Nature Physics now requires a statement of authors' contributions to a paper.
In the past, at the acceptance of a manuscript for publication in Nature Physics, we have gently suggested to the corresponding author that a statement of 'author contributions' be included in the final version. It seemed good practice, and most authors obliged. Now, such a statement is mandatory for any paper published in Nature or a Nature journal.
It's nothing onerous: just a simple listing of the initials of all authors with a comment on what they contributed to the work reported — be it designing, preparing, performing, collecting, analysing, modelling, writing or something else. There is no required format beyond that. These statements can vary greatly in their degree of detail, as is appropriate when the content of Nature Physics papers is so diverse and 'authors' may constitute anything from a lone pair of theorists to a substantial experimental collaboration. (For examples of statements, see http://tinyurl.com/39mmyw.)
It's not hard to imagine, either, why it is a good idea for all papers in the journal to carry an author-contributions statement. It might serve to ensure that the author list includes only those who really did make a recognizable contribution to the paper. It might be useful for younger scientists, seeking grants or positions, to point to a record of their efforts in producing particular results. It will certainly be beneficial for all concerned, if ever a question of fraud is raised, to know exactly who was responsible for what.
Details of our editorial policies on authorship are available at http://www.nature.com/authors/editorial_policies/authorship.html.