The possibility that the tropical rain forest is an important carbon sink is also a hot topic under debate in environmental science circles. By measuring permanent sample plots that had been established by foresters and ecologists to monitor tree growth and mortality, the authors found that biomass gain by tree growth exceeded losses in old-growth humid tropical forests. The neotropical forest plots accumulated 0.71 tons of carbon per hectare per year in recent decades. The authors caution that deforestation, logging, and regional drying and warming may limit or reverse the carbon sink provided by mature forests. As scientists try to determine what impact human activity is having on the carbon dioxide load in the atmosphere, it's necessary to track natural carbon dioxide sources as well.
Estuaries are rich marine ecosystems that are created when freshwater mixes with saltwater.
The authors measured CO2 emissions from nine European estuaries and found that they emit between 30 and 60 million tons of carbon per year to the atmosphere. That represents 5 to 10 percent of the total amount of carbon dioxide emissions from human activity in Western Europe. The largest amounts of CO2 occurred in the upper estuary, where there is low salinity and a decrease in saturated oxygen. Although there is limited data available, the authors expect high carbon amounts to be reflected in other estuaries around the world.