- United States I

w Southern

Experime

so-294

May, 1993

A Surved of Rural Population Density and Forest Fire Occurrence

in the South, 19564970

A. T. Altobellis

SUMMARY

Rural residen s comprise a high risk potential

population regarding person-caused wildfire incidence in the So

sity (RPD=numk

th. However, rural population dener of people per square mile) was

found to be ind terminately associated with fire occurrence rate ( OR=number of fires per million

acres protected in protected lands in 13 Southern

states. Thus, c anges in density patterns of rural

residents are p

I

o r indicators of real or potential

wildfire inciden e, and Southern Regional fire problems most likely result from the activities of a small

percentage of t e total rural population at risk.

Keywords: R ,ral residents, risk, fire occurence

rate, rural population density, southern region, fire

incidence.

INTRODUCTION

Forest fire ris is sometimes defined as a function of the prese ce and activity of causative agents

(USDA, Forest ervice 1956). Because it is a prerequisite to ac ivity, presence takes on primacy.

Since we rarely know the actual number of causative agents wit

1

in a given human population, we

ascribe levels of, risk to the presence of these populations in their entirety. That is, we assume everyone

in a given population is a potential fire risk. In this

context, presence can be considered an indicator of

fire-causing activities, hence, potential fire incidence.

In general, woods-burning is a rural cultural practice of long standing in the South (Bertrand and

Baird 1975 Doolittle and Lightsey 1979). Most reported person-caused wildfires, of whatever administratively ascribed cause, are the result of the activities of rural residents, i.e. persons residing in or

close to the areas in which fires occur. A logical extension of this is an assumption that in the South’

rural population size would be a singularly strong

factor in assessing the potential for fires occurring;

that is, the greater concentration of people, the

more fire potential. Indeed, previous research in

selected Southern counties (Doolittle 1972; Hansbrough 1961) has shown direct statistical relationships between fire occurrence and density of rural

populations. But are high rural population densities

consistently associated with high rates of fire occurrence, making density a practical indicator of

fire incidence potential?

A qualified answer to this question was obtained

by considering it in a regional perspective, i.e., surveying macro-level relationships between rural pop-

‘The South as used here includes: Alabama, Arkansas, Florida,

Georgia, Kentucky, Louisiana, Mississippi, N. Carolina, Oklahoma, S. Carolina, Tennessee, Texas, and Virginia.

Southern Fore4 Experiment Station/l-102lO U.S. Postal Services Bldg., 701 Loyola Avenue, New Orleans, La. 70113

Forest Service, U.S. Department of Agriculture.

Serving Alabama1 Arkansas, Louisiana, Mississippi, E. Oklahoma, Tennessee, E. Texas, Puerto Rico, U.S. Virgin Islands

1
ulation density (RPD=number of people per square

mile) and fire occurrence rate (FOR=number of

fires per million acres protected) on state lands under organized fire protection, 1956 to 1970.

METHODS

The period 1936-1970 was selected because it

included three decennial population censuses and

coincided almost entirely with data from Doolittle’s

summaries of forest fire occurrence for Southern

counties, 1956-1965 and 1966-1975 (Doolittle 1969;

Doolittle 1977).

Fire occurrence rates for protected area (counties) in each State by year were available from Doolittle’s data. With exceptions explained later, populaton data for the same area were extracted from

final census reports for States (U.S. Bureau of the

Census, 1960; 1976). The total rural population* was

used to represent protected areas’ fire-risk-potential

populations. Use of this figure assumed general

comparability in the composition-sex, age, birth,

and death rates-of rural populations region-wide.

Yearly intercensal population counts were arrived

at by arithmetic interpolation (Smith and Zope,

1970).

Rural population densities were computed on the

basis of total land area. Except in the cases of a

few large metropolitan areas, which were taken

into consideration, bias introduced by inclusion of

area occupied by urban entities was insignificant.

Also, both RPD and FOR represent an average distribution of people and fires, respectively, per unit

of area. They do not take into account the general

patterns of concentration known to exist with regard to where fire occur and where rural people

reside. Even so, these parameters permit the normalization of size variation when comparing areal

units, e.g., county, state.

The survey, then, was limited to State-protected

areas in the Sotuhern Region included in Doolittle’s

county fire occurrence report summaries. A further

limiting factor to protected area usable for the survey was the unavailability of county level fire data in

some States. For example, data for Arkansas, Cklahoma, and Florida were reduced to four, one, and

14 years, respectively.

lAccording to Bureau of Census definition, rural population is

comprised of those people residing in incorporated and unincorporated places of less than 2500, which includes open

country.

RESULTS

County based data were combined, and RPDs and

FORs for total protected area in each state were

computed by year (table 1). This provided a regional view of RPD along with FOR.

With the exception of Kentucky (15 percent decrease) and Tennessee (nine percent decrease),

changes in RPD in states ranged from none in Louisiana to relatively insignificant for the other States.

Year-to-year fluctuations were minor and in some

states trends were evident.

On the other hand, without exception the FOR

fluctuated markedly in all States during the survey

period. Since fire occurrence is greatly affected by

factors such as weather and a significant (but unknown) amount of deliberateness regarding activities of the potential risk populations, some fluctuation was expected. However, fluctuations were such

as to preclude the emergence of any period trends

in FOR by State. The average regional RPD and FOR

for each year in table 1 serves to illustrate the obvious trend in the former and the lack of any trend

in the latter.

A look at state average RPD and FOR for the entire period in table 1 further reinforces the lack of

association between these two parameters. RPD

averages varied from a high of 55 in North Carolina to lows of 19 in Texas and Arkansas. FOR averages varied from a high of 552 in Louisiana to a low

of 161 in Texas. Only South Carolina appeared in

the highest five as ranked by RPD and FOR, respectively. Louisiana with the highest FOR ranked ninth

in RPD. Virginia with the lowest FOR ranked third

in RPD.

A statistical test of the relationship between FOR

and RPD was conducted on the basis of a ten percent sample of the 990 counties that provided the

data base for this survey. The sample population

was stratified by State, and the 99 samples resulted

from a ten percent random selection within each

State. Average annual RPD and FOR for the survey

period were computed for each sample county, and

a scatter diagram of FOR and RPD was constructed.

By inspection a weak linear relationship was inferred, and a simple linear regression was run on

the data as:

FOR = 181f 2.72 RPD, r= .272

Although the resultant equation had a significant

correlation coefficient (97 degres of freedom), less

than 10 percent of the variation in FOR was explained by RPD.

A. T. Altobellis is a Forester, Southern Forest Experiment Station, Forest Service-USDA, Starkville, Mississippi.

2
Table l.-Rural po/

1956-197

State 1

A L

A R

RPD

FOR

RPD

FOR

FL

RPD

FOR

G A

K Y

L A

M S

N C

RPD

FOR

RPD

FOR

RPD

FOR

RPD

FOR

RPD

FOR

O K

RPD

FOR

S C

RPD

FOR

T N

RPD

FOR

T X

RPD

FOR

V A

RPD

FOR

Region RPD

Average FOR

‘Rural Population D(

acres of protected I

ZData Not Available.

Results of thi

dicate that dens

per se, is at be

the general incic

Southern Regior

that changes in

are poor indicat

cidence. Further

ship between fir

this high risk poi

an assertion abo

fire situation: m

the activities of a

lation at risk.

R

Bertrand, A. L.;

ern forests: a

Mississippi Si

Stn. Bull. 838;

lation densities and fire occurrence rates on state protected lands in the southern region by state and year,

1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1966 1969 1970 State

average

3 1 3 0 3 0 2 9 2 9 2 9 2 9 2 9 2 6 2 6 26 2 6 2 6 2 6 26 2 9

314 201 262 302 295 292 347 532 266 391 334 364 511 450 367 351

2 ,, ,,. .., . . 19 19 16 16 19

‘ii ‘ii ‘24 ‘25 ‘ii’ ‘ii ‘ii ‘iii

231 141

2 4 23 2 3 2 5 2 5 215 226 24 203 24

493 260 266 226 303 362 495 384 288 306 284 392 378

‘3;

457 350

32 3 2 32 3 1 3 1 3 1 3 1 3 1 3 2 3 1 3 1 3 1 3 1 3 1 3 1

354 238 330 298 383 401 365 443 271 288 342 404 480 351 467 381

4 6 4 5 4 8 4 5 4 3 4 2 4 2 4 1 41 40 4 0 4 0 3 9 3 9 3 9 4 2

253 190 226 438 335 163 319 457 267 279 214 215 271 279 210 274

2 5 2 5 2 5 2 5 2 5 2 5 2 5 2 5 2 5 2 5 2 5 2 5 2 5 2 5 2 5 2 5

801 209 393 522 537 302 772 872 506 580 479 797 507 709 509 552

2 9 2 9 2 8 2 8 2 8 2 8 2 7 2 7 2 7 2 7 27. 2 8 2 8 2 6 2 6 2 7

518 328 408 486 459 325 486 828 336 376 480 437 399 435 387 446

5 4 5 4 5 4 5 4 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5

189 135 145 182 173 197 184 276 193 269 280 307 357 233 275 225

,,, .., ,,. .,, ,.. . . . . . 17

.44 .,; ‘4s ‘4s ‘4s .lls ‘4s .46 ‘4s ‘46 .45 .,; ‘45 ‘45 279 45 .qj

431 288 318 306 353 409 360 500 223 318 454 414 575 323 401 378

43 4 2 4 1 4 1 4 1 4 1 4 0 4 0 4 0 3 9 3 9 3 8 3 8 3 9 3 9 4 0

371 188 284 365 292 277 282 441 252 284 329 367 280 255 248 301

2 1 20 2 0 2 0 19 19 19 19 19 19 1 9 19 19 2 0 19 19

501 7 1 136 198 167 9 7 176 242 149 100 6 5 187 8 5 151 8 7 161

4 2 4 3 43 4 3 4 3 4 3 4 3 43 4 3 4 3 4 3 4 3 4 3 4 3 43 4 3

101 75 77 172 108 8 2 115 236 118 172 150 133 187 134 126 132

3 6 3 5 3 5 3 5 3 5 3 5 3 5 3 5 3 5 3 4 3 4 3 3 3 3 3 1 3 1

375 198 261 318 310 284 355 474 261 304 310 354 346 296 312

sity (RPD) = Number of people per square mile. Fire Occurrence Rate (FOR) = Number of fires per million

rd.

DISCUSSION

macro-level survey strongly iny of rural residential populations,

indeterminately associated with

rice of person-caused fires in the

On a practical level this suggests

lensity patterns of rural residents

rs of real or potential wildfire inthe absence of a strong relationoccurrence and the presence of

ntial population tends to reinforce

t the Southern person-cause wild-

;t fire problems are the result of

imall percentage of the total popu-

~FERENCES CITED

aird, A. W. Incendiarism in southdecade of sociological research.

te, MS: Miss. Agric. & For. Exp.

375.40 p.

Doolittle, M. L. Forest fire occurrence in the South,

1956-1965. Res. Note SO-97. New Orleans, LA:

U.S. Department of Agriculture, Forest Service,

Southern Forest Experiment Station; 1969. 16 p.

Doolittle, M. L. The dimensions of man-caused fire

risk: a systematic assessment. Seattle: University

of Washington; 1972. 119 p. Dissertation.

Doolittle, M. L. Forest fire occurrence in southern

counties, 1966-1975. Res. Note SO-227. New

Orleans, La: U.S. Department of Agrciulture, Forest Service, Southern Forest Experiment Station;

1977.41 p.

Doolittle, M. L.; Lightsey, M. L. Southern woods

burners: a descriptive analysis. Res. Pap. SO-151.

New Orleans, LA: U.S. Department of Agriculture,

Forest Service, Southern Forest Experiment Station; 1979.6 p.

Hansbrough, Thomas. A sociological analysis of

man-caused fires in Louisiana. Baton Rouge, LA:

Louisiana State University; 1961. 297 p. Dissertation.

Smith, T. Lynn; Zope, P. E., Jr. Demography: princi3
ples and methpds. Philadelphia, PA: F. A. Qauis tion: number of inhabitants, final state reports.

co.; 1970, 550 /I. Washington, DC: U.S. Department of Commerce;

U.S. Bureau of the Census. U.S. census of popula- 1970.

tion: number of inhabitants, final state reports. U.S. Department of Agriculture, Forest Service.

Washington, DIG: U.S. Department of Commerce; Glossary of terms used in forest fire control. Agric.

1960. Handb. 104. Washington, DC: U.S. Department of

U.S. Bureau of the Census. U.S. census of popula- Agriculture; 1956.24 p.