One of the major effects on the boys, and this was something that Golding purposely set out to do, is the fact that the environment is one without any adults or structured type of society. The fact that the environment is one that can support life and allow the boys the chance to try and develop some type of society is important as it allows Golding the opportunity to craft his vision of what would happen in that type of situation.
Some of the direct effects are at first hunger, whereas fresh water appears to be plentiful it takes some time to establish how to hunt the boars and have meat. The boys are driven to some extent by this hunger to follow Jack in the hopes of getting more meat.
There is also a sense of fear of the unknown as the island is large enough that exploration is not completely straightforward nor is it always clear what is happening in one place compared to another.
One last effect, one that mimics the boys losing the trappings of society, is the way they quickly lose their clothes to be more comfortable in the hot tropical environment.