Federal Government: 

U.S. Forest Service, National Park Service, U.S. Army Corps of Engineers, Bureau of Land Management and the U. S Fish and Wildlife Service, as well as numerous other Federal Agencies.

State Government: 

Texas Parks and Wildlife Department and Texas Forest Service.  Each state has a similar entity or entities.

Local Governments: 

Municipalities, counties, or other local government entities often manage parks, museums, zoos or nature centers which employ park managers or interpreters. 

Private Sector:  

Resorts and commercial camping, youth camps, ecotourism companies, outfitters, museums, nature centers.