Earth Day around the world (VIDEO, PHOTOS)

Tens of millions of people across the world have taken part in the world’s foremost environmental festival – Earth Day. But organizers say any festivities should be laced with a warning.

­From teach-ins to tree-planting to demonstrations, the day was commemorated by a network of independent local events inspired by the occasion.

Dutch electronics giant Philips marked Earth Day by unveiling a new environmentally-friendly LED light bulb in the US that can last for more than a decade. Despite a hefty initial $60 price tag, makers say the bulb will save money over its lifetime.

Instigated by a US senator in 1970 in response to an oil spill before being taken up by the United Nations, Earth Day was at the heart of the budding environmental movement.