Urban environments are made up of both natural and human-made systems, making it difficult to understand how carbon, water, and energy move through city landscapes. In this study, we used a high-resolution urban observatory in Chicago—part of a national Department of Energy network—to track how urban trees and turfgrass influence carbon uptake, water use, and energy balance. We combined many types of measurements, including tracer of photosynthesis, human activity, industry sources, meteorological measurements, and air quality. These data helped us separate plant activity from signals caused by cars, buildings, and other human sources. We found that vegetation plays a larger role in regulating carbon and water during the growing season, especially when leaf area and transpiration are highest. Trees and turfgrass responded differently: tree water use was strongly linked to root activity, while turfgrass carbon uptake depended on sunlight and soil temperature. Our study shows the power of combining atmospheric and ecological data to better understand how plants help regulate urban climate—and how cities can use this knowledge for more resilient, greener designs.