Given the task definition and input, reply with output. Given a scientific passage and an answer, generate a question for the given answer.

Passage: With less ozone in the stratosphere, more UV rays reach the ground. More UV rays increase skin cancer rates. Just a 1 percent loss of ozone causes a 5 percent increase in skin cancer. More UV rays also harm plants and phytoplankton. As a result, they produce less food. This may affect entire ecosystems. Answer: ozone
More uv rays reach the ground due to a decrease in what layer in the stratosphere?