Thomas Malthus theorized that population grows exponentially while food production grows arithmetically, leading to periodic catastrophes from famine and disease. He argued this would keep population in check. The Club of Rome warned that at current growth rates, limits to growth from resource depletion would be reached within 100 years. Esther Boserup argued that population growth spurs technological innovation and higher agricultural productivity, increasing food supply. While their theories differ, all raised important issues around sustainability and limits to growth that remain relevant today.