You need to find someone who has written on the topic of ethnobiology. Ethnobotanists are those who study the relationship between people and nature, and usually deal with a specific group of people in a defined region and how they interact with specific species. Remember that ethnobiology branch into many different fields of study, so they may not offically be identified as a ethnobiologist; researchers may identify closer with another field of study such as biology, anthropology, ecology, or conservation/sustainability.
Here are some techniques for finding ethnobiologists.
1. Start with the library's Biosis Preview database or other article databases.
If you're not familiar with many ethnobiologists, start with the Biosis Preview database and searching for the topic "ethnobiology." Biosis Previews can sort your results by author through clicking the ANALYZE button and then rank the results by author. This will list some of the most prolific ethnobiology authors, plus rank them according to who has published the most. You can also use your textbook or the internet to help identify ethnobiologists.
2. Browse ethnobiology publications.
Society of Ethnobiologist, Journal of Ethnobiology and Ethnomedicine, and Ethnobiology Newsletters are some of the major publications in this field. Databases are a good tool to use because they index hundreds to thousands of journals. Keep in mind that the databases tell you what literature exists; they may not link to the full text of an article, so you may need to request a copy through interlibrary loan.
3. After you have selected an author, see what they've written.
For example, Wade Davis wrote the book Passage of Darkness: the Ethnobiology of the Haitian Zombie. Check the library catalog to see if he has written books other books. If we use one of the library's article database to search for "Wade Davis and ethnobiology," we discover he also wrote an article called "The Ethnobiology of the Haitian Zombi."
4. Check if other people have cited their work.
Check Google Scholar or Biosis Preview to see if anyone has cited this book (Google Scholar currently lists 164 citations). The database Science Citation Index is another really useful resource for exploring article citations.
5. Some articles list the instituion the authors are currently associated.
Institutions frequently post info about researchers on their web site. However, they may move to different institutions and info about past employees are not always preserved by former institutions.
6. Search the Internet for your person's "CV" or biography (see Wade Davis example).
This will give you a list of the employment history, education, and publications. More likely, authors will have a personal web page with additional information, such as their publications, research interests, etc. what got them intested in their field of research originally.
7. Use some library reference books to find professional info about your researcher.
Here is a link to some potentially useful books. Keep in mind that there may not be much info on the person you choose to research. You may also try your textbook which may provide additional info your ethnobiologist.