The government unveiled a proposal Tuesday that would allow the country to meet more than half of its greenhouse gas emission reductions simply by maintaining and managing its forests.

The document puts forth two options, proposing that 3.2 percent or 3.7 percent of the nation's greenhouse gas emissions be attained under reforestation, afforestation and forest management activities.

The higher figure is based on carbon absorption potential of all of the nation's forested area, while the lower one is based on calculations that include only managed forests. The government submitted the national proposal on land use, land change and forestry to the United Nations climate change secretariat.

The plan proposes that parties to the U.N. Framework Convention on Climate Change adopt a more lenient definition of activities that reduce carbon emissions.

This broad definition would allow management of much of the nation's forests to figure in as "sinks" -- carbon dioxide-absorbing trees and soil that mitigate emissions of the global-warming gas -- and ease the government's treaty commitments. Specifically, the plan calls for 0.3 percent of the nation's carbon-sink absorption -- based on the 1990 emissions of 334 million tons of carbon -- to come from reforestation and afforestation activities, and 2.9 or 3.4 percent to be recognized as being absorbed by the country's forests.

The smaller figure uses only managed forests as a base, while the larger figure includes all of Japan's forests.

However, the proposal was met with stiff criticism from citizens' groups, which are afraid that sinks will be abused as a loophole and potentially render the treaty meaningless.

"The whole (sinks) decision-making process has been very obscure," said Mie Asaoka, head of Kiko Network, a climate-change oriented citizen's group.

By manipulating the figures this way, the government is twisting the spirit of the Kyoto Protocol, she added.

Environment Agency officials say that the government tried to settle on one figure, but that because there is no established definition of exactly what activities might be included under "additional human activities," as outlined in the treaty, it opted for a two-pronged approach.

Signatories to the international treaty are to meet in The Hague in November to hash out a more detailed plan on stemming global warming by stabilizing the concentrations of global-warming gases in the atmosphere. The 1997 Kyoto Protocol on global warming requires developed countries to reduce their emissions of carbon dioxide and other greenhouse gases by an average of 5.2 percent from their 1990 levels between 2008 and 2012.

Among the world's largest emitters, the reduction target is 8 percent for the EU, 7 percent for the U.S. and 6 percent for Japan. Limited use of sinks is stipulated in the protocol as one of various methods to cut greenhouse gases.