After years of complaints that there were no rules to determine what constitutes a "sustainable" investment, investors are now fretting that there will soon be too many to navigate easily.

More than 30 taxonomies outlining what is and isn't a green investment are being compiled by governments across Asia, Europe and Latin America, each one reflecting national economic idiosyncrasies that can clash with a global capital market that has seen trillions pour into sustainable funds.

The European Union will introduce its green investment taxonomy, or common framework, in January to help asset managers inside the bloc while making green activities more visible and attractive to investors. The rules also aim to stamp out "green washing," whereby organizations overstate their environmental credentials.