 More of us live in cities than at any point in human history. But unprecedented urbanization doesn't need to equal polluted concrete urban sprawl. We have the knowledge to make cities cleaner, greener, healthier places to live for current and future generations. By 2050, 6 billion people will live in cities. Trees are a natural air conditioner, cooling the air by between 2 and 8 degrees. Urban forests filter harmful pollutants from the air and actors of carbon sink helping mitigate climate change. So let's make our cities greener, healthier, happier places to live.