Climate change: how your grass clippings can help track greenhouse gas levels
A climate scientist is asking volunteers to collect grass clippings so she can measure the changes in carbon dioxide as we move out of lockdown . The country's air pollution and greenhouse gas output took a dive after our move into Alert Level 4 restrictions to fight Covid-19 . Jocelyn Turnbull, a GNS Science carbon researcher, wants to measure the emissions changes as life returns to normal. But as the alert level restrictions prevent her team from measuring carbon dioxide by collecting air samples, she's turning to volunteers and their nearby patches of grass to help out. Turnbull says plants constantly absorb carbon dioxide from the air to grow. "They all lay the carbon from that carbon dioxide down into their leaves and into their wood." READ MORE: * Earth's carbon dioxide levels continue to soar, at highest point in 800,000 years * Lockdown emissions have dropped to levels only seen on Christmas Day * Coronavirus: Should you work from home after the Covid-19 pandemic to save the planet? The carbon dioxide comes from two sources: naturally made gas (including the stuff animals and humans breathe out) and that produced when we burn fossil fuels, she says. There's a key difference the naturally-produced gas occasionally has a radioactive form of carbon, known as radiocarbon. "It's very rare, but it's everywhere in the world," Turnbull says. Because fossil fuels are "millions and millions of years old", they lack any radiocarbon. "By measuring how much radiocarbon is in the air, we can figure out how much of that carbon dioxide came from the natural, modern stuff and how much came from the fossil fuels," she says. Simply by growing, plants will record the radiocarbon levels in the air around them and help answer a million-dollar question: how much of a break did our atmosphere get from the fossil fuel usage that is driving climate change ? "What we're looking for is not a reduction in the amount of carbon dioxide, but it just not increasing as much as it normally does. It's a tiny little change if you look over the whole globe," she says. Turnbull is asking volunteers to cut grass clippings, then return to the same (potentially marked) spot every week and collect the regrowth. "I'm recommending you want to cut an area the size of a laptop or an oven tray. You're only going to keep a small amount of it but if you just cut one centimetre square, you'll never find the same spot again." Because it grows so quickly, grass is an ideal plant to sample the week-by-week carbon dioxide changes as the country revs back up. By cutting the grass down to the roots each week, the new growth only contains the carbon dioxide taken from the air that week, Turnbull says. Grass clippings will need to be stored in a freezer in a bag, with the date, sample number and location written on. When collecting the clippings, Turnbull advises participants to check their phone for the location's GPS coordinates. At the end of the project, all samples will go to GNS for chemical testing and analysis. "We're estimating 10 weeks, but that could of course change depending on what happens, but we want people to keep sampling until we're back to normal," she says. "We want to have that whole range." She's also particularly keen for people living near a motorway, busy road or shopping centre to take part. "In urban areas, where most of the emissions happen, the signals are bigger," she says. The results will be shared with volunteers and will likely be published as a scientific study, Turnbull says. You can sign up on the Great Greenhouse Gas Grass Off Facebook page . Turnbull hopes all participants will be able to take their first sample before the country moves to Alert Level 3 at midnight on Monday.