Climate change hits the Clare Valley

The blue diamonds are long-term average monthly temperatures for Clare. Pink squares are averages of the temperatures measured in particular months. Note that in most cases the temperatures (and in particular those of the spring and summer of 2007/08) were higher than those for average months (pink plots are above blue plots) – evidence that the climate is warming in the Clare Valley. On average the temperatures during the whole of the period shown on the graph were 0.79° warmer than the long-term average. These data are extracted from Bureau of Meteorology records available on the Net.   Epicormic growth on one of the trees that previously appeared dead, photo July 2008

Introduction

Environmentalist have been predicting for years that as temperatures rise due to climate change, species on hills or mountains would tend to die-out at lower altitudes and gradually spread toward higher altitudes, where the lower temperatures would suit their needs. Of course species isolated on or near the tops of hills and mountains would have nowhere to go; they would become, at least locally, extinct.

It seems that the red stringybarks of Spring Gully Conservation Park have taken a big first step on the journey toward that local extinction. It is more a guess than an estimate, but something like a third to a half of the trees have come very close to dieing, or have died. As these trees are at or near the top of the Clare hills, the species cannot migrate to a cooler habitat at a higher altitude.

I revisited the park on 2008/07/27 and observed epicormic growth on many of the trees that earlier appeared to be dead. Interestingly the shooting is on the northern side of the tree trunks and larger branches, although apparently on all sides of smaller branches. Another visit on 2009/07/26 showed that many of the trees that had produced epicormic growth had died.

The Spring and early Summer of 2007 were dry in the Clare Valley of South Australia, a premium and famous wine-growing region. To make matters worse the first three months of 2008 were exceptionally dry; only about 16mm of rain fell in this period. The final blow was an all-time record long heatwave in mid-March. The results can be seen in the photos below...

Clare rainfall record

Note the decline in rainfall in recent years

The average annual rainfall from 1863 to 1990 was 632mm, from 1991 to 2008 it was 557mm, 75mm lower. In the period from 1994 to 2008 the average was 525mm, 107mm lower than the 1863 to 1990 average. The curved line was calculated as a line of best fit to the data.

The steepness and persistence of the decline in rainfalls since about 1970 seems to be unprecedented in the data. Plainly the declining rainfalls, combined with higher temperatures, will stress perennial plants.

Worryingly, the decline in rainfall seems to be becoming steeper, there is no reason to think that the bottom has been reached.

Photos, May 2008

The trees with the dark bark in this photo are red stringybark (Eucalyptus macrorhyncha). The live tree is, I believe, a bluegum (Eucalyptus leucoxilon). Wyman's Track 11th May, 2008; Spring Gully Conservation Park Home Top Index

The trees with the dark bark on the left of this photo are red stringybark. Those with the smooth white bark on the right could be bluegums. Most of the bluegums, perhaps the most common Eucalypt in the Clare Valley, are quite healthy. The difference is remarkable; thousands of stringybarks are dead or near dead, more thousands of bluegums going on the same as ever. Wyman's Track 11th May, 2008; Spring Gully Conservation Park

Another stand of Eucalyptus macrorhyncha. Note that these trees are mainly very young. Many of the trees that appear dead in this photo will recover in time. Wyman's Track 11th May, 2008; Spring Gully Conservation Park

Most of the trees on the left are highly stressed stringybark, while the trees on the right (bluegums?) have survived with little apparent damage. There is always a danger that when a major species is set back to this extent that the area will be colonised by weed species such as Spanish lavender. Wyman's Track 11th May, 2008; Spring Gully Conservation Park Home Top Index

The majority of the trees in this photo are red stringybark. It seems that those on the right, being less crowded together, have survived well because they had a greater volume of soil from which to access water. Wyman's Track 11th May, 2008; Spring Gully Conservation Park

Live bluegums(?) in the foreground, near-dead stringybark in the distance On the track along the roadside 11th May, 2008; Spring Gully Conservation Park Home Top Index

The tree near the center of this photo is exceptionally large for the red stringybarks of Spring Gully. It appears quite dead (but may recover given sufficient time). The green shrubs are Acacia. On the track along the roadside 11th May, 2008; Spring Gully Conservation Park

Thankfully the stringybarks along the ridgetop walk were not in quite such a bad way as those on the Cascades Trail and Wyman's Trail. However, many are near dead even here too. Ridgetop walk 12th May, 2008; Spring Gully Conservation Park

This beautiful stringybark, on the park boundary at the end of the ridgetop walk, looks very healthy. Again, this is probably because it is not as crowded as where many have been stressed to the point of seeming to be dead. Ridgetop walk 12th May, 2008; Spring Gully Conservation Park

Bennys Hill Road

It was easy to find red stringybarks on the Clare ranges in May 2008. They seemed to mostly be dead and were easy to see because of their pale leaves. I now know where there were scattered patches of stringybark that I didn't know were there. What a pity to learn of the existence of something by its apparent death! We can only hope that they recover and that the next bad summer does not come for a few years yet. 12th May, 2008; Adjacent Bennys Hill Road There appear to be a number of other similar small patches of 'dead' stringybarks along the same ridge, on the western side of Clare. Most of these are on private property.

Climate change or freak event?

Australian mean annual temperature anomaly - credit: Aust. Bureau of Meteorology, 2008

The graph on the right shows the change in average annual temperatures from 1910 to about 2007. For each year it shows how the average temperature for that year compares to the average temperature for the base period, 1961-1990. Years below that average are represented by blue bars going downward and years above average temperature are represented by red bars going upward. The length of the bars show how far the temperature of that year deviated from the average.

The stringybark dieing was a freak event - to some extent. There was no dieing last year or the few years before that, even though climate change hasn't heated the world much in that time. But, looking at the graph and considering that there is a trend for each year to be a little warmer than the one before, how could any reasonable person doubt that the dieing is a combination between global warming and a freak event. Freak events such as this are going to be more common as temperatures rise.

Of course I am not going to convince the remaining climate change skeptics. There is a hard core of these who will die believing that it is not happening or that it is 'normal' or that it is nothing to do with human activity.

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A year later

2009/07/26

My wife and I visited Spring Gully again on 26th July 2009, a year and a couple of months after the visit on which most of the photos above were taken. Many of the stringybarks had not recovered.

Quite a few of the trees that had produced epicormic shoots had not survived. Here the tree on the right of centre has survived, while its neighbour left of centre has died after shooting.

Another view of an area with many dead trees over a year after the main 'dieing' event.

Afterword