Unemployment is of course an important issue, but environmental problems are important too.
Literal
Unemployment-problem [also-も] needless-to-say [ending-ながら], environment-problem [also-も] important is-[copula-だ].
~もさることながら is a fixed expression meaning 'of course X, but also Y / not to mention X, but also Y' — used when you want to acknowledge one thing while adding another. Literally 'even leaving X aside, Y is also.' The さる is the classical verb for 'to depart, leave aside,' and ながら is the conjunctive ('while'). A literary register stock phrase.