Nature Bulletin No. 377-A   April 11, 1970
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

****:Grass Fires

Illinois is the Prairie State.  Perhaps we should not mention it here but 
the curious fact is that some of our original midwestern prairies were 
actually preserved as such by fire -- fires started every spring by the 
Indians to drive out the game hidden in that tall thick growth; fires to 
deprive their enemies of cover through which they might creep 
unobserved. Trees and shrubs grew along the streams, on wooded 
knolls or ridges, and in occasional "oak openings", but any woody 
seedlings that managed to get started in the adjacent prairie were 
killed by fire. The prairie plants survived because the sod was so thick 
and they were largely perennials with deep root systems or had other 
protective habits of growth.

In the Chicago region, in autumn and early spring, it was customary 
for people to burn off vacant lots in built-up areas and set fire to the 
grasslands in outlying subdivisions where there were but a few 
scattered homes. When it was windy and the vegetation thick and tall, 
these became leaping crackling flames that raced faster than a man 
can run. Some fires spread into nearby forest preserves and did 
irreparable damage Thousands of acres were left black and bare.

It was a foolish dangerous custom. It originated from the mistaken 
notion that fire destroys the weeds and gives desirable grasses a better 
chance to grow. In outlying subdivisions, isolated home owners burned 
to "improve" the pasture for their cows, goats or other livestock and, 
also, to protect their homes against fires started accidentally or by 
mischievous youngsters when the men were away at work.

It is far better to mow such vacant lots and meadows in early fall, and 
rake or plow a narrow firebreak around adjacent buildings. The 
mowed vegetation protects the soil and, as it decays, adds humus and 
fertility. Burning robs the topsoil of its fertility, kills the valuable 
forage plants such as bluegrass, clover and timothy, and actually 
increases the growth of quackgrass, weeds, and other unwanted, 
troublesome, perennial plants -- most of them introduced from foreign 
lands. Many of these have hardy seeds so well protected that they are 
not destroyed by fire; or vigorous rootstocks that remain undamaged.

There was a time when burning was also advocated as means of 
controlling insect pests. It is now known that burning encourages them 
by destroying beneficial insects, such as those that prey on other 
insects, and by destroying the necessary cover and food for ground-
nesting birds such as the meadow lark, horned lark, bobolink, the 
native sparrows, killdeer, spotted sandpiper, quail, pheasant and 
marsh hawk. Some of these, and their young, feed largely on insects.

Grasshoppers, and other insects pass through the winter as eggs within 
the soil where fire cannot reach them. Others hibernate there as pupae. 
White grubs and wireworms burrow below the frost line. Many insect 
pests harmful to crops -- such as the army worm, chinch bug, corn 
borer and others -- burrow deep into large plant stalks which 
frequently are not consumed by a grass fire.

Fire, admittedly, was an ally of the native plants in our original 
prairies but only a few remnants of them remain. In their place we 
have many pesky worthless weeds and grasses from other countries 
Annual burning helps these spread and replace the valuable Plants we 
need. Fire is their friend.