Trees pull carbon dioxide out of the atmosphere. Mangroves, trees that grown on tropical and subtropical coasts, store large quantities of this CO₂ in peat composed of dead leaves, roots, and other plant material. Mangrove systems are more effective than most forests on land in storing CO₂ belowground. We compare natural mangrove systems and restored ones in Florida in a north-south gradient that covers areas where mangroves thrive to areas where mangroves survive lower temperatures, but do not get as large as the ones further south. We measure environment variables at our sites to compare the rates at which mangrove systems accumulate belowground carbon, both between restored and natural site pairs and between north and south sites. Our findings will be useful in determining not only how well restored mangroves store carbon, but also how newly formed mangrove systems will provide natural solutions to climate change as they move further away from the equator with climate change. Although our research is in Florida, it has global implications.