Did you know that we can identify fossil fuel emissions in the air by sampling annual plants? Knowing where greenhouse gases are and at what concentrations can help policymakers fight climate change. All major cities in Arizona have developed action plans to reduce greenhouse gases, but they still lack quality data regarding carbon dioxide sources and the ability to monitor how well actions work. You can help!
This spring, Sky Island Alliance is partnering with Northern Arizona University’s ACE Isotope Lab, Arizona State University’s Southwest Urban Corridor Integrated Field Lab, and Desert Botanical Garden in Phoenix to measure fossil fuel levels in Arizona’s biggest cities. For this particular collaboration, our role is to contribute data specifically from Tucson. What we need are volunteers to help sample invasive annual plants in different places around town to understand which areas have the highest emissions.
When fossil fuels are burned in our communities, they leave an imprint on atmospheric carbon dioxide. Plants record their level of fossil fuel exposure in the radiocarbon content of their stems, leaves, and flowers. For annual plants — i.e. ones that will complete their entire lifecycle this spring — their tissues will have lower radiocarbon signatures in areas with higher fossil fuel emissions. Learn more about how it all works and how to help us with this project below.
Get Started
For full project details and answers to frequently asked questions, watch our virtual training. We’ll be collecting plants throughout April, and after this training you’ll be ready to hit the streets and volunteer with confidence.
You can also jump right in and follow the guide below. Either way, you’ll need to schedule a time to pick up sample envelopes and an assignment from the SIA office. Contact Emily Burns to arrange a time. Generally, our staff will be available on Wednesdays from 1-4 p.m. and Thursdays from 9 a.m. to noon.
Locate an invasive annual plant in the greater Tucson area. We recommend looking for London rocket(Sisumbrium irio) right now as it’s sporting yellow flowers all around the city. (Here’s a full list of annual plants the project will accept.)
Label your paper collection envelope with the following info:
Individual ID code — this will be SIA + the first three letters of your last name + 1, 2, 3, etc. to show the sequence of your samples. (For example, my first three samples will be labeled SIABUR1, SIABUR2, SIABUR3).
Date
Scientific name of the plant
Brief description of location
Open the iNaturalist app on your smartphone:
Click Observe.
Click on Camera and take a photo of the annual plant you found. Click the + at the top of the screen to add a second photo with the labeled collection envelope visible in the photo.
Click What did you see? Select the plant you found based on iNaturalist’s suggestions.
Click on the Location and verify that it’s accurate. If not, move the crosshairs to your location and click Save.
In the Notes section of the observation, write your Individual ID code (example: SIABUR1).
Click Share to upload your sample to iNaturalist.
Cut the plant sample, taking at least one stem segment with leaves the length of your index finger. If you pulled the invasive out by the roots, discard the roots and soil. Put the stem sample into a collection envelope.
Repeat for any other plant samples, one per envelope.
Return your samples to the SIA office. Contact Emily Burns to arrange a time. Generally, SIA staff will be available on Wednesdays from 1-4 p.m. and Thursdays from 9 a.m. to noon starting on March 27.
We’re focusing on collecting annual plants because their carbon signature only reflects fossil fuel emissions this spring season. Since they’ve only just sprouted, they are able to provide a reliable, specific time period of measurement for the study: what’s in the air right now. A longer-lived plant would integrate emissions over the span of years, and that would be a harder signal to interpret.
This science behind this project and radiocarbon dating would work just as well with native plants. But we’re focusing on invasive plants because it’s helpful to remove them and leave the native wildflowers for the pollinators.
Carbon-14, also known as radiocarbon, is a variant isotope of carbon that’s found in the atmosphere naturally. So plants growing with exposure to normal clean air will have an expected amount of this isotope in their tissues. When plants get a lot of fossil fuel emission exposure, however, that changes the chemical composition of the surrounding air. Fossil fuels are also carbon based but do not contain the specific isotope carbon-14. That means that in polluted areas, the amount of carbon-14 in the air is diluted. And that’s recorded in plant tissues as a lower radiocarbon signature. An easy way to remember this dynamic is that more pollution = less radiocarbon.
