CLIMATE CURVE BALLS
I have taken this heading from a presentation Guy Midgley from the Climate Research Working Group at SANBI has given at the Fynbos Forum last week. Here is a short summary of his lecture. Or at least how I understood and interpreted it.
The reason why so much research is going into detecting and predicting climate change is ultimately to influence policy, behaviour and new technology on a world wide scale. That the climate is changing is difficult to dispute and is accepted by most people in the scientific community. Can we stop climate change? No, but we could possibly slow it down or change its course somewhat.
Adaptation is the only option and the doomsday scenarios that seem to be getting a lot of attention in the media lately have got a positive side to them. They are essentially unmitigated worst case scenarios and could be used to tactically galvanize mitigation responses. A fairly recent paper by Thomas et al. (2004) was widely quoted in newspapers. But as sensation is what sells, the media usually concentrates on the worst case scenarios… and omit the mitigated scenarios. According to Thomas et al. (2004) there could be an 11% extinction rate of global biodiversity by the year 2050 even if the climate only changes minimally (minimum climate change scenarios), but this could rise to a whopping 58% extinction rate of global biodiversity for the maximum climate change scenarios. (Although the media apparently focused on the 58% and elaborated on the how great such a loss would be, I find 11% also quite shocking!!!)
Guy Midgley focused on four factors that will have a major influence on the environment as the climate changes. These are climate extremes, fire, water and carbon dioxide. For climate extremes, it is not only the mean values that are changing, but also the number of extreme climate events. These extreme events could exceed the tolerance levels of many species, especially if these events become more frequent. Should the low extremes of temperature shift just slightly towards warmer temperatures, this could also have an adverse effect on some species as some seeds need that extra cold temperature as a cue to germinate.
Although the overall average temperature increase in the Western Cape over the past century was not much, the average minimum temperature has increased by two degrees Celsius! There are also definite changes in the precipitation trends of the Western Cape over the past 50 years. Although trends are difficult to analyze, there seems to be a definite increase in extreme rainfall events. Here it is vital to understand how important institutional memory is!
As conditions are becoming hotter and drier, fires will become more frequent. These fires are likely to become very large scale fires, burning to the ground huge areas at a time. Although natural habitats in the Western Cape are fire dependent, too frequent fires could have detrimental effects on the fynbos biome. Many plant species have a relatively long juvenile period and do not set seed before they have reached a certain age, which can be up to 10 years for some Proteaceae species. Thus too frequent burns can wipe out populations, especially if these fires cover large areas! Some climate scenarios are predicting a doubling or even tripling of fire risk days in the Western Cape by 2050. This means education is paramount in achieving minimal accidental ignitions. Having a ‘braai’ in or close to fire prone vegetation should not even be an option! (And places like Table Mountain should be declared smoke-free zones… )
Water is a scarce commodity in the Western Cape, although the majority of our population hasn’t caught on to this fact yet! Capetonians know all about water restrictions, but most seem to think it was just a temporary problem (and so does the municipality apparently, for why did they abolish the water restrictions after the first good rains???). Climate modelling for precipitation has only been done at a course scale up to now and fine scale modelling needs to be done as techniques improve. Present models predict less precipitation overall, but an increase in heavy downpours. The conundrum in Cape Town is however the fast expansion of the city… so even without climate change, we are going to run out of water.
There are already possible indicators that the water table is dropping. Some fynbos species occupy water micro-niches and these will probably be affected first. Some species occur according to water table depth and already some dye back of Proteaceae species has been noted in an otherwise healthy stands. Could this be an indicator of a drop in the water table? There has also been much talk of tapping into aquifers around Cape Town (I have heard of one in the Kogelberg Biosphere Reserve that has been earmarked for tapping…) to try and meet water demands of the growing city. (Again, I feel education is the starting point and not sourcing more water supplies… we could all do with using less water!)
The increase in carbon dioxide in our atmosphere is acting as a fertilizer to many plants. This however apparently is not true for Mediterranean-type shrubland vegetation… According to Dr. Midgley, fynbos species do not respond to the increase in carbon dioxide available, but invasive species could very well do. It has already been proven that Acacia karoo responds very favourably to an increase in carbon dioxide as more carbon is fixed in its roots that then become more robust. If this holds true for the alien Acacias we have here in the Western Cape, they might just have an unfair advantage!!
The theory behind climate change models is still incomplete and one therefore has to look at a range of scenarios. Careful monitoring right down to species level is necessary to try and detect early signs of adverse effects to a changing climate and then compare that to scenarios to see how accurate they are.
I found the presentation truly thought provoking and I hope that I have been able to portray the main points as they were intended by Dr. Midgley. (Take note that comments in brackets are my own and were not part of the presentation.)
Have we got the will and guts to change and to adapt our lifestyles to one that is more sustainable or are we going to wait until it is too late??
Thomas CD, Cameron A, Green RE, Bakkenes M, Beaumont LJ, Collingham YC, Erasmus BFN, Ferreira de Siqueira M, Grainger A, Hannah L, Hughes L, Huntley B, van Jaarsveld AS, Midgley GF, Miles L, Ortega-Huerta MA, Townsend Peterson A, Phillips OL and Williams SE. 2004. Extinction risk from climate change. Nature 427:145-148.
Image credit: http://www.flickr.com/photos/twmlabs/29463820/
BCB Hons NISL student
University of the Western Cape
Private Bag X17
1.I know that plagiarism is wrong. Plagiarism is to use another’s work and to pretend that it is one’s own.
2. I have used the CSE/CBE convention for citation and referencing. Each significant contribution to, and quotation in this project from the work, or works, of other people has been attributed, and has been cited and referenced.
3. This assignment is my own work.
4. I have not allowed, and will not allow anyone to copy my work with the intention of passing it off as his or her own work.