What a great combination!
Find slides of a presentation on the topic here.
Math, Loose Parts Nature Play Blog Post
Math, Loose Parts Nature Play Podcast Episode
Gull, C., Bogunovich, J., Goldstein, S. L., & Rosengarten, T. (2019). Definitions of Loose Parts in Early Childhood Outdoor Classrooms: A Scoping Review. International Journal of Early Childhood Environmental Education, 6(3), 37-52. https://naturalstart.org/sites/default/files/journal/6._gull_et_al._formatted_draft_v2.pdf
Resources from Juliet Robertson:
Suggested materials for maths outdoor—good list of basics to considerMessy Maths Handout–Great content! Sammy the Metre Snake—consider a yard snake in the US
Books from Juliet Robertson:Messy Maths—great book that goes through all mathematical domainsDirty Teaching—general information about learning outdoors—General suggestions for outdoor maths from NAEYC—good suggestions to consider!
Math and Nature Connected Books and Resources—Natural Start Alliance
Math Resources and Tools on Amazon (including book suggestions!)Mirrors for Mirror Books
Loose Parts Nature Play 