Fire in Land Use and Management' 
 
Herbert C. Hanson 
Causes of Fire 
In ecology fire is usually classified as a biotic factor because man is in

most cases, the causative agent. It should also be classified with climatic

factors because fire may be due to lightning and less frequently to sponta-

neous combustion, meteors, materials ejected from volcanoes, and by friction

developed by avalanches, falling boulders, and possibly by tree branches
or 
bamboo canes rubbing against each other in the wind. 
Averill and Frost (1933) have named the following causes of man-made 
fires and the percentage for each cause in the timberlands of Massachusetts

from 1926 to 1931 inclusive; smokers 35.0 per cent, railroads 25.0, children

11.0, brush burning 10.0, incendiary 6.4, rubbish burning 5.1, miscellaneous

4.0, grass burning 2.0, campers 0.7, dwellings 0.6, fishermen 0.2. Of the
total 
number of 2230.4 fires during this period, lightning started only 0.4 per
cent. 
For Minnesota forests Mitchell (1927) has contributed the following table:

1916-20         1921-25 
Land clearing ------------------------------------29.7%             26.3%

Railroads --------------------------------------- 24.7          20.1 
Campers and smokers        ------------------        15.4           23.2

Miscellaneous ------------------------------------   30.2           30.4

100.0%          100.0% 
Lightning was responsible for less than 1 per cent and incendiarism for about

3 per cent. In California, however, lightning caused about 41 per cent of
the 
10,476 fires on and adjacent to 12 timbered national forests from 1911 to
1920 
inclusive. Campers were responsible for about 20 per cent, incendiaries 17,

unknown 6, brush burning 3, miscellaneous 4, lumbering 6, railroads 3. The

following data are available for forest fires in Michigan (Mitchell &
Sayre). 
1918-1922       1923-1927 
Land clearing ----------------------------------- 28.3%           25.0% 
Railroads --------------------------------------- 20.1             19.4 
Campfires-                                         26.5             S17.0

Sm okers                                           2 ---------------------.
5.   (24.1 
Incendiary ---------------------------------------  3.1             3.6 
Lightning ---------------------------------------  1.8              1.2 
L u m b e rin g  . . . . . . . . . . . . . . . . . . . . . . . . . . ...
. . . . --- - - - -  4 .6   1 .2 
Miscellaneous ------------------------------------- 15.6            8.5 
Unknown --------------------------------------- 21.4              27.82 
T o t a I ----------------------------------- 100.0%          100.0% 
1 One of the papers given as the joint symposium of the American Association
for 
the Adv. of Science and The Ecological Society of America at Ottawa, Can.,

June, 1938. 
2 Unknown prorated among other causes, railroads excepted. 
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