Botulism Outbreak Strikes Tule Lake Wildlife Refuge Amid Ongoing Water Challenges

“The amount needed to make an impact in the wetlands would lower the overall lake level by about an inch.” KWUA.ORG

In mid-August 2024, a severe botulism outbreak struck the Tule Lake National Wildlife Refuge, part of the Klamath Basin National Wildlife Refuge Complex straddling the Oregon-California border. This outbreak, compounded by cases of avian influenza, has resulted in a significant die-off of migratory birds, bringing to light the ongoing water management challenges in this ecologically crucial region.

The scale of this ecological disaster is staggering. As of mid-September 2024, estimates suggest that between 45,000 and 55,000 birds have perished, with some reports indicating the death toll could be as high as 75,000. At the peak of the outbreak, refuge staff were collecting approximately 1,000 dead birds daily.

The victims are primarily migratory birds using the Pacific Flyway, including northern pintails, green-winged teals, long-billed dowitchers, and American widgeons. The outbreak began with the discovery of avian influenza (H5N1) in several hundred dead and dying eared grebes, which then created conditions conducive to the spread of botulism.

The botulism outbreak is attributed to a perfect storm of environmental conditions:

• Low water levels in refuge wetlands
• Warm water temperatures
• Poor water circulation
• Decomposing bird carcasses from the initial avian influenza outbreak

These conditions create an ideal environment for the soil bacterium Clostridium botulinum to thrive. Birds can become infected after ingesting decaying organic matter or live invertebrates carrying the toxin.

The impact of the outbreak is exacerbated by reduced wetland areas, which have concentrated birds in smaller spaces. Over 75% of the Klamath Basin region has been converted to agriculture, leaving the remaining wetlands as critical havens for migrating birds.

The Klamath Basin is no stranger to water-related crises:

• In 2020, a similar botulism outbreak killed 60,000 birds in the same area.
• Two years ago, the Lower Klamath National Wildlife Refuge, established by Theodore Roosevelt as the nation’s first waterfowl refuge, went completely dry.
• The region has been grappling with prolonged drought, affecting water availability for wildlife, agriculture, and endangered species.
• Dam removal on the Klamath River has been a contentious issue in efforts to restore struggling salmon and steelhead populations.
• The Upper Klamath Lake must maintain certain water levels to ensure the survival of endangered c’waam and koptu suckers, species found only in this area and vitally important to Klamath tribes.

In response to the crisis, wildlife officials and conservation groups have implemented several strategies and are calling for immediate action:

• Diverting additional water from Upper Klamath Lake to the refuges
• Establishing a field hospital (by nonprofit Bird Ally X) to treat and rehabilitate affected birds
• Improving water management with “dynamic operations” to circulate water
• Restoring wetland habitats and hydrologic connectivity in the Klamath Basin
• Developing climate-resilient strategies for future management

However, allocating water to the refuges is a complex issue. While the Upper Klamath Lake’s water level is currently one foot above the end-of-season threshold required by the U.S. Fish and Wildlife Service, every aspect of the region – from endangered suckers to salmon, crops, and waterfowl – needs water.

Despite the current crisis, there have been some positive developments:

• In spring 2024, the Bureau of Reclamation diverted additional water to the refuges to avoid creating unsafe conditions while dam removal on the Klamath River is underway.
• This action resulted in “the highest and most diverse waterbird population we’ve had on Tule Lake in three or four decades,” according to John Vradenburg, Fish and Wildlife Service Biologist for the Klamath Basin Refuge Complex.
• Cooling seasonal temperatures are expected to help slow the progress of botulism.
• The overall success of the wetlands this year suggests that bird populations may not be seriously impacted in the long term.

Vradenburg remains cautiously optimistic, noting, “The wetlands are extremely productive right now, and they should be even better next year as water quality continues to improve. There’s good stuff happening along with the bad stuff.”

The path forward will require innovative thinking, as migratory birds continue their journeys along the Pacific Flyway. The urgency to find sustainable solutions that will protect these vital species and the habitats they depend on has never been greater, with cooperation among diverse stakeholders, and a commitment to long-term ecological health alongside human needs. Only through such comprehensive efforts can we hope to prevent future outbreaks and ensure the survival of these critical wetland ecosystems for generations to come.

(Note: This article is based on information from various sources reporting on the Tule Lake botulism outbreak in 2024 and historical context from previous years.)