1. Thomas Malthus believed that population grows exponentially while food production grows arithmetically, leading to periodic crises from famine, disease, and war that keep population in check. 2. The Club of Rome warned in 1972 that unlimited population and economic growth could deplete resources within 100 years if trends continued unchanged. 3. Esther Boserup argued that population growth can spur agricultural innovations to increase food production, challenging Malthus' view. She believed people have the ability to adapt.