Fire regimes in the fynbos biome: Is there cause for concern? Brian van Wilgen CSIR Natural Resources and Centre for Invasion Biology

© CSIR Topics covered What are fire regimes? What is the concern? What evidence is there to support the concern? What are the consequences of altered fire regimes? What should be done about this? Ideas for research

© CSIR What is a fire regime? Concept first proposed by Gill (1975) Frequency – return period (1/yr) Season – summer, winter, spring, autumn; wet season, dry season Intensity –rate of energy release Type – surface, crown, ground Severity – measure of impact on ecosystems Size – the size distribution of individual fires Variability – in all of the above in successive fires

© CSIR What is the fire regime in the fynbos biome? KNOWN Fires every 10 – 15 years, in summer or early autumn, of moderate intensity (5000 – kW/m) Severity affected by invasion by alien plants which increase fuel loads NOT KNOWN Fire size distributions altered by fragmentation, fire control and prescribed burning Degree of variability that can be tolerated

© CSIR Appropriate and inappropriate fire regimes Altered fire regimes can be:  Ecologically acceptable (still able to maintain plant and animal populations)  Ecologically unacceptable (species are lost) Current “wisdom” - Fires in winter, fires that are too frequent ( every years) are inappropriate

© CSIR Fire regimes as surrogate measures for biodiversity First proposed by van Wilgen, Richardson & Seydack (1994) The achievement of biodiversity goals too complex to monitor Diversity in fire regimes (within limits) should be easier to monitor, and could act as a surrogate measure for biodiversity

© CSIR What are the major concerns around fire regimes? Fires may be becoming too frequent as a result of increased sources of ignition Habitat fragmentation and fire control means that historic (appropriate?) fire patterns do not establish Invasion by alien plants increases fire severity Climate change may alter fire regimes in future, making them inappropriate Our inability to control fires impacts on benefit streams (eg flower harvesting) Fires cost us bags of money

© CSIR Measuring fire regimes - Swartboskloof catchment example

© CSIR yrs 5 yrs 15 yrs Calculating fire return periods

© CSIR Cumulative probability of fire at Swartboskloof Probibility of fire Time since last fire (yrs)       

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What evidence is there to support the main concerns? Fire frequency assessed from fire records, remote sensing, or people’s memories or perceptions Each has problems Most reliable evidence is for fire severity associated with alien plant invasions Very little known about fire patterns, or the costs of fires

© CSIR < 60% of area burnt at age < 7 years

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Richardson and van Wilgen 1984 SA Forestry Journal Cover down 1/3 Species down 50% Holmes et al (Austral Ecology) Some important guilds missing

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Business day article

© CSIR The main economic costs of fires Total losses: R750 million per year Forestry and downstream industries: R250 Livestock losses R150 Alien plant control in fynbos R100 Costs of fire control: R70 million per year This kind of analysis does not consider the value or loss of biodiversity

© CSIR Cost of houses lost in fires not known, but relatively small

© CSIR Unplanned fires in invaded areas may be costing a great deal Unplanned fires - additional follow-up. The 4.3 million ha fynbos burns once in 15 years Roughly ha burns every year. 33% invaded to some degree CapeNature estimated additional costs at R1000 per ha. Assuming invaded ha burns in unplanned fires every year, additional costs around R100 million annually.

© CSIR What would constitute an unacceptable fire regime? Too much area that burns too frequently (or in the wrong season) too often. How much is too much? How often is too often? The key seems to be to define the amount of variability that can be tolerated – “thresholds of potential concern”

© CSIR The origin of thresholds of potential concern From savanna ecology – shift from “balance of nature” to “flux of nature”; and stable-state to a heterogeneity paradigm Rainfall

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What evidence is there that we can influence or control fire regimes? Very few no attempts to quantify this – two from South Africa CEDERBERG: Fire Records “... effects of prescribed burning (introduced in 1973) on the extent and frequency of wildfires are not yet evident.” KRUGER PARK: Fire Records “the probability of a fire of any size occurring is principally a function of grass biomass.”

© CSIR – 1975 Fixed-cycle burning 1980 – 1990 Flexible-cycle burning 1990 – 2002 Lightning fires

© CSIR Effects of management on the extent of fires in the Kruger National Park 1100 Fixed Burning Area burned (ha x 1 000) Mean rainfall in preceding 2 years (mm) All Fires Flexible Burning Lightning

© CSIR The concept of adaptive management Set goals based on current understanding Monitor achievement of goals against thresholds of potential concern If thresholds exceeded, intervene, or re-set the threshold This is hard work, not a cop-out! We need long-term monitoring to inform us.

© CSIR Max age Median fire return period Min age Post-fire age (years) Proportion burnt THRESHOLDS OF POTENTIAL CONCERN IN FYNBOS THRESHOLDS OF POTENTIAL CONCERN IN FYNBOS

© CSIR What are the consequences of altered fire regimes or an inability to control fires? Loss of species and ecosystem stability (biodiversity) Spread of alien plants (impact on water resources and catchment stability; or increased control costs) Loss of property, crops (forestry big, houses small) Tourism?

© CSIR Do we have the capacity to practice good fire management?  Catchment management system (published in 1994 in International Journal of Wildland Fire)  National Fire Danger Rating System  Capacity (and willingness to risk) prescribed burning  Working on Fire – genuine attempt to gain control, but no mandate; staff turnover

© CSIR Some questions for research Ecological research – variability in fire regimes and their impacts. Long-term monitoring sites and simulation models. Fire regime research – develop thresholds of potential concern, and implement effective monitoring Management – integrated control of invasive plants; effective models for intervention (suppression and prescribed burning) Economic research – cost of fires, and returns on investment from management (control and suppression vs other forms of management) Climate change?

© CSIR Thank you