Articles in The West Australian newspaper on 15th and 17th September 2007 suggested that global warming will lead to the virtual disappearance of Western Australia’s iconic karri forest. The articles quote Dr Ray Wills, a research scientist at the University of Western Australia’s Geography Department, who asserts that karri forests could be reduced to small pockets and marginal remnants in the years to come. He bases this view on projections that the southwest of Western Australia (WA) will become warmer by 2 to 3 degrees in the years ahead, and on the assumption that this warming will in turn lead to a decline in rainfall to the extent that karri will basically die out.
Karri forests are part of the so-called “southern forests” of Australia’s southwest corner. They comprise about 1.3 million hectares of pure karri and karri mixed with jarrah, marri and red and yellow tingle. Apart from several outliers, such as at Boranup (near Margaret River) and Porongorup (east of Mt Barker), all of the present karri forest is found in areas with a long-term annual rainfall of >1100 mm.
However, the present karri forest is also a remnant. Analysis of pollen in geological strata has demonstrated that karri once occupied a very much wider area; indeed it is still possible to find typical karri forest understorey in moist gullies in the northern jarrah forest. The shrinkage of the karri forest appears to have resulted mainly from a decline in rainfall many thousands of years ago.
Karri is well able to survive much higher temperatures than those predicted. The species is adapted to a present-day climate which every summer experiences well above the average temperature, including days over 40 degrees. I have successfully grown karri in Perth and the Darling Ranges, regions with much warmer average temperatures than the lower southwest, and I even succeeded in establishing karri in my arboretum in the Avon Valley where the temperature exceeds 40 degrees day after day from January through to March. Karri was unaffected by these high temperatures. What killed them was winter frosts not summer heat. A feature of the current natural distribution of karri is that frost is very rare and when it does occur it is relatively mild and short-lived.
I believe that a predicted rise in average annual temperature of 2-3 degrees per se will not worry karri, especially if this occurs as a result of milder winters rather than hotter summers.
The problem of lower rainfall is another matter, and already forests all over the southwest of WA (especially wandoo and tuart) are observed declining in the face of below-average rainfall in recent years. The karri forest has also experienced a similar reduction in rainfall, but is not yet showing the same drought symptoms as wandoo and tuart. If there is another substantial decline in the current rainfall pattern, it probably will, unless some action is taken by forest managers.
Luckily something can be done to ameliorate the impact on the karri forest of lower rainfall. This is a well-planned and professionally conducted program of thinning of overstocked regrowth forests plus regular (7-9 year rotation) mild prescribed burning across the whole forest area. Such a program will lead to a higher proportion of rainfall getting through to recharge soil moisture, and will ensure less competition for water at the root zone. Prescribed burning will also reduce bushfire fuels and render old growth forests less susceptible to conversion to dense rainfall-gulping regrowth by high intensity summer fires.
Opponents of thinning and prescribed burning will immediately rise up and condemn this strategy, claiming that it will cause “a loss of biodiversity”. There is no scientific basis for this fear. But if no action is taken and Dr Wills’ doomsday predictions are correct, the biodiversity is going down the tube anyway. Even a 60% reduction in greenhouse gas emissions will not stop the 2-3 degree killer temperature rise according to Dr Wills.
It is my understanding that the jury is still out on the link between a projected higher temperature due to global warming and a projected lower rainfall. Never mind. Even if “normal” rainfall patterns return to south-western WA, the forests will be healthier and more biologically diverse if overstocked regrowth stands have been thinned and mild burning undertaken to reduce fuels and thus minimise high intensity wildfires. And if the predictions of Dr Wills and his colleagues are right, well-managed forests will be better able to cope if a still-drier climate eventuates. The other good thing is that both thinning and burning are standard forestry operations which have been conducted for generations and subject to a great deal of research and monitoring. We know how to do it and that it will work, with no environmental downside.
Incidentally, Dr Wills is by not the first distinguished scientist to predict the extinction of Australia’s southwest forests. In the 1970s geography Professor Arthur Connacher predicted that logging for woodchip-quality logs would result in the “desertification” of the karri forest. Thankfully this has not occurred. And in the 1980s ecologist Dr Wardell-Johnson warned of the imminent loss of the tingle forests on the south coast due to “continental drift”. Australia was at that time thought to be drifting towards the equator at a rate of a few millimetres per century. It has also been too early to detect any evidence of this calamity.
Roger Underwood worked as a forester in the karri forest in the 1960s and 1970s.
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
If anyone is claiming that the south-west of WA will be 2 to 3 degrees warmer in future I hope they have some damn good proof. The output of climate models isn’t proof, nor is a collection of opinions.
For more intelligent readers I draw attention to Hendon H.H., Thompson D.W.J. and Wheeler M.C (2007), “Australian rainfall and surface temperature variations associated with the Southern Hemisphere Annular Mode”, Journal of Climate, v20, issue 11 (June 2007). This paper discusses how rainfall and temperature in the south-west and east are at the mercy of the SAM (also known as the Antarctic Oscillation).
Strong correlations exist between the SAM and the El Nino Southern Oscillation (ENSO) so there’s a very strong possibility that changing climate in s-w WA is ultimately due to the relatively sustained conditions in the Pacific over the last 6 years, conditions corresponding to negative values of the Southern Oscillation Index (and which one might describe as “towards El Nino”.)
Jennifer, do you accept his belief in climate change then?
SJT,
You know that I am an AGW skeptic.
But I am definately concerned about climate change – it will happen for sure. The climate has always changed.
Roger suggests a solution – forest thinning – given a particular scenario.
Jen – “the climate has always changed”. That’s dreadful from a scientist. You’re supposed to ask why.
If you’re concerned about climate change you aren’t going to get anywhere without an understanding – otherwise how do you base any action (or inaction).
I know – it’s “nature”.
Gotta go – off to a Druid ceremony to worhsip “nature”. Ain’t it grande.
P.S. For those intelligent readers they might explore the blog archives as to possible explanations for SAM changes.
an example ….
Science 3 May 2002:
Vol. 296. no. 5569, pp. 895 – 899
Interpretation of Recent Southern Hemisphere Climate Change
David W. J. Thompson,1* Susan Solomon2
Climate variability in the high-latitude Southern Hemisphere (SH) is dominated by the SH annular mode, a large-scale pattern of variability characterized by fluctuations in the strength of the circumpolar vortex. We present evidence that recent trends in the SH tropospheric circulation can be interpreted as a bias toward the high-index polarity of this pattern, with stronger westerly flow encircling the polar cap. It is argued that the largest and most significant tropospheric trends can be traced to recent trends in the lower stratospheric polar vortex, which are due largely to photochemical ozone losses. During the summer-fall season, the trend toward stronger circumpolar flow has contributed substantially to the observed warming over the Antarctic Peninsula and Patagonia and to the cooling over eastern Antarctica and the Antarctic plateau.
1 Department of Atmospheric Science, Foothills Campus, Colorado State University, Fort Collins, CO 80523, USA.
2 Aeronomy Laboratory, National Oceanic and Atmospheric Administration, 325 South Broadway, Boulder, CO 80305, USA.
In assessing a scientist’s reliability it can be interesting to look at pedigree. The views of Dr. Grant Wardell-Johnson on the fate of the tingle forest of SW Australia should be taken very seriously, as his family has a long and distinguished association with the area.
Mrs. Margaret Walpole noted, in her 1883 diary, the devotion to his flock of the vicar of Albany, the Rev. William Wardell-Johnson. She commented on his musical ability, and his habit of beating time by banging a hymn book on his desk (Sellick, 1997).
Now that the Holy Trinity of Ecology, Biodiversity, and Climate has, for many, replaced that of Christianity, we should pay devout attention to the extant Dr. Grant Wardell-Johnson’s ecological sermons, and try to sing in time from the same hymn sheet. Our eternal souls may depend on it. Repent ye sinners … and pass the collection box.
P.S. I once heard Dr. Ray Wills suggest that the word ‘fuel’ should not be used, possibly because it encouraged burning and hell-fire by sinners. I think the preferred term was something like ‘non-living biomass’. Yea verily, hold fast the form of sound words (Timothy ch.1, v.11).
Ref: Sellick, D.R.G. (1997) First Impressions Albany: Traveller’s Tales 1791-1901. Western Australian Museum, Perth.
Another great post Roger,although I am a amazed at the ability to grow great forests with a rainfall just above 1100 mm, you must have some great foresters over there.
Compare that to Australia’s only cool temperate western maritime climate dominated by a wet western mountain range with rainfall of over 3,000 mm.
For a visual picture on just how good these forests are why not go to http://www.australiassouthwest.com/en/Natural+Wonders/Forests/default.htm It shows the four dominant tree species through the Australia’s South West region – jarrah, karri, tingle and tuart.
Cinders,
I visited the site you gave. I don’t know who wrote it, but they need to learn a bit more about the jarrah forest, and wildflowers. They say that the jarrah forest copes with “occasional fires”. In fact the jarrah forest has evolved with frequent, mild fires at 2-4 year intervals. Current “occasional” fires at 15-20 year intervals are killing mature jarrah. The writers also mention the “profusion of wildflowers” in the jarrah forest. In fact, flowers are only profuse after fire. Large, long unburnt areas now have few wildflowers. They are senescent, and smothered by sticks and leaf litter. Some claim that occasional, fierce fires are best for seed germination. In fact, they sometimes incinerate the whole seed bank. In other places they cause too much germination, so exhausting the seed bank in one hit. Given a dry spring, end of story. Nyoongar people have been saying that for years.