Wildfires in Botswana and Their Frequency of Occurrence

Fires play an essential part in the maintenance of the environment, but am-plified fire activity often leads to adverse effects in the environment such as destruction of property and loss of life. Botswana has experienced wildfires that are caused by humans intentionally and unintentionally. Some of these wildfires grow into mega fires such as the 2008 wildfires. Data of wildfires reported in Botswana from the Department of Forestry and Range Resources and the frequency of occurrence was studied and analyzed. It shows the period of 2006-2017, Ghanzi and Ngamiland districts were mostly affected by wildfires. These districts have protected land such as the wildlife parks which may lead to the outbreak of natural wildfires that burns unnoticed due to minimal movements of people. The wildfires reported in each district show an increase over the years and this may affect the smooth running of operations.

started through the use of "fire as a tool", and that include agricultural management, honey collection, grazing and harvesting management. Some are accidental and that includes recklessness when cooking, disposing of the cigarette without making sure that it's out among others. Fire management records show that most of the wildfires are reported to have started near settlements which support the fact that wildfires are human-induced. Wildfires reported well in time are usually controllable and can be extinguished before they turn into mega fires.
Mega fires are usually defined by their impacts and according to (William et al., 2011 [2]) these are the most damaging, costly and destructive. Botswana recorded mega fires in the year 2008 where 3.6 million hectares of Ghanzi district was burned and most of which was the Central Kalahari Game Reserve (CKGR).
This affected the country negatively as lots of funds were used in fighting these fires. Animal and plants lives were also affected. Records by Statistics Botswana show that the Ngamiland region usually records a greater number of fire occurrences followed by the Central District. By US standards, most fires recorded in the country are enormous. The largest total area affected by fires was recorded in 2011 (15,439,034 hectares). Districts which were affected mostly were Ghanzi, Ngamiland, and Kgalagadi respectively [3]. Because of the district sizes, sometimes fires may start and be extinguished by the rainy season in these areas without being spotted.

The El Niño-Southern Oscillation (ENSO) and Wildfires in Botswana
ENSO is a good predictor of seasonal forecast in Southern Africa [4]. El Niño It is also highlighted in the Asian regional report that in the years

Annual Fire Trends in Botswana
Statistics for annual fire reported and size of area burnt were collected from Department of Fire and Range Resources. The data is for the years 1994 to 2019. It is observed that the number of fires recorded has been increasing over the period. Figure 1 shows an increase over the years with the highest number of fires reached in 2015. This is the year the country suffered from drought. Drought is usually experienced every 3 -5 years and in periods of sufficient biomass, burning is favored. The years 2008 and 2010 have been classified as two of the warmest on record in the Southern hemisphere compared to a global average. This correlates fairly with fire frequencies. A linear graph drawn shows an increase in the number of fires with a positive slope of 4.868.
Wildfires in Botswana are usually recorded from August to October. This is the time when there is minimal amount of rainfall recorded in the country so there is drying of biomass from the previous rain season [8]. Also, the low temperatures of the winter season help speed up the drying of the biomass.    shows the total area burned over the years from 1994 to 2019. It is seen that the large burn area of 15,000,000 km 2 was reported in the country in 2011. This large area burn was linked to the exceptional high rainfall due to the effect of the la Niña episode and also the build up from previous low burning.
A linear graph shows that the size of area burned in the country continues to grow yearly even though there are some practices (such as the response team) put into place to fight the wildfires.

Total Area Burned vs Frequency
There is no strong correlation between the total area burned and the number of wildfires. The year 2015 shows the highest number of wildfires recorded but only 1,168,362 km 2 of land was affected by this. This is because the government has put efforts to curb these wildfires before they cause a devastating damage.
This includes using skilled personnel to fight the fires. The districts have been grouped into three (3) zones according to their fire risks. Zone 1 being the most fire prone, includes Ngamiland, Chobe and Ghanzi, has five (5) camps. This is the zone with high burning frequency and large area burned. Other two zones have fewer camps because of the small sizes of the districts and low rainfall. The duties of fire camps include daily patrols, reducing fuel where required and acting as first respondents of fire incidents [5].   to be responded to until they grow into large fires. The type of vegetation in these areas is found to be different from the rest of the other districts. Ngamiland district is characterized by Colophosphermum mopane and in the southern part of the country Acacias become more dominant and significantly [9]. Mopane is said to burn slowly and produce a constant heat rate. It therefore takes time for mopane fire to be put out naturally and can take time burning and spread significantly in the presence of unstable weather such as a blowing wind.
Other districts such as Kgatleng, Kweneng and South East with settlements may record several fires but are usually attended to by the marshals before they can grow into mega fires. Kweneng district recorded 264 wildfires in the 11-year period with only 3,930,515 km 2 of land burning. This is 79 more wildfires compared to Ngamiland which experienced 6-fold of land burning.

Conclusion
Fires provide an environmental service and are an integral part of the maintenance of the environment, but increased fire activity can lead to adverse effects on the environment. The effects may include disasters such as loss of human and animal life as well as property. There is no strong correlation between the total area burned and the number of wildfires. Some districts have reported many wildfires compared to other ones, but still recorded small areas of land burned.
This is due to the efforts put by the government to curb these wildfires before they cause devastating damage such as using skilled personnel to fight the fires.
The results shown here show an increase in the number of fires recorded yearly, this will continuously affect the running of operations smoothly.