In a mere forty years, the earth's population grew from 3 billion in 1960 to 6 billion in 1999. This unprecedented growth strains the soils, forests, water supplies, fisheries, oceans, and atmosphere. In short, pressures arising from the need to feed, clothe, and sustain so many people force ecosystems over their “carrying capacity.” Prior to this threshold being reached, an ecosystem can withstand pollutants or other influences without noticeable impairment; but once this threshold is surpassed, demands on the ecosystem result in permanent degradation. This damage does not respect political borders; pollutants can travel in air and water currents far from their sources and may even traverse the globe. National borders, once secured by armies and artillery, are now invaded daily by emissions generated by economic activities abroad. Satellites and other modern means of monitoring the planet have shown that transboundary pollutants are ubiquitous and on the rise.

Although this chapter examines a few select cases of atmospheric pollutants, its real purpose is to illustrate how seemingly identical pollution (public goods) problems may have vastly different collective action prognoses. To accomplish this end, I contrast collective action outcomes for providing two global public goods (GPGs): actions to curb stratospheric ozone shield depletion stemming from chlorofluorocarbons (CFCs) and bromide-based substances, and efforts to reduce global warming stemming from greenhouse gases (GHGs). For a second collective action contrast, I examine two acid rain problems – one due to sulfur emissions – and one due to nitrogen emissions to show that two regional public goods (RPGs) problems may have greatly different prognoses.