1. Google - Searching Google first will allow you to collect some general information just to get you familiar with your topic. Also, tryGoogle Advanced Search. Using Google Advanced Search allows you to limit to a dot.gov, dot.int, ordot.org domains, which is likely to return more credible results.
2. Google Scholar- This is Google's specialized search for finding scholarly (a.k.a. peer-reviewed) articles.
3. CAB Abstracts- This database is chock full of peer-reviewed articles about forestry topics. You might also consider addingWeb of ScienceandBIOSISinto your search as well, as shown below.
4. EBSCO Databases - There are several databases from this company that could be useful to search for forest, climate, or policy information. You can search them individually or all at once. Here are the links to search them individually: