Father's Day is Sunday, four days before summer officially kicks off. So many traditional Father's Day gift ideas—from fishing gear to golf balls—emphasize outdoor activities. Here are some eco-friendly gift ideas that will help you and your Dad enjoy some time in nature together, while showing it as much care as your father has shown you.

1. A Gas Grill: Nothing brings the family together like a backyard BBQ. Grist did the math back in 2015 and determined that gas grills are the best outdoor cooking option for the environment. Charcoal grills release ozone and particulate matter into the air, which cause air pollution, and also have larger carbon footprints. Gas grills are even better for the environment than indoor cooking during the summer, since they are more efficient than ovens and don't heat the house, forcing AC to work overtime. This is a more expensive option, though, so maybe consider it as a joint gift if you have lots of siblings who want to collaborate on a gift for Dad.

2. A National Parks Pass: Give your dad a ticket to a year's worth of adventure, and support America's breathtaking public lands in the process. The America the Beautiful—The National Parks and Federal Recreation Lands Pass gives your father access to 2,000 Federal Recreation sites including national parks and national wildlife refuges. If your dad wants to take the family, the pass will cover the vehicle fee for one car and all of its passengers, or four adults at parks with a per-person entrance fee. Children under 15 can always enter for free. This costs $80 for the year, unless your dad is over 62. Then you can buy him a lifetime pass for only $10!

3. Recycled Gear: More and more, companies are devising ways to help you enjoy nature while also cleansing it of plastic pollution. Repreve turns plastic bottles and other recycled materials into strong fibers that many companies incorporate into outdoor equipment. Parley for the Oceans has partnered with Adidas to make shoes and other athletic clothing from plastics gathered from oceans and coasts.

4. Bird-Watching Starter Kit: Fishing and hunting are perhaps the archetypal dad-and-child outdoor sports, but if you want something that includes the potential bonding time of long hours spent waiting for wildlife without harming any animals, why not get your dad a field guide to birds in your region and a pair of binoculars? Ask a Biologist's Beginning Birders' Guide recommends regional guides by Roger Tory Peterson and David Allen Sibley and binoculars with power x lens-width measurements of 7 x 35 or 8 x 42.

5. Eco-Friendly Socks: Socks are another Father's Day staple, but good, comfy socks are truly essential for any outdoor activity that requires boots or shoes. Why not treat your dad, and the planet, to Sierra Club's official socks. Parker Legwear is a three-generation family-owned sock maker in North Carolina that uses recycled materials and organic cotton to produce comfortable socks using limited amounts of energy.

6. Second-Hand Books: Not every outdoor activity has to work up a sweat! One of the best things to do in summer is sit out on the grass with a good book. Hit up your local used bookstore or thrift shop for a budget-and-tree-friendly previously owned title to get your dad started on his summer reading.