DR. LAURA JACKSON'S Toyota pickup barrels down Route 87 south of Casa Grande. The young scientist, a sturdy Midwesterner with a thick braid the color of Kansas wheat, has the windows rolled down so she can point out the cancers that afflict abandoned farmland: last year's tumbleweed, black and clotted in the fields; mustards and stork's-bill, ephemeral winter weeds that will dry up and blow away with this summer's heat, leaving baked and cracked clay flats.
If the landscape is monotonous, the commentary is not. There's a couple of mesquite," she says, pointing out an anemic bristle rising above the weeds. There's some creosote...that's a good sign."
She pulls a hard right onto a dirt road. A roadrunner explodes from the undergrowth, flutters frantically in front of the truck and disappears into a hedge of burroweed, a noxious little bush that was once rare to these parts but that now chokes out other local flora.
Jackson, 30, is a research ecologist for Desert Botanical Garden. She's working on a desert-restoration project funded largely by the Heritage Fund. Specifically, she's trying to learn how abandoned farmland can be returned to some semblance of its original state.
Restoration ecology is a promising and optimistic new disciplineÏat least as it pertains to prairie and wetlands. Lowland Sonoran saltbush scrub has always demanded a bit more vision and a higher threshold for heartbreak.
Farmers migrating west early in the century assumed that with a little water, hard work and Yankee ingenuity, they could do with the desert what they had done elsewhere. And so between 1917 and the early 1950s, they planted cotton and melons and pecans in the Santa Cruz flats south of Coolidge. When their finances and enthusiasm dried up with the water supply, they moved on, leaving the land to return to its natural stateÏexcept that Sonoran desert scrub, once tamed, doesn't make the ecological round trip so readily as the prairies or boreal forests of the farmers' experience. The climate is too harsh, the soil too arid, the seed sources too far away. Instead of reverting to scrub, it falls victim to opportunistic weeds that steal the spring rains, then burn out with the summer heat, leaving the soil exposed and at the mercy of the wind, and leaving the native animals without the food or habitat with which they evolved.
Of the 300 square miles that Jackson surveyed here in Pinal County, at least 60 square miles are abandoned fields; by some estimates, there are as many as 2.2 million acres (about 3,500 square miles) of abandoned farmlands in the five southern Arizona counties. As Jackson points out, It's a mess you can see from space," a barren blotch picked up by Landsat cameras.
It's ugly from the ground, too, flat and monochromatic brown in summer. If it's not prime for farming, it's not good for grazing or animal habitat, either. About all you can do with it is drive through it on your way from one small, depressed town to another. You turn the radio up louder to distract yourself and don't notice the lack of scenery until the wind whips it up into a dust storm. DESERT VEGETATION depends so much on serendipity it's a wonder it exists at all. Wolfberry bushes sprout under trees or wires where a bird perched and defecated undigested berry seeds. Mesquite seeds travel in coyote scat. Creosote bushes advance in slow waves of seeds dropped by rodents, and then only germinate under rare conditions. Saltbush seeds just drop and rot unless they're washed on by floodwaters. Now, with the vast expanse of cultivated fields, sometimes the nearest seed sources of native species are in relict stands miles away, distances they can't travel alone.
In the desert, everything is held hostage by water. Once upon a time, the rains and the rivers went where their momentum carried them, sometimes jumping their banks to wander and whiplash across flatsÏrecharging groundwater and depositing seeds and moisture as they wentÏother times going underground or drying up altogether. They've long been tamed, confined to channels, trained to travel through irrigation canals. In its natural state, every ridge and roll and hummock of the land would route or delay or hold water where plants could take root. But the fields were plowed level, surrounded by ditches that might as well be moats.
This is not to say that farming is an affront to nature, but rather that it changes the circumstances of nature, and makes the accident of germination even more accidental.
Jackson's pickup stops abruptly on a deserted, blacktopped two-lane. Now look to the left, look to the right," she says. North of the road is virgin desert scrub, give or take a few empty beer bottles. The vegetation is thick: chest-high saltbush with rubbery thin leaves wavering in the breeze, greasewood thickets. The soil is sandy, dotted with black lichens and tiny wildflowers. This is how the land is supposed to look.