What international effort to document nature in cities took place from April 24-27, 2026?

The global initiative that encouraged people to document the natural world in cities from April 24-27, 2026, was the City Nature Challenge. This annual event is a worldwide community science effort where participants, often using the iNaturalist app, act as citizen scientists to find and record observations of wild plants, animals, and fungi within urban environments. The four-day period focuses on data collection, turning everyday sightings into valuable scientific information.

The City Nature Challenge originated in 2016 as a friendly competition between Los Angeles and San Francisco, aiming to see which city could document more urban biodiversity. Due to its success and growing interest, it quickly expanded to include cities across the United States in 2017, and then became an international event in 2018. While it initially had a competitive aspect, the focus shifted in later years to emphasize collaboration and the collective goal of understanding and celebrating urban nature on a global scale.

The primary goal of this effort is to engage the public in collecting biodiversity data, which helps scientists track species distributions, monitor changes in local ecosystems, and better understand urban biodiversity. The observations made by participants contribute to open-access data, supporting conservation efforts and environmental education worldwide. It empowers individuals, regardless of their scientific background, to contribute to real scientific research and foster a deeper connection with the natural world around them.