THE ROLE OF FIRE IN THE
Report by Professor Kirkman after four day visit to
There are two levels of decisions in the decision making process.
It must be emphasised that non-intervention is the result of a decision, and not merely the default option.
The two levels of decision considered here both carry inherent risks:
The reasons for burning need to be considered in some detail because both the decision to burn or not, and the implementation of a decision to burn both carry substantial risks. The reasons for burning include the following:
Should a decision to apply a fire management program be made, the following points should be considered:
Fire intensity can vary tremendously depending on conditions, and can be manipulated. The impact of fire intensity on vegetation can be significant.
The frequency of fire can be controlled to a large degree. Decisions on fire frequency should be made after considering all the relevant factors, including the following:
Most of the areas visited where fire could be considered were dominated by shrubs/forbs had a low grass fuel load. Fire will be low intensity and patchy. In many of the shrubby areas the first fire may not kill the shrubs, but should give the grass a competitive advantage. Subsequent fires (two or three years later) may kill a significant proportion of the shrubs.
Fire frequency should always be flexible and based on a specific decision with defensible reasons as opposed to a regular program. Decisions can often be based on fuel load.
Area burned should be related to number of animals expected to congregate on burned area after the fire. High numbers of animals attracted to a small burned site may impact the vegetation through grazing and trampling.
Create a mosaic of grassland – shrubland – open savanna – closed savanna – woodland (forest).
Frequent fire No fire
Grassland Shrubland Open savanna Closed savanna
Impressions of the state of the vegetation in the Mana Pools (specifically Chitake Springs area) after a short, first visit should be considered within the following constraints:
The vegetation comprised a mosaic of relatively thick, closed canopy savanna woodland, through open savanna and shrubby areas to grassland. The grassland areas appeared to be quite heavily utilised by grazing animals. Dominant grasses included Digitaria species and a range of annual grasses. In terms of the classical succession models of grassland function, there was no evidence of under utilisation with succession through to Increaser I type species that would be considered a precursor to bush encroachment or thickening. In contrast, the impression is one of heavy utilisation with a tendency to be dominated by annuals. Many of these annuals are probably largely driven by rainfall. In wet years they will probably increase in abundance and in dry years they will probably decline. Fire would probably not be considered necessary in such a system if the shrub and woody layer were ignored.
However, there are a number of shrub species that dominate the grass layer in many areas. The shrubs appear able to compete effectively with the grasses for nutrients and light, dominate and act as a precursor to woody species. This is probably exacerbated by the relatively heavy utilisation of the grass layer. There was not much evidence of the shrubs being utilised by any herbivores. In areas utilised by buffalo, particularly corridors, shrub abundance declines dramatically due to trampling. Controlled burning (correct intensity and frequency and suitable area in relation to animal numbers) may play a role in allowing the grass layer to compete more effectively with the shrubs and maintain or increase the area of grassland relative to shrub and woody dominated landscapes. Incorrect use of fire may result in increased grazing pressure on the grass layer in burnt areas and may exacerbate the situation.
Mana Pools (floodplain)
The presence of the exclosure plot allows some assessment of the impact of animals on the vegetation. Apparently the plot was fenced in 1986. A survey was carried out inside and outside the plot in 1994. The results indicated that there were differences between the plot and the surrounding areas. Ten years later, there is a substantial visual difference. It would be very useful to have the plots resurveyed.
There is evidence of heavy utilisation of both the browse and grass layer. The appearance and dominance of the Indigophera sp in recent years is striking. The role of the Indigophera on an ageing floodplain is an interesting topic for debate. It may be that it is an integral part of the succession process initiated by the northward river migration, or that it is an opportunist plant which has appeared in response to a stressed system. Either way, it is there, and it is part of the system. It would be useful to examine similar areas up- and downstream with differing levels of herbivory in an attempt to better understand the origin and role of the Indigophera.
Whatever the role of fire may have been or should be on the floodplain area, there is currently probably not enough of a fuel load to carry a fire, particularly in the areas dominated by Indigophera. With the obvious herbivore pressure in the area, this is not likely to change in the short term.
The decision making process surrounding the role of fire in the Zambezi Valley is critically important and will determine whether controlled burning should and will take place or not. If a decision is made to implement a burning management program, then further decisions have to be made regarding area, intensity and frequency of fire. The final step is the implementation of the program with due consideration to safety.
Season of Burning
Research in southern
Excerpts from Oliver West’s booklet “Fire, Man and Wildlife as the interacting factors limiting the development of climax vegetation in
1) Grassland is the ultimate product of fire because it is composed of the plants, grasses and forbs most tolerant of fire.
2) Fire, which usually originates in grassland, destroys forest, produces savanna and ultimately grassland.
3) Descriptions written by Selous (1893) and other travelers --- stress the openness of the countryside and indicate that during the Iron Age occupation, a small human population, with fire and shifting cultivation, had established a trend which favored the development of open savanna and grassland while it discouraged dense bush and forest.
Letter to the Editor of the
AN OBSERVATION ON THE EFFECT OF FIRE EXCLUSION ON THE ACTIVITIES OF HARVESTER TERMITES IN RELATION TO GRASS COVER IN THE ZAMBEZI VALLEY
During the past nine years, a marked and progressive degradation of the
annual grass cover (mainly Urochioa sp), has been observed over some twenty
square miles of bushland, which is dominated by a small tree species,
(Combretum elaeagnoides), surrounding and extending Westwards from
Rekometjie Field Research Station in the Zambezi Valley. The affected area
lies within the boundaries of a controlled hunting area and a game reserve,
and domestic stock in the form of cattle, sheep and goats are involved only
in the immediate vicinity of the Research Station. No systematic assessments
of changes in the flora have been made, but the deterioration is visibly
obvious. Earlier in each successive year the cover of annual grasses has
been removed by harvester termite, to be replaced by an increasing
population of herbaceous weeds which effectively prevent hot clean grass
It has been the practice in this area to exclude fire completely. As a
sequel and possibly a consequence, the harvester termites have been provided
with a copious source of food each year in the form of annual grasses which
they have utilised until the ground has become denuded of these with only
weeds remaining, the time at which this time has been reached becoming
progressively earlier in each succeeding year. The increase in harvester
termite activity has led, it is believed, to the progressive degradation,
and the situation has now been reached where attempts to introduce fire are
quite ineffective because of the absence of burnable grass.
The exclusion of fire, followed by increased harvester termite activity has
deprived grazing animals of an important element of their dry season forage.
Unless controlled early fire can be encouraged when burnable grass is still
available, the situation may deteriorate still further.
R. D. Pilson
Branch of Tsetse and Trypanosomiasis Control,
Department of Veterinary Services.
Excerpts from documents compiled by Professors Winston Trollope and Kevin Kirkman (Grassland Science,
. It is concluded that human beings have used fire for over a million years and in
Sweet (1982) in
On the contrary the withdrawal of fire for extended periods of time appears to have a more predictable effect. For example on the Accra Plains in southeastern
This led to the conclusion that in all the burnt savannas of Lamto the pressure of forest elements on savanna vegetation is very high and the exclusion of fire initiates the development of forest (Menaut, 1977). Similar trends have been found in the more arid savannas (500-700 mm p.a.) in southern Africa where in the Kruger National Park the exclusion of fire caused both an increase in the density and size of tree and shrub species (van Wyk, 1971).
The effect of frequency of burning on the quality of forage is that generally frequent fires improve and maintain the nutritional quality of grassland particularly in high rainfall areas making it highly attractive to grazing animals.
West (1965) stated that the fresh green shoots of new growth on burnt grassland are very high in protein and quotes Plowes (1957) who found that the average crude protein content of 20 grasses after burning at the Matopos Research Station in
. At the turn of the century the Serengeti-Mara area was described as open grassland with lightly wooded patches, much as it is today. Following the great rinderpest epidemic of 1890, human and animal populations are thought to have been reduced to negligible numbers in the Serengeti-Mara region. Fires were infrequent due to the low human populations and elephant numbers were low having suffered from heavy ivory poaching during the previous decades. Over the next 30 to 50 years these prevailing conditions of low fire frequencies and low elephant numbers saw the establishment of dense woodlands and thickets. This woody vegetation provided ideal habitat for infestations of the tsetse fly that further prevented any significant human settlement within the Serengeti-Mara ecosystem. Consequently by the early 1940’s the area had become densely wooded and the
Finally it was shown that frequent fires favour the abundance of the highly productive and palatable grass species, Themeda triandra in southern African grasslands (Scott, 1970; Dillon, 1980; Forbes & Trollope, 1990). ) This raises the possibility of using fire to improve range condition by increasing the abundance of valuable forage species like Themeda triandra.
“Veld and Pasture Management in
On page 21 - 1.4.4 it says that there is a general belief that fire is harmful to vegetation and upsets the natural ecological balance and should be prevented. Burning is often condemned but many ecologists believe that it is natural and that no fire causes profound negative changes to the vegetation. It is an accepted fact that fire maintains grass cover and prevents undesirable thickets. Foresters and amateur ecologists and preservationists are the people who automatically condemn burning without scientific backing, playing on the emotions of the public. Bush fires have been part of the African ecology for thousands if not millions of years. According to Sim (1907) the Portuguese called the interior “Terra de Fume” because of the smoke from fires. Roux (1966) wrote that burning in winter was common long before European settlement.
The fact that many plants have evolved to withstand fire indicates that fire has influenced the grassland, woodland and savanna for millennia. Many flowers only appear after fire and disappear if there is no fire. Many species of tree resist fire when mature even though they are susceptible as seedlings whereas species in the Evergreen Forests succumb to fire even when they are mature. Most grasses have evolved so that if they are not burnt they become moribund and die. Many birds and other animals are therefore regulated by fire according to the environmental changes therefore fire is a natural ecological factor and as a management tool would be natural and without it would lead to undesirable changes in the vegetation and animals.
On page 374 17.2 it says that fire is used to prevent bush encroachment which reduces the amount of grass (du Toit 1972; Trollope 1977).
1) Soot particles reduce global warming (p 8)
2) Fire is a source of tropospheric ozone (p 8)
NB: there is only 10% of the original North American Prairies left due to fire prevention during the last 200 years (National Geographic, vol.184,no4 October 1993) – that means there is 90% less grass fire smoke in the atmosphere – therefore there is 90% less soot particles to contribute to global cooling and chemicals contributing to ozone – has this contributed to global warming and do anti fire policies compound the problem?
3) Tool for bush control (p 8)
4) Humans have burnt savannas for thousands of years (p 8)
5) African savannas have highest biomass and biodiversity of large mammal herbivores on earth (p 26)
6) Exclusion of fire leads to woody component of savanna (p27)
1) Restoration of woodland by early burning (p68)
2) Termite population low because frequent fires destroy food supply (p 69)
3) Woody stems vulnerable to fire in late dry season when food reserves are being transferred to new leaves (69)
4) Hot fire can prevent the recovery of shrub land into woodland (p 69)
5) After 10 to 15 years of protection from fire new saplings are sufficient to suppress grass. (p 70)
6) Low elephant population and early burning encourage woodland over 40 years – (was the Kariba cull in 1984
to establish woodland?- S. Pope)
7) Introduction – 1) In 15 years on burnt plot the trees declined by only 28 % but on unburnt plots trees increased
by 87 % (p 8)
2) Burning increases nutritional value of grass (p 14)
Eleven Years in
Page 85 – In the spring and summer, vegetation grows so luxuriantly and rapidly that the thousands of cattle cannot keep one tenth of even the sweet part of it under, and they have soon to be closely followed and kept in sight, that they may not be lost. In the autumn, these pasturages resemble immense fields of ripe corn; and in winter, when seedless and dry, they are swept away, one after the other, by conflagrations that are always raging in some part or other of the country. During the day, the smoke is seen at a great distance, ascending cloudlike towards the skies; and in the night, the flare is reflected brilliantly upon the ascending clouds of smoke. With this yearly clearance, by the cleansing element, comparatively few of the trees are destroyed; but, while the larger timber escape with little injury the shrubs and underwood are destroyed, and all dry plants are reduced, in some localities, to complete ashes.
Wankie the Story of a Great Game Reserve by Ted Davison – (1967)
Edward Hartley Davison was given the task of establishing Hwange Game Reserve in 1928. He held the post of Warden for 34 years and “did more than anyone else for the preservation of our wild game” - Ian Douglas Smith.
“The game itself did not suffer to any great extent. More often than not animals would walk calmly ahead of the flames about a mile away. When the flames died down at night (as they usually did) the game would find gaps in the chain of fire and get back onto the burnt – out areas.
Game of all types show a marked preference for burned off country, when the new grass grows. Localities which have not been burned for two or three years are not nearly so popular as feeding grounds as those which have been burnt and cleared of old grass. Quite apart from the grazing aspect, an area which had not been burned or heavily grazed for a number of years takes on an unhealthy appearance. Dead grass, leaves, and other types of litter accumulate, and in many cases this layer of dead material suffocates the growing grasses.
To exclude fire altogether might have a very detrimental effect on many animals, particularly those such as gemsbuck and tssessebi who prefer the sparse but succulent early grasses after a fire; as well as buffalo, who show a marked preference for grazing veld which was burnt the year before.
“Creatures of Habit” – Peter Apps (
Each year in
one point 6 million square kilometres. Nearly all of southern
vegetation is subject to periodic or sporadic fires, and considering the
fury of a wind driven fire in grasslands, savannah woodland or fynbos, cases
of mammals being killed by fires are remarkably rare. Small mammals simply
disappear down their burrows- the heat from even the fiercest of blazes
penetrates no more than a few centimetres into the soil. A radio-tracked
genet survived a fire in its
boulders. The main danger comes not from the fire itself, but from the
destruction of food supplies and cover that offers shelter from predators.
The wind that drives the fire along also carries for kilometres the smell of
smoke that warns of its approach, and larger animal species have the ability
to move out of the fires path, onto rock outcrops or across rivers. Fires
are likely to catch them only when fences block their escape routes.
“Sometimes When it Rains”
Keith Meadows - Writing about Charlie Mackie – In 1984 Mr. Mackie headed the resurrection of
Factors affecting the ratio of Lions to Spotted Hyaena – Dr. Gianetta Purchase
On Page 44 - the
From: "Justine Blackbeard" <firstname.lastname@example.org>
Subject: Bush Encroachment
Date: Thursday, July 20, 2006 5:05 PM
Gavin Blackbeard -
Many thanks for your email and information that you have collected and forwarded to me.
I agree with your findings but unfortunately the Botswana Government have been swayed by the young ecologists from other countries and has made a law that anybody starting a fire whether by accident or intent will be liable to a jail sentence for no less than 10 years. As a result there have been no bush fires and the bush encroachment has now become a very serious problem to the cattle ranchers and wild game in our country...
I do hope that your research in the
Ian Nyschens referring to his time in the
It was not just the valley that used to burn but the savannah country as well – you could sometimes see the whole length of the escarpment on both sides of the valley glowing. These fires were lit by the tribesmen who feared that the dense cover gave lions hiding opportunity. These fires were especially noticeable along the footpaths between the villages – they were fanned by the August winds
and the air currents as you know always come up the
Portuguese as Tierra Del Fume – land of smoke. Read “The Months of the Sun” – chapter 12 – page 157 to 160. I hope this information will be of some value to you.
Claude Meredith who hunted and managed the Dande North Concession stated that because of continued anthropomorphic burning there is still abundant grassland and large herds of
Before the villagers were relocated out of the
At a time when Tsetse Fly Control Department’s operations are compromised by the economic situation the lack of late dry season hot fires are creating the ideal habitat for tsetse fly. In the last few years there has been a noticeable increase in the Tsetse fly population and incidents of Sleeping sickness. Dense bush and forest is the ideal habitat for tsetse fly, therefore, if the current trend of forestation continues we can expect an even greater increase in tsetse fly problems in the
It is imperative that a grassland management program be adopted in the
In the 1960’s there were references to a herd of 5000 buffalo in Mana Pools. More recently two ex National Parks officers, Dolph Sussien and Steve Edwards, have both informed me of recordings of a herd of similar size in the 1970’s. Dolph Sussien’s sighting was in 1978 and the herd stretched from the Lodges to Mana Mouth, a distance of about 3 km. Currently a herd of 200 is considered to be a large herd.
Animal population sizes are related to their food supply.
During most of the 1990’s there was a herd of 1000 buffalo on the Matusadona shoreline in the region of
In 1999 the lake level was allowed to rise and inundate the tree line. This occurred again in 2000 and 2001. Within 2 seasons the large herd of buffalo had all but disappeared. This was followed by a crash in the Lion population. In 2003 there was only 1 male and 2 females in the vicinity of Fothergill and Spurwing. There were even sightings of Lion hunting and feeding on Hippo and Crocodile. In fact, a Hippo killed one of the 2 females in November 2003.
The significance of this occurrence in Matusadona is that it illustrates what is happening in the
It is a well-known and researched fact that fire inhibits bush encroachment and forestation but maintains grassland. There is now only 10 % of the North American Prairies left in a patchwork of isolated pockets because of anti fire policies. The growing points of grasses are below ground and within weeks of even a hot fire new shoots appear. They may have begun evolving while the earth was still cooling down. Volcanoes would have started the original fires under which grasses evolved millions of years before man appeared. Since the evolution of man most fires have been anthropological where man has lit fires to provide grass for ease of hunting (the American Indian and in Africa), protection from dangerous game (in