Could Climate Change Impact the Mosquito-Human Disease Ecosystem?

Background Information for Teachers

This section contains a quick review for teachers of the science and concepts covered in this lesson.

Mosquitoes thrive in warm, wet habitats. Because of this, scientists are worried that as global temperatures rise due to climate change, mosquitoes will expand to new regions that were previously too cold. This poses a threat to human health since mosquitoes can carry diseases like malaria, West Nile virus, and Zika virus. The resources in the Additional Background section contain more information about mosquitoes, their habitat, and the potential effects of climate change.

In this lesson, your students will access data from the National Ecological Observatory Network (NEON). NEON consists of a network of sites around the U.S. where a wide variety of ecological data is recorded, including counts of different mosquito species found in traps set by scientists. This will allow your students to explore the effects of weather on mosquito populations. For example, Figure 1 plots total mosquito count and average monthly temperature on a dual-y-axis graph for a single location. From this graph, you can see that mosquito populations are highest in the warmer summer months. Figure 2 shows a scatter plot of the same data with mosquito count on the y-axis and average monthly temperature on the x-axis. Table 1 shows mosquito species (and the diseases they carry) that were found in a cold, northern location and a warm, southern location over a span of several years.

It is very important to remember when looking at all this data that correlation does not imply causation. In other words, just because two variables appear to be related, it does not mean that a change in one causes a change in the other. There can be many other variables not present in this data that could affect mosquito populations. For example, governments may enact mosquito control programs that include spraying pesticides or other mitigation efforts. A flood, hurricane, or other natural disaster could result in unusually high amounts of standing water—prime breeding ground for mosquito larvae. In this project, your students will not be doing a controlled experiment where they breed their own mosquitoes. However, they can certainly do background research on relevant topics, and present a scientific explanation for why they do or do not think there is a causal link between two variables.

Additional Background Links

• Mosquito Habitats, Orkin
• Oh, the Places Mosquitoes Will Go!, Citylab
• Climate change and mosquito-borne diseases in China: a review, Global Health
• NSF NEON | Open Data to Understand Our Ecosystems, National Ecological Observatory Network
• Mosquitoes and the Diseases They Transmit, Texas A & M AgriLife Extension

Prep Work (15 minutes)

Familiarize yourself with how to select and download data from the Simplified NEON Data Download Tool.

Engage (5 minutes)

Remote learning adaptation: This lesson plan can be conducted remotely. Students can work independently on the Explore section of the lesson plan using the Student Worksheet as a guide. The Engage and Reflect sections can either be dropped entirely, done in writing remotely, or be conducted over a video chat.

1. Start the lesson with a discussion about mosquitoes in your area and your students' experiences with mosquitoes. Here are some example questions you can use as prompts:

   Has anyone ever been bitten by a mosquito?

   When and where are mosquitoes usually "the worst"?

   Have you ever traveled to a place that had more (or fewer) mosquitoes than your home? What was different about that place?

   What are some ways you try to avoid or get rid of mosquitoes?

   Answers to these questions can vary quite a bit depending on where your students live. Answers may even vary between students in the same school. For example, maybe one student lives closer to a pond that acts as a mosquito breeding ground. Maybe you live in a cool or dry climate, but some students have been on vacation to warmer/wetter areas with more mosquitoes (or vice versa). Students might know that they can avoid mosquitoes by staying inside, using mosquito netting when outside, or using bug spray; but might also know that they can help prevent mosquitoes from breeding by preventing standing water from accumulating around their house.

2. Explain that mosquitoes are not just annoying pests—they can also carry and transmit diseases that are dangerous to humans. In this lesson plan your students will analyze data about real mosquito populations, collected by scientists at locations around the United States as part of the National Ecological Observatory Network (NEON). They will examine data to determine factors that could impact the spread of these diseases.

Explore (2 hours)

1. Have students start out by researching the life cycle of the mosquito and factors that affect it. This can be done as a homework assignment. You can direct students to the references in the Teacher Background section to get started.
2. Next, students should briefly do research on the types of diseases that can be carried by mosquitoes, and the mosquito species that carry these diseases. They do not need to worry about understanding the symptoms of and treatments for the diseases, that is beyond the scope of this lesson.
3. Based on their research, students should make a hypothesis about how temperature affects mosquito populations.
4. Walk students through using the Simplified NEON download tool to access mosquito population data.
   1. The tool allows you to download a spreadsheet for each location where NEON collects data.
   2. On the "Basic" tab, the spreadsheet contains columns with monthly totals for different mosquito species found at the site, along with climate data (average monthly minimum, average, and maximum temperature; and total monthly rainfall collected from two sensors—one on the ground, and one mounted on a tower).
   3. The "Advanced" tab contains the same data, but the mosquito counts are broken down by habitat type, such as "evergreenForest" vs. "mixedForest."
   4. Note that data is not always collected for every month. For many locations, mosquito traps are not collected in the winter. Rainfall and temperature sensors may also malfunction and fail to report data.
   5. Rainfall and temperature sensors may also malfunction and report erroneous values. Students should use common sense when looking at the data. For example, if the spreadsheet says that there was only 1 inch of rain in Alabama for the entire year, or that the average temperature in Maine in January was 212°C (100°F), the sensor data is probably wrong.
   6. Make sure your students are comfortable downloading and navigating a spreadsheet before you proceed.
5. Students should choose two locations that they believe have different climates, and download the spreadsheets for both locations. If either location is missing a large amount of data, they should choose a different location. After downloading the spreadsheets, students should make two graphs for each location. Students who need help making graphs in a spreadsheet program can watch one of the videos below, assignable in any LMS. Note that most of the videos show how to graph data that is already in adjacent columns. To select non-adjacent data, hold down the CTRL key on Windows or the Command key on Mac.
   1. A scatter plot of the total monthly mosquito count on the y-axis ("Total" column on the "Basic" tab) vs. the average monthly temperature on the x-axis.
   2. Line graph showing total mosquito count and average monthly temperature on the y-axis vs. month on the x-axis.

   Do you see any correlation or trends in your data?

   Students should see that, while it is not a perfectly linear relationship, in general there is a positive correlation between temperature and mosquito population. Below a certain temperature, there are no or very few mosquitoes. Students might see a decline in the population at extremely high temperatures, as these temperatures often come with low humidity and little standing water, causing mosquitoes to dehydrate and die without reproducing.

5. Next, students should make a data table comparing the mosquito species found at each location. Note that you cannot directly compare the absolute number of mosquitoes counted between different locations, as different locations may have different numbers of mosquito traps that are collected at different frequencies. Instead, students can represent each mosquito species as a percentage of the total mosquitoes collected at that location.
   
   
   Swipe left to see more

   Mosquito Species	Human Disease(s) Carried	Warmer Location (% of total count)	Cooler Location (% of total count)

   Table 2. Example data table for comparing percentage of mosquito species found at different locations.
   
   
6. Explain that climate change is leading to new climate patterns around the world. Online tools like this Climate 2050 page allow us to predict what the climate may be like at different locations in the future. Students should look up the climate prediction for both of their locations several decades from now.
7. How will the climate change at each location? Write a paragraph explaining what effects you predict this change will have on mosquito populations and human disease. Be as specific as possible, use your data as evidence, and explain your reasoning.

Reflect (15 minutes)

As a class, summarize and discuss the following points:

• What students learned about the mosquito life cycle and diseases that mosquitoes carry.
• Trends that students discovered when using the NEON tool. How does data compare between students or groups who analyzed different locations? Did they all identify similar trends?
• Mosquito species that students identified at different locations. Again, how does data compare between groups? Is there a trend across the entire class, i.e. certain species that were only identified in warmer locations?
• Predictions about the impacts of climate change on mosquito populations and human disease.

Students can share their data and conclusions with the teacher or each other more formally using a written report, poster, or presentation.

Assess

Collect your students' worksheets as an assessment for this lesson. You can also assess their reports, posters, or presentations.

Lesson Plan Variations

• Mosquito traps at a single NEON site can be miles apart. The "Advanced" tab of each spreadsheet contains mosquito populations broken down by habitat (different types of forests, swamps, meadows, etc.). Are mosquitoes more common in some habitats than others? How could climate change affect mosquito populations in these local habitats?
• The spreadsheets for each location also include rainfall data. Is there a correlation between rainfall and mosquito populations? If so, how could climate change affect these populations in the future?
• This interactive map from the CDC shows the number of cases reported across the U.S. for certain diseases each year. Can your students find a relationship between the case count for each disease and populations of disease-carrying mosquitoes?