The problem with saying use cloth nappies is where is all that cotton/bamboo going to come from and how much forest land will be cut down to grow it, as it will be a growth market.
Then you have the problem of all the chemicals used to make the cloth, then bleach it white, which all need to go some where and some of which will enter the water system.
Its like saying just use paper bags but where is all that wood coming from at least a plastic bag can be reused a lot more then paper bags, the human race is to quick to jump to knee jerk reactions that have unintended consequences, that have not been thought out. Once we got our milk in nice glass bottles that could be washed and reused now its all plastic. We used to have drinking fountains for free water now just mineral water with all the carbon that brings with it. To be honest we play around the edges, doing tiny things, to feel better about our self's ,then jet of on holiday and using more carbon then we would ever save by recycling.
Trick is not to panic and look out for the consequences of our attempts to solve the problem. if we wish to use less plastic, drinking bottles are a much better place to start as we have a proven replacement with low waste and good re-usability glass.