I guess they mean it's harsh because it's Colorado. Bad soil, scarce rain, scorching summers, freezing winters... So they have to take extra care with the species they plant.

I too would like to know what such a bold statement could mean

How many of this trees survived this year? Planting is easy. Assuring that the trees will not be stolen or destroyed later is getting more and more difficult each year by the antiscience/antihuman current trend.

The provoked wildfires in most of US, Canada and Europe this year had destroyed decades of work. And the changing climate too fast to allow the forests to adapt to much more heat, and dry spells, and stronger storms, and more salt from the sea level raising... is a big challenge.

And is an asymmetrical game. The group of people that spend their own resources (and get poorer) to save nature can't win against the group of people that get richer destroying nature, even if they pay a small fine eventually only the bad actors can win. Many people has the feeling that the huge efforts on conservation of rainforests, oceans or local nature is just fattening the goose until some criminal eventually come, grab and cash.

After some decades playing of this game one group starves and shrinks while the other have a feast of resources and buys everything