Pinpointing Invasive Plants and Protecting the Sonoran Desert

By Jonathan Horst

Sonoran Desert habitat by BongoInc

At Tucson Audubon we recognize that frequently the most important way to protect birds is to protect the landscapes and habitats that support them. These days this often means stopping the spread of invasive plants into a landscape to prevent catastrophic fires that cause the permanent loss of habitat through ecosystem conversion.

When it comes to invasive plants in the Sonoran Desert, the choice boils down to wildfire and its effects (loss of saguaros, and the 14 bird species that nest in them, people's lives and property, and vast sums of money), or treatment. We choose treatment. Tucson Audubon’s treatment philosophy is to use the most ecologically appropriate alternative available for each specific context. That includes an array of tools including manual, mechanical, cultural, and yes, our last resort is chemical.

Please understand we don’t like using herbicides and whenever possible we try to avoid using them. However, along with all the other members of the Sonoran Desert Cooperative Weed Management Area (which includes the Univ. of Arizona, local and federal agencies and municipal land managers, local tribes and conservation groups), we have determined that in many cases spot spraying—pinpoint herbicide application to individual invasive plants—is frequently the most ecologically sensitive and least damaging approach when considering all factors (things like erosion, germination from the residual seed bank, impacts to existing vegetation, and animals, including pollinators.

After over a decade of research and ongoing evaluation, we have determined that glyphosate is the least toxic (to the environment and our applicators) and most effective herbicide option available for buffelgrass and our best chemical option to save Sonoran Desert habitat. Glyphosate is absorbed quickly into the plant and any that dries on the soil surface is quickly degraded by UV light. Because it kills the plant, the chemicals are not translocated into seeds that any birds would be eating, nor does it produce nectar that could be contaminated. As a non-native grass, there are very few insects that eat buffelgrass foliage and any that do will eat healthy growing material, not plants that are sprayed and rapidly drying up. Among larger mammals, native grasses are generally the preferred forage over buffelgrass due to its high silica content and coarse texture.

With the existing lawsuits against Monsanto and the inappropriate ways that RoundUp or other formulations of glyphosate are commonly used, people have a right to be concerned—the vast majority of the uses of these chemicals are unacceptable. Those uses (for instance, blanket spraying of crops or "weeds" in a community) are a far cry from the way we and our partners use it to target individual plants for the protection of our wild areas, natural heritage, and health and human safety.

Rest assured, Tucson Audubon takes great care in treating invasive plants, always choosing the least impactful option. All of Tucson Audubon’s applicators are thoroughly trained and licensed by the AZ Department of Agriculture. And, like you, their primary concern is always the health and safety of our local bird populations.

For the future of the Sonoran Desert and saguaros,
-Jonathan Horst, Tucson Audubon Director of Conservation and Research