Climate Change and Mosquito Control: The Effect of Atmospheric River Events and California’s Central Valley
Atmospheric rivers, often referred to as “rivers in the sky,” are narrow swaths of concentrated moisture in the atmosphere that can stretch for thousands of miles, capable of moving as much water as 15 Mississippi Rivers. These powerful weather phenomena play a significant role in the distribution of water vapor and are responsible for a large portion of precipitation in the western United States. However, climate change is enabling atmospheric rivers to carry more moisture and occur more frequently. Their hurricane-like conditions can cause devastating floods and landslides, but many people do not know the intricate relationship between atmospheric rivers and mosquito-related emergencies.
Though typically known for its wildfires and droughts, atmospheric rivers have intensified in California over the last 5 years. The state’s response to atmospheric river events in 2023 offers valuable insights into the challenges and lessons learned in managing mosquito populations and mitigating disease risks following weather disasters.
What are atmospheric rivers?
Atmospheric rivers uptake and transport heat and moisture from the tropics to the poles. When multiple atmospheric rivers occurred over California in early 2023, increased moisture led to record-high snowpack in the mountains. The statewide snow accumulation surpassed average levels by 237%, enough to bury chair lifts at many ski resorts. However, a heatwave weeks later triggered rapid melting of the snowpack, overwhelming flood management systems and causing widespread flooding. Subsequently, only 8.5% of the state remained classified under severe, extreme, or exceptional drought, down from 94% in September 2022.
The state quickly assisted local agencies by diverting excess water from populated areas, but the sheer volume surpassed preparedness measures, leading to a Major Disaster Declaration by the President on April 4th. While FEMA provided essential aid, shelters, and equipment to rebuild, another concern began to emerge: the proliferation of nuisance and disease-carrying mosquitoes.
After a natural disaster, mosquitoes are usually not top of mind for states, municipalities, and community leaders. But in the following weeks, mosquito eggs that were previously laid by floodwater mosquitoes in moist soil areas began to hatch. Container-breeding mosquitoes began reproducing in standing water in outdoor debris and containers like gutters, buckets, plant saucers, and ornamental ponds. Though many mosquito species that appear after storms don’t pose an immediate disease threat, nuisance populations impeded recovery efforts and had the potential to become disease vectors if left unmanaged.
How Mosquito Problems Develop After Natural Disasters
In June 2023, VDCI was contracted to begin executing emergency response efforts, which included surveillance, disease testing, and insecticide applications. Both larval and adult mosquito control strategies were utilized in response to the data collected.
As exemplified by this disaster, climate change is increasing the frequency and severity of weather events, from atmospheric rivers to storms and hurricanes. While coastal regions receive the most attention, inland areas are also vulnerable to weather and mosquito-related emergencies. This underscores the importance of emergency preparedness, no matter where you are located.
Effective Emergency Response Planning
Severe weather emergencies often catch us off guard, but proactive measures taken in advance can facilitate rapid response to mosquito-related issues and enhance communication among stakeholders and the public. With the guidance of an experienced mosquito management partner, leaders can meticulously prepare emergency contingency plans, allowing them to focus on other pressing matters when crises occur.
Challenges That Decision-Makers Face
One of the key challenges that decision-makers face during mosquito-related emergencies is the complexity of coordinating various stakeholders, including industry partners, state entomologists, and local entities. Jurisdiction for mosquito control varies widely across regions and states. For instance, local health agencies hold authority in 16 states, while local governing bodies (e.g., city, county, or municipality) oversee it in eight. Additionally, 31 states have statutes allowing special districts or programs to be established for mosquito control. Clarifying these responsibilities ahead of time not only prevents confusion, but also presents a unified front when tackling the emergency.
Moreover, funding concerns can pose significant obstacles following severe weather events. With emergency response budgets stretched thin by post-storm challenges, securing adequate funding for mosquito control efforts creates additional pressure. Urgent needs such as restoring power and clearing roads tend to be prioritized over less imminent problems, so allocating funds in advance can help ensure resources are readily available for mosquito control, rather than scrambling to locate funds at the eleventh hour.
In addition, a mosquito management partner can offer assistance in accessing FEMA funds following a storm. Districts seeking federal aid for mosquito control must prove the need for emergency mosquito suppression. Establishing a comprehensive mosquito abatement program before disasters occur enhances the likelihood of securing this funding. Districts equipped with baseline data from routine surveillance and disease testing can more effectively showcase the surge in mosquito populations, justifying the allocation of funds.
Proactive surveillance also allows professionals to map the physical characteristics of the region, identifying areas that may pose accessibility issues during a disaster, contain endangered species, or be most vulnerable to flooding. After emergency conditions have passed, experts will resume mosquito surveillance and laboratory analyses to verify the effectiveness of their efforts. The gathered data is then disseminated to pertinent authorities and stakeholders.
As climate change escalates the frequency and intensity of weather emergencies nationwide, California’s response to the 2023 atmospheric river events offers valuable lessons in mosquito control and public health preparedness, highlighting the importance of proactive planning, collaboration, and communication.
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Since 1992, Vector Disease Control International (VDCI) has taken pride in providing municipalities, mosquito abatement districts, industrial sites, planned communities, homeowners associations, and golf courses with the tools they need to run effective mosquito control programs. We are determined to protect the public health of the communities in which we operate. Our mosquito control professionals have over 100 years of combined experience in the field of public health, specifically vector disease control. We strive to provide the most effective and scientifically sound mosquito surveillance and control programs possible based on an Integrated Mosquito Management approach recommended by the American Mosquito Control Association (AMCA) and Centers for Disease Control and Prevention (CDC). VDCI is the only company in the country that can manage all aspects of an integrated mosquito management program, from surveillance to disease testing to aerial application in emergency situations.