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Traveling in groups is more social, cuts down on gas, and is better for your carbon footprint (which is the sum of all greenhouse gases created and released by your activities). Using public transit, like buses and trains cuts down on the gas it takes to get somewhere and is cheaper and better for the environment than cars. It takes a lot of fuel to fly or drive long distances, and that fuel creates greenhouses gases. Donate some money to a company that offsets those emissions. When you donate to a group that tries to offset carbon emissions, they use that money to fund projects that prevent that same emission elsewhere. That could be as simple as planting a new tree, or funding projects to reduce someone else's carbon footprint.
Carpool to holiday events. Take the bus or train whenever you can. Donate to offset your carbon footprint if you travel.