Dear HCN,
Congratulations on the
Sid Goodloe story (HCN, 4/15/96), which stuck a cattle prod into
conventional narratives.
I need to explain my
sure-to-be-maligned comments about saguaros. I lump them, properly
I think, with “woody” plants. But I do not mean to imply that they,
like piûon-juniper, have exploded over the landscape. They
have always been around.
To my knowledge, no one
knows the fire history of the Sonora Desert. Certainly, the desert
can burn (driven by winter rains, not as in the mountains by summer
drought). I would guess that an average site would experience three
fires a century, some places more, some less. Saguaros survive
light burns readily and their fire adaptations have been recorded
by a British (!) ecologist. But they succumb to the fire-girdling
that can result when woody plants and debris build up around them
and hold flame.
Last summer a lightning-caused
fire blasted the McDowell Mountains Park in north Scottsdale. Was
this event within historic ranges or not? Yes and no. I believe its
occurrence was perfectly normal but its effects probably abnormal
due to an excessively “woody” landscape composed largely of shrubs,
low-growing trees, and (probably) an increased density of
succulents.
In the absence of any evidence to the
contrary, it seems to me that the most plausible narrative is that
the Sonora desert restates the larger fire narrative of the
Southwest: overgrazing and drought pummeled the prior biota, woody
plants have replaced grasses, that fires burn less frequently but
with greater intensity. Worse, the niche vacated by indigenous
grasses and ephemerals has filled with exotic pyrophytes like red
brome, which support flash fires. Wildfire from roads and housing
developments is now pushing into the desert like a bow
wave.
Steve
Pyne
Phoenix,
Arizona
Pyne is professor of
history at Arizona State
University.
This article appeared in the print edition of the magazine with the headline More about saguaros.
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