One thing I've noticed over the years is that it can take me awhile to wrap my head around some things. In seminary, especially, this was true. I could read a text or hear a lecture and it may have been days later, after reading and re-reading, ruminating and otherwise pondering that the light would turn on and I would 'get it.' This has been the process for understanding a question that has bothered me about some folks' understanding of the new heaven and new earth mentioned in Scripture.
Let me offer some background. I began following Christ a long time ago. Over the years I have been involved with faith communities that are pretty much fundamentalist in their approach to Scripture. As a result, much of their 'gospelling' has been to state that we should not be concerned about ecology or economics, (unless it's conservative), but, rather we should get people saved so as to populate some disembodied heaven of the future. After all, the physical realm is going to burn up and pass away. Now, I have to say that this never really resonated with me. There seemed to be a disconnect between this mindset and what Jesus actually did and said. But, there was a certain logic to the idea that if this cosmos is going to be, at the very least, replaced, why should we concern ourselves with running out of fossil fuels or holes in the ozone layer.
After reading N. T. Wright's Surprised by Hope: Rethinking Heaven, the Resurrection, and the Mission of the Church 3 times, (I said I was slow), something clicked. In the book Wright mentioned that people should be involved in bringing justice and wise stewardship to this world, now, in anticipation of that new creation. If humans are to be stewards and co-regents with God in the care and oversight of the new creation, then we should be about that business today, in this world. Not that it's a practice run, but Paul wrote that nothing that is done in this life will be lost on the next in the resurrection. We can, therefore, justify social justice and ecological justice here and now without diminishing the importance of the kerygma of the Gospel.