There has beeen some research recently that indicates that spending some time in a natural setting can lower one's stress level significantly. Since stress is responsible for a wide variety of aliments, this means that getting out into nature regularly is important for our health. 

Nature can offer inspiration and a particular kind of connection that we can't get elsewhere. In the woods, in the wild, at the ocean...there is a scale and a quietude that is not matched in the town or the city. 

This is not necessarily more true today than it was one hundred years ago but it is certainly still true - nature provides a landscape for thought very different from anything offered by "development".

I think people today feel very isolated.  We are in concrete and steel all day long. We drive home on asphalt and steel.  I know that when I am outside, I do have transporting experiences.  A butterfly lands in front of me, I see a ladybug crawling, I watch a squirrel eat a nut.  These are all special, small, meaningful moments that we need in our lives to feel connected.

Nature provides opportunities for us to experience the physical world rather than the daily cyber one we are so familiar with these days. I'm thankful for the Cub Scouts program for my 9-year-old that gets him away from the computer or gaming console and gets him outside hiking and serving others. They went to a local park last week and picked up trash! He got outside and he participated in a community service project. I feel better as a parent when I get him out into the world experiencing it in a physical way.  He will have ample amounts of time to learn about and live with computers and video games in his lifetime. I'm a bit worried that he may not experience how much fun the outside world can be, though. Being outside, thinking about what to do next, helps pique the imagination and creativity in any human mind, not just in kids. Thoreau didn't have all of the digital distractions and he still learned from his experience in the wilderness.  My political science professor once stated, however, that Thoreau eventually came back to society; meaning, he didn't stay out there forever and become a hermit. He learned what he needed to learn and he came back to society and contributed to it.  I learned from that lesson that we all need to find balance between all of the different settings of life.

Many of the concerns that Thoreau held about his society- the fast pace of life, the lack of solitude, the corrosive effects of luxury, and above all, materialism, could certainly be said to be true of our own time. Many people may find fulfillment in getting away from all this. However, just as Thoreau didn't exactly escape by going to Walden, today's technology makes it difficult to get away today.

I absolutely agree with the above post.

I would add that persons who are connected to nature and care about the world around them are probably more likely to take care of the world, which could use all the help it can get to reduce pollution, encourage conservation of natural resources, preserve endangered species and threatened wilderness areas, and all the rest.

If it is important, it's so that we can get away from the hustle and bustle of everyday life.  You could argue that this is more important than ever today because of all of our electronic devices.  They keep us tethered to our everyday concerns much more than we were in Thoreau's day.  So if he needed to escape, how much more do we need to?