There is a wide variety of research available to support the use of environmental education and outdoor instruction. Research indicates improvement in students' critical thinking, motivation, and achievement in core subject areas, classroom behavior, and more.
The Children & Nature Network has great research summaries and links to full research papers on environmental education and outdoor instruction. They also have infographics to help share information on the benefits of nature including health, academics, play, and physical wellbeing.
The National Wildlife Federation has released various reports that discuss how being outdoors affect children. Topics include children’s well-being, school readiness, and academic performance.
Environmental Education Week is a program of the National Environmental Education Foundation. Their site features research on the benefits associated with environmental education. (It also includes some great educational materials).
North American Association for Environmental Education has worked with partners and led initiatives to help understand how to practice and communicate about environmental education.