Normally people go to their moral intution to answer these questions, but I'm dubious of mine because it tells me things that are unreasonable:

• Someone physically close to me is more important than someone in another country.
• Doctors should treat people first-come-first-served instead of treating inexpensive diseases first.
• Charities should spend all their money on helping people instead of measuring how well what they're doing works.
• The suffering of a person matters less if they're being emulated on a computer.
• The suffering of cuter animals and more attractive people matters more.
• One person with a problem is more important than many.

Cutting chunks off a tree for fun seems wrong. So does going around stomping on ants, raising chickens in massively overcrowded conditions, kicking puppies, and torturing people in video games. But I'm not sure which of these, if any, are actually wrong and not just my moral intutition being overly empathic in what to identify with.