The average American boy or girl spends as few as 30 minutes in unstructured outdoor play each day. Only 6% of children nine to 13 play outside on their own in a typical week.But if you're reading this, you probably already know that outdoor play is essential for children's health and well-being. Here are eight science-backed reasons that prove you're right. 1. Better vision - Multiple studies show that sunshine and the natural light of outdoors lowers the chance of nearsightedness and improves distance vision in children. Kids who spent more time outside had better distance vision than those who prefer indoor activities. A recent study from Ohio State University College of Optometry says that 14 hours a week of outdoor light is effective for better vision. 2. Better resistance to disease - Multiple studies show that playing in the dirt (soil) outdoors helps kids stay healthy. Bacteria, viruses and other gross things in the soil actually help the immune system, and brain develop. Playing the dirt can also improve a child's mood and reduce anxiety and stress. 3. Increased Vitamin D - It's difficult to get enough of this nutrient strictly from food. 80 to 90 percent of our vitamin D actually comes from sunshine. Sensible unprotected sun exposure of 10 to 15 minutes will do it. After the first 10 - 15 minute exposure, it's best to cover up with sunscreen. 4. Less Stress - More than 100 research studies have shown that outdoor recreation reduces stress. This comes from a combination of factors producing positive physiological and psychological responses. Also, in this poll, 90 percent of kids who spent time outside said being in nature and taking part in outdoor activities helped relieve stress. 5. Better attention spans, even for kids with ADHD symptoms - Several studies done by the University of Illinois Urbana-Champaign show that natural settings and green outdoor activities reduced ADHD symptoms in children. Activities outdoors specifically had greater positive impact than other settings. These positive effects are measured in children as young as age five. A 2008 study at the University of Michigan found that memory performance and attention spans improved by 20 percent after subjects spent an hour out in the nature. Likewise, 78% of educators in a large survey reported that "children who spend regular time in unstructured outdoor play are better able to concentrate and perform better in the classroom." 6. Better physical fitness - Outdoor play increases fitness levels and builds active, healthy bodies. One in three American kids who are obese. Running around, climbing, walking, exploring, and getting dirty burn calories and strengthen growing bodies. Bonus: there's ample evidence linking physical fitness and academic achievement. Likewise, there's evidence that simply taking a stroll outside increases creativity. 7. Better physical coordination - Another way to say this is better sensory skills. Playing outside involves uneven surfaces, rocks, branches, holds and unstable surfaces like gravel, sand and mud. Playing around these elements takes balance, agility, dexterity, and depth perception. 8. Better classroom performance - Multiple studies show that kids who spend time outside (including during the school day) do better in all academic subjects. Exposure to environment-based education significantly increases student performance on tests of their critical thinking skills. Factoring out other variables, studies of students in California and nationwide show that schools that use outdoor classrooms and other forms of nature-based experiential education produce significant student gains in social studies, science, language arts, and math. For example, one study found that students in outdoor science programs improved their science testing scores by 27 percent. BONUS POINTS! 9. Spark curiosity & imagination - As kids grow, indoor environments become known, understood, and familiar. However, outside environments are dynamic and ever-changing. They are outside our control. As such, they invite the mind to wander, looking, observing. 10. Better nature literacy and local understanding - From TV, movies, books and apps, many kids know a lot about dinosaurs, pandas and sharks. Bringing them outside lets them explore and learn about their own local ecosystem. Kids take immense, healthy pride from learning the names of the plants and animals in their own neighborhood.