Roughly six inches of top soil separates humanity from extinction, according to the UN agency which works to protect this resource.

The UN Convention to Combat Desertification (UNCCD) says each year, desertification and drought rob the planet of  12 million hectares of land which could produce as much as 20 million tonnes of grain.

Kehkashan Basu, a 12 year old girl from Dubai, has been planting trees as a means to fight this problem.  On the World Day to Combat Desertification, observed annually on 17 June, she calls on young people to act now because the planet cannot wait.

Kehkashan told her story at a UNCCD press conference in Rio de Janeiro, Brazil, where the Rio+20 conference on  sustainable development opens on Wednesday.

Dianne Penn reports.