers", N. papa and Acianthus sinclairii on the West Coast.

"Climate change threats to plant diversity in Europe" by Thuiller et al. appeared in the 7 June 2005 issue of Proceedings of the National Academy of Sciences of the United States of America.

The Climate Change Task Force and the Red List Programme of the IUCN Species Survival Commission prepared a commentary on the article in response to several inquires. Although they were critical of the detail of Thuiller et al's model, much of what they had to say is interesting....

Results of modelling exercises usually agree with changes observed over the last century. Throughout the world, a large number of wild species have been shifting their ranges polewards and upwards in elevation, at the same time as regional climate warming trends. Warming over the last 30 years has been caused primarily by increases in atmospheric greenhouse gases.

Modelling exercises indicate that movements of species' distributions upward in latitude and altitude will continue and even accelerate. The agreement between modelling and observational studies provides a very strong, well-supported qualitative conclusion that biodiversity is seriously threatened by continuing global warming.

Furthermore that agreement gives a clear indication that the current network of nature reserves is ill equipped to protect the very species it was designed for. Climate change is rapidly joining habitat destruction as a major conservation problem.

The results of Thuiller et al support previous studies in Europe, Mexico, South Africa and Australia - all of which conclude that small, fixed reserves are poorly suited to protect species which are dynamically shifting their global distributions in attempts to track a moving climate envelope.

Through a long consultative process with scientists, managers and local naturalists, IUCN is studying ways in which climate change impacts might be incorporated into the IUCN Red List (quantitative) Criteria for assessing extinction risk for individual species.

The trouble is, there is no consensus on how to assess the risk for any individual species - understanding the responses of a species to future climate change is not yet sufficiently robust, with little certainty about future emissions, sensitivity of the global climate to particular CO2 levels, variation among climate models, variation among biological models, and poor understanding of the mechanics and distribution data for many species.

So, are our NZ orchids moving south and up? Or is there another explanation?

Perhaps more of us are looking for orchids in NZ, and perhaps we are more observant, or more knowledgeable than our forebears - since Dorothy Cooper's description in 1983, Pterostylis cardiostigma has been found further and further north. Perhaps there are more roads in the south than there were, giving access to enthusiastic northerners; and so it follows there is a better chance that isolated colonies will be discovered further south than hitherto.

Perhaps. But I think global warming is shifting the New Zealand orchids southward too.