Estimating the ecosystem service of Aleutian cackling goose droppings on pastures

• Main Author: Fagundes, Brian G
• Format: Text
• Language: unknown
• Published: Digital Commons @ Cal Poly Humboldt 2022
• Subjects: California; Branta hutchinsii leucopareia; Greenhouse experiment; Rangelands; Conflict management; Natural Resources and Conservation; Aleutian Cackling Goose
• Online Access: https://digitalcommons.humboldt.edu/etd/583; https://digitalcommons.humboldt.edu/cgi/viewcontent.cgi?article=1632&context=etd

The Aleutian cackling goose (Branta hutchinsii leucopareia) experienced a population low of 790 geese in 1974 and has recovered to the current estimate of 186,100 geese in 2021. Private livestock producers view geese as pasture competitors and use hazing and hunting to scare geese from private lands to adjacent public lands. I investigated if geese provide an ecosystem service via dropping fertilizing effects to improve pastures in northern California. A greenhouse experiment was conducted from February-August 2019 at Cal Poly Humboldt, divided into two experiments: freshly sown ryegrass pasture and established plant and soil communities removed intact from pastures. Fresh goose droppings were added at different amounts every two weeks for two months and vegetation hand clipped to simulate grazing by geese in the spring. To imitate the departure of geese during summer, no droppings were added after 14 April, and vegetation was clipped twice to simulate two periods of summer haying by ranchers. Pasture forage production significantly increased with the addition of goose droppings. Average forage weights were significantly higher than the control groups in both the ryegrass pasture system (108-334%) and the established pasture system (12-45%). I measured several soil properties to connect dropping additions with vegetative growth and documented improved soil levels of phosphorus, potassium, and sodium in the ryegrass pasture system. I estimated an ecosystem service for enhanced hay production due to goose dropping additions of $79-$243/acre ($32-$98/ha) for newly sown ryegrass pasture, and $69-$251/acre ($28-$102/ha) on established pasture. Investigating the function of goose droppings on pastures is a first step towards estimating ecosystem services of Aleutian geese, which are benefits currently underappreciated by Del Norte and Humboldt County land managers.