What is the market size of the ecotourism industry in the US?

"While there are no consolidated data on all ecotourism activities
taking place in the U.S., it is estimated that Americans spend
billions of dollars annually. On federal lands alone, there are an
estimated 900 million visits a year to national forests, parks,
monuments, historic sites, recreation areas, protected areas and
wildlife refuges, reserves and management areas -- most of these
visits include sightseeing, hiking, wildlife observation, swimming,
snorkeling or other forms of ecotourism."

U.S. Department of State
http://www.state.gov/g/oes/rls/or/19412.htm

Bobbie7

Thank you for the attempt. It's not quite what I'm looking for-maybe I
need to rephrase my question.

Thanks.

You can purchase this book from the World Tourism Organization
(http://www.world-tourism.org/):

http://www.world-tourism.org/cgi-bin/infoshop.storefront/EN/product/1353-1

or

http://www.world-tourism.org/cgi-bin/infoshop.storefront/EN/product/1339-1

which probably contain the statistics you are looking for.