managed by all agencies in the other States is 

 slightly more than 3 million. The area burned 

 per fire in Alaska averages some 4,400 acres, 

 whereas, on lands protected by all agencies in 

 other States, the area burned averages only 30 

 acres per fire (fig. 43). 



Number of Fires 



The number of reported fires in Interior 

 Alaska is only 1.1 per million acres protected, 

 while for all protected land in the other States 

 the number is 168 (fig 44). The low number of 

 fires per unit area protected is in sharp contrast 

 to the acreage burned per fire as noted in the 

 preceding paragraph. 



Severe and Light Fire Seasons 



Number of fires. — In comparing numbers 

 of fires between severe and light seasons, we 

 note that each protection group faces comparable 

 difficulties. In numbers of fires, Alaska shows a 

 ratio of 3 fires in a heavy season to 1 in a light 

 season, whereas in other States this ratio is 

 about 2 to 1 (fig. 45). Also, at least for the period 

 of record, both the severest and the lightest sea- 

 sons in Alaska were not the same years as the 

 severest and lightest seasons in other States. 



Acreage burned. — The difference between 

 acreage burned in severe and light years in 

 Alaska is far greater than the difference in acre- 

 age burned in severe and light years in other 

 States. The ratios are approximately 1 35 to 1 

 and 5 to 1, respectively. In Interior Alaska the 

 greatest number of fires is 1.6 times normal and 

 the area burned is 4.6 times normal, as opposed 

 to 1.3 and 2.2 for all protected land in the other 

 States (fig. 45). The data indicate that an over- 

 load of fires causes more destruction in Alaska 

 than in the other States. 



The area burned per fire is another indica- 

 tor of the greater damage encountered in In- 

 terior Alaska than in other States when fire- 

 weather conditions become critical. In Interior 

 Alaska a fire may then become 3 times as large 

 as in a normal year and 62 times as large as in 

 an easy year. Suppression forces on protected 

 land in other States have been fortunate in hav- 

 ing sufficient strength to confine the ratio to 1.2 

 and 2.8, respectively (fig. 46). The percent of 

 fires that exceeds Class B size — 10 acres — in 

 worst, normal, and easy years does not vary 



greatly between areas (fig. 47); the great differ- 

 ence comes in the size of the fires that do exceed 

 10 acres, as noted above. 



Number of Fires by Specific Cause 



Lightning causes 24 percent of all fires in 

 Alaska and 35 percent in the other States. A 

 year-by-year record, however, indicates that the 

 apparent ratio of lightning fires to others in 

 Alaska is gradually increasing; this is probably 

 a result of more accurate reporting procedures. 

 Campfires cause 27 percent of all fires requiring 

 suppression action in Alaska, but only 4 percent 

 in other States. Also, in Alaska 21 percent of the 

 wildland fires are caused by debris burning com- 

 pared to 14 percent in the other States (fig. 48). 

 This indicates the same type of activity in Alaska 

 that occurred in Montana and northern Idaho in 

 the late 1920 s and early 1930's when consider- 

 able land was being cleared. 



Number of Fires by Size Class 



A greater percentage of fires is of Class A 

 size (one-fourth acre or less) on Interior Alaska 

 lands than on lands protected by the Bureau of 

 Land Management in the other States — 42 

 percent compared to 19 percent, respectively. 

 Both Alaska and other States show a larger per- 

 centage of Class E fires (larger than 300 acres] 

 than Class D (100-300 acres). Records indicate 

 that if a fire is not controlled by the time it 

 reaches 300 acres in size, it may not be con- 

 trolled until it reaches several hundred or even 

 several thousand acres (fig. 49). 



Number of Fires per Million Acres Protected 



Fire occurrence per million acres protected 

 in Interior Alaska is low compared to that in 

 other States protected by BLM; an average of 

 only 1 fire per million acres occurs annually on 

 Alaskan land while nearly 5 fires per million 

 acres occur on other BLM lands (fig. 50). This 

 occurrence ratio contrasts strikingly to the aver- 

 age acreage burned per fire: 4,400 acres in In- 

 terior Alaska versus 267 acres on other BLM 

 lands (fig. 46). 



Area Burned According to Fuel Type 



The rate-of-spread and resistance-to-control 

 characteristics of fires in Interior Alaskan vege- 

 tation is described in reference to cover types 

 instead of fuel types, as explained in chapter 4. 



50 



