Hall of Shame
Heat Pollution. Over the next millennium and for the rest of human history, earth's major environmental problem will be warming due not to greenhouse gases but rather to increased waste heat from non-solar energy (initially petrochemical, but then fusion). The problem emerges when a world population in the tens of billions all enjoy an energy budget equivalent to levels in the industrialized West in 2000. Humans in 2000 consume 10 terawatts, wherease the total solar energy received by Earth is estimated variously at 109000 or 174000 terawatts. Ten billion humans at U.S. levels of energy use would consume 1000 terawatts. All the waste heat from all the energy uses adds up, and the laws of thermodynamics guarantee that energy use always creates heat exhaust. Heat pollution will have to be managed to prevent a runaway greenhouse effect like on Venus.
Population. The primary long-term environmental problems caused by human population increase will be heat pollution and pressure on habitats and ecosystems. By contrast, the traditional environmental worries of pollution and resource scarcity are subject to increasingly-effective technological and economic solutions. As Earth's population stabilizes, some will worry that decreasing birth rates will lead to declining population. Any actual decreases in population will be minor and temporary, and underpopulation will never be a long-term problem.
Resource Scarcity. The scarcity of a resource is measured by the cost of satisfying the need that it satisfies. By this measure, almost all resources have throughout human history been getting less and less scarce. Fossil fuels will remain abundant at least through 2050, and will likely not be very scarce before fusion replaces them as humanity's primary energy source starting around 2150. Arable soil will through conservation remain abundant, and minerals will continue to decrease in scarcity (i.e. cost). Many species of fish and game will become increasingly less abundant in the wild, but the cost/scarcity of food in general will continue to decline. Demand for fresh water will outpace most of its natural supply, but the cost of fresh water will eventually plateau at and decline with the energy cost of its desalinization and transportation.
Biodiversity. While food will continue becoming less scarce, the wild plants and animals that constitute earth's ecosystem will come under increasing pressure from humanity's increasing population. Loss of forest and wetlands will threaten fragile ecosystems that harbor rare species. The lost information content of extincted species is effectively impossible to replace.
Pollution. Pollution levels in humanity's air, water, and land will continue to decrease as per-capita income increases and as government requires that economic transactions internalize their polluting externalities. Earth's crust has sufficient volume that solid waste disposal will be simply a problem of transportation. Human population will be limited much more by heat pollution much than by solid waste pollution. Property interests will ensure that soil erosion is mitigated. Government will successfully prevent destruction of the ozone layer.Infectious Disease. Pathogens will continue their natural evolutionary race against humanity's immunological and pharmacological defenses. Further progress against some pathogens may be frustratingly slow, but genetic engineering will by 2300 make most infectious diseases subject to treatment and many subject even to prevention.