The main timber growing area of Zimbabwe is Manicaland, the moist easterly province of the country. Annual rainfall between ca. 900 and 1800 mm allows the growth and management of softwoods on more than 100,000 ha. The rotation period is ca. 25 years. The mountainous area is of great landscape beauty and very attractive for recreation.
For the past eight years daily forecast of burning conditions during the dry season (from March/April to October/November) have been issued by the Meteorological Department and broadcasted by the Zimbabwe Broadcast Corporation.
Up to 1990 the fire danger estimates were issued only for the North and the South of Manicaland Province (eastern highlands). In 1991 this service was extended to cover the main centres of Zimbabwe, Harare, Bulawayo, Mutare and Gweru. This is the latest step to promote fire awareness all over Zimbabwe.
The Fire Danger Estimate (FDE) is an objective assessment of burning conditions based on the weather history and the expected weather conditions. It is therefore applied equally to forested lands, open savannas and grasslands, and the transition types between forest and savanna. The main local variables are particularities in fuel type and loads, topography and local weather conditions.
The fire danger estimates are based on three variables of weather, ambient temperature, relative humidity and windspeed. These components, plus a factor for the number of days since the last rainfall, are computed in a model which was developed in Chimanimani in 1964 on the base of other models. This system has been refined in recent years.
The fire danger index is expressed in “points” (also indicated in a colour code). Prescribed burning, for instance, may be undertaken under conditions up to 39 points (Green). Greater care must be given under conditions between 39 and 59 points (Orange), and burning is not permitted at all if the FDE is above 60 points (Red).
We find that by using this system we have a common understanding of what to expect and what is required for the state of readiness of fire fighting. It also gives us a final check when assessing conditions prior to a programmed (prescribed) burn. This is of special importance because our records show that more than 60% of all wildfires are started in the wake of prescribed fires in savannas and forests. We have also found that the FDE is useful for obtaining an increase of public fire awareness. It has contributed significantly to a reduction of the number of wildfires.
The writer would welcome comments from those individuals or countries who operate similar systems. In particular he would appreciate details of current methods of harnessing meteorological forecast data in the prevention and control of wildland fires.
From: Frank Elias Chairman, Chimanimani Fire Protection Committee Address: P.O.Box 19 Chimanimani ZIMBABWE