Global wetlands appear to contribute about 75% of natural methane emissions, relatively larger in peat-rich wetlands. Since most of the methane produced in organic soils of wetlands is oxidized within 20 cm of the water table, changing water tables can dramatically alter the role of wetlands as large source or sink. Past drainage of temperate swamps may already have reduced global emissions from these sources, and additional drainage of swamps or development of drier conditions due to global warming could cause further reductions and even add new sinks.
About 70% of the estimated 510 Mt of methane released into the atmosphere each year comes from natural and human-induced surface biological processes, about 20% from the escape of natural gas from fossil fuel sources, and 10% from biomass burning.
The Encyclopedia of World Problems and Human Potential is a collaboration between UIA and Mankind 2000, started in 1972. It is the result of an ambitious effort to collect and present information on the problems with which humanity is confronted, as well as the challenges such problems pose to concept formation, values and development strategies. Problems included are those identified in international periodicals but especially in the documents of some 60,000 international non-profit organizations, profiled in the Yearbook of International Organizations.
The Encyclopedia includes problems which such groups choose to perceive and act upon, whether or not their existence is denied by others claiming greater expertise. Indeed such claims and counter-claims figure in many of the problem descriptions in order to reflect the often paralyzing dynamics of international debate. In the light of the interdependence demonstrated among world problems in every sector, emphasis is placed on the need for approaches which are sufficiently complex to encompass the factions, conflicts and rival worldviews that undermine collective initiative towards a promising future.
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