The reflexive (but not entirely unjustified) fear of the possibility of spreading pathogens from one region to another will almost certainly be used to justify onerous restrictions on immigration and potentially even justify xenophobic persecution of undocumented immigrants. This is problematic because it will further increase the reluctance of these populations to report or interact with public health authorities in preventing the spread of contagion. The people who live in countries that are not served by a robust public health apparatus and medical system will be under the most stress and will thus be induced to try to immigrate regardless of public health concerns. Of course, the kind of indefinite detention in adequate facilities that was and is being done at the US-Mexican border right now actually increases the chance of another epidemic outbreak given the close contact, poor sanitation, lack of medical services, and public health education, and in fact epidemiologists have been significantly concerned about an influenza outbreak because of these policies.
The impact upon climate change is not as clear. In the short term, the restrictions on travel have already had a positive effect on the emissions of greenhouse gases and other pollutants used in transportation. However, in the long term there will probably be at least a modest decrease in the use of public transit when people have other options which may negate any of the near-term gains. Longer term, the industrialized nations which have outsourced the production and manufacture of critical goods such as medical PPE, foodstuffs, et cetera may seek to bring back some of the capacity as a national security measure, although how feasible that is from an economic standpoint is unclear.
Realistically, the United States does not have any comprehensive policy to abate the causes and effects of global climate change; there is a patchwork of policies and funding of climate surveillance, alternative energy and mitigation strategies spread across the Department of Defense, Department of Energy, Department of the Interior, Environmental Protection Agency, National Oceanographic and Atmospheric Administration, National Aeronautic and Space Administration, as well as various state-level efforts of which California is in the forefront, but under the current presidential administration many of these efforts have been curtailed or eliminated. Europe in general and many European states in particular have more comprehensive policies regarding climate change monitoring and abatement but aside from transitioning away from coal as the most polluting source of power production and inducements to the transportation sector to find less polluting alternatives there really isn’t much of the way of effective abatement or remediation.
The cheapest method of climate change abatement that could be effected starting now with significant long term effects right now would be to reintroduce wetlands and forests, and prevent the destruction of existing wetlands and rainforests being clearcut for agriculture and grazing, and despite the existential threat posed by climate change there is virtually nothing being done in that regard on a large enough scale to matter.
Anyway, it’s an interesting question that we really won’t have the answer to until we see how the COVID-19 pandemic plays out of the next couple of years but we definitely need to take lessons from this because this is certainly not going to be the last pandemic. In fact, epidemiologists have been warning about this kind of outbreak for decades now, and it is frankly surprising it took this long for one to become a global pandemic.