Earth Day has had a long passage since Mother Earth Day in 1970. (We gave a relevant history lesson last year.) Bolivia was the UN progenitor in 2009 with 50 countries signing the declaration for 22nd April as Earth Day. Now we see to have taken to the day much more as Green Cities for the basis of action for 2014 with an official one billion participants! Here are some basic examples.
You personally can share a ride to your work, plant a tree, use public transport or even make your building zero energy, using solar energy or new technology to transform the properties of the surface. More generally, the US is the biggest emitter of greenhouse gases, - just, but it has been decreasing it's electricity use annually since 2007. Germany is the leader in solar energy (with California keeping up very well) while the UK is the greatest consumer of wind power. It also looks like a future leader in harnessing tidal and wave power.
Slightly off centre for Green Cities, Caribbean and Oceania islands are competing to have more and more renewable energy installation. Diesel powered generators are about as un-green as you can get, so the move by remote communities is welcome. With cities more in mind electric-powered cars are becoming more common in Norway and in cities worldwide, wherever their essential chargers are being installed.
To join one or more of a variety of environmental-based groups would be ideal for Earth Day's Green City year. Online activists have seen their work result in clean energy and smart grids, more transport options and cleaner vehicles, especially trucks. Green schools everywhere are investing in sustainable waste management and solar panels, while the red white and blue is being replaced in US embassies worldwide, making their facilities "green."
However if a city near you needs greening, plant a strategic tree, clean up and stop using plastic bags around unnecessarily. You still have another 364 days before next Earth Day. One day will never be enough for the Earth! Lots of information is available in - Earth Day: Green Cities.