The article explores how Yantai City is using the ecological footprint theory to figure out if it's developing in a sustainable way. They measured how much the city's population uses up the earth's resources compared to how much nature can actually renew. The calculation showed that Yantai is using more resources than the earth can handle for long-term sustainability. The finding suggests that Yantai needs to take steps to balance out this resource use to protect the environment and ensure sustainable growth.