Look up any list of global environmental problems and you’ll see roughly the same ones listed everywhere: climate change, biodiversity loss, freshwater overuse, and air and water pollution. Some lists include overpopulation; others single out indoor air pollution, overfishing or soil erosion. Doubtlessly, all these problems affect people and ecosystems throughout the world. However, for the purposes of designing global governance structures and considering actions that might be taken by an eventual world government, it is important to identify which of these problems are truly global and which are just local problems writ large.
We can distinguish between local and global environmental problems by looking at how they might be solved. A local problem in a certain place can be solved by actions taken in that place. (Note that this term does not imply anything about scale; a local environmental problem might involve areas of hundreds or thousands of square miles.) A local problem that appears in many places throughout the world may be referred to as worldwide. On the other hand, global environmental problems manifest in particular places but cannot be solved by action in those places.
As an example, let’s consider the problem of air pollution in Los Angeles. The city’s notorious smog in the latter 20th century was caused mainly by emissions from its cars and was largely solved by city and state emission regulations. This is a local issue, although since many cities throughout the world face the same problem, it is worldwide. By contrast, air pollution from wildfires driven by global warming can be mitigated locally through land use practices but cannot be solved at that level. Even if California went 100% carbon-free tomorrow, it would still face the same problems. Climate change is the quintessential example of a global problem for exactly that reason.
The governance implications are clear. Global problems are clear targets for global legislation and, before then, binding treaties. Worldwide problems, on the other hand, are more appropriately addressed through supporting and coordinating local measures. Other than climate change, persistent pollutants such as PCBs and mercury are global problems, as is plastic in the oceans, because these pollutants often cause problems far from their places of origin. Many other environmental problems typically labeled global, such as biodiversity loss due to hunting or habitat destruction, are actually worldwide.
Of course, it could hardly be that simple. The description of biodiversity loss in the previous paragraph omits migratory and wide-ranging oceanic species such as whales, as well as global markets in poached rhino tusk or rainforest beef. Other problems, although local by the definition above, involve multiple nations and can spark conflicts. Disputes over river water, such as that between Ethiopia, Sudan, and Egypt over the Nile, are common examples of such international problems. These situations require political and legal means of conflict resolution; failing that, negotiation is critical. And some local problems, such as deforestation, can have global consequences if taken beyond a certain level and thus might be legitimately restricted by a global authority. Still, the conceptual distinction between worldwide and global problems is helpful in figuring out how different environmental problems are best addressed and which ones could be handled by a world federal government limited to addressing issues that nations cannot.