Speaking at Forest Day 6 on the sidelines of COP 18 in Doha, social and human rights campaigner Bianca Jagger urged negotiators at the United Nations climate change conference to extend the Kyoto Protocol - the UN agreement requiring developed countries to reduce their greenhouse gas emissions.

"We need leaders who come here to really understand what the science requires to keep us under two degrees Celsius [global temperature rise]. The changes that anything beyond two degrees will bring to the world are very disturbing and very worrisome to all of us," Jagger said.

"How can we not be reacting, and why are leaders not signing the Kyoto agreement beyond 2012?"

Jagger is an Ambassador for an online campaign 'Plant a Pledge', which was launched at the Rio+20 Summit with the aim of mobilising public support for a major land restoration initiative led by the International Union for Conservation of Nature (IUCN).

It aims to restore 150 million hectares of forest and degraded land around the world by 2020 - the equivalent of 15 percent of the estimated area of degraded forest worldwide.

"This is not simply about reforestation - it has communities and people at the heart of this initiative," she said.