On Mount Lemmon, 10 volunteers turn loose rocks into small dams

I like the phrase the volunteers use for the stones they gather on Mount Lemmon: "unemployed rocks." It sounds playful until you see the work. On Aug. 2, 2026, 10 people climbed the Crystal Spring Trail with the nonprofit Sky Island Alliance, looking for loose rocks they could fit into the mountain's natural drainages. They were building small structures to slow water, hold soil, and give a burned landscape a little more time to recover. 1

A rock rundown is a low-tech erosion-control structure. Volunteers place stones across a drainage so water slows as it moves downhill. The structure catches soil and debris that might otherwise travel into streams, city washes, and rivers. 1

The need grew after the Bighorn Fire burned almost 120,000 acres of the Santa Catalina Mountains in 2020. With trees and plants gone, bare soil became more exposed to heavy monsoon rain. Sky Island Alliance began working with the Coronado National Forest to map areas that needed help. Since 2023, the organization and its volunteers have built more than 500 erosion-control structures near springs on Mount Lemmon. 1

The repair is deliberately modest. A stone wall will not restore a forest on its own. The point is to start a chain of small changes: a structure slows water, sediment settles, and plants gain a place to take root. Those roots can hold the soil more firmly, shade the ground, and help it retain moisture. One storm can fill a new structure with sediment and create a terrace that slows the next flow. 1

The volunteers did not simply stack whatever stones they could lift. Sky Island Alliance field technicians Becca Thompson and Andres Martinez marked locations with red flags and explained how to choose rocks without digging out new patches of soil. The group mapped each finished structure so the organization could revisit the sites and track the work. 1

The day also had its own small vocabulary. Someone called "Water!" when it was time for everyone to drink and rest. "Rock!" warned the group when a stone started moving downhill. The practical reminders fit the whole project: restoration here depends on attention, repetition, and people noticing what the person beside them needs. 1

Ella Marshall first joined a Mount Lemmon work trip about a year earlier. She has returned for about 10 volunteer trips since then. At first, she wondered whether a few dozen structures could matter across such a large mountain. Later, she saw that earlier structures had caught debris, and she noticed a small oak growing from one of them. 1

Her reason for coming back was practical and human. She had fun. She could see the work when she returned. "If we even helped this one drainage, then that's fine," she said. 1

Orion Leslie carries a different connection to the same place. His mother brought him to Mount Lemmon after moving the family from the Four Corners region of the Navajo Nation to Tucson. He later took his own children camping there. Leslie joined Sky Island Alliance because he wanted to give time back to the landscape that had helped shape his life. 1

The work will remain vulnerable to fire, rain, and time. The volunteers know that. They keep going anyway: one marked drainage, one fitted stone, one weekend at a time. At the end of the day, they walked past a burned tree trunk that could still fall into the channel. Around it, the mountain held the record of what had been lost—and the smaller, quieter record of people helping it grow back. 1