Daniel Janzen is an American biologist known for his work in ecology and conservation. He has made significant contributions to the understanding of tropical ecosystems, particularly in Costa Rica. Janzen's research focuses on the interactions between species and their environments, emphasizing the importance of biodiversity. In addition to his research, Janzen is a prominent advocate for conservation efforts. He co-founded the Area de Conservación Guanacaste, a large protected area in Costa Rica that aims to preserve the region's rich biodiversity. His work has influenced conservation policies and practices, highlighting the need for sustainable management of natural resources.