How could people have believed a century ago that nature is so vast and fertile that human actions could never have a lasting impact on wildlife populations? are there similar examples of denial or misjudgment occurring now?

There is denial and misjudgment occurring today as some groups of individuals do not accept that human actions are to be blamed for present day global warming. The events that kick started global warming began in Europe in the 1750s with the industrial revolution. This period marks when fossil fuels started to be used widely as industry developed. The use of fossil fuels and deforestation that comes out of the need for space for industry and development has lead to contemporary global warming.    

If there was no gravity then their would be no downword force on the football to have it return the the grownd, and if there was no friction (mainly air friction) then there would be no opposing force the stop the ball from moving through the air allowing the ball to travle ∞.