hello

günümüzdeki en büyük çevre sorunu buzulların erimesi.

can someone explain why can not use buzullar erimek

thanks in advance

In English, ice field´s melting is the biggest environmental problem in our generation. 

That´s why buzulların erimesi. Coz buzullar erimek would sound just like a fact or title without the suffixes.

Turkish infinitive is used as an object of the verb. 

thanks but I did not understand the second post

so can we use

buzullar erimek günümüzdeki en büyük çevre sorunudur

Yes, that´s right. You can use that way too..