Bush Fires: Part 4 – Fire as a Bush Management Tool

This is the last of four articles on bush or veld fires, their impact on the environment and their use as an environmental management tool. The others are

• Bush Fires: Part 1 – Effects & Management
• Bush Fires: Part 2 – Feedback Loops That Shape Grasslands
• Bush Fires: Part 3 – Management of Fire in Conservation Areas

Introduction

Fire has shaped African landscapes for millennia. Areas like Zimbabwe have strong seasonal rainfall patterns and long dry periods which create ample fuel in the form of dead vegetation, making fire an inevitable and influential ecological factor. When used responsibly, fire can rejuvenate tired vegetation, stimulate fresh growth, and restore balance in habitats suffering from bush encroachment. Yet the same fire that sustains ecosystems can cause severe ecological and social harm when mismanaged or allowed to occur too frequently.

Fire Regimes are the Problem – not Fire

Fire has been creating African savannas for thousands of years. The real management question is therefore not whether fire should occur, but how, when, where, and why it should occur. Evidence from long‑term research in places such as Kruger National Park shows that:

• Only part of the landscape burns in any given year (about 16% on average),
• Fire return intervals vary widely (from 1 to more than 30 years), and
• Most fires historically occurred late in the dry season.

This variability is crucial. Savannas are not adapted to uniform, frequent, or landscape‑wide burning. Ecological problems arise when fire becomes:

• Too frequent,
• Consistently late‑season and intense,
• Spatially uniform, or
• Poorly aligned with grazing pressure or elephant impacts.

Controlled fire, used intelligently, can restore this lost variability while reducing the risks of uncontrolled fire.

Habitat Diversity Is the Real Goal

Wildlife does not require uniform landscapes. Different species depend on:

• Open grasslands for grazers,
• Shrubby zones for mixed feeders,
• Tall trees for shade, nesting, and browsing,
• Patchiness for predators, birds, insects, and reptiles.

Research consistently supports patch‑mosaic burning, in which:

• Different areas burn at different times,
• Fire intensity varies deliberately, and
• Some areas remain unburnt for long periods.

Fire Is a Tool with Different Uses

There can be a number of different goals for the use of controlled fire. The following table is taken from the article,  ‘A review of fire management practices in African savanna-protected areas’, by W.A. Nieman and colleagues (Koedoe 63(1), 1921) The article compares the effectiveness of burning at different seasons to achieve different specific results.

Different fire intensities, seasons, and patterns produce very different outcomes. Below we look at only four of the possible goals of controlled fires.

1. Improving grazing quality through rejuvenation of grasslands

As the dry season progresses, grasses often become moribund, that is, coarse, dry, and nutritionally poor.

 Cool to moderate burns:

• Remove old, dead and unpalatable grass,
• Stimulate fresh green nutritious regrowth,
• Attract grazers and redistribute grazing pressure.

The post‑fire flush of grass is richer in nutrients and more digestible than the old grass it replaces and is greatly preferred by herbivores. This spreads grazing pressure and improves animal condition and reproduction.

This is particularly valuable after high‑rainfall seasons when grass biomass is excessive.

2. Control of bush encroachment

Research shows that:

• Low‑intensity fires alone rarely halt woody expansion,
• Woody plants may even increase after repeated cool burns,
• High‑intensity fires can reduce woody cover, especially if repeated. (See Bush Fires: Part 2 – Feedback Loops That Shape Grasslands)

Bush encroachment occurs when woody plants expand into grasslands, reducing grazing capacity and altering ecosystem structure. Key drivers include overgrazing, fire suppression, and changing rainfall patterns.

Well‑timed dry‑season burns produce fires that:

• Kill or suppress young woody saplings,
• Reduce densities of fire‑sensitive shrubs, and
• Maintain open savanna structure

By opening dense thickets and allowing light back to the understory, fire gives grasses the opportunity to reclaim space and function.

However, hot fires can be seen as a surgical tool, not a blanket solution. If they are over-used, they can kill large, ecologically important trees and over-simplify landscapes.

3. Vegetation thinning and coppicing – refreshing browse

In woodlands, excessive stem density can restrict animal movement and reduce browse quality. Many savanna trees and shrubs respond to fire by resprouting vigorously from the base or lower stems. After fire, woody plants resprout with highly nutritious shoots that are strongly favoured by browsers. While large‑scale hot burns can temporarily reduce total browse, smaller or patchy burns improve short‑term forage quality without eliminating habitat.

This produces coppicing which:

• Replaces old or damaged limbs,
• Produces accessible, nutritious browse, and
• Maintains long‑term plant vigour.

Fire therefore rejuvenates woody vegetation rather than simply destroying it .

4. Reducing uncontrolled bush fire risk

Strategic early‑season burns:

• Reduce fuel loads,
• Break up continuous grass cover,
• Prevent late‑season runaway fires, and
• Protect boundaries and infrastructure.

Why Timing, Intensity, and Conditions Matter

Fire behaviour, and its ecological effects, depend on four main factors:

Fuel load

• More grass produces hotter fires.
• Heavy grazing reduces fuel, leading to cooler fires and higher tree survival.

Season

• Early dry‑season fires are cooler, slower, and easier to control.
• Late dry‑season fires are hotter, faster, and more damaging.

Weather

• Wind speed controls spread.
• Low humidity and high temperatures increase intensity and tree mortality.

Fire type

• Back fires (see diagram) are cooler with longer heat exposure near the ground.
• Head fires are hotter, faster, and more damaging to woody plants.

Responsible fire use depends on aligning these factors with management objectives.

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Theoretical Example of a Deliberate or Controlled Burning Program in Action

Fire is a natural ecological process that operates at a landscape scale as a disturbance agent. When applied appropriately, fire creates spatial and age diversity in vegetation (in other words a fairly even spread of vegetation from young saplings to large mature trees) and helps to maintain healthy, productive ecosystems.

(In ecology, a disturbance agent refers to any specific physical, chemical, or biological force—abiotic or biotic—that causes a significant, relatively abrupt change in ecosystem structure, biomass, or resource availability that initiates ecological succession and, in the long term, shapes the landscape’s ecosystem dynamics and biodiversity. )

Key considerations when implementing a deliberate or controlled burning program

The most important factors to consider are:

1. Objectives of a Burn Program
2. The Fire Regime, specifically frequency, intensity & timing (season) of fires

Objectives of a Burn Programme

Primary objectives:

• Improve grazing quality by removing moribund (dead or nutritionally empty) plant material;
• Reduce the height of browsable vegetation, making it accessible to a wider range of browsing species;
• Manage woody and undesirable herbaceous encroachment.

Secondary objectives:

• Increase the palatability, nutrient content, and digestibility of forage (grass and browse) following a burn;
• Attract grazing herbivores to underutilised areas;
• Reduce the risk of uncontrolled bush fires;
• Increase biotic and habitat diversity;
• Contribute to nutrient cycling;
• Reduce tick loads.

The Fire Regime

Burning Approach: “Range Condition Burning System”

A “range condition burning system” involves areas being selected for burning based on a close study of the condition of the vegetation and its known response to specific fire regimes (intensity, frequency, and season).

This approach ensures that:

• Burning decisions are informed by assessments of the condition of the bush in specific areas;
• Fire is used as a practical management tool to maintain or improve ecosystem health and diversity.

Ecological criteria for selecting areas to burn

Areas considered for burning must meet the following criteria:

1. The general grass cover is dominated by nutritious and desirable species of grass (as opposed to those tough, wiry, or unpalatable grasses that livestock and wildlife avoid and that come to dominate after over-grazing.
2. The grass fuel load exceeds 4,000 kg per hectare (or 4.4 tons per hectare). (Grass fuel load refers to the total amount of dry, combustible grass and other fine vegetation in a specific area, measured typically in tons per acre or hectare, which directly dictates wildfire intensity and spread – high loads mean hotter, faster fires).  At this stage, the grass cover is typically moribund and provides low-quality forage that is avoided or selectively grazed.
3. Although up to 33% of arid areas (defined as <500 mm annual rainfall) may be burned under this system, it is probably a good idea to limit the burned area to approximately 10%, depending on preceding season’s rainfall figures and predicted rainfall for the coming season.

Fire Regime Implementation

a. Type of fire

Block burning, involving perimeter ignitions of selected blocks.

  Burn Block Design and Rotation

A large area of a number of square kilometres can be divided into “burn blocks” based on vegetation types, roads, rivers, and any management sections that are in place.

• The burn programme will rotate controlled burns through these blocks over time.

• Burns need to be staggered annually across the area to distribute grazing pressure and allow recovery of previously burned areas.

• Areas selected for burning will form subsets of the larger burn blocks. The diagram suggests the pattern of burning might look like over three years in our theoretical Block 5

• Certain sections within blocks are unlikely to qualify for prescribed burning and will act as natural firebreaks.
• To prevent overgrazing of recently burned areas, relatively large areas will be burned. (There needs to be a relatively large area of the hugely desirable new green grass available to grazers.)

b. Fire intensity

• An intense fire is required to achieve the primary objectives.
• Conditions required include:
  • Grass fuel load ≥ 4,000 kg/ha
  • Ambient temperature > 25°C
  • Relative humidity < 30%
• For safety reasons, wind speeds should not exceed 20 km/h, as stronger winds increase fire intensity, raise the risk of canopy fires, and the likelihood of runaway fires.

c. Season of burning

Late dry season (September–October).

This timing coincides with end of the season of grass dormancy and shortens the interval between fire and the onset of the rainy season, reducing negative effects on regrowth and general grass cover, and allowing for a rapid recovery of the grass cover.

The timing of prescribed burning is not just about controlling fuel loads aboveground; it is a critical measure to safeguard subterranean biology. As detailed in [Part 1: Effects and Management], intense late-season wildfires generate topsoil temperatures high enough to cook delicate surface biological soil crusts and sever the obligate ectomycorrhizal fungal networks that supply Brachystegia and Julbernardia trees with vital nutrients. By contrast, executing low-intensity “cool burns” early in the dry season (May to July) ensures the fire moves quickly across the surface, leaving unburnt leaf litter patches and keeping topsoil cool enough to preserve these essential fungal partnerships.

d. Frequency of burning

• Fire application depends on vegetation condition, which is strongly influenced by preceding rainfall.
• Excessively frequent fires, especially when combined with elephant impacts, can negatively affect woodland structure, particularly the density and recruitment of larger tree species.
• Research indicates that soils with higher clay content should not be burned more frequently than once every six years.
• Accordingly, burns should occur no more frequently than every 6–7 years, and then only provided ecological conditions are suitable.

Process for Selecting Areas to Burn

Managers of a area of bush need to:

• Identify areas within their sections with adequate grass fuel loads.
• Review the previous year’s veld condition assessments where sufficient fuel loads were present but burning did not occur;
• Conduct veld condition assessments (grass cover and woody vegetation) in May–June;
• Confirm that assessed sites meet the criteria for prescribed burning.

There are a number of factors that affect the final decision about burning a particular area:

1. Rainfall during the preceding season: insufficient rainfall reduces primary grass production;
2. Long-term rainfall outlook, including forecasts of El Niño (drier conditions) or La Niña (above-average rainfall);
3. Bush condition assessment results, including:
   1. Ecological status of the grass cover
   1. Grass fuel load
   1. Uniformity of fuel load across the block
4. Burn objectives and whether the identified objectives will realistically be achieved.

Burning

The actual burning takes place after careful assessment of:

• Ambient temperatures
• Humidity
• Wind direction and speed

Blocks are ignited simultaneously from opposite ends and the two fires burn towards each other and cancel each other out where they meet.

Obviously it is highly desirable to have on hand a collection of firefighting equipment, vehicles and personnel standing by to manage any possible escape of fire from the designated burn area.

Post-Burn Management and Monitoring

• Burn intensity and the percentage of each block burned  can be assessed using satellite imagery and NASA’s Fire Information for Resource Management System (FIRMS).

• Post-burn veld condition assessments need to be conducted in May–June of the following year (once again grass cover and woody vegetation are assessed).
• These assessments allow evaluation of vegetation responses across different soils and vegetation types.

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Conclusion

Fire is neither inherently destructive nor universally beneficial. It is a powerful ecological force that must be used with respect and understanding. In bush and savanna environments, carefully managed burns can rejuvenate grasslands, maintain open ecosystems, and restore balance where woody plants threaten to dominate. However, over‑burning or uncontrolled fires can quickly degrade the very landscapes they are intended to protect.

Responsible fire management recognizes this dual character. By choosing the right season, frequency, and conditions – and by monitoring ecological responses – fire can be used as a practical and sustainable tool for maintaining healthy bush and vibrant grasslands.

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Sources

• Nicolay, R., M. Tedder, N. Mkhize and K. P. Kirkman, “Frequent Prescribed Burning Contributes to the Sequestration of Soil Carbon in South African Mesic Rangeland Systems” African Journal of Ecology · June 2025
• Nieman, W.A., Van Wilgen, B.W. & Leslie, A.J., 2021, ‘A review of fire management practices in African savanna-protected areas’, Koedoe 63(1), a1655. https:// doi.org/10.4102
• Pringle, Robert M. and D. M. Kimuyu, R. L. Sensenig, T. M. Palmer, C. Riginos, K. E. Veblen and T. P. Young, “Synergistic effects of fire and elephants on arboreal animals in an African savanna”,  Journal of Animal Ecology, 2015, 84, 1637–1645
• Smit, I.P.J. and G. P. Asner, N. Govender, N. R. Vaughn and B. W. van Wilgen, “An examination of the potential efficacy of high-intensity fires for reversing woody encroachment in savannas”, Journal of Applied Ecology, 2016
• Trollope, W. S.W. and L. A. Trollope,  “Prescribed burning in African grasslands and savannas for wildlife management “, Arid Lands Newsletter, No. 55, May/June 2004
• Trollope, W. S.W. and L. A. Trollope, “Fire Effects and Management in African Grasslands and Savannas”, part of eBook Range & Animal Sciences & Resources Management, Vol. II, Encyclopedia of Life Support Systems (EOLSS), April, 2022
• Trollope, W.S.W., L.A. Trollope, H.C. Biggs, D. Pienaar, and A.L.F. Potgieter, “Long-term changes in the woody vegetation of Kruger National Park, with special reference to the effects of elephants and fire”, Koedoe, 1998, 41(2): 103-112. Pretoria. ISSN 0075-6458
• van Wilgen B.W. and H.C. Biggs, S.P. O’Regan and N. Mare, “A fire history of the savanna ecosystems in the Kruger National Park, South Africa, between 1941 and 1996”, South African Journal of Science, 96, April 2000