New detailed map shows carbon in Peru's Amazon

* Could ease global climate deal on deforestation

* 3-D image shows where carbon is stored in forests

* Map details how cutting down forests releases carbon

By Deborah Zabarenko, Environment Correspondent

WASHINGTON, Sept 6 (Reuters) - A new, highly detailed map of part of Peru's Amazon shows how much climate-warming carbon is stored there, and where cutting down vegetation has sent this greenhouse gas into the atmosphere, scientists said on Monday.

The three-dimensional map could help clear the way for an international agreement to curb deforestation and forest degradation, which account for up to one-fifth of all greenhouse gases released by human activities, according to United Nations estimates.

Climate negotiators have been working on an international deal to slow global warming, including a U.N. proposal known as REDD, short for Reducing Emissions from Deforestation and forest Degradation.

This proposal has been hampered by the difficulty of figuring out how much carbon forests keep out of the atmosphere -- because plants take in carbon dioxide and use it in the process of photosynthesis -- and how much deforestation contributes to the greenhouse effect by releasing this stored carbon into the air.

The details in the new map could help change that, said Greg Asner of the Carnegie Institution for Science, lead author of a study that produced the map. The study is being published in Proceedings of the National Academy of Sciences.