If you are completing a photography or art degree, the dissertation topic you choose can mean the difference between success and failure. It's important to choose something you can reasonably expect to complete, that you enjoy, and that your dissertation advisers will accept. If you can turn the dissertation into a book, all the better for your career.
People are always a hit for a dissertation topic. The difficult part is finding people who are comfortable being photographed and will sign a model release form. Look for a theme like people living on the streets, immigrants, people at work, for example. Make sure your theme tells a story, for example showing the difficult lives of migrant workers.
If you are interested in photographing the natural world, a timely topic might be the affects of global warming on plant and animal habitats. Be sure to narrow the topic to something manageable. Do not decide to document polar bears in your dissertation if you cannot travel to their environment relatively easily.
Consider travelling to an exotic or remote locale to photograph the way local people live their everyday lives. Search photography books to see what the latest places of interest are. A photography dissertation could be used to nicely showcase a lifestyle completely different than what you and your dissertation advisers are accustomed to.
Children, growth, and change
Photography freezes moments in time. Multiple photographs presented together can also show a span of time. Consider the idea of showing growth or change. For example, the same landscape looks completely different depending on the time of day and season on which it is viewed.
Children and how they grow up also makes for a wonderful dissertation topic, provided you have the resources, and parents' permission, to photograph them for an extended period of time. Document their milestones, such as first steps, first days of school, birthdays, or just take the same exact portrait of a child every day for a year. Display all the photos for a time line that can only be expressed through photography.