So we have these three approaches to excess in some system: reduce the quantity; reduce the impact; change the system. Let's look at these in reverse order.
Changing the system means altering some aspect so that the system is more resistant to the pollutant or resilient to the extraction. With man-made systems this is generally possible, if only because, being man-made, we have access to all the elements. In a domestic system (living in a house) people might light their way with candles, risking damage to the house from fire. This damage might be averted by building in brick, instead of wood. In a city system people need to get rid of waste. The city is modified to provide sewers and waste collection services. These things are possible because the system is reasonably well understood, the result of the excess is clear, and, for the city at least, a political will can be generated to get things done. Unfortunately, for the domestic home, not everyone can afford a brick house.
A planet-wide system, on the other hand, is generally very complex and often not well understood. Global temperature control, for example, involves the entire plant and animal kingdoms for production and absorption of CO2, with different production and absorption depending on temperature, daylight, inter-species competition and so on. It also involves the land and oceans as a heat store, with the complexity that the ocean has currents which can move heat (and cold) from one place to another, taking decades in the process. Plus, there are albedo effects from the ice caps and clouds, and a few other things I haven't mentioned. The only way to deal with this is through computer modelling and a large amount of effort has gone into creating such models. We can now say that we understand the global temperature system well enough for the purposes of predicting what might happen, with excess CO2, for example. Changing the system to make it more resistant to CO2 pollution is now possible in that we can point to parts of the system and predict what changes would do. Accordingly, we can, for example see that we could try increasing cloud albedo by seeding the atmosphere to force cloud formation; and this would work, up to a point. On the flip side, if clouds are reflecting sunlight away from us, they are also preventing sunlight getting through to plants. Now, plant and animal ecosystems are less well understood than global temperature control, but we can at least guess that creating a nuclear winter would severely reduce plant photosynthesis, reducing plant populations, correspondingly reducing populations of bacteria, fungi, insects, and all higher animals. Oh, and we wouldn't be able to use solar power.
An alteration to a system in this way comes under the heading of a technical fix. It is the application of technology to a problem and generally history has shown that one fix leads to a further fix to address the side effects of the first fix. The series can go on until the money runs out and either people live with a sub-optimal result, or the original problem reasserts itself and we're back where we started..
So, if technical fixes are unhelpful, can we look at changing the polluting or extracting process in some way? This often comes under the rubric of efficiency - welcome to the Jevons Paradox. This was discovered in the early days of CO2 pollution, during the Industrial Revolution, by William Jevons who noted that doing something more efficiently simply meant that more of it happened. The original case was comparative efficiency of steam engines and Jevons showed that more fuel efficient steam engines resulted in more steam engines and much the same use of coal. The result seems to be quite general and warns us against reading too much into a proposal to reduce the impact of some process or other1.
It seems then that, for global systems, changing the system is playing with fire, and making things more efficient is counter productive. We may be able to change man-made systems, such as agriculture, but generally we need to focus on removing the pollutant or the need for extraction altogether.
See https://solar.lowtechmagazine.com/2018/01/bedazzled-by-energy-efficiency.html for more detailed arguments on energy effiency, and impact on energy policy. ↩