FILM SCREENING, DEC. 13

Santa Rosa: The Laguna de Santa Rosa Foundation presents “The Most Unknown,” a documentary film by Ian Cheney about nine scientists who journey to extraordinary parts of the world to explore the universe’s toughest questions, 7-9 p.m. in Heron Hall at the Laguna Environmental Center, 900 Sanford Road. $5-$20 sliding scale fee. Registration required at lagunafoundation.org.

ORIENTATION HIKE, DEC. 15

Healdsburg: Visit several trailheads and learn about access to the Modini Mayacamas Preserves on Pine Flat Road, then take a guided 2- to 3-mile orientation nature walk with education specialist David Self or head out on your own, 9 a.m.-2 p.m. Bring water and lunch, and dress for the weather. $20 suggested donation. 707-431-8184, ext. 503.

HERBAL MEDICINE WORKSHOP, DEC. 15

Healdsburg: Herbalist Allie Cuozzo discusses natural medicine making from herbs 11 a.m.-2 p.m. at Riddell Preserve. Herbal and packaging materials provided. Space limited to 12 people. $30 for adults and $20 for youths. Participants will walk up a steep, well-graded trail to a cabin during this event. Details available when you register at LandPaths.org.

NATURE HIKE, DEC. 15

Sonoma: Take a free, slow-paced 1-mile hike with minor elevation changes on the lower Montini Preserve Trail at Sonoma State Historic Park noon to 1:30 p.m. Meet at the Vallejo Home parking lot, 363 Third St. All ages welcome. Bring water and wear sturdy shoes. Steady rain cancels the hike. 707-938-9560.

GARDEN TENDING, DEC. 15

Santa Rosa: Help improve soil fertility through composting and planting, and harvest winter greens at Maddux Ranch Regional Park, 4655 Lavell Road, 10 a.m.-2 p.m. Email Community Soil Foundation at info@communitysoil.org for information, or visit SonomaCountyParks.org.

10K and 2-mile RUN, DEC. 15

Santa Rosa: The Empire Runners Club holds a final 10K and final 2-mile run along paved paths in Spring Lake, Howarth and Trione-Annadel parks. Free for members, $10 nonmembers. Race day registration is $20. 9 a.m. to noon. The event starts and ends at Howarth Park, 600 Summerfield Road. Visit empirerunners.org.

FAMILY BIRD WALK, DEC. 15

Santa Rosa: Identify bird species during a 1-mile easy stroll at Spring Lake Regional Park, 393 Violetti Road, 10 a.m.-1 p.m. Bring binoculars or borrow some at the park. Parking is $7. 707-539-2865.

WILDFIRE RECOVERY HIKE, DEC. 15

Windsor: See how nature has responded to and rebounded from the wildfires, and learn why forests actually need fires, 10 a.m.-1 p.m. at Shiloh Ranch Regional Park, 5750 Faught Road. 707-539-2865, SonomaCountyParks.org.

MISTLETOE MYSTERIES, DEC. 16

Sebastopol: Learn the back story about mistletoe, why we kiss under it and how the opportunistic plant has a beneficial relationship with oak woodlands during a 1- to 3-mile walk 10 a.m. to noon at Ragle Ranch Regional Park, 500 Ragle Road. Parking is $7. Meet at the Peace Garden. 707-539-2865, SonomaCountyParks.org.

ANIMAL TRACKING, DEC. 16

Bodega Bay: Learn animal tracking basics in the sand at Doran Regional Park, 201 Doran Beach Road. Parking is $7. 9-11 a.m. Meet at the Cypress day use area. 707-539-2865, SonomaCountyParks.org.