South Africa: Ecological Requirements for the Maintenance of Western Cape Fynbos Biodiversity and Compromises Recommended to Meet Metropolitan Pressure (IFFN No. 22 – April 2000)
Ecological Requirements for the Maintenance of Western Cape Fynbos Biodiversity and Compromises Recommended to Meet Metropolitan Pressure
(IFFN No. 22 – April 2000, p. 76-78)
Introduction
The Fynbos vegetation of the southwestern and southern Cape in South Africa, also described as evergreen sclerophyllous heathlands and shrublands, covers 59,282 km2, or 5.3% of the territory of South Africa. The exclusive area where the fynbos biome is found has a typical winter rainfall in the west, but further to the east spring and autumn peaks characterise the rainfall pattern. The annual rainfall in the area ranges from as low as 200 to over 3000 mm per year, and with such extremes it is clear that the rate of above-ground biomass production in the biome will also vary significantly (Huntley 1984). Kruger (1977) reported fynbos biomass values of between 2000 to 26,000 kg/ha in stands ranging from 2 – 17 years in age, with an average annual biomass production rate of 1000 – 4000 kg/ha. Natural fires in the biome occur within 6 – 40 year rotations (Kruger 1979, Kruger and Bigalke 1984).
In the Western Cape, fynbos shrubland covers the most prominent mountain catchment areas, and are managed for a variety of goals, the most important of which include maintaining sustained yields of high quality streamflow, nature conservation, fire hazard reduction, afforestation, grazing, tourism and recreational opportunity. Many areas are managed for more than one of these goals simultaneously, and as a result the role of fire between communities within the biome will differ significantly (van Wilgen et al. 1990).
During 1999 and 2000 there was a marked increase in the number of fires experienced (as well as size of areas burned-over) throughout the fynbos-covered part of the Cape regions. During Bergwind (Föhn wind-like) conditions in 1998 and 1999 most of some mountain ranges (such as the Outeniquas and Tsitsikamma mountains) were burned by wildfires, including thousands of hectares of adjoining industrial plantations. During mid-summer 1999, and again during January 2000, more mountain catchment areas were burned-over by uncontrolled fire, causing millions of Dollars of damage to urban houses, adjoining vineyards and industrial plantations. Tragically, some human lives were lost in the southern Cape during the 1998 and 1999 fires. The loss in fynbos biodiversity maintenance as a result of these too hot (and in some cases) too frequent fires, will be difficult to quantify, but was substantial.
The question now arises if we can still meet ecological requirements to maintain diversity in the fynbos biome, or whether these goals are now threatened by increased population pressure and access, encroachment of build-up areas (Cape Town and environment in particular), climate change and the spread of alien woody weeds?
Fire Frequency, Season and Intensity
Research achievements in the past now make it possible to determine optimum fire frequencies with an acceptable degree of accuracy, not only considering fuel dynamics, but also maintaining species diversity in the process. Fynbos is rich in species, and has complex requirements for survival. Almost 20% of plant genera are endemic (Bond and Goldblatt 1984), making nature conservation a high priority, and prescribed burning and weed control are important management tools to achieve this.
The optimum fire frequency for fynbos is 10 – 15 years, but fire intensity and season of burn also play an important role to fulfil ecological requirements in the fynbos biome. These requirements vary from region to region, and also with topographical and climate variation. However, these requirements have been published by scientists in the past, and we know what the optimum maintenance requirements are for the biome as a whole (e.g. Bond et al. 1984).
As a result of delays in the prescribed burning programme for various reasons (e.g. public pressure, staff shortages, a high staff turnover, lack staff with prescribed burning experience, weed infestation and urban expansion), fynbos in certain catchments was allowed to become too old, making it therefore impossible to apply fuel reduction by means of prescribed burning because this would now be too hazardous. The accumulation of fuels increased further by the spread of alien weeds such as Hakea sericae, Acacia longifolia and Pinus pinaster, until a situation was reached where serious wildfires just could not be avoided, particularly during abnormal weather conditions as experienced in Southern Africa during recent years.
The prescribed burning programme required was further disrupted by the sudden increase in wildfire occurrence, complicating the achievement of ecological goals even further. The intended mosaic of burns, that would have produced vegetation of different ages in plant communities was upset, with some areas burned too frequent or producing a fire of a too high intensity as a result of the added weed biomass. Where weed control measures were intensified, more tons of fuel were added to these systems which were already experiencing high biomass loading as a result of extended age. As a result, extremely high intensity wildfires will burn through these areas, which will trigger the seed beds of most weed species, and ensure that an ever larger alien weed problem than before will develop.
The Solution: Integrated Fire Management with some Compromises
There is no magic solution for the unacceptable status of the fynbos biome at present, but for a start it will help if we accept certain realities which are here to stay. They are:
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We have to live will the population pressure, and subsequent increase in fire hazard, as more and more people will in the future access nature conservation areas, resulting in increased fire hazard.
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Global changes in weather patterns will have to be accepted as a fait complis, and planners will have to consider this issue in the future seriously.
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Urban interface problems must be identified, and a plan of action will have to be drawn up by local authorities as a matter of urgency.
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Although the Department of Water Affairs and Forestry has an excellent weed control program going, more consideration should be given to the biomass created in the process (and subsequent fire hazard), particularly along lines with regular public access. This programme should also include regeneration control soon after wildfire.
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Optimum ecological requirements can never be reached, and recent wildfires in the Cape have underlined this. However, we must continue to attempt to come as close as possible to these objectives. Realistic compromises in the ecological burning programme must also be made to reduce the wildfire hazard to acceptable levels.
I would like to suggest the following to reach ecological goals for the fynbos biome in the region:
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Map the status of wildfires (fire perimeters), alien weeds and fynbos vegetation by approx. age for the whole Cape region where fynbos occurs. This should be done as soon as possible, so that future planning can commence. Adjustments in weed control programmes and prescribed burning programmes will also have to be implemented as soon as possible thereafter, as delays could have serious affects on e.g. future weed regeneration control.
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Map and evaluate fire hazard (for the present and over time) by considering the status quo, ecological requirements and fuel dynamics (both within fynbos communities and on bordering land).
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Draw up an integrated, regional fire protection plan which includes all the important role players and disciplines (more about this in the next section). Ecological burning programmes must form the core of this plan, but drastic changes in existing fire protection plans and burning programmes may be required.
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Start a public awareness campaign to educate the local population in the role of fire in maintaining the ecological balance, to stamp out (with stricter law inforcement) negligence with fire, weed control on private properties and the protection of dwellings bordering fynbos conservation areas.
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Provide specialised training for selected nature conservation staff in fynbos fuel dynamics, prescribed burning application and integrated fire protection.
Conclusions
The worlds’ richests floral kingdom, the Cape Fynbos, needs to be conserved as best as we can. Changes in human population density, weather patterns and land-use, as well as an increase in alien weeds are the reasons why nature conservators are now facing new challenges, particularly after the recent disastrous wildfires.
Policy makers, nature conservators, municipal authorities, fire fighting organisations and other land-users such as forest managers and farming representatives, need to sit down and re-think a plan for the future that will be realistic, and satisfying all requirements. This plan will have to be fully integrated, as this is the only way in which all can contribute towards objectives, which all disciplines will understand and apply successfully.
Cornelius “Neels” De Ronde
SILVA Forest Services
du Toit Street 16
P.O.Box 612
7280 Bredasdorp
SOUTH AFRICA
Fax/Tel: ++27-2841-52546
e-mail: nderonde@dorea.co.za
References
Bond, P., and P.Goldblatt. 1984. Plants of the Cape flora: a descriptive catalogue. J. SA Bot. (Suppl) Vol 13.
Bond, W.J., J.Vlok, and M.Viviers. 1984. Variation in seedling recruitment of Cape Proteaceae after fire. J. Ecol. 72: 209-221.
Huntley, B.J. 1984. Characteristics of South African Biomes. In: Ecological effects of fire in South African Ecosystems (P. de V. Booysen and N.M. Tainton, eds.), 1-18. Ecological Studies 48, Springer-Verlag, Berlin-Heidelberg-New York, 426 p.
Kruger, F.J. 1977. A preliminary account of aerial plant biomass in fynbos communities of the Mediterranean-type climate zone of the Cape Province. Bothalia 12: 301-307.
Kruger, F.J. 1979. Fire. In: Fynbos ecology: A preliminary synthesis (J. Day, W.R. Siegfried, G.N. Louw, and M.L. Jarman, eds), 43-57. SA Nat. Sci. Prog. Report no. 40.
Kruger, F.J., and R.C.Bigalke. 1984. Fire in Fynbos. In: Ecological effects of fire in South African ecosystems (P. de V. Booysen and N.M. Tainton, eds.), 67-114. Ecological Studies 48, Springer-Verlag, Berlin-Heidelberg-New York, 426 p.
Van Wilgen, B.W., C.S.Everson, and W.S.W.Trollope. 1990. Fire management in Southern Africa: Some examples of current objectives, practices and problems. In: fire in the tropical biota. Ecosystem processes and global challenges (J.G. Goldammer, ed.), 179-215. Ecological Studies 84, Springer-Verlag, Berlin-Heidelberg-New York, 497 p.
