I ask Ritter about Sweet Springs. He hates to see big trees taken down, he says. But at the same time, he supports well-designed native plant restorations and considers Audubon's Sweet Springs plan to be one. "If you remove some of the eucalyptus and plant 10 to 15 species of native plants in their place," he says, "you should end up with a more stable and diverse ecosystem."

Back at Sweet Springs, I walk from the central part of the preserve, with its towering eucalyptus, to Sweet Springs East, the eight-acre tract that Audubon acquired in 2008.  Slightly under half of it consists of wetlands, including a luxuriant salt marsh that borders the Morro Bay estuary. Higher up is an open expanse, now covered in veldt grass, which used to be native dune scrubland. This is the core of the area the Audubon Society wants to restore.

Ripping into the veldt grass, shovel in hand, is David Chipping, a retired Cal Poly geologist who is also president of the local chapter of the California Native Plant Society. He points to a row of blue gums along the boundary with the main preserve. "Audubon's idea was to target the trees along the edge of the wash there," he says. "You can't see it now, but wintertime, those eucs plunge almost all of this into shade, when, for these natives, it's meant to be sun all around." The blue gums hamper restoration in other ways as well, smothering plants with bark and leaf litter. They also reseed themselves and require regular weeding.

Around two dozen of the roughly 120 blue gums here are still small enough to be removed without a permit. The others fall into a different category. Some look to be almost 100 feet tall, with trunks as sturdy as the columns of a courthouse and outer bark that peels away to reveal a multi-hued inner layer. Many people like them, Chipping acknowledges. Nor do they lack ecological value. Consultants hired by the Morro Coast Audubon Society have confirmed that monarch butterflies and raptors, including great horned owls and red-shouldered hawks, make at least occasional use of the blue gums in Sweet Springs East.

No wonder that people who agree about other issues, such as the importance of open space, disagree so sharply where blue gums are concerned. "It's simply different values, and it's hard to say what's absolutely right and what's absolutely wrong," Chipping says. "I'm so worried about the species we're destroying that I'm on one side here. I'd just like to see a native ecosystem at Sweet Springs that is relatively intact and that helps support pollinators like the Morro blue butterfly and all the other animals that might otherwise disappear."

At the end of the day, after Chipping and the other volunteers have left, the veldt grass they've pulled sits stashed in bags, awaiting composting. To the west, the contested line of blue gums reaches for the sky. A football field away, hundreds of newly planted natives – mock heather, dune buckwheat, sand verbena, California croton – are starting to settle in.

In November, a couple of months after visiting Sweet Springs, I learn that the Morro Coast Audubon Society board backpedaled on its plan to remove blue gums. While approving the removal of small trees – those with trunk diameters of eight inches or less – it took the larger trees off the table. Flagged as exceptions to be considered on a case-by-case basis were trees that pose risks to life or property. Otherwise, the board left open the possibility of pursuing a broader tree removal at some later date, assuming sufficient "money, patience and time." For now, it seems, an uneasy truce prevails between the blue gums, the natives and the people fighting passionately for the future of them both.