I'm in the midst of writing a paper on the proper methodology for estimating the economic impact of national parks. That will be out soon.
"National parks support more than $30 billion in economic activity and more than a quarter million
private-sector jobs. Many of these jobs are in rural and urban communities that are gateways to these
popular travel destinations."
This is misleading at best, an outright lie at worst. It is true that individual parks almost always have an economic impact on the local areas they serve. However, to claim that this is extra economic activity for the country is completely wrong. These parks are funded by US taxpayer dollars. For every dollar that supports jobs, that's one less dollar Americans can spend to support other jobs.
The only economic impact that National Parks should be claiming for the national economy is the money from out-of-country tourists that wouldn't have made the trip if not for the parks, or Americans that visit the parks that would have traveled out of country if not for the parks. This must be at tiny fraction of park spending. Hence, the national economic impact of National Parks is tiny.
For reviews of several studies on the economic impact of parks and recreation areas, go to my website, economicimpactreview.com.