Stewart Island is DRY
I’ve been carting water for our lawn and vegie garden since early December.
Technically Stewart Island is temperate rain forest. We actually don’t have a particularly high annual rainfall, these last 10 years averaging around 1.43 m. Not all that spectacular compared with Fiordland which reaches around 10m in places. But historically we get lots of days with measurable amounts of rain, and in the past, this spread out through the year, We actually get more rain days than Fiordland. Iris’ diary tells us that when we were building Sails Ashore in 2003/04 we had rain at some stage each day for 100 consecutive days. …..the builder was getting really pouty.
But what we’ve been noticing these last few years are extended dry periods, with very few rain days and very little falling when it does. This can be an issue, as our rainforest soils are very free draining, and so dry out very quickly. Even with the water I’ve pumped onto our lawns and garden it’s noticeably dry if you dig down a couple of spade depths. In a couple of places the soil level has dropped 20 mm odd, exposing roots which were previously just at surface level. The soils have dried back from a couple of retaining walls, leaving 10 or 15mm gap.
Successive extended dry period over the last several years has seen
a noticeable increase in the number of dead tree ferns
Under these dead tree fern stumps the forest floor is dust dry
Normally a strong moss green colour. Now dry and brown
Film fern should be green and translucent. Here black and shriveled..
Film fern is the first to suffer, as it often grows in shallow duff on top of a branch or log. This duff can dry out completely in as little as 5 warm dry days.
The film fern has no ability to conserve moisture, and will then start to shrivel, and can be quite dead in 10 days, though the rhizomes do survive until the duff becomes wet again.
We’ve had several years of these extended dry spells, and many of our ferns are not happy. Dicksonia squarrosa in particular are noticably suffering, with more dying each year. Their trunks can be quite thin, and thus vulnerable to drying out, which if for long enough is terminal for them. We are seeing increasing large patches of umbrella moss browning off, and film ferns wilting even when growing on the forest floor. These latter growing in thin duff on the upper slope of a branch are the first signs of a dry period, as they will wilt after 4 or 5 days of warm dry conditions.
Pohutukawa on Petersons Hill
I think these two large specimens are the oldest on Stewart Island and were large trees when I arrived in 1969.
I would guess they are the parents of many of the seedlings which have appeared since around 2000.
Wildling Pohutukawa on the roadside
Wildling Pohutukawa on the roadside
We have several Pohutukawa trees at Sails Ashore. Some we found as seedlings on the road side on Great Barrier Island, some are local seedlings
All of this is just part of the significant changes that have been happening to our Island climate. Looking back I think it was around 2006 that things really started to change. Prior to that every winter we’d get at least one coating of snow down into the village. Maybe 25mm deep, gone in a few hours. Since then we’ve never managed more than 5 or 6mm.
When I arrived in ’69 there were a couple of really spectacular Pohutukawa growing on the Petersons Hill Road. Planted of course as we are well south of their normal zone of New Plymouth/Gisborne and Abel Tasman National Park. But now we have seedlings popping up in several places, and by the look of them around 20 odd years old.
We don’t get much in the way of frosts, so in the past, with a bit of care it was not that difficult to get trees like Kauri, Karaka, Puriri and many years ago we’ve fruited both Tamarillo and Kiwi fruit outside. Back then more trouble than it was worth, But now perhaps time to try again. Maybe an avocardo as well.
Carting water for our garden is not that big an issue, and our warmer milder climate is really appreciated by Iris & I at least. I can’t remember when I had a really wet day on an Ulva Tour, nor when we’ve had to cancel a tour due to wind. Climate change is quite obviously causing all sorts of problems world wide, but just maybe Stewart Island will see a milder less “vigorous” climatic future.