Simplify the following text for a Grade 7 native English-speaking person.
Original: Initially about 30,000 people moved to the goldfields , but by 1863 this had declined to about 3,500 because of the difficult mining conditions .
Simplified: About 30,000 people moved to the goldfields , but by 1863 this had dropped to about 3,500 because mining the gold was too hard .