looks like your settings are on default, a few things to try out:
- turn your camera light off
- try rendering without the trees, assuming that you are trying to render what I see in your screen shot, those are a lot of trees in the background. If it does render with all the trees off, then I guess you've found your problem. And if it is indeed the problem, then I'd start by using "lollipop" trees for the ones in the back. Or simply reduce the number of trees you have for the purpose of rendering.