Not sure if it is possible in 80 years without a decrease in population, but there are definitely a lot of variables that we can try to change. I think it really has to start with a paradigm shift in how the world, especially the developed world, tackles consumerism. We need to reduce our carbon footprint like crazy, but that can only happen if we start to reduce our love for materials. The average US house has like 300k things or something like that, most of which are totally inconsequential for living a fulfilling and productive life. This is a very complicated issue to tackle.
Another one needs to be figuring out what kind of renewable energy sources we want to invest in. Nuclear seems like a solid choice to me, but I am not that well versed in the negatives of it. There is a huge stigma against the word nuclear that needs to change. For instance, MRI (magnetic resonance imaging) uses the nuclear magnetic resonance (NMR) of nuclei in our bodies to construct visuals. The medical industry initially called in NMRI, but left out nuclear because people would get the big scared. There are other new forms too, like tidal energy that is slowly becoming bigger (Nova Scotia Bay of Fundy Project seems promising).
There are plenty of other things too: consuming less livestock (beef) with high carbon footprints, creating farms with more biodiversity and buying or growing local, using more carbon efficient modes of transport like walking, biking and PT, education about the natural world, carbon taxes, improvement in waste management (reduce first, reuse second, and recycle third - many recycled items just go to the trash anyways). Those are just some more surface level ones, there are a lot of economic policies that have to be put in place as well, but I don't know much about that stuff right now.