1. The Montreal Protocol of 1987 was an international treaty, agreement, in order to protect and revitalize the ozone layer. This treaty has been seen as a major success, as it has been accepted by pretty much all countries, and they were all cooperating and helping in order for the ozone layer to be saved and revitalized.
The ozone layer indeed was saved with this treaty. After the implementation started, two years after the Montreal Protocol, the ozone layer started to gradually recuperate, and it is expected that if few decades it will be back to its levels of 1980.
The lesson that can be learned from this treaty is that if there is a will, and if all the nations collaborate for the greater good, they can achieve pretty much everything, including saving the environment and our planet as a whole.
2. The ozone layer challenge and the global climate change challenge are both similar and different. The similarities can be seen in that the humans were/are responsible for these changes in the atmosphere, which means that something should be done in order to stop those processes.
On the other hand, there are differences. While the damaging of the ozone layer was totally because of the human activity, the global climate change is mostly natural process, with the humans only being responsible for a fraction of it. Even if the human start releasing greenhouse gasses, the climate will change on a global level anyways, just with slightly slower rate (probably).
Another major difference and challenge is that in order to save the ozone, several chemicals needed to be put out of use, and they were not affecting the economies and development of the countries. That is not to say with the greenhouse emissions, as the greenhouse emissions come mostly from the industry and transportation, which are crucial for the economies and development. Because of it, lot of countries don't want to reduce the emissions, as they are afraid that their economies will crumble, and also a big problem is that a proper replacement for the agent that produce the greenhouse gasses have still not been found.
3. The sustainable resources are the resources that can be replenished, be it naturally or with human intervention, at least at the same rate as they are used. There are numerous sustainable resources, such as the sunlight, wind power, water power, wood, and even algae in more recent times.
There is only two major problems with the sustainable resources at present, problems that stop them to become the dominant energy sources. Those problems are that they occupy lot of space, and that they either don't produce the same amount of energy, or it is more expensive than the fossil fuel energy.
This type of resources don't need to have any particular resilience to something so that they can be used and replenished, as they are simply part of the natural processes, though with some there are human interventions as well.
As an example we can take the sunlight. The sunlight produces lot of energy, and that energy is yielded by the solar panels which convert it into electrical energy. The sunlight comes from the sun, so there isn't anything that that can really stop it on the long run. It doesn't need to have any resilience as there isn't really anything that harms it.
