ABSTRACT
One hears debates today on what is the most serious, current challenge to human sustainability. Actually, there are many important factors affecting human unsustainability, and it is difficult to rank them by their gravity. Most adverse factors are slowly acting; their effects at present are felt at a rate that it easy for people to adapt to or even ignore. These factors also interact, which makes it hard to separate their effects on unsustainability. They include, but are not limited to the following: (1) population growth; (2) loss of fresh water due to climate change, overuse, and pollution; (3) famine, resulting from decreased food production due to water shortages, insects, crop diseases, and so forth; (4) economic collapse following inflation and mass unemployment, leading to governmental crisis; (5) exhaustion of fossil fuel (FF) energy sources leading to inflation; (6) failure to develop alternate energy sources in a timely manner; (7) loss of arable land due to overfarming and drought; (8) profligate, anthropogenic greenhouse gas (GHG) emissions accelerating global climate change; (9) human migrations; (10) conflict; and (11) pestilence (affecting humans, domestic animals, ecosystems, and plants). Pestilence and death also lead to decreased food production, starvation, and economic collapse, a positive-feedback loop.
