Emma Watson is causing a stir thanks to a series of photographs promoting an upcoming photography book benefiting charity. 

The 22-year-old former "Harry Potter" star appears topless in a number of sultry photos that show her grasping a flower and covered in what appears to be mud. The shots are all part of a new photography book called "Natural Beauty" by James Houston, with proceeds going to the environmental organization Global Green USA. Other celebs taking part include former "Entourage" star Adrian Grenier, as well as supermodels Christy Turlington, Elle Macpherson, Arizona Muse and Anja Rubik.

"My latest project, NATURAL BEAUTY, is a photographic series inspired by the connection I feel to nature in my design work and in the environment," Houston says. "I shot some of the world’s leading celebrities and top models who are also environmentally conscious. The project will launch during World Earth Week 2013 in New York and Los Angeles in collaboration with MILK Galleries NYC.

"By celebrating the incredible beauty that exists in nature, my hope is that these images will inspire people to appreciate and value nature’s beauty," he adds. "The environment is a gift we can’t afford to take for granted. We all need to do our part to protect it."

You can view a behind-the-scenes video of some of the photo shoots for "Natural Beauty" below. To pre-order, jump here

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