Are the externalities associated with common resources positive or negative?

[Goose]

Is the free market use of common resources generally greater or less than the efficient use?

[Sipra M]

*Common resources are bast described as public goods. For example sea resources, over use will have negative effect on environment. Forest resources, regular planting will have positive effect on environment.
* Free market may use the resources more efficiently but social cost mostly outweigh the gain of social benefit.
For more : read the chapter on public goods from the book on microeconomics and read any book on cost benefit analysis.