In the heart of Mexico City, a lone kayaker glides through ancient canals.br Omar Menchaca, 63, is a former mining engineer turned environmental advocate.br For over three decades, he’s paddled through Xochimilco, collecting trash and raising awareness.br A UNESCO World Heritage site, Xochimilco is known for its Aztec-era canals and floating gardens.br But pollution and urban expansion now threaten this fragile ecosystem.br Despite a city-wide plastic ban, bottles and bags still choke the canals.br Menchaca says the wetlands are critical for recharging the aquifers that supply drinking water to millions.