The native forests of Patagonia (Argentina) are located east of the main Andean divide along the Cordillera in a narrow, partly continuous strip which is approximately 30 – 80 km wide and more than 2000 km long. The forests cover an area of approximately two million hectares and are distributed over the five provinces Neuquén, Rio Negro, Chubut, Santa Cruz and Tierra del Fuego. The Andean ridge creates a climate divider east of which the drying effect of Foehn winds lead to a sharp decrease of precipitation from West to East. For instance, the amount of precipitation dwindles from 4,000 mm in the high altitudes to 250 mm in the vicinity of Esquel (Chubut) which is located in the Andean foothills.
The climate diagram of Esquel (Fig.1) illustrates the extreme precipitation deficit, especially during the summer months. There are often several months of dryness between the individual rainfall events. In 1987, for instance, 59 days were without precipitation. Furthermore, the region is subjected to the strong Patagonian winds.
These climatic conditions lead to extreme wildfire risk in the whole region. The forest fire season starts in October during which thousands of hectares of ‘matorral’ (shrubland) are often burned within a few days. Most of the large forest fires occur in the month of February (Fig.2). The frequency correlates with the climate diagram shown in Figure 1. In autumn, which normally represents a low in the fire season, fires can be found in the forests of Nothofagus pumilio. These native forests store immense amounts of decaying and partly dead timber (> 100 t/ha). The relative moisture content of this thick material reaches a critical value of less than 20 percent only after a long period of dryness.
Organic material accumulates in all types of vegetation. The process of humification through microorganisms is slowed down because of the dryness in the summer and the coldness in the winter. While the grasslands have accumulated about 12 t/ha of dead organic matter after 15 years of non-grazing, the humus layer in the forested areas may reach 30 t/ha or more.
One would have expected a certain adaptation of the endemic vegetation towards forest fires; at least in a few species. However, this is not the case. Especially towards the borders of the prairie, the forest fires cause either total damage or prolong the recovery and succession process immensely. A reason for this could be that natural fire causes account for less than one percent of all fire starts. Lightning storms are extremely rare, although a slight increase has been detected over the past years. The main origin of forest fires remains human. The break-down of forest fire causes is shown in Figure 3. The settlement of the region by European immigrants, which began about 100 years ago, was associated with large forest fires. Hundreds of thousands of hectares of forest disappeared in this way along the prairie, especially in the frontal Cordilleran. Today, tourism contributes to the fire-caused losses.
The climatic conditions in the three northern provinces of Patagonia are similar which can result in concurrent, large forest fires. The largest wildfires destroying over 25,000 ha of forest were registered in 1987. Cooperative support during such catastrophic fires is not achievable. However, the average fire season is not quite so spectacular. Statistical data of the extent of forest fires (excluding grass and shrub vegetation) in Chubut Province are given in Figure 4.
Over the past ten years 25,000 ha of forest have been destroyed by fire in the province of Chubut. The smaller forest fires which make up the majority of all fires (71%) affected only 1,200 ha. Large forest fires represented by only five percent of all the fires devastated 75 percent of the area (Fig.5). The number of forest fires has increased steadily. It tripled over the last ten years.
Approximately 200 people are employed in the vast, thinly populated areas to fight fires during the fire season. They are often not adequately equipped for fighting the fires on the ground. The efficiency not only suffers from the lack of personnel, but also from the low standard of infrastructures (including vehicles and roads), and inadequate communication systems as well as the lack of aerial support.
Fig.1. Climate data (average of the past 50 years) of Esquel, Chubut Province, Argentina.
Fig.2. Annual distribution of forest land affected by fire during the period 1984-1991, Region S.C. de Barlioche, Argentina.
Fig.3. Causes of forest fires, Region S.C. de Bariloche, Argentina.
Fig.4. Forested area affected by fire between 1982 and 1991, Province of Chubut, Agentina.
Fig.5. Number of forest fires and area affected by fire during the period 1982-1991, Province of Chubut, Argentina.
Under the impact of the destruction of the native forests (not only through forest fires) the forestry centre CIEFAP (Centro de Investigacion y Extension Forestal Andino Patagonico) was founded in January 1990. It is financed by the three provinces of Patagonia, and the National Universities of Patagonia and Comahue and also receives development funds from Germany (GTZ). The main objectives of the institute are broad research subjects, one of which is forest fires. The main research objectives are:
Fire ecology of the native forests of Nothofagus pumilio and Austrocedrus chilensis. One main topic is the regeneration of the forests after fire.
Fire Management: The main emphasis here lies in the study of prescribed burning for wildfire hazard reduction (fuel reduction), mainly in pine plantations.
Increasing the efficiency in fighting forest fires in the region Andino-Patagonico. This includes topics such as public relations, the organization of courses, introduction of forest fire management maps and the improvement of fire detection. Additional goals are the development of a fire danger rating system and fuel models.
At this time only 35,000 ha are planted with pine species. The potential area for plantations is estimated to be 2.5 million hectares in Patagonia alone. Forest fires are going to gain in significance even if only a part of the potential plantation area will be afforested. Are the large fires still to come?
From: Paul Cwielong and Norberto Rodriguez Address: Centro de Investigacion y Extension Forestal Andino Patagonico (CIEFAP) C.C. 238 RA-9200 Esquel, Chubut