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NATURAL VIEW: Fire disrupts natural habitats

The Santiago fire, at this time still moving slowly through the Cleveland National Forest, has already burned about two-thirds of the inland 20,000 acres of the Nature Reserve of Orange County.

This includes Limestone Canyon, Whiting Ranch Wilderness Park and 1,000 acres adjacent to the Orange County Great Park, the richest California Gnatcatcher habitat in the state.

The coastal half of the reserve is the Laguna Greenbelt, most of which burned in 1993. If well-meaning agencies refrain from trying to “speed up" the fire recovery this time, the habitat and wildlife populations can reestablish themselves in a few years; but we learned after the Laguna fire that one bird species may need help.

At first glance, burned landscape looks flat and completely barren. Boulders provide most of the vertical relief, and smaller rocks litter the ground and roads. All color is gone; the landscape is rendered in shades of gray and black.

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The shrubs have vanished, and where logs once lay there is only white ash. Here and there are piles of small charred bones. Leafless, blackened oaks and sycamores look like cartoon Halloween trees.

But by 10 days after a burn, tiny green blades of grass have appeared, water flows in the creeks, spider webs blanket the ground, and soft mounds of dirt appear; the pocket gophers are active, munching on underground roots. Vultures soar above the charred landscape searching for carcasses.

It’s a tough time for the small survivors. Ground squirrels, rabbits, lizards, and mice, deprived of cover, are easy targets for their predators: hawks, coyotes, great blue herons, and owls.

Within weeks, the underground root crowns of coastal sage shrubs send up tender, protein-rich sprouts relished by mule deer returning from unburned refuge areas. Given a normal winter rainfall to allow seeds to sprout, wildflowers will carpet the hills next spring.

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Among them are rare plants that we see only after fires, called “fire followers." Even unusual mushrooms appear the first year after a fire. The abundance of flowers and seeds supports insects, birds, and small mammals.

Among the refugees from the fire are two sensitive bird species for which the reserve was first established: the California gnatcatcher and the coastal cactus wren.

After the 1993 fire, monitoring research revealed that the number of gnatcatchers in the burned area returned to pre-fire numbers. The cactus wren population, however, is still very low: only 13-15% of pre-fire numbers. The difference stems from their different habits. The gnatcatcher is a tiny gray bird with a black cap that nests in local sagebrush.

The cactus wren is twice the size of the gnatcatcher, with a white eye stripe and boldly speckled breast. Wrens live in family groups in tall cactus. And here’s the problem: They build their football-shaped nests only in prickly pear or cholla cactus taller than three feet.

After a fire, the sagebrush comes back within a couple of years, but cactus take much longer to reach the minimum height for a cactus wren nest. In the 1993 burn area, the majority of the cactus is still too small.

Adequate unburned refuge areas, like Aliso Woods Wilderness Park in 1993, allowed most wildlife to return and recolonize the burned area within a few years. But cactus wrens depend on slow-growing cactus for their nests.

Returning birds survived in the burned area, but did not reproduce. After a few years, the fire veteran generation had all died, leaving no offspring.

If we don’t want this same fate for the inland cactus wrens, this time we will have to intervene. But only in this limited situation.

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ELISABETH M. BROWN is a biologist and the president of Laguna Greenbelt Inc.


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