New Yorkers planted a tiny forest in a spot where the city used to warehouse prisoners and smallpox patients

• New York City got its first tiny forest, planted on Roosevelt Island on April 6. 
• The planting method, developed by a Japanese botanist, uses minimal land to maximum effect.
• The effort is designed to both boost biodiversity and connect the community.

On a chilly Saturday morning in early April, a few hundred people gathered in a park on Roosevelt Island, a skinny strip of land in New York City's East River, to dig around in the dirt.