It was once believed dam is a net producer of greenhouse gases. However, new studies has shown otherwise. The older the dam the more CO2 it will take up due to it's ability to promote organic production and is responsible for the high uptake of CO2.
--I would say each is different and would have to be accessed.. for larger deep pondage dams.. one should conscider the amount of vegetation that was in the valley prior and how many years before aquatic veg will start to compensate for that loss in addition to the amount left to rot.
--Smaller shallow dams...especially in dry climate, I would expect... might produce aquatic veg much more rapidly and would not have had BC size trees all over the valley prior to the flooding.
--Just try fishing behind Mica dam without a spare prop... how many years has that been in place.
--I'm not hung up on Co2 just that its a complicated web that we could use less spin doctors and more thoughtful science.
--I think we should be working on more efficient ways to use and produce electricity with the dams we have and not get on the total back to nature band wagon... If you are going to have the same or increasing population... especially in cities you need to exploit resources from a much larger area.
--I've been a proponent of limiting populations since the early 70's... and looking to long term solutions. In practicing what I preach we had one child and waited until we were near 40 ... that was one of many proposals made in population ecology for limiting population growth.
-- I say we each must choose... to do something but choose your own path..
--I'm not always goody two shoes either... I have an aluminium boat and we all know that it takes a bunch of electricitly to produce one.