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Remote sensing technology has detected what could be a win for both spotted owls and forestry management, according to a study led by the University of California, Davis, the USDA Forest Service Pacific Southwest Research Station and the University of Washington.

For 25 years, many forests in the western United States have been managed to protect habitat for endangered and threatened spotted owls. A central tenet of that management has been to promote and retain more than 70 percent of the forest canopy cover. However, dense levels of canopy cover leave forests prone to wildfires and can lead to large tree mortality during droughts.

In , scientists found that cover in tall trees is the key habitat requirement for spotted owl — not total canopy cover. It indicated that spotted owls largely avoid cover created by stands of shorter trees.

“This could fundamentally resolve the management problem because it would allow for reducing small tree density, through fire and thinning,” said lead author Malcolm North, a research forest ecologist with �鶹��ý’ John Muir Institute of the Environment and the USDA Pacific Southwest Research Station. “We’ve been losing the large trees, particularly in these extreme wildfire and high drought-mortality events. This is a way to protect more large tree habitat, which is what the owls want, in a way that makes the forest more resilient to these increasing stressors that are becoming more intense with .”

Measuring a million acres

The previous tree canopy guidelines were largely drawn from past studies showing that spotted owls were more prevalent in forests with 70 percent or higher tree canopy cover. But those studies could not distinguish whether the presence of tall trees or high canopy cover were more important to the owl.

For this study, scientists at the University of Washington used the relatively new technology of light detection and ranging imaging, or LiDAR. The tool uses laser pulses shot from an instrument mounted in an airplane to measure a forest’s canopy in detail. The study’s authors used it to measure the height and distribution of tree foliage and forest gaps across 1.2 million acres of California’ Sierra Nevada forests.

Researchers used LiDAR imaging, such as this point cloud representing good habitat for spotted owls, to determine that tall trees rather than total tree cover are most important for spotted owls. (Credit: Jonathan Kane/University of Washington) 

“Field-based studies of forests are expensive and time-consuming, which means that measurements are generally taken over areas