How much knowledge in indigenous North American cultures (for example, because it's what I'm more-familiar with) has been lost in the ongoing Euro-colonial stea

How much knowledge in indigenous North American cultures (for example, because it's what I'm more-familiar with) has been lost in the ongoing Euro-colonial steamroller? That knowledge is not gone, but the oral and practical traditions have been significantly stressed. If we care about existing for another, say, fifty thousand years it seems likely the knowledge, skills, and abilities from the last fifty thousand will be useful, along with the wisdom to set and respect some limits.