American authors reflect on the nation's highs and lows as the USA approaches its 250th anniversary

Despite the delusion of infinity that America's vastness has always encouraged (and that may underlie our wasteful approach to space and resources), some Americans had the foresight to recognise, early on, that our landscape was finite and needed protection.

Starting with Yellowstone national park in 1872, at least 34m hectares (85m acres) of American land has been designated national parks, along with 8m hectares or more as state parks.

In all, that's more than 42m hectares (about 164,000 sq miles, or 425,000 sq km) of mountains, shoreline, grasslands, ancient redwood trees