In most states (with a few noted exceptions such as AR, MO, and VA) non-hunters and anglers pay nothing for wildlife conservation.
In my state a recent survey noted that nearly 70% of the general public thinks their state taxes help pay for wildlife conservation when in fact the FW agency doesn't get a dime from anything other than license sales and excise taxes paid by sportsmen and women.
A pet peeve of mine is when the Federal Government (or even the archery industry) claims the excise taxes paid by manufacturers are "Federal or Industry" dollars. We hunters pay those taxes to the industry and the industry pays them to the feds and the feds aportion them to the states. All the money though came from you and I.
By the way, the 12.5 million number for hunters is low. These numbers come from a survey conducted by the USFWS. These figures don't count youth under the age of 16 or people who don't buy licenses such as certain landowners and older folk in some states.