History Of Kruger Plant Life & The Effects Elephant Have Had
Excerpts from 'The Kruger National Park - A History' by Dr
Prehistory and Early Formative Years:
Influence of early inhabitants on the ecosystem
Although the Iron Age populations of the Park were never very large,
it is still quite
possible that the people had some influence, even if only temporarily, on the ecosystems
surrounding their settlements. The general climate was not very suitable for agriculture.
Long-term cycles of high and low rainfall could have led to similar fluctuations in the
densities of the human populations in the area, which in turn could have led to different
levels of impact on the environment.
Analyses of bone fragments excavated from Iron Age archaeological
sites in the
Park indicate that animal protein was obtained mainly through hunting. On a few sites,
the remains of cattle and goats were found, but there is no evidence that large-scale
herding was a mainstay of economic activities. and it is unlikely that the people in the
central and northern regions regularly relied on agriculture as a source of food.
However, evidence of domestic sorghum on at least one site and grindstones on others,
suggest that some farming was taking place.
Agriculture and herding, even on a limited scale, entail clearing the
bush to open up
fields or to extend grassland for grazing. The land was used until its capacity had
been exhausted and then new areas were cleared. When all the available land
around a village had been used, the people moved away to settle elsewhere.
These practices, combined with hunting and gathering, probably had some
impact on the wildlife and plant communities of the Park, especially in areas
where settlements were common, such as along the Letaba River. From the
earliest documented history it is obvious that extensive annual veld fires were
a feature of inhabited areas.
The presence of Bushpig remains at Early Iron Age sites on the Letaba
is interesting as these animals have not been recorded there in modern times.
In the past the rainfall could have been slightly higher, creating a more suitable
habitat for bushpigs, and agriculture and human activities may have increased
the food supply, while reducing the carnivore population.
The severe drought conditions caused a general emigration of the
population from the Sabie and Shingwedzi Reserves (which later became
the Kruger Park). It was stated that "... now that the large locations (villages)
in the north-west have disappeared, the total number of 'native' inhabitants
amounts to only a few hundred men, women and children, living in isolated
and widely scattered kraals. During the past ten years the tendency has
been to emigrate westwards on account of the lack of rain"
The Era 1926 to 1946
Descriptions of the vegetation during this era of the Park's history
and far between. Whatever information does exist is superficial, the most
detailed accounts coming from Stevenson-Hamilton's own observations and reports.
Through the looking glass
It was said that the large numbers of impala along the Sabie River
owed their comparative immunity mainly to ... the denseness of their favourite
thorn bush ..."
There may have been fewer trees along the banks of the Sabie River at
as the view upstream and downstream from 'Reserve' (later Skukuza) was
of "... wooded islets, rocky barriers, and reed-fringed banks." Old photographs
taken of the Sabie River in the Skukuza area reveal the lack of large trees on its banks.
The banks of the Olifants River were "... densely covered with many beautiful
wild-fig trees 40 years ago the greater part of what was then the Sabie Game Reserve
presented a very different picture from what it does today."
Primary vs Secondary Forest
Stevenson-Hamilton's observations led him to believe that the
the Lowveld was progressing from primary to secondary forest. He surmised
that "... it is possible, could we see this area [the Kruger Park] as it existed in
the remote past, we should find some of it, including possibly the Lebombo Hills,
to have been covered with primary rain forest, consisting of large trees, such as
are now found growing only along the banks of the waterways." Instead, the
vegetation of the Lowveld, at the time he was writing, consisted of secondary
forest (stunted fireproof growth which grows on the ruins of the old primary forest).
In his opinion, only two factors prevented the area from becoming a barren,
treeless desert - the presence of vegetative cover and the depressions (pans)
made on the watersheds by wild animals, notably wildebeest.
Grass fires, customarily raging through the area towards the end of
season, were lit annually by the resident communities and workers on the
railway line to the Selati goldfields. Stevenson-Hamilton considered these
fires undesirable and attempted to gain control over them by instituting
reprisals against people who were found guilty of lighting fires.
The grass fires were believed to have been responsible for the death
established trees, on the one hand, and for preventing the growth of saplings,
on the other. This led to the denuding of the soil and consequent erosion.
The bedrock was covered by only a thin layer of soil and was soon exposed
once erosion had set in. "Owing to the generally shallow nature of the soil
above the granite through most of the Reserve, I doubt indeed if it would
sustain any very high timber, except near the rivers and some of the spruits,
but the gnarled, twisted, and stunted appearance of practically all the trees
is due mainly, if not entirely, to the grass fires" (Stevenson-Hamilton 1912).
However, Stevenson-Hamilton (1906) also refers to " ... huge tracts of
absolutely uninhabited country where no grass has been burned for many years".
In some instances controlled fires were believed to be desirable "... by
burning strips alternately in different places and at the proper season,
especially where rank grass exists ..." (Stevenson-Hamilton 1912). Thus,
the first burning programme was envisaged.
First concepts of bush encroachment
The accumulation of large amounts of leaf litter resulted in
bush fires during the dry season, and an increase of woody vegetation.
This had a profound effect on the composition and structure of the
vegetation and associated animal populations.
In 1943 Stevenson-Hamilton remarked that "... wildebeest are
less numerous than they used to be in the eastern and central portions south
of the Olifants River. On the other hand at Pretoriuskop and 10 miles west of
Satara, they are as numerous as ever. I am inclined partly to attribute this
situation to the spread of the thick bush and the consequent decrease in the
amount of open grazing which is becoming increasingly manifest all over the
Park. The western areas still remain comparatively open, though much grown
up compared with what I recollect of them 40 years ago. The tendency
therefore will increasingly be for wildebeest, zebra and other types of
migratory game, which are of the purely grazing type, to work further
and further westwards."
In his subsequent annual report, however, Stevenson-Hamilton (1944)
and admitted that his 1943 assessment of the bush encroachment was not as
universal or regionally accurate as he had presented it. Rather, bush encroachment
was only especially prominent in the Pretoriuskop and Tshokwane areas, for
which he had photographs taken some 20 years previously.
The Era 1946 to 1960
Changes in vegetation
The question of veld burning as an effective method of veld
management in the
Kruger National Park repeatedly came under discussion. Sandenbergh (1950),
referring to wildebeest, recorded that "... their numbers have gone down in the
Pretoriuskop area. There can be no doubt that there has been a change in the
vegetation of the Pretoriuskop area, and, together with zebra, it seems
apparent that these animals have been affected thereby".
Could the lack of fires over a period of two or three years be held
for bush encroachment, which is a very slow process? Changes in veld
conditions usually take place over a number of years before they are noticed.
The worst bush encroachment species were Dichrostachys cinerea subsp.
nyassana (Sickle-bush) and Terminalia sericea (Silver Cluster-leaf).
The opposing view also was held - that the problem of bush encroachment in
the Pretoriuskop area was attributable to regular veld fires. "The germination
of grass seeds and the establishment of seedlings are retarded by veld fires
and in this way an advantage is gained by the hardier seeds of trees and
shrubs in an uneven competition. In some cases fire is even conducive to the
germination of the seeds of some intrusive plants and trees with hard seed coats."
Although the actual causes of bush encroachment were not known, it was
speculated that there were a number of contributing factors.
- The disturbance in the animal-shrub-grass relationship by humans.
- The spreading of seeds and fruits by animals.
- The lack of browsers.
A total of 42 shrub and tree species were listed as 'encroachers'.
Before 1948, the fire-burning policy applied was that "... the area
burnt must be small, and must not have been burnt earlier than three years
previously, or where a heavy infestation of ticks occurred" (Van Graan 1951).
Sandenbergh noted that the policy regarding veld burning was that "... no veld
shall be burnt more often than once every five years; that all such burning
shall only be done after the first good spring rains, that by every means at
our disposal accidental fires must be avoided. The whole question of veld
burning has been submitted to the Scientific Advisory Board for its recommendations".
Furthermore, if controlled burning were to be undertaken in the future, it would "...
only be done in areas where the grass was inadequately grazed".
A change of heart
Controlled burning for vegetation management purposes, was stopped
1948, after very little of it was actually done for two years. It was stated that "...
instructions have been issued, in terms of the Board's resolution, that no burning
whatsoever is to be done without the authority of the Board).
Sandenbergh (1950) stated that: "I am convinced that the past policy
has caused a change, for the worse, in our vegetation, and that this change has
had a profound influence on the distribution and breeding rate of the wildlife in the
Park. Deliberate burning in an area which must be kept natural, must cause an
upset to any natural balance ... It is astounding that so many people still do not
realise that the fertility of the soil is dependent upon the organic matter incorporated
in it; that our water supplies are very largely dependent on the covering of vegetation;
that grass growing on fertile soil can support life far more effectively than grass
growing on unfertile soil!"
The Research Section
The question of veld burning was probably one of the major reasons
creation of the Research Section in the Kruger Park in 1950. Although no
opinion for or against burning was expressed, a number of questions were
raised about the past veld-burning policy. For example, the game
populations in the northern areas of the Park had shown sharp increases -
was this perhaps due to the lack of burning during the preceding few years?
Could the bush encroachment noted in the Pretoriuskop area be ascribed
to the lack of fires, given that until recently the area had been burned regularly?
What was causing large numbers of Dichrostachys cinerea (Sickle-bush)
shrubs along the Lower Sabie road to die? Could this be due to the fact that
the area had not been burned for a long time? Was the northern mopane veld
severely damaged by fire? Did fire stimulate the germination of the seeds of
various types of pod plants? With these issues at the forefront, the Research
Section decided to embark on a comprehensive fire research programme.
The effects of fire
In December 1950 the Biologist, Dr Nel, inspected the Pretoriuskop
Tshokwane sections to compare burnt and unburnt areas and to determine
the effects of fire.
- The soil in unburnt areas was moist and covered with litter,
burnt areas it was dry, hard and denuded of litter (dead grass).
- Game trampled the old grass into the moist soil and green growth flourished.
- The grass in unburnt areas flushed three to four times sooner than
that in burned areas.
- Fodder trees in the unburnt areas were in full leaf and/or
whereas those in the burnt areas were still devoid of leaves.
- Thorn trees were reduced to stunted shrubs by fire.
- In burnt areas, felled trees burnt open patches on the ground, while
in unburnt areas such trees provided shelter for lush stands of palatable
- It was found that higher densities of animals frequented unburnt veld.
Preliminary veld burning policy
A resolution was passed "... that the Board declares as a preliminary
that the entire Kruger National Park be divided into blocks by proper firebreak
roads and strips. All grass that becomes tall and rank is to be burned every
three years, on the understanding that only one third of a block may be burned
annually. Burning must only take place after the first spring rains. This is to
continue until such time as the policy may be proven incorrect" (Brynard 1958b).
These measures were accordingly implemented, with the exception of the
Pretoriuskop sourveld where a biennial burning programme was applied.
The Research Section felt that it was not correct to subject the entire Kruger
Park, with its rich botanical diversity, to a rigid burning schedule. It therefore
proposed that certain areas be excluded from the burning programme,
due to their vulnerability, their role in water conservation, or their uniqueness
and floral richness (Brynard 1958b).
The era 1960 to 1970
Various references were made throughout the 1960s to changes in the
vegetation, and particularly, to the phenomenon of bush encroachment.
The increase in the woody component of the vegetation caused much concern in the open plains habitats of cheetah.
Even the hottest fires were not sufficient to kill Colophospermum
(Mopane) shrubs completely, but only caused them to coppice. This was
ascribed to their extremely fire-resistant underground parts. The tree
stratum was lowered drastically and thinned out, allowing the penetration
of more and more sunlight, and giving rise to an even lush (rank) grass
cover. Over large portions of the northern areas a coppiced Mopane or
seedling has little chance of ever reaching tree size even if it is protected
from fire for a long time. The grass cover here is so rank that even a tree
of 10-12 years will be burnt to the ground by only one veld fire that is accidentally
lit in such old veld."
Use of chemicals
The perceived encroachment by Mopane had reached such proportions
remedial measures other than rotational veld burning were contemplated. Large
parts of the north were "so infested with Mopane shrub" that they were
avoided by plains-loving animals such as roan antelope, tsessebe, blue
wildebeest, zebra and eland. As a result of this, attempts were made to
determine experimentally whether other methods, such as the use of
chemicals, would have the desired effect of attracting the animals back.
Reclamation project - Pafuri
During the 1960s, a major project was launched to rehabilitate areas
where the field layer had been depleted on the Luvuvhu flood plains at Pafuri.
The problems were mainly ascribed to the severe floods in 1958 during
which the Luvuvhu River overflowed its banks and deposited a thick and
largely impervious layer of silt on the flood plains. The situation regarding
the grazing at the end of 1960/61 was critical. There were no more
signs of grass, but bush encroachment, mainly Azima tetracantha
(Needle-bush), and Anisotes sessiliflora was becoming more obvious.
The good condition of the game was ascribed to the fact that the animals
moved out of Park at night into Mozambique, where conditions were more
Seeds of indigenous grasses were collected during the summer of
and an experimental grazing re-establishment programme was envisaged for
the next spring.
During January 1962 a bulldozer was used to open furrows, intended to
serve the dual purpose of improving water absorption and preventing
excessive run-off. The strips were also used to re-establish grass species
such as Eragrostis curvula, Themeda triandra, Rhynchelytrum repens,
Bothriochloa insculpta and Eragrostis sp.
In 1962/63 it was stated that *"... the attempts to recover the veld
undertaken last year in the trampled Pafuri area were unfortunately a total
failure due to the very poor rainfall after the sowing of the seed.
The era 1970 to 1985
Elephant impact on the vegetation
During the early 1980s the elephant population rapidly increased, and
1983 a total of 8 678 elephant were recorded - the second highest total
ever recorded and the highest since 1970, when the population stood at
8 821. The increase occurred at a time when the Kruger Park, especially
the far northern areas, was subjected to a severe three-year drought.
The impact of elephant was particularly severe on four tree species.
- Adansonia digitata (Baobab):
During the August/September 1984 helicopter census, a total of 213
dead Baobab trees were counted. The majority of these trees were
judged to have died within the last year. On a subsequent flight in
September 1984 over the area to the immediate north of the Park
and the Tuli Block area in south-eastern Botswana, no dead Baobab
trees were seen and it was concluded that the severe drought was not
solely responsible for the deaths, but that elephant impact was probably
the primary cause. It was also suggested that *"... the present death rate
cannot be sustained for an extended period without serious damage to
the Baobab population" (Joubert 1984b).
- Combretum apiculatum (Red Bushwillow):
It was reported that "... over extensive areas, particularly between
and Mphongolo rivers, Red Bushwillow trees have been extensively impacted.
In many of these communities not a single Red Bushwillow tree still has its original
Certainly the absence of grass in these areas has made the fallen
obvious, dramatising the impact that elephant have had on this species. It is
accepted that the present situation may reflect the accumulated effect of
prolonged heavy utilisation. The fact is, however, that the sustained high
elephant densities in this area have led to excessive utilisation and have
resulted in extensive destruction of Red Bushwillow trees. The lack of
grass as an alternative food resource in this area over the past three
years has most likely also led to heavier demands on the woody vegetation".
- Acacia nigrescens (Knob-thorn Acacia) trees: Knob-thorn trees
occurring on the patches of heavy, water-logged soils in the predominantly
Mopane communities on the eastern basalt plains were almost entirely
eliminated in some areas.
- Kirkia acuminata (White Kirkia/Wild seringa): These trees suffered
considerable damage from heavy elephant utilisation in the area between
the Luvuvhu and Limpopo rivers and on the isolated rocky inselbergs in the
northern districts (Joubert 1984b).
In several other areas, severe elephant impact was also evident. It
that the heavy utilisation of trees, and the consequent coppicing that resulted in
many cases, did not necessarily imply a change in the vegetation composition but
rather of its structural features. In this respect it was felt that *"... the habitat
preferences of animal species are largely determined by the structural features
of the vegetation. [Thus] the changes brought about by elephant could well lead
to a readjustment of the relative densities of the various animal species
inhabiting the area in the short- and medium-term. [This could even mean the
eventual disappearance of some, and the appearance of others, in the long-term.
At stake, therefore, is the diversity of habitats and the species richness
associated with each habitat" (Joubert 1984b).
The era 1985 to 1994
A burning policy based on lightning-induced fires
In compliance with the views of the majority of the Research and
Management staff, Joubert submitted a proposal to the Executive Committee in
favour of a more natural fire regime. This meant instituting a burning policy based
on lightning-induced fires throughout the Park. He stated that lightning fires were
accepted as "... a natural ecological factor and a very important factor in maintaining
the integrity of natural ecosystems. After careful consideration ... it was also felt
that, with the necessary control measures, it could be recommended that veld
fires as a process should be allowed in their natural state."
Joubert also listed a number of factors to allay fears of
- Lightning fires were frequently associated with rain, which in
place limits on the intensity of the fires.
- Lightning normally occurred in the late afternoon or early morning,
giving rise to cooler night fires.
- Natural barriers such as watercourses, previously burned patches, and
rain, would tend to create a mosaic pattern of burned and unburned areas.
- Fires at less than two to three-year intervals were unlikely due to the
general inability of Lowveld pastures to produce sufficient combustible material
in shorter periods.
- A system of barriers (roads and rivers) was identified to curb the spread
of fires if they should, for some unforeseen reason, threaten excessively large
areas (Joubert 1993a).
A more natural fire regime
The proposal for the more natural fire regime was supported by the
Committee and approved by the Board in 1993.
The approved policy was drafted with eight major parameters.
- All lightning-induced fires within the Kruger Park would be allowed to take
their course "... in order to create a natural mosaic of burned veld".
- All efforts would be made to extinguish accidental (unnatural) fires.
- Lightning fires would only be extinguished under the following circumstances:
- if they posed a danger to humans
- if the property, structures and/or infrastructure of the Board or the property
of visitors were endangered
- if areas of special scientific significance were endangered.
- Parallel firebreak roads would be graded along all Park boundaries to
safeguard adjoining areas against fires originating in the Park.
- Natural fires should be assisted over unnatural impediments (roads, etc.)
if "...conditions are judged to be suitable for sustaining the fire".
- Natural fires would be monitored regarding:
- the source and locality of ignition, pattern of spread and final extent
- prevailing climatic conditions
- the fuel load and its condition.
- Firebreak roads had to be maintained to monitor lightning fires and to
combat unnatural fires.
- Guidelines and rules regulating the management of fires were to be drawn
up for the benefit of the field staff responsible for the implementation of the policy.