Wallis Annenberg has long been a leading champion of environmental causes. Through her philanthropic efforts, she has expanded public access to green spaces, supported wildlife rehabilitation, and advanced environmental education throughout the Los Angeles region and beyond. She also spearheaded the Wallis Annenberg Wildlife Crossing — a monumental overpass across US‑101 in Agoura Hills that will reconnect vital habitats for mountain lions and other species. When completed, it will be the largest wildlife corridor in the world. In 2021, she and The Annenberg Foundation launched a record-breaking $25 million Conservation Challenge Grant in partnership with the National Wildlife Federation, calling on fellow philanthropists to help protect one of the world’s most threatened biodiversity hotspots — the Los Angeles urban ecosystem. The grant, currently the largest private initiative of its kind, continues to inspire large-scale action for urban conservation.